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Michelle Victoria Chan, Elise Noel Harb, Amanda Tran, Christine Frances Wildsoet; Subjective Questionnaires Overestimate Habitual Outdoor Activity in Young Adults. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2492.
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© ARVO (1962-2015); The Authors (2016-present)
Recent reports suggest that outdoor activity confers a protective effect against the development of myopia. However, most studies rely on subjective questionnaires to measure outdoor activity. In this study, the reliability of such questionnaire data was assessed by comparison with objectively measured habitual outdoor activity.
UC Berkeley students aged 18-23 (n=5 non-myopes, SER range: +1.63 to 0 D; n=12 myopes, -2.25 to -6.25 D) participated in this study. Subjects wore light sensor wristwatch devices (Actiwatch Spectrum Pro) on their non-dominant arm over clothes for 2 weeks during the “academic year.” Data was collected and averaged over 1-min epochs and white light intensity ≥1000 lux was used as a proxy for outdoor activity. A subjective questionnaire about habitual weekday and weekend outdoor activities was completed by each subject at the start of their wear period and was repeated once during the 2-week period. Questionnaire repeatability (n=15) and reliability (n=17, as compared to objective Actiwatch data) was assessed.
As expected, questionnaires reported more outdoor activity on weekends than on weekdays, though the data showed wide variation. In general, the questionnaire displayed varied repeatability with a mean absolute difference (s.d., range) of 47 (55, 0 to 180) minutes on weekdays and 84 (75, 0 to 240) minutes on weekends. In comparison with their objective Actiwatch measures, subjects significantly overestimated their outdoor behaviors on both weekdays and weekends (both p<0.0005). The mean individual difference (mean of both questionnaires - Actiwatch) was 105 (62, 9 to 264) minutes on weekdays and was even more pronounced on weekends (mean difference: 151 (135, -7 to 520) minutes). There were no differences in either questionnaire repeatability or reliability measures between refractive error groups.
These results demonstrate the unreliability of questionnaire data used to capture the outdoor activities of young adults, who tend to overestimate such outdoor exposure. These results represent a strong argument for using objective measures of habitual activity to obtain accurate assessments of an individual’s outdoor behaviors and to better investigate the role of outdoor activity in myopia development and/or progression.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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