Can young adults accurately recall their time spent outdoors during childhood?

Abstract

Purpose : Reduced time spent outdoors (TSO) during childhood increases risk of myopia onset, which typically occurs between childhood and young adulthood. Studying the relationship between childhood TSO and myopia prevalence in later life may require participants to recall past TSO over decades. However, the validity of these data is unknown.

Methods : This study uses an established cohort who were born in 1989 and participated in the Kidskin Study between 1995 and 2001 in Perth, Western Australia. During this study, parents of the cohort completed surveys at the end of summer reporting their child’s TSO in the prior summer holidays at ages 8, 10 and 12 years (termed parent-reported [PR-TSO]). The Kidskin Young Adult Myopia Study (KYAMS) is a follow-up of the Kidskin Study cohort. KYAMS participants report their leisure TSO in summer for each year of life from age 5 to 26 years (termed self-reported [SR-TSO]). Conjunctival ultraviolet autofluorescence (CUVAF) area, an objective marker of ocular sun exposure, is measured in the KYAMS. All TSO data were categorical. Linear regression was used to analyse the association between CUVAF area (outcome) and either PR-TSO or SR-TSO (exposure).

Results : Complete CUVAF and SR-TSO data were available for 209 (72.8%) of 287 participants. Of these, mean age was 27.6 years (range: 25.5-29.2) and 61.2% were female. Sex and corneal curvature were identified as confounders. SR-TSO at age 8, 10 or 12 was not associated with CUVAF area (all p>0.05), nor was PR-TSO at age 12 (p>0.05). Increasing category of PR-TSO at age 8 or 10 was associated with increasing CUVAF area after adjustment for covariates (β=3.9mm², p=0.003 and β=3.7mm², p=0.007, respectively). Increasing SR-TSO at age 26 was associated with increasing CUVAF area (β=2.9mm², p=0.02). Increasing PR-TSO at age 8 and increasing SR-TSO at age 26 were independently associated with higher CUVAF area after adjustment for each other and confounders.

Conclusions : Retrospective, long-term self-recall of childhood TSO is likely not a valid measure. Objective or prospectively collected measures of TSO should be used when investigating the association between childhood TSO and myopia prevalence at an older age. This is the first study to show that both recent and past TSO are independently associated with CUVAF area, suggesting that CUVAF area may be a better surrogate of cumulative sun exposure, and also reflect childhood sun exposure.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.