Adaptation and validation of the Niigata PPPD questionnaire in Turkish: A clinical study

Introduction

Vestibular disorders, commonly presenting with vertigo, dizziness, and postural imbalance, substantially impair daily functioning and overall quality of life. Persistent Postural-Perceptual Dizziness (PPPD) is a distinct clinical entity characterized by persistent dizziness, unsteadiness, or non-spinning vertigo arising from an interaction of sensory, perceptual, and psychological mechanisms that alter neural processes responsible for postural control and locomotion. ¹ PPPD consolidates several previously used diagnostic labels including phobic postural vertigo, visual vertigo, space-motion discomfort, and chronic subjective dizziness into a unified diagnosis supported by standardized criteria. ² According to the International Classification of Vestibular Disorders, PPPD symptoms persist for at least 3 months and are consistently exacerbated by upright posture, motion, and visually complex environments. ²

The diagnosis of PPPD remains challenging because it frequently coexists with other vestibular and psychological conditions. Accurate identification requires a detailed clinical history, targeted vestibular assessment, and the exclusion of alternative causes, often through multidisciplinary evaluation involving neurology, otolaryngology, and mental health specialists. ¹ Despite its clinical relevance, PPPD is often diagnosed late, with delays extending several years in many patients.^3–5 The condition is more common among females and individuals between 30 and 50 years old.^5,6 The absence of objective biomarkers and the subjective nature of symptoms continue to complicate diagnostic accuracy.^6–8

To improve diagnostic consistency and symptom characterization, recent research has focused on standardized assessment tools. The Niigata PPPD Questionnaire (NPQ), developed by Yagi et al. ⁹ based on the Bárány Society criteria, ² is one of the leading instruments designed to capture PPPD-specific symptom patterns.^2,9 It has demonstrated utility in distinguishing PPPD from other vestibular disorders, quantifying symptom severity, and identifying individuals at risk of developing PPPD following acute vestibular events.^7,10,11 The NPQ has been translated and validated in Spanish- and German-speaking populations,^5,12 yet no validated Turkish version has been available to date. Given the global prevalence of dizziness and the clinical importance of culturally adapted measurement tools, establishing such a version is essential. Considering the relatively high prevalence of dizziness and vestibular disorders in Turkey, and the potential benefits of having a validated tool to assess PPPD symptoms in Turkish, this adaptation could be valuable for enhancing clinical diagnosis and management in Turkish-speaking populations.

In clinical settings, the Dizziness Handicap Inventory (DHI), originally developed by Jacobson and Newman, is widely used to assess the functional, emotional, and physical impact of dizziness. ¹³ Although it effectively quantifies dizziness-related disability, the DHI does not distinguish PPPD from other vestibular conditions. Therefore, combining a PPPD-specific scale such as the NPQ with a general disability measure such as the DHI enables a more comprehensive assessment of symptom burden.

The aim of the present study was to translate and culturally adapt the NPQ into Turkish and evaluate its psychometric properties in PPPD patients, other vestibular patients, and healthy controls. In addition to NPQ scores, dizziness-related disability was assessed using the DHI, enabling comparisons between PPPD-specific symptoms and general dizziness handicap. Although selective serotonin reuptake inhibitors (SSRIs) are commonly used in the management of PPPD and have been discussed as potential confounders in symptom assessment by Yagi et al., ⁹ the present study did not include an analysis of medication effects. We hypothesized that PPPD patients would demonstrate higher NPQ and DHI scores compared with other groups.

Materials and methods

Results

The study included a total of 114 participants: 36 patients with PPPD, 40 patients with other vestibular disorders, and 38 healthy controls. The demographic and clinical characteristics of the study groups are presented in Table 1. There were no statistically significant differences between the groups regarding age (p = .573) or sex distribution (p = .710).

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Table 1.

Demographic and clinical characteristics of the PPPD, vestibular, and control groups.

Variable	PPPD Group (n = 36)	Vestibular Group (n = 40)	Control Group (n = 38)	p-value
Age (years), mean ± SD	44.28 ± 7.30	45.90 ± 9.79	44.24 ± 5.99	.573 a
(Range)	(31–60)	(29–61)	(31–60)
Sex, n (%)
Female	21 (58.3%)	20 (50.0%)	19 (50.0%)	.710 b
Male	15 (41.7%)	20 (50.0%)	19 (50.0%)
DHI scores, mean ± SD
Total score	50.03 ± 10.32	41.43 ± 9.04	2.16 ± 1.17	<.001 c
Emotional	19.86 ± 8.26	14.55 ± 7.94	0.21 ± 0.62	<.001 c
Functional	15.69 ± 8.27	13.93 ± 6.65	0.10 ± 0.45	<.001 c
Physical	14.47 ± 7.34	12.95 ± 8.21	1.84 ± 1.17	<.001 c
Diagnoses/Precipitants, n (%)			-	.229 d
BPPV	10 (27.8%)	12 (30.0%)	-
Vestibular neuritis	6 (16.7%)	8 (20.0%)	-
Meniere’s disease	4 (11.1%)	6 (15.0%)	-
Bilateral vestibulopathy	-	2 (5.0%)	-
Vestibular migraine	8 (22.2%)	8 (20.0%)	-
Psychogenic vertigo	4 (11.1%)	-	-
Head trauma/Whiplash	2 (5.5%)	-	-
Idiopathic/Unknown	2 (5.5%)	4 (10.0%)	-

The DHI total and subscale scores differed significantly among the groups (p < .001). The PPPD group exhibited the highest DHI total scores (50.03 ± 10.32), followed by the vestibular group (41.43 ± 9.04), while the control group showed minimal scores. Regarding clinical history (Table 1), the most common precipitating condition for the PPPD group was Benign Paroxysmal Positional Vertigo (BPPV) (27.8%), followed by vestibular migraine (22.2%) and vestibular neuritis (16.7%). Similarly, BPPV was the most frequent primary diagnosis in the vestibular group (30.0%).

The internal consistency and test-retest reliability of the Turkish NPQ (T-NPQ) were evaluated (Table 2). Cronbach’s alpha (α) coefficient was 0.919 for the total score. The internal consistency coefficients for the subscales were 0.762 for Upright Posture/Walking, 0.749 for Movement, and 0.841 for Visual Stimulation.

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Table 2.

Internal consistency and test-retest reliability coefficients of the Turkish NPQ and its subscales.

Subscale/Total score	Cronbach’s alpha	T1–T2 correlation (r)	p-value
Upright posture/Walking	0.762	0.750	<.001
Movement	0.749	0.723	<.001
Visual stimulation	0.841	0.781	<.001
Total	0.919	0.832	<.001

Test-retest reliability, assessed in the PPPD group (n = 36) with a 14–30 day interval, showed a Pearson correlation coefficient of 0.832 (p < .001) for the total score. Item-level test-retest correlations ranged from 0.595 to 0.804, and all were statistically significant (p < .001) (Table 3).

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Table 3.

Item-level test and retest means, standard deviations, and test–retest correlations of the Niigata PPPD questionnaire (PPPD group).

Item	Test mean ± SD	Retest mean ± SD	Test-Retest correlation (r)	p
Item 1	2.33 ± 0.89	1.75 ± 1.18	0.595	<.001
Item 2	2.81 ± 1.04	2.00 ± 1.37	0.762	<.001
Item 3	2.56 ± 1.00	1.94 ± 1.33	0.605	<.001
Item 4	2.44 ± 1.34	2.03 ± 1.48	0.784	<.001
Item 5	2.75 ± 1.25	2.31 ± 1.58	0.733	<.001
Item 6	2.14 ± 1.42	1.78 ± 1.69	0.788	<.001
Item 7	2.56 ± 1.21	1.83 ± 1.28	0.730	<.001
Item 8	2.61 ± 1.10	2.11 ± 1.45	0.707	<.001
Item 9	2.17 ± 1.16	1.86 ± 1.74	0.804	<.001
Item 10	3.06 ± 1.19	2.44 ± 1.65	0.772	<.001
Item 11	2.22 ± 0.93	1.58 ± 0.97	0.646	<.001
Item 12	2.64 ± 1.20	2.25 ± 1.56	0.800	<.001

CFA was conducted to test the original three-factor structure (Postural, Motion, and Visual). The three-factor model yielded the following fit indices: χ²/df = 1.47, CFI = 0.964, TLI = 0.945, NFI = 0.900, and RMSEA = 0.064 (Table 4, Figure 2).

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Table 4.

Fit indices for the NPQ (3-factor model).

Fit index	NPQ	Acceptable thresholds
χ2/df	1.47	≤3.00
CFI	0.964	≥0.90
TLI	0.945	≥0.90
NFI	0.900	≥0.90
RMSEA	0.064	≤0.08
PCLOSE	0.220	>0.05

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Figure 2.

CFA path diagram for the Turkish NPQ (T-NPQ) three-factor model. Rectangles represent the observed items (Q1–Q12) and ellipses represent latent factors (F1–F3). Small circles labeled e1–e12 denote item-specific error terms (residuals). Single-headed arrows from latent factors to items indicate factor loadings (standardized estimates displayed), and curved double-headed arrows between latent factors indicate factor associations (correlations/covariances). Numbers adjacent to error terms represent residual variances.

The correlations between T-NPQ scores and DHI scores are presented in Table 5. The T-NPQ total score showed a strong positive correlation with the DHI total score (r = 0.709, p < .001). Among the subscales, the Visual Stimulation score of the NPQ showed the highest correlation with the DHI Emotional subscale (r = 0.430, p < .001) and DHI-Total score (r = 0.504, p < .001).

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Table 5.

Pearson correlation coefficients between NPQ domains and DHI measures in differentiating PPPD from vestibular disorders (N = 76).

Variable	1	2	3	4	5	6	7	8
1. Upright posture/walking	—	0.11	0.18	0.33**	0.18	0.07	0.01	0.16
2. Movement		—	0.24*	0.64**	0.52**	0.20	0.24*	0.25*
3. Visual			—	0.72**	0.50**	0.43**	0.27*	−0.05
4. NPQ_total				—	0.71**	0.44**	0.32**	0.18
5. DHI_total					—	0.54**	0.46**	0.32**
6. DHI_Emotional						—	0.07	0.20
7. DHI_Functional							—	0.21
8. DHI_Physical								—

ROC curve analysis was performed to evaluate the diagnostic performance of the T-NPQ (Table 6). The T-NPQ total score yielded an AUC of 0.746. An optimal cut-off score of 27.5 was identified, which provided a sensitivity of 86.1% and a specificity of 57.5%. The AUC values for the subscales were 0.625 for Upright Posture/Walking, 0.627 for Movement, and 0.674 for Visual Stimulation.

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Table 6.

ROC analysis for NPQ total and subscale scores in discriminating PPPD from other vestibular disorders.

Measure	AUC	Optimal cut-off score	Sensitivity	Specificity
Upright posture/walking	0.625	8.5	0.694	0.525
Movement	0.627	10.5	0.417	0.825
Visual stimulation	0.674	9.5	0.778	0.575
T-NPQ total	0.746	27.5	0.861	0.575

Discussion

This study represents the first successful translation, cultural adaptation, and psychometric validation of the T-NPQ. The principal finding confirms that the T-NPQ is a reliable and valid instrument for assessing symptom severity and characterizing the three main exacerbating factors of PPPD in Turkish-speaking patients. The need for a standardized, PPPD-specific tool is paramount, given that PPPD is one of the most common chronic neuro-otological conditions yet remains underdiagnosed due to the subjective nature of its symptoms and the absence of objective biomarkers.^1,6

The internal consistency of the T-NPQ was found to be excellent, with a Cronbach’s alpha (α) coefficient of 0.919 for the total scale. This finding is highly consistent with the original Japanese validation (α > 0.90) ⁹ and the Spanish validation study which reported a similarly high internal consistency (α = 0.938). ⁵ These results across diverse languages suggest that the NPQ items measure a common underlying construct PPPD symptom severity consistently, regardless of cultural differences.

The internal consistency of the subscales was also acceptable to good (Upright Posture/Walking α = 0.762; Movement α = 0.749; Visual Stimulation α = 0.841). Notably, the Visual Stimulation subscale showed the highest α value. This aligns with recent epidemiological findings by Aishwarya et al. (2024), who reported that visual dominance was the primary exacerbating factor in a significant portion of the PPPD population in South India. ¹⁷ Furthermore, the test-retest reliability demonstrated strong temporal stability (Total NPQ correlation r = 0.832), confirming that the T-NPQ provides consistent scores when administered to clinically stable patients over time. This stability is crucial for monitoring treatment outcomes, as highlighted by Yagi et al. (2024), who emphasized the need for reliable metrics to track the often waxing and waning course of functional dizziness. ¹⁸

The psychometric evaluation of the T-NPQ’s underlying structure yielded findings that require careful interpretation within the context of existing literature. In the present study, construct validity was examined using CFA to test the hypothesized (a priori) three-factor model. CFA showed acceptable fit indices for the original three-factor structure (χ²/df = 1.47, RMSEA = 0.064, CFI = 0.964).

This result aligns with the theoretical framework of PPPD, which posits that symptoms are exacerbated by three distinct factors: upright posture, active/passive motion, and visual stimulation.^2,9 Recent neuroimaging studies support this three-factor distinction; for instance, Yagi et al. (2023) demonstrated specific changes in functional connectivity between visual and vestibular cortices during visual stimulation tasks, providing a biological basis for the “Visual” subscale as a distinct symptom dimension. ¹⁹ Specifically, they found that visual inputs dominate over vestibular inputs in PPPD patients, altering the integration of spatial orientation.

In contrast, some Western validation studies have suggested a single-factor structure. ⁵ Our CFA findings supporting the three-factor model suggest that in the Turkish population, patients can distinctly identify and categorize their triggers. This distinction is clinically relevant because, as shown by Azami et al. (2023), different physiological subtypes may exist; they found that 44.2% of PPPD patients had isolated otolith dysfunction, which might differentially impact the “Upright Posture/Walking” or “Movement” subscales compared to patients with purely visual dominance. ²⁰

The T-NPQ exhibited good discriminatory ability between the PPPD group and the “other vestibular disorder” group. The ROC curve analysis yielded an AUC of 0.746. This AUC value indicates good diagnostic accuracy and is higher than the AUC of 0.661 reported in the Spanish validation. ⁵

The calculated optimal cut-off score of 27.5 (Sensitivity: 86.1%, Specificity: 57.5%) is almost identical to the threshold of ≥27 points initially proposed by Yagi et al. ⁹ This consistency suggests that a total score of 28 or higher is a globally reproducible threshold for identifying patients with a high likelihood of PPPD. However, the relatively lower specificity (57.5%) warrants careful clinical interpretation. As recently highlighted by Sereda et al. (2025), patients with other chronic vestibular conditions, such as bilateral vestibulopathy, may also report high symptom burdens on the NPQ due to shared functional impairments, leading to potential false positives. ²¹ Therefore, the T-NPQ should not be used as a standalone diagnostic test but rather as a sensitive screening tool to quantify symptom severity and identify patients requiring further neuro-otological evaluation.

The Visual Stimulation subscale showed the highest individual AUC (0.674). This diagnostic utility is supported by Goto et al. (2025), who found that postural instability induced by moving visual stimuli (specifically checkerboard patterns) was significantly higher in PPPD patients compared to other vestibular disorders. ²² This reinforces “visual dependence” as a hallmark of the condition that the T-NPQ successfully captures.

The T-NPQ demonstrated strong concurrent validity through significant correlations with the DHI. ¹³ A moderate-to-strong positive correlation was observed between the NPQ Total score and the DHI Total score (r = 0.709, p < .001). The Visual Stimulation subscale showed the strongest correlation with the DHI Emotional subscale (r = 0.430, p < .001). This reinforces the complex interplay between sensory processing and psychological distress. Fukushima et al. (2024) recently highlighted age-related differences in this interplay; they found that younger PPPD patients exhibit significantly higher anxiety levels (HADS-A scores) compared to older patients, who are more likely to have peripheral vestibular precipitants. ²³ This suggests that for younger patients with high scores on the Visual and Emotional domains, integrating cognitive behavioral therapy to address potential “perceived injustice” and anxiety mechanisms recently identified by Sereda et al. (2025) as mediators of symptom severity is crucial. ²¹ Conversely, older patients might benefit more from vestibular rehabilitation targeting otolith dysfunction. ²⁰

Conclusion

The findings suggest that the Turkish version of the Niigata PPPD Questionnaire exhibits satisfactory psychometric properties. The results indicate a three-factor structure consistent with the original theoretical model and propose a cut-off score (≥28) that may be clinically useful. The T-NPQ appears to reflect the unique visual and motion-induced sensitivity of PPPD, aligning with recent insights into the disorder’s pathophysiology.^19,22 Consequently, this instrument could facilitate standardized research and has the potential to contribute to the clinical management of this challenging disorder in Turkey.