Factors associated with self-reported sun exposure in a multi-ethnic community sample from New Zealand

Sun exposure, the main source of vitamin D, may have beneficial effects in humans, including for cardiovascular health. However, little is known about the characteristics related to sun exposure. Previous studies have surveyed participants with a demographic profile that is restricted by sex and ethnicity. We carried out an analysis to identify factors associated with self-reported sun exposure in a large multi-ethnic study of men and women. The study was a cross-sectional analysis of baseline data collected in a large vitamin D supplementation randomized controlled trial. The weekly amount of sun exposure in the past three months was assessed using a questionnaire. Multivariable prevalence ratios (PR) of high sun exposure (≥ 15 h/ week) associated with demographic and lifestyle variables were calculated using Poisson regression to adjust for covariates. A P-value of < 0.05 (2-tail) was used to determine statistical significance. A total of 5039 participants aged 50-84 years were analysed, who comprised 330 Pacific Islanders, 267 Māori, 242 South Asian and 4200 Other ethnicities (mostly European ancestry). For demographic variables, high sun exposure was associated with sex (higher in males), ethnicity (highest in Māori, lowest in South Asian), and education (highest in those completing secondary level education), but was lowest in the oldest age-group (80-84 years). For lifestyle variables, high sun exposure was associated with higher levels of alcohol drinking, TV watching and physical activity, but was not associated with tobacco smoking. Weekly sun exposure was lower in participants who were overweight or obese (compared to those with normal body mass index), and in those who reported a skin reaction to sun exposure of burning only (compared to those who reported tanning). These associations remained when all variables were included in the same model. In conclusion, several demographic and lifestyle factors were associated independently with the sun exposure, the primary source of vitamin D. Understanding how these factors are associated with sun exposure may refine strategies to minimise vitamin D deficiency.