Abstract
Introduction
Repetitive stress injuries (RSIs), or musculoskeletal disorders, are often not referred to as a specific diagnosis nor condition, but as an umbrella term for conditions that developed as a result of excessive repetitive movements and forces, as well as awkward postures [1]. Many studies have documented the costliness of the condition and its impact on the individuals. The United Nations and World Health Organization have recognized RSIs as a major cost burden for the individual, industry and the community in general [2], with an estimated economic burden of US$45–54 billion a year [3]. In Singapore, musculoskeletal disorders were found to be responsible for 5.6% of the total disease and injury burden in 2010, an increase from 4.8% in 2004 [4, 5]. This proportion was found to be similar to the results of the Global Burden of Diseases, Injuries, and Risk Factors (GBD) 2010 study, which reported an increase from 2.0% in 2004 to 6.8% in 2010 [33]. Often, compensations for RSIs are found to be more costly than disorders arising from acute trauma [6]. In addition, there is a significant impact on the lives of those with RSIs, affecting their participation in household management and leisure activities such as bowling and playing of musical instruments [32, 35]. In more severe cases, it may also result in permanent disability and an inability to return to the workforce [36, 37]. As such, many studies have been carried out to explore the risk factors associated with RSI, in an attempt to prevent their occurrence or reoccurrence through the design of effective interventions. Studies on paid employment have confirmed three main physical risk factors (excessive repetition, excessive force and awkward postures) that are associated with upper limb RSIs [7–14]. Other studies have also included the important role of psychosocial factors such as work stressors [11] and individual factors (e.g. gender, age) [12].
While the physical, psychosocial and individual risk factors contributing to upper limb RSI have been well-documented in other countries, no such study have been carried out in Singapore. Hence, the objective of this study was to identify the potential demographic risk factors associated with upper limb RSIs with a focus on occupational groups amongst the clients referred to an outpatient occupational therapy hand clinic in Singapore.
Methods
A retrospective cohort study of clients who were referred to outpatient occupational therapy services in a Singapore tertiary care hospital in 2012 was performed. All referrals were hand-searched and only those with a RSI diagnosis according to the classification by the Swedish National Institute for Working Life under the Samarbetsprogram mellan Arbetslivsinstitutet, LO, TCO och SACO (SALTSA) program were included in this study [15]. In this classification system, a total of twelve diagnostic groups were identified as shown in Table 1. This classification system guides data collection, recording and reporting of information based on diagnostic groups. As it only includes diagnoses with a high prevalence, it would also be reflective of the conditions commonly seen in an occupational therapy hand clinic.
Demographic data on occupation, gender, age, hand dominance and side of injury were also extracted from the electronic therapy records of the clients. To classify and aggregate occupational information, the International Standard Classification of Occupations (ISCO-08) was used [16]. Based on a 4-level hierarchy, this classification system groups occupations based on their similarities in terms of skill level and specialization required. In this classification system, occupations are classified into 10 major groups and subsequently divided into 43 sub-major groups and 130 minor groups (see Table 2). Clients who did not fall under the 10 major groups and did not engage in any paid work were classified as unemployed, a new group created by the authors which was also included in the subsequent data analysis. All demographic data was then computed into Microsoft Excel to report the distribution of four individual factors. They are gender, age, hand dominance and diagnostic groups. The Statistical Package for the Social Sciences (SPSS) Version 17 was then used to investigate association between these factors. Significance was set at the level of p < 0.05.
Results
General demographic information
Out of 6715 outpatient referrals made to the occupational therapy hand clinic in 2012, 1108 (16.5%) were diagnosed as upper limb RSIs and recruited into the study. There were 827 females (74.6%) and 281 males (25.4%), with a mean age of 53.74 years (s.d. 13.03). The majority of the clients (38.4%) were within the age group of 51–60 years old. A summary of the demographic information obtained from the records of these clients is shown in Table 3.
There were consistently more females than males within each age group and within each diagnostic group (see Table 4). Approximately half of the clients had their dominant upper limb injured.
Diagnostic distribution of upper limb RSIs
Flexor tenosynovitis was the most common cause of referral (33.5%) to the occupational therapy hand clinic, followed by DeQuervain’s tenosynovitis (19.2%) and carpal tunnel syndrome (17.1%). There was no incidence of ulna entrapment at the Guyon’s canal or Raynauud’s peripheral neuropathy observed. The number of clients with rotator cuff syndrome were observed to be low as they are traditionally referred to the physiotherapists for rehabilitation in this facility. Table 4 shows the number of cases for each diagnostic group based on the SALTSA classification.
Distribution of occupations
A significant proportion of those referred into the study were categorized under the “unemployed” group (41.4%), and the “professionals” group (30.7%). Table 5 summarizes the distribution of occupations based on the ISCO-08, and clients who did not involve in any paid group were classified as ‘unemployed’.
An in-depth analysis of the clients under the group ‘unemployed’ showed that at least half of them (50.9%) were full time homemakers, with the rest being either retirees or truly unemployed. Most of these homemakers (70.1%) were within the age range of 51–70 years old. The most prevalent upper limb RSI amongst these homemakers was found to be flexor tendinitis (36.3%), followed by carpal tunnel syndrome (21.8%) and DeQuervain’s tenosynovitis (17.5%), consistent with the general trend found in the entire study population. Demographic characteristics amongst the homemakers and the professionals (the second largest occupation group) revealed little differences between the two groups. It was not surprising to note a relatively younger mean age in the professionals group (48.57 years, s.d. 10.43 as compared to 59.73 years, s.d. 11.053 in the homemakers group), and a significant proportion of females amongst the homemakers group (99.1%). The three most common diagnoses were also similar in both groups (flexor tendinitis, DeQuervain’s tenosynovitis and carpal tunnel syndrome). However, it was interesting to note that while most of the homemakers and professionals were right hand dominant (78.2% of professionals, 79.9% of homemakers), there was significantly more homemakers (26.1%) with bilateral upper limbs affected as compared to that amongst the professionals (16.8%). This was likely due to the involvement of bilateral upper limbs in the repetitive actions required in most household chores.
Discussion
Upper limb RSIs as a major client group
Our study showed that a significant proportion (16.5%) of those who presented to the outpatient occupational therapy hand clinic had some form of upper limb RSI. These results are consistent with previous studies conducted in other countries in the last decade. A cross-sectional survey conducted in the United Kingdom amongst 10,000 adults showed a prevalence rate of 44% for neck and upper limb pain over one month’s period [17]. Another study conducted in the United States found a prevalence rate of 22.4% for upper limb RSIs, confirmed with physical examinations at the point of assessment [18]. A third national study was conducted in Taiwan in 1998, on a general population using a cross-sectional design methodology [19]. Musculoskeletal pain in the upper limb was identified by trained interviewers through interviews and respondents’ self-reports of pain. However, no physical examinations were performed to confirm the reports by the trained interviewers. Hence, the actual prevalence rate of upper limb RSIs could have been less than that was reported in the study. Although there are differences in the reporting time frames for the prevalence rates in both the working and the general populations, the differences in classification systems and terminology used within these studies have made it difficult to compare the results.
Women with upper limb RSIs
Out of 1108 clients with upper limb RSI, there were nearly three times as many females than males. In 2004, Treaster and Burr [20] reviewed 56 articles and found that in more than half of these articles, there was a significantly higher prevalence rate for upper limb RSIs amongst females than males. This trend was found to be consistent despite very different data collection methods used across studies: self reports, compensation records, physical examinations etc. [20]. Many other studies have also reported a higher prevalence of upper limb RSIs amongst females as compared to males [21, 22]. It has been suggested that the higher prevalence of upper limb RSIs amongst women may be attributed to their greater tendency to report their symptoms and to seek medical attention for their discomfort [23]. In certain cultures, there may also be a larger negative social consequence for men to complain of discomfort and pain, which may then lead to under-reporting amongst males in the general population [20].
Housework as an occupation
From our study, it was clear that there was a significant proportion (21.2%) of clients engaged in daily unpaid work as a full-time homemaker. Studies conducted in the last decade have all agreed that women generally perform most of the housework within the household and have a larger role to play in other unpaid work within the home, such as, childcare and elder care [24–28]. In a review of housework distribution amongst 34 countries, it was found that the mean division of housework between men and women was 1:3.9 [27]. While housework may carry different meanings to women from different socio-cultural contexts and may have evolved with time, women generally still continue to carry out most of these chores within the household. When women performed housework in addition to their paid work, it could possibly result in their excessive exposure to both physical and psychological stressors compared to men, with reduction in available recovery time [29–31]. In fact, the work that women engage in at home is often characterized by high static loading of neck and shoulder regions [23]. They also often work at a fast pace, requiring high levels of precision and repetitive use of small muscles [23]. Unfortunately, women who engage in unpaid manual work (e.g. housework) have attracted little ergonomic attention in the research. Little effort has also been made to improve the women’s well being by investigating the nature of occupations that they engage on a daily basis [32]. In the International Standard Classification of Occupations (ISCO-08), housework was also not included as a category. Based on the results of this study, the authors suggest that participation in housework should be considered as the eleventh category in the ISCO-08, and this is especially important within the context of research on upper limb RSI.
Conclusion
In this study, upper limb RSIs were found to be common within the general population and are more significant amongst females, especially those within the age group of 51–70 years old. The top 3 upper limb RSIs amongst the study population were found to be flexor tendinitis, DeQuervain’s tenosynovitis and carpal tunnel syndrome. It is also suggested that participation in housework may entail important biomechanical loads, which could result in contributing to and the worsening of the upper limb RSIs. Hence, the authors suggest that occupational classification systems should include homemakers as a standalone category. The relationship between biomechanical loads experienced by homemakers while performing housework and the possible risk for related musculoskeletal disorders should also be examined in greater detail.
Conflict of interest
The authors have no conflict of interest to report.