Prevalence of low back pain in young Brazilians and associated factors: Sex,physical activity,sedentary behavior,sleep and body mass index

Abstract

BACKGROUND:

Low back pain (LBP) has become increasingly common, but the prevalence of this complaint and associated factors in young people remains controversial.

OBJECTIVE:

This study aimed to identify the prevalence of LBP and to explore the existence of associated factors (sex, physical activity, sedentary lifestyle, sleep, body mass index and waist circumference).

METHODS:

This study considered all complaints of the lumbar region (acute or chronic) as LBP, which can irradiate to the backside and legs, lasting a minimum of 24 hours.

Youngsters aged 15 to 18 years from a school in the south of Brazil were evaluated. Descriptive statistics was used, in particular Chi-square, Mann-Whitney U tests and binary logistic regression. A significance level of $p<$ 0.05 was adopted.

RESULTS:

A total of 330 youngsters answered a questionnaire and had their anthropometric measurements measured (response rate 84%). The prevalence of LBP in the present was 30%, quarterly 63% and throughout life 77%. There was a significant association between LBP and sex: girls have an increased risk of LBP in the last three-month period (PR $=$ 1.3, 95% CI 1.06–1.56) and throughout life (PR $=$ 1.2, 95% CI 1.04–1.43). The practice of physical activities was also associated with LBP, but as a protection factor in the present and in the last three-month period (PR $=$ 0.7, 95% CI 0.47–0.90). Physical education at school has demonstrated a protective factor regarding LBP throughout life (PR $=$ 0.9, 95% CI 0.77–0.97). Most of the students did not comply with recommendations related to sleep and time spent doing activities in front of a screen, and no association of these factors with LBP was detected. This exposure (physical activity, sleep time, sedentarism) did not present significant association with LBP when adjusted by the confusion factors (sex, age, BMI).

CONCLUSIONS:

Youngsters reported a high prevalence of LBP. Girls were at greater risk of LBP than boys. It is recommended that prevention strategies focus on the practices of physical activities and scholar physical education. No association of LBP with sedentary lifestyle (TV and computer use time, sleep time), anthropometric measures and sleeping duration was observed.

Keywords

Adolescents back pain prevalence physical activity overweight

1. Introduction

Low back pain (LBP) has become increasingly common in young people [1, 2, 3, 4]. Studies show that 13% of 7 to 10-year-olds [2], 17% 12-year-olds and 60% 18-year-olds had LBP at some point in their life [3]. This complaint has been associated with several risk factors (biomechanical, anthropometric and psychosocial) that contribute to different doses and compositions depending on the individual [4, 5]. The sedentary lifestyle of youths is indicated as a predictor for LBP [6, 7, 8] due to the great amount of time spent in sitting position activities where postural changes and increased joint tensions occur [7, 8, 9, 10]. Another explanation for LBP related to the sedentary lifestyle is the decrease in energy expenditure and the increase in body weight since overweight youths present postural changes, a higher prevalence of musculoskeletal discomfort and, consequently, back pain [8, 10, 11]. When experiencing discomfort and pain, youngsters tend to engage less in physical activity (PA), favouring weight gain and in that way maintaining a cyclical behaviour [11]. On the other hand, there is evidence that physical activity is associated with a lower risk of back pain [4, 12].

Early and cumulative exposure to risk factors contributes to the appearance and recurrence of back pain [13]. Manchikanti and Hirsch [5] have recommended more studies related to LBP in youths and associated factors in order to establish prevention and treatment strategies to be adopted in the control of it. The early detection of complaints is of great importance, since back pain in adolescence is a relevant predictor of this complaint in adult life, the chronic back pain approach is more complex and has higher number of associated comorbidities [5, 13, 14].

In this sense, the objectives of this study were: a) To identify the prevalence of LBP complaints in youngsters from a school in the south of Brazil; b) To explore the existence of potential factors associated with LBP such as: sex, physical activity (PA), sedentary lifestyle (time spent in activities in front of a TV of computer screen), sleep duration and anthropometric measures (body mass index – BMI and waist circumference – WC).

2. Methods

This is a descriptive, exploratory, transversal and ret- rospective study to determine the prevalence of back pain in young individuals in the present, in a three-month period and throughout life and the associated risk factors.

2.1 Participants

The study involved 330 youngsters aged 15 to 18 years old, with a mean 16.0 $\pm$ 0.8 years, in the 1 ${}^{\text{st}}$ and 2 ${}^{\text{nd}}$ year of high school in the city of Florianópolis, southern Brazil. The State Education Institute was chosen for being a public school (free education) recognized as the largest teaching institution in the State of Santa Catarina with approximately 8000 students in elementary and high school (around 1100 students in the 1 ${}^{\text{st}}$ and 2 ${}^{\text{nd}}$ year of high school). These students belong to different social classes. The social indices of that State are among the highest in the country, presenting one of the lowest economic inequality and illiteracy rates.

We included those students indicated by the school who did not have cognitive, physical and/or psychiatric problems that prevented them from answering the questionnaire or participating in the physical evaluation. The youngsters were recruited during the school hours (either morning or afternoon). The physical measurements were carried out individually in a private environment during the physical education lesson; while the questionnaires were answered by the students in the classroom in the presence of the researcher the teacher.

The study was approved by the Committee of Ethics in Research of the Santa Catarina State University under process number 35004014.4.0000.0118/2014 CAAE (Submission Certificate for Ethical Assessment). All participants and their responsible parent or guardian signed the consent form.

2.2 Study instruments

The youths answered the Oliveira Questionnaire on Low Back Pain in Youths – OLBPYQ [4, 15, 16, 17]. The Brazilian version was considered adequate and similar to the original, presenting good levels of validity, reliability and reproducibility (ICC $=$ 0.51 to 1, Spearman Correlation Coefficient 0.53 to 1; internal consistency – Cronbach’s Alpha 0.76) [18]. The only question with the least reliability in the Oliveira questionnaire referred to low back pain at the moment of filling it in. This value is believed to result from the time interval between test and retest; although a 1-week period was considered proper for the retest, it was sufficient time for the pain complaints of the young people undergo modifications, since the majority of the young people reported more passing complaints [4, 18].

The OLBPYQ has an accessible language to the age group selected. It is clear and objective, consisting essentially of closed questions that could be filled out in 10 to 15 minutes. It refers to LBP as all complaints of pain in the lower back (acute or chronic) that may radiate to buttocks and legs, with a 24-hour duration at least [4, 18]. It aims to answer the questions: age, sex, and psychosocial variables related to the physical activity level, time in sedentary activities, sleep duration and smoking habits. In relation to LBP the questions are: occurrence at the time of the research, in the last 3 months and throughout life, age of first complaint, frequency in the last three months, intensity (measured by analogue visual scale of pain – a numerical scale from 0 to 10 was used, in which 0 represented no pain and 10 the worst pain), activities that aggravate the pain, the need of consultation or treatment with a health professional.

Height, weight and waist circumference (WC) were evaluated by means of a portable scale and a measuring tape. The youths were barefoot, in light clothes and evaluated individually by the same examiner. The weighing was accomplished with a 100-gram-precision digital scale (Filizola), calibrated for all subjects before starting the collection. The youngsters were positioned in the center of the scale with weight well distributed over the two lower limbs, with horizontal gaze. The height was measured using a 200-centimeter tape measure fixed to the wall. The measurement was performed at the end of a maximal inspiration with the individual maintaining his back to the wall, his feet joined and his head in the horizontal plane. The WC was measured with the 200-centimeter (inextensible) tape measure after a normal expiration, obtaining the measurement of the midpoint between the last rib and the iliac crest. All measurements were performed twice and, in case of divergence, the averaged value was taken. The body mass index (BMI) was calculated by dividing weight in kilograms (kg) by height in meters (m) squared.

2.3 Variables

The level of physical activity (PA) was detected by OLBPYQ through three indicators: physical education at school, physical activity outside school and home-school types of trips. The data were compared to the recommendation of at least 60 minutes of moderate to vigorous physical activity per day [19]. PA levels below those recommended are considered insufficient and are frequently associated to obesity, metabolic diseases, sleep disturbance, musculoskeletal imbalance and back pain [6, 20].

The sedentary time, also measured through the questionnaire, was investigated by questions regarding the time of TV and computer (or similar) use. The investigation of sedentary lifestyle based on this is widely used in studies because of the ease of participants in recalling the activity time [21]. This variable was classified as normal ( $<$ 120 minutes/day) and excess ( $\geqslant$ 120 minutes/day) [15, 22].

For sleep duration, the cut-off point stipulated by Felden et al. [23] of 8 hours and 33 minutes was used and values were categorized as sufficient (equal or superior time) and insufficient (shorter time).

The BMI classification (eutrophic, overweight, and obese) followed the method proposed by Cole et al. [24]. The cut-off point of 17 kg/m ${}^{2}$ was used to indicate underweight children, despite the low allowance to validate this value as a marker of health risk [24]. The reference values for WC were based on a study by Rocco et al. [25], with 319 Brazilian adolescents aged 10–19 years, in which they detected the abdominal measure related to cardio metabolic risk. The values of excess abdominal fat considered as risk were 81.4 and high risk 85.9 centimeters for boys and 71.5 and 73.5 centimeters, respectively, for girls.

2.4 Statistical analysis

A descriptive analysis was performed using the mean, standard deviation and frequency distribution of data.

The statistical analysis of association between LBP at present, quarterly and lifelong was performed in the software The Statistical Package for Social Sciences (SPSS), version 20.0, using Chi-square test for the variables sex, physical education, physical activity, walking (trips from home to school) and BMI (eutrophic, overweight, above and below the weight); correction for Chi-square; G-test for BMI classification; Mann-Whitney U test for age, BMI (values), WC and TV and/or computer, physical activity and sleep duration. A significance level of $p<$ 0.05 was adopted.

When significant associations of variables regarding pain episodes were observed, the confidence interval (CI) for the prevalence ratio (PR) was used to demonstrate the value of the risk.

Table 1
Description of the youngsters regarding the variables: BMI, WC, pain complaints, TV and computer (similar) time use, physical activities and sleep duration by sex

		Sex
Variable	General	Male	Female
Total – N (%)	330 (100%)	86 (26%)	244 (74%)
Age (years) – mean $\pm$ SD	16.0 $\pm$ 0.8	16.1 $\pm$ 0.8	16.0 $\pm$ 0.8
BMI 1 ${}^{\text{st}}$ – N (%)	235 (71%)	54 (63%)	182 (75%)
BMI 2 ${}^{\text{nd}}$ – N (%)	58 (18%)	23 (27%)	35 (14%)
BMI 3 ${}^{\text{rd}}$ – N (%)	18 (5%)	6 (7%)	12 (5%)
BMI 4 ${}^{\text{th}}$ – N (%)	19 (6%)	3 (3%)	15 (6%)
BMI (kg/m ${}^{2}$ ) – mean $\pm$ SD	22.0 $\pm$ 3.9	22.5 $\pm$ 4.3	21.9 $\pm$ 3.8
WC (cm) – mean $\pm$ SD	70.5 $\pm$ 9.4	75.3 $\pm$ 11.0	68.8 $\pm$ 8.1
LBP present point
Yes – N (%)	100 (30%)	20 (23%)	80 (33%)
No – N (%)	230 (70%)	66 (77%)	164 (67%)
LBP quarterly
Yes – N (%)	207 (63%)	38 (44%)	169 (69%)
No – N (%)	123 (37%)	19 (22 %)	28 (11%)
LBP throughout life
Yes – N (%)	154 (77%)	57 (66%)	197 (81%)
No – N (%)	76 (23%)	29 (34%)	47 (19%)
Physical education (school)
Yes – N (%)	261 (79%)	80 (93%)	181 (74%)
No – N (%)	69 (21%)	6 (7%)	63 (26%)
Minutes/week – mean $\pm$ SD	84.1 $\pm$ 32.9	88.5 $\pm$ 34.2	82.1 $\pm$ 32.3
Physical activity (outside school)
Yes – N (%)	195 (59%)	56 (65%)	139 (57%)
No – N (%)	135 (41%)	30 (35%)	105 (43%)
Minutes/week – mean $\pm$ SD	359.9 $\pm$ 345.4	515.5 $\pm$ 461.3	297.1 $\pm$ 262.8
Walking (home-school)
Yes – N (%)	122 (37%)	36 (42%)	86 (35%)
No – N (%)	208 (63%)	50 (58%)	158 (65%)
Minutes/week – mean $\pm$ SD	137.9 $\pm$ 142.6	168.9 $\pm$ 177.7	124.9 $\pm$ 123.9
Minutes/week physical activities total – mean $\pm$ SD	357.2 $\pm$ 356.7	500.4 $\pm$ 497.1	302.7 $\pm$ 268.0
Time_ minutes/day TV – mean $\pm$ SD	187.4 $\pm$ 140.0	183.8 $\pm$ 146.2	189.3 $\pm$ 140.1
Time_ minutes/day PC – mean $\pm$ SD	627.2 $\pm$ 390.8	506.2 $\pm$ 345.1	669.7 $\pm$ 431.3
Minutes/day sleep (week days) – mean $\pm$ SD	435.9 $\pm$ 97.9	422.4 $\pm$ 81.6	440.7 $\pm$ 102.8
Minutes/day sleep (weekends) – mean $\pm$ SD	563.5 $\pm$ 135.6	548.0 $\pm$ 135.9	568.9 $\pm$ 135.3

${}^{\text{a}}$ Body mass index – BMI classification by Cole [14]: 1 $=$ normal, 2 $=$ overweight, 3 $=$ obese, 4 $=$ below the weight; N $=$ Number of subjects; SD $=$ standard deviation; WC $=$ waist circumference; LBP $=$ low back pain.

To verify the influence of exposures (sedentary time, physical activity, sleep time) finally, back pain (at the moment of the research, in a three-month period and throughout life), the binary logistic regression analysis was carried out, adjusted by the confounding factors (sex, age and BMI).

3. Results

Most of the youngsters in this study were girls (74%), all of them had already had their first period; 82% of the youngsters did not work (those that had some kind of job did general service in offices, looked after children or were waiters); 95% of the participants did not smoke; 71% were eutrophic (normal weight), mean BMI 22.0 $\pm$ 3.9 kg/m ${}^{2}$ , mean WC 70.5 $\pm$ 9.4 centimeters. The prevalence of LBP in the present was 30%, quarterly 63%, and throughout life 77% (Table 1).

Table 2
Low back pain in the present (moment of evaluation) and risk factors: sex, anthropometric measures, physical activities, sedentary lifestyle and sleep duration

Variable	Pain in the present		$p$ value ${}^{\text{a}}$
	Yes	No
Sex			0.098
Female	80 (80%)	164 (71%)
Male	20 (20%)	66 (29%)
Age (years) – mean $\pm$ SD	16.0 $\pm$ 0.9	16.0 $\pm$ 0.8	0.820
BMI 1 ${}^{\text{b}}$ N (%)	69 (69%)	166 (72%)	0.305
BMI 2 ${}^{\text{b}}$ N (%)	16 (16%)	42 (18%)
BMI 3 ${}^{\text{b}}$ N (%)	9 (9%)	9 (4%)
BMI 4 ${}^{\text{b}}$ N (%)	6 (6%)	13 (6%)
BMI (kg/m ${}^{2}$ ) – mean $\pm$ SD	22.5 $\pm$ 4.6	21.8 $\pm$ 3.6	0.406
WC (cm) – mean $\pm$ SD	71.7 $\pm$ 11.1	69.9 $\pm$ 8.6	0.343
Physical education (school)			0.928
Yes – N (%)	80 (80%)	183 (80%)
No – N (%)	20 (20%)	47 (20%)
Physical activity (outside school)			0.009
Yes – N (%)	48 (48%)	146 (63%)
No – N (%)	52 (52%)	84 (37%)
Walking (home-school)			0.0895
Yes – N (%)	45 (43%)	79 (34%)
No – N (%)	57 (57%)	151 (66%)
Total time of physical activity/week – mean $\pm$ SD	303.4 $\pm$ 334.2	341.7 $\pm$ 364.8	0.192
Time_ minutes/day TV – mean $\pm$ SD	179.7 $\pm$ 136.9	190.7 $\pm$ 141.6	0.510
Time_ minutes/day PC – mean $\pm$ SD	639.7 $\pm$ 401.3	621.78 $\pm$ 386.9	0.717
Minutes/day sleep (week days) – mean $\pm$ SD	432.0 $\pm$ 108.2	437.6 $\pm$ 93.3	0.424
Minutes/day sleep (weekends) – mean $\pm$ SD	569.4 $\pm$ 148.5	560.9 $\pm$ 129.8	0.292

${}^{\text{a}}$ $p$ – Significant values are highlighted in bold. ${}^{\text{b}}$ Body mass index – BMI classification by Cole [14]. 1 $=$ normal, 2 $=$ overweight, 3 $=$ obese, 4 $=$ below the weight. N $=$ Number of subjects; SD $=$ standard deviation; WC $=$ waist circumference.

Table 3

Low back pain in the last three months and risk factors: sex, anthropometric measures, physical activities, sedentary lifestyle and sleep duration

Variable	Quarterly low back pain		$p$ value ${}^{\text{a}}$
	Yes	No
Sex			0.001
Female	169 (82%)	28 (60%)
Male	38 (18%)	19 (40%)
Age (years) – mean $\pm$ SD	16.1 $\pm$ 0.8	16.1 $\pm$ 0.8	0.647
BMI 1 ${}^{\text{b}}$ N (%)	69 (72%)	166 (68%)	0.305
BMI 2 ${}^{\text{b}}$ N (%)	16 (17%)	42 (21%)
BMI 3 ${}^{\text{b}}$ N (%)	9 (6%)	9 (2%)
BMI 4 ${}^{\text{b}}$ N (%)	6 (5%)	13 (9%)
BMI (kg/m ${}^{2}$ ) – mean $\pm$ SD	22.1 $\pm$ 4.0	21.7 $\pm$ 3.3	0.797
WC (cm) – mean $\pm$ SD	70.5 $\pm$ 9.6	70.2 $\pm$ 8.7	1.000
Physical education (school)			0.918
Yes – N (%)	160 (77%)	36 (77%)
No – N (%)	47 (23%)	11 (23%)
Physical activity (outside school)			0.009
Yes – N (%)	48 (45%)	146 (63%)
No – N (%)	52 (55%)	84 (37%)
Walking (home-school)			0.685
Yes – N (%)	77 (37%)	16 (34%)
No – N (%)	130 (63%)	31 (66%)
Total time of physical activity/week – mean $\pm$ SD	317.6 $\pm$ 344.9	351.1 $\pm$ 373.7	0.137
Time_ minutes/day TV – mean $\pm$ SD	184.8 $\pm$ 128.4	191.7 $\pm$ 158.2	0.612
Time_ minutes/day PC – mean $\pm$ SD	646.3 $\pm$ 388.5	595.1 $\pm$ 394.0	0.717
Minutes/day sleep (week days) – mean $\pm$ SD	433.8 $\pm$ 103.6	439.5 $\pm$ 87.9	0.554
Minutes/day sleep (weekends) – mean $\pm$ SD	564.5 $\pm$ 138.7	561.71 $\pm$ 130.8	0.567

${}^{\text{a}}$ $p$ – Significant values are highlighted in bold. ${}^{\text{b}}$ Body mass index – BMI classification by Cole [14]: 1 $=$ normal, 2 $=$ overweight, 3 $=$ obese, 4 $=$ below the weight. N $=$ Number of subjects; SD $=$ standard deviation; WC $=$ waist circumference.

Table 4

Low back pain throughout life and risk factors: sex, anthropometric measures, physical activities, sedentary lifestyle and sleep duration

Variable	Low back pain throughout life		$p$ value ${}^{\text{a}}$
	Yes	No
Sex			0.006
Female	197 (78%)	47 (62%)
Male	57 (22%)	29 (38%)
Age (years) – mean $\pm$ SD	16.1 $\pm$ 0.8	16.0 $\pm$ 0.7	0.310
BMI 1 ${}^{\text{b}}$ N (%)	181 (71%)	54 (71%)	0.915
BMI 2 ${}^{\text{b}}$ N (%)	46 (18%)	12 (16%)
BMI 3 ${}^{\text{b}}$ N (%)	13 (5%)	5 (7%)
BMI 4 ${}^{\text{b}}$ N (%)	14 (6%)	5 (7%)
BMI (kg/m ${}^{2}$ ) – mean $\pm$ SD	22.0 $\pm$ 3.9	22.0 $\pm$ 4.9	0.802
WC (cm) – mean $\pm$ SD	70.5 $\pm$ 9.44	70.4 $\pm$ 9.7	0.914
Physical education (school)			0.037
Yes – N (%)	196 (77%)	67 (88%)
No – N (%)	58 (23%)	9 (12%)
Physical activity (outside school)			0.093
Yes – N (%)	143 (56%)	51 (67%)
No – N (%)	111 (44%)	25 (33%)
Walking (home-school)			0.807
Yes – N (%)	93 (37%)	29 (38%)
No – N (%)	161 (63%)	47 (62%)
Total time of physical activity/week – mean $\pm$ SD	334.3 $\pm$ 370.2	316.1 $\pm$ 304.3	0.548
Time_ minutes/day TV – mean $\pm$ SD	190.8 $\pm$ 137.0	176.6 $\pm$ 150.1	0.101
Time_ minutes/day PC – mean $\pm$ SD	650.0 $\pm$ 397.2	551.1 $\pm$ 360.7	0.065
Minutes/day sleep (week days) – mean $\pm$ SD	435.8 $\pm$ 104.1	436.2 $\pm$ 74.2	0.869
Minutes/day sleep (weekends) – mean $\pm$ SD	561.0 $\pm$ 141.3	571.6 $\pm$ 114.9	0.972

${}^{\text{a}}$ $p$ – Significant values are highlighted in bold; ${}^{\text{b}}$ Body mass index – BMI classification by Cole [14]: 1 $=$ normal, 2 $=$ overweight, 3 $=$ obese, 4 $=$ below the weight; N $=$ Number of subjects; SD $=$ standard deviation; WC $=$ waist circumference.

Table 5

Main results of the study

Key points

•

The prevalence of low back pain in young Brazilians (15–18 years old) at the time of evaluation was 30%, quarterly 63% and throughout life 77%;

•

Low back pain was associated with sex (girls are at greater risk than boys) and physical activity practices (young people who do physical activities have less risk);

•

No associations were seen between low back pain and sleep duration, activity time in front of a screen (TV and computer) and anthropometrics measures (BMI and WC);

•

Most of the young people did not comply with the recommendations regarding the activity time in front of a screen (55% TV and 91% computer/mobile), sleep duration (82%), and physical activities (72%). Also, 23% were overweight or obese and, out of these, 22% presented risk and 7% high risk of abdominal fat;

•

The results of the present study add contributions to strategies to promote health and to prevent the complex complaint of low back pain.

Regarding the recommendation of 60-minute daily physical activity, only 28% fulfilled the orientation (42% of boys and 24% of girls), with 8% of youths being completely inactive, not doing physical education, walking trips or physical activity outside school.

The youngsters reported computer use was being replaced by mobile phones. 48% adolescents got to spend 720 minutes/day in front of the TV and 71% using the mobile for 1440 minutes/day. They answered that they used the cell phone all day long, including in class or during sleep and they remain available, wake up during the night to receive and send messages. In view of this, the total time of activities in front of a screen (TV and computer) could not be calculated. Despite the high time spent and the fact that most of the youngsters in this study had exceeded the daily recommendation of screen time, 55% (50% boys and 57% girls) spent over 2 hours watching TV and 91% (88% boys and 92% girls) using the computer, there were no significant associations of LBP and time of TV or computer (mobile) use.

The majority of the youngsters, 82%, did not follow the orientation to sleep at least 8 hours and 33 minutes/day during the week (87% of boys and 40% of girls) while, at the weekend, 68% followed this recommendation (62% of boys and 70% of girls). Other characteristics of the sample are described in Table 1.

Regarding LBP in the present moment, a significant association was observed only with outside school physical activity ( $p=$ 0.009) (Table 2), which is a protective factor. Youngsters who practiced physical activity demonstrated a risk of at least 0.7 times lower of occurrence of pain episodes than those who did not practice (PR $=$ 0.7, 95% CI 0.47–0.90).

The quarterly prevalence of LBP was significantly associated with sex ( $p=$ 0.001) and with outside school physical activity ( $p=$ 0.009) (Table 3). The calculated risk level showed that girls presented a risk of LBP of at least 1.3 times higher in the last three-month period (PR $=$ 1.3, 95% CI 1.06–1.56), while physical activity was a protective factor since youths who practiced it had a risk of at least 0.7 times lower of pain episodes than those who did not (PR $=$ 0.7, 95% CI 0.47–0.90).

Lifelong LBP in youngsters was observed to be significantly associated with sex ( $p=$ 0.006) and physical education at school ( $p=$ 0.037) (Table 4). The risk level calculated according to prevalence showed that girls presented a risk at least 1.2 times higher than boys for lifelong LBP (PR $=$ 1.2, 95% CI 1.04–1.43), and physical education at school was considered a protective factor since youngsters who practiced it had a risk of 0.9 times lower of having pain episodes throughout life when compared to those who did not practice (PR $=$ 0.9, 95% CI 0.77–0.97).

Exposures (physical activity, sedentary time and sleep time) did not present significant associations with low back pain when adjusted to the confounding factors (sex, age and BMI) (Tables available in the Appendix).

The main findings of this study are presented in Table 5.

4. Discussion

This study found high prevalence of LBP in youths and the association of this complaint with sex, practice of physical activity outside school and physical education in school, but no associations were detected with other lifestyle factors.

4.1 Prevalence of LBP

The prevalence of LBP was 30% of subjects at the present point, 63% quarterly and 77% throughout life. Minghelli et al. [15] investigated 966 Portuguese youngsters aged 10–16 years with the same instrument and found lifelong prevalence of 62% and at the present point of 16%, prevalence values lower than the ones found in this study. Meziat Filho et al. [22] evaluated 1102 14 to 20-year-old Brazilians and the presence of LBP throughout life was 47%. Differences in prevalence values may be related to the age group studied, the methodological designs adopted, the sample size and the definition of LBP. However, the high prevalence values in this and other studies reinforce that urgent actions related to LBP in youngsters should be adopted.

4.2 Sex and LBP

In this study, quarterly and lifelong LBP was associated with girls, corroborating other studies that also detected this difference between sex [15, 22, 26, 27]. The factors that justify this disparity have not yet been clarified, but studies suggest it is a result of the interaction of bio morphological, psychosocial and cultural factors [28, 29, 30]. Among bio morphological factors, endogenous pain-inhibiting systems are believed to be less efficient in women [29] and that female sexual hormones influence pain sensitivity [28] whereas in men, testosterone for example, seems to have an anti-nociceptive effect [31]. Regarding psychosocial factors, differences in the form of coping with pain are observed: men tend to use distraction and women use techniques focused on emotion and perception of complaint. In addition, manifestation of pain is more socially accepted in women [28, 30]. Behavioral issues contribute because girls have lower levels of physical activity and spend more time in sedentary activities than boys [9, 32]. In this study girls also presented lower levels of physical activity than boys (24% and 42%, respectively, followed the recommendations).

4.3 Physical activity and LBP

Insufficient levels of physical activity were detected in the majority, 72% (boys and girls), in agreement with other studies [22, 33]. Hallal et al. [33] detected that almost two thirds of adults and 80% European young people did not reach the minimum PA levels recommended. Insufficient PA levels are associated to a series of bad health indicators, such as increase in body fat/obesity, metabolic and cardiovascular problems [19, 34], complaints of musculoskeletal pain and LBP [35]. However, in this study, the association of LBP with physical activity and physical education showed to be a relevant factor since youngsters who practiced physical activities appeared to be protected, demonstrating a lower risk of LBP. These findings are supported by other studies [4, 12], however, further investigations are necessary since this result has no consensus in the literature [15, 36]. The study by van Hilst et al. [37], for example, revealed that youngsters that practiced high performance physical activity (elite sports people) had greater occurrence of LBP (3 to 5 times) than the youngsters of the general population at the same age, supporting the conception of the U-shaped exposure response curve between physical activity and LBP. One possible explanation is related to the axial load that the spine supports when in movement (quantity and time of physical activity), slow and moderate movements result in disc adaptations, while high impact loads, explosive and extreme movements, as well as the sedentary behavior lead to deformations in this structure [38]. In this study, considering the physically active participants, 98% carried out PA as recreation (they were not elite sports people), and the most cited activities were: walk, dance and play football. The lower level of LBP risk detected in young people who practiced physical activities is due to the type of physical exercises of low intensity and the sporadic frequency of this practice, promoting positive adaptations in the vertebral column.

With regard to home-school walking, most of the participants, 63% (58% of boys and 65% of girls), did not perform this activity and there were no significant associations of this variable with LBP. Meziat Filho et al. [22] also observed that most youngsters used public transportation or other mean of transportation to go to school. Onofrio et al. [39] and Coelho et al. [4] found significant associations between walking to school and back pain, with students that walked to school showing a higher prevalence of LBP. In this case, walking displacement may represent a risk of LBP and have other risk factors associated as the transport of backpacks (weight and way of carrying it). Belavý et al. [38] reported walking as a beneficial activity for the vertebral column, since the axial load is distributed dynamically, with slow to moderate movement speed.

The divergences between these studies on the existence of associations between LBP and walking may be related to the different populations studied (sex, age, physical conditions, biotype), type and intensity of the activity practiced and also to the instruments used for data collection. Self-response questionnaires, for example, depend on the interpretation and memory of individuals and may underestimate or overestimate complaints or physical activity.

4.4 Sedentary lifestyle (TV and computer use time) and LBP

Decreased levels of physical activity and excessive use of electronic devices have been the focus of attention of researchers in many countries and are often associated with obesity, sleep disorders, musculoskeletal imbalance, and back pain [6, 20]. By using a mean of two to four hours a day in text message readings on their mobiles, individuals remain excessive time in anterior flexion of head, overloading cervical structures and other regions of the spine [6, 10, 20].

In this study, the average time youths spent watching TV was 187.4 (SD $=$ 140.0) minutes/day and 627.2 (SD $=$ 390.8) minutes/day using electronic devices. In the study by Foley et al. [40], 484 15 to 18-year-olds from New Zealand had a 193.6 (SD $=$ 3.9) minutes/day mean time of gadget use. Olds et al. [41] detected 230 (SD $=$ 114) minutes/day in 2200 Australians (9–16 years). Considering the 2 hours per day recommended maximum time in front of a screen, the majority of the youngsters in this study exceeded it watching TV (55%) and using the computer (91%). Recent studies by Meziat Filho et al. [22] and Minghelli et al. [15] also observed that most of the youths exceeded the recommended time watching TV (74% and 78%, respectively) and using the computer (81% and 86%, respectively). Despite the high percentage of youngsters who exceeded their time in front of a screen, no significant association between LBP and time watching television or using the computer was found in this study or in the ones cited above. This finding runs counter to what has been found in other studies which have observed that youngsters who spend significantly more time watching TV and using computer tend to have more back pain [4, 6, 7]. One possible explanation is that youngsters have recently been replacing TV and computer by mobiles, a lighter and more portable device that allows them to use it simultaneously in daily activities, alternating body posture frequently, decreasing tension in biomechanical structures [22]. The data collection tools might not have been updated to this new reality hampering the analysis of the effects of time spent in activities with their mobiles.

The reduced rate of physical activity and the increase in time in sedentary activities such as being in front of a screen tend to lead to an unhealthy cyclical behavior, favoring the weight gain that increases discomfort, complaints of pain and lack of engagement in physical activities [6, 8, 11, 15, 22].

The literature emphasizes the contribution of postures adopted during occupational activities to the appearance of LBP [42]. This study, however, did not investigate the posture used by the participants in everyday activities, or during work. It was not possible to evaluate the association of LBP and work due to the reduced number of youngsters with jobs. The activities most cited by youngsters as LBP triggers, either in everyday activities or even during work were: carrying weight (60%) and remain sitting (36%) or standing (35%) for long periods. These activities are believed to promote asymmetric distribution of the mechanical load for the column, resulting in a tissue tension mechanism and pain [38]. Being in a certain position for a long time or incorrectly requires tonic/static and repetitive contractions of the postural muscles, the muscle relaxation phases become shorter and the oxygen sent to the tissues reduces, resulting in accumulation of residue, pain and a sensation of muscular tiredness [43, 44].

4.5 Anthropometric measures (BMI, WC) and LBP

In this study, the majority of youths, 71%, were considered eutrophic. Brink et al. [10] and Minghelli et al. [15] evaluated the BMI of 194 South Africans (15–17 years old) and 966 Portuguese (10–16 years old), respectively, and found values close to those in this study with 75% and 73% of the youngsters in normal weight condition. Measurement of WC is used to confirm overweight since BMI does not distinguish between fat and lean mass [27, 45]. The majority of the youths in this study (72%) had WC values below to those recommended by Rocco et al. [25]. Although BMI and WC values of most youths were considered adequate, 23% were overweight or obese and, out of these, 22% were at risk and 7% at high risk of abdominal fat. Obesity entails several health risks, and the earlier it manifests itself, the greater the consequences, such as spinal overload and increased compression of the lumbar spine structures [19, 45]. In this study, there was no significant association between excess weight and LBP, reinforcing the results of some studies [8, 46] and contradicting others [47, 48]. Literature findings on the association of LBP and excess weight are contradictory, suggesting that more research is needed.

4.6 Sleep and LBP

Regarding sleep duration, it has also been pointed out as an important pain modulator since it produces analgesic action [49]. It is believed that interruption, reduction or deprivation of the sleep stages promote a decrease in the tolerance to noxious stimuli and an increase in musculoskeletal pain [50, 51] and LBP [12, 52]. On the other hand, Coelho et al. [4] found a significant correlation between sleep duration over 11 hours and the occurrence of LBP. In this case, the time spent in inappropriate positions may explain the complaint [9].

In this study, there were no associations between LBP and sleep duration, although the majority did not follow the recommendations. It is suggested that data related to sleep quality should be explored, since the youngsters of this study were connected with the electronic equipment even at night while sleeping (wake up during the night to receive and send messages).

4.7 Strengths and weaknesses

This study presented limitations: the transversal design does not allow the inference of causality; the evaluation through self-answer questionnaires may show memory bias and interpretation errors; the number of boys was smaller than that of girls. Longitudinal studies are recommended to explore the relationship between LBP and the factors analysed in this study. The need for more detailed analysis on the quality of sleep of youngsters and the association with LBP is suggested; and also instruments adapted to the technologies used by youth capable of perceiving and analysing new behaviours.

The results of this study add contributions to the knowledge of factors associated with the complex complaint that is LBP, supporting the discussion about adoption of preventive and therapeutic actions related to the practice of physical activity and reflection on differentiated care for girls.

5. Conclusions

This study showed that 330 youngsters from a public school in the south of Brazil, aged 15–18 years, reported a high prevalence of LBP. Girls were at greater risk and youths who practiced physical activity and physical education had a lower risk of LBP.

No association of LBP with TV and computer use time, with anthropometric measures (BMI, WC) or sleep duration was observed. Although associations between sedentary lifestyle and LBP have not been detected, investing in strategies to prevent LBP in youngsters should be based on studies of this nature, so that risk factors associated with LBP occurrence may be better understood.

Footnotes

Conflict of interest

None to report.

Appendix: Binary logistic regression

OUTCOMES: Low back pain in the present, throughout life and in the last three months.

EXPOSURE: Physical activity, sedentary time and sleep time.

CONFOUNDING FACTORS (USED IN THE ADJUSTMENT): sex, age, BMI.

Table 1

Low back pain in the present (moment of evaluation)

	Gross analysis	Adjusted analysis ${}^{\#}$
	OR (IC 95%)	OR (IC 95%)
Physical activity
Active	1	1
Insufficiently active	1.51 (0.92–2.46)	1.5 (0.91–2.57)
Sedentary time
Normal	1	1
Excess	0.32 (0.07–1.44)	0.31 (0.07–1.42)
Sleep time during the week
Sufficient	1	1
Insufficient	0.82 (0.44–1.51)	0.858 (0.46–1.61)
Sleep time at the weekend
Sufficient	1	1
Insufficient	0.86 (0.52–1.42)	0.891 (0.53–1.49)

Key: ${}^{\#}$ adjusted by sex, age and BMI.

Table 2

Low back pain throughout life

	Gross analysis	Adjusted analysis ${}^{\#}$
	OR (IC 95%)	OR (IC 95%)
Physical activity
Active	1	1
Insufficiently active	1.06 (0.63–1.79)	0.95 (0.55–1.65)
Sedentary time
Normal	1	1
Excess	2.57 (0.56–11.74)	2.99 (0.65–13.87)
Sleep time during the week
Sufficient	1	1
Insufficient	0.79 (0.38–1.61)	0.88 (0.42–1.84)
Sleep time at the weekend
Sufficient	1	1
Insufficient	0.95 (0.55–1.63)	1.06 (0.61–1.85)

Key: ${}^{\#}$ adjusted by sex, age and BMI.

Table 3

Low back pain in the last three months (three-month period)

	Gross analysis	Adjusted analysis ${}^{\#}$
	OR (IC 95%)	OR (IC 95%)
Physical activities
Active	1	1
Insufficiently active	1.08 (0.56–2.06)	0.99 (0.50–1.96)
Sedentary time
Normal	1	1
Excess	–	–
Sleep time during the week
Sufficient	1	1
Insufficient	1.24 (0.57–2.72)	1.50 (0.66–3.44)
Sleep time at the weekend
Sufficient	1	1
Insufficient	0.95 (0.49–1.85)	1.03 (0.51–2.07)

Key: ${}^{\#}$ adjusted by sex, age and BMI.

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Prevalence of low back pain in young Brazilians and associated factors: Sex,physical activity,sedentary behavior,sleep and body mass index

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

2. Methods

2.1 Participants

2.2 Study instruments

2.3 Variables

2.4 Statistical analysis

Table 1 Description of the youngsters regarding the variables: BMI, WC, pain complaints, TV and computer (similar) time use, physical activities and sleep duration by sex

Table 2 Low back pain in the present (moment of evaluation) and risk factors: sex, anthropometric measures, physical activities, sedentary lifestyle and sleep duration

4.1 Prevalence of LBP

4.2 Sex and LBP

4.3 Physical activity and LBP

4.4 Sedentary lifestyle (TV and computer use time) and LBP

4.5 Anthropometric measures (BMI, WC) and LBP

4.6 Sleep and LBP

4.7 Strengths and weaknesses

5. Conclusions

Footnotes

Conflict of interest

Appendix: Binary logistic regression

References

Table 1
Description of the youngsters regarding the variables: BMI, WC, pain complaints, TV and computer (similar) time use, physical activities and sleep duration by sex

Table 2
Low back pain in the present (moment of evaluation) and risk factors: sex, anthropometric measures, physical activities, sedentary lifestyle and sleep duration