a1 Division of Epidemiology and Biostatistics, Department of Internal Medicine, MSC10 5550, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA
a2 Alberta Health Services, Calgary, Alberta, Canada
a3 Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada
Objective To assess the inter-method reliability of the Ovarian Cancer in Alberta (OVAL) survey developed to estimate adult vitamin D exposure from sun and diet for every tenth year, against the longer Geraldton Skin Cancer Prevention Survey (the assumed ‘gold standard’). We also estimated total vitamin D exposure using the OVAL survey.
Design A randomized crossover design to assess the inter-method reliability of sun exposure (OVAL v. Geraldton survey), using intra-class correlation and estimated total vitamin D exposure from sun and diet.
Setting Calgary, Alberta, Canada.
Subjects Randomly selected women (n 90) aged 40–79 years.
Results The average lifetime sun exposure of 13 913 h (average 411 h/year) from the Geraldton survey was not significantly different from the 13 034 h (average 385 h/year) from the OVAL survey for periods with sufficient UV radiation to stimulate vitamin D production. The intra-class correlation coefficient for average lifetime sun exposure was 0·77 (95 % CI 0·69, 0·86); the annual average was 0·60 (95 % CI 0·47, 0·74). Estimated vitamin D from diet and supplements increased with age.
Conclusions Our OVAL survey reliably estimated adult sun exposure relative to the Geraldton survey, suggesting that assessing sun exposure every tenth year is a reliable and efficient method for estimating sun contributions to lifetime vitamin D exposure.
(Received November 04 2012)
(Revised March 25 2013)
(Accepted June 04 2013)
(Online publication July 25 2013)