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. 2016 Aug 5;26(8):405-12.
doi: 10.2188/jea.JE20150169. Epub 2016 Feb 6.

Percentage-Method Improves Properties of Workers' Sitting- and Walking-Time Questionnaire

Tomoaki Matsuo  1 , Hiroyuki Sasai, Rina So, Kazunori Ohkawara
Affiliations

Percentage-Method Improves Properties of Workers' Sitting- and Walking-Time Questionnaire

Tomoaki Matsuo et al. J Epidemiol. .

Abstract
in English, Japanese

Background: Does asking for the percentage of time spent sitting during work (P-method) instead of asking for the absolute length of time spent sitting (T-method) improve properties of the workers' sitting- and walking-time questionnaire (WSWQ)? The purpose of this study was to investigate whether questioning technique influences test-retest reliability and criterion validity of the WSWQ.

Methods: Sixty-five Japanese workers completed each version of the WSWQ in random order. Both questionnaires assessed quantities of time spent sitting or walking (including standing) during work time, non-working time on a workday, and anytime on a non-workday. Participants wore the thigh-worn inclinometer (activPAL) as criterion measure. Intraclass correlation coefficients (ICC) and Spearman's ρ were used for the analyses.

Results: For all three domains, values of reliability and validity with the P-method tended to be higher than with the T-method: ICC values ranged from 0.48-0.85 for the T-method and from 0.71-0.85 for the P-method; Spearman's ρ values ranged from 0.25-0.58 for the T-method and from 0.42-0.65 for the P-method. The validities with both methods on a workday (0.51-0.58 for the T-method and 0.56-0.65 for the P-method) were higher than validities on a non-workday (0.25-0.45 for the T-method and 0.42-0.60 for the P-method). In post-survey interviews, 48 participants (77%) chose the P-method as their preferred questioning style.

Conclusions: The study revealed that the P-method WSWQ had better reliability, validity, and ease of answering than the T-method, suggesting that the P-method can improve properties of the WSWQ and consequently advance the quality of epidemiological surveys in this field.

【背景】: 労働者の座位・歩行時間を評価する質問紙（Worker’s Sitting- and Walking-time Questionnaire: WSWQ）の質問方法として、座位時間を直接問う方法（時間法）ではなく、就業時間全体に対する座位時間の割合を問う方法（割合法）を用いることは有用だろうか。本研究では、質問方法の違いがWSWQの再検査信頼性や基準関連妥当性に及ぼす影響を検討した。

【方法】: 日本に在住する65名の労働者を対象に2種類（時間法と割合法）のWSWQによる調査を行った（順序をランダム化）。本研究で用いたWSWQは、時間法、割合法ともに、勤務中、勤務日の余暇時間、休日それぞれの座位時間および歩行時間（立位時間含む）を調査するものである。WSWQの妥当性を検証するため、対象者には身体活動量計（activPAL）の装着を求めた。信頼性の評価に級内相関係数（intraclass correlation coefficients: ICC）を、妥当性の評価にスピアマン順位相関係数（ρ）を算出した。

【結果】: 3つの時間領域全てにおいて、信頼性と妥当性の評価値はいずれも時間法より割合法が高い傾向にあった。すなわち、時間法のICC値は0.48～0.85、割合法のICC値は0.71～0.85であり、時間法のρ値は0.25～0.58、割合法のρ値は0.42～0.65であった。一方、時間法でも割合法でも、勤務日の妥当性評価値（時間法0.51～0.58；割合法0.56～0.65）は、休日の評価値（時間法0.25～0.45；割合法0.42～0.60）より高かった。また、質問方法に関する調査では、48名（77％）が時間法より割合法が回答しやすいと答えた。

【結論】: 本研究により、信頼性、妥当性ともに時間法より割合法の評価値が高い傾向にあること、また、対象者の多くが時間法より割合法が答えやすいと感じたことが明らかとなった。WSWQに割合法を用いることで質問紙の質が高まり、その結果、疫学調査そのものの質を高められるかもしれない。

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Figures

Figure 1.
Figure 1.. Bland-Altman plot comparing time 1 questionnaire sitting time with the criterion sitting time (activPAL with daily log). (A) T-method sitting time at work; (B) P-method sitting time at work; (C) T-method sitting time on a non-workday; (D) P-method sitting time on a non-workday. The mean difference and the 95% limits of agreement appear as dashed lines. Regression line and correlation coefficients between X and Y are displayed. CI, confidence interval; P-method, percentage method (questionnaire); T-method, time method (questionnaire).
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