Out-of-hospital cardiac arrest attributable to sunshine: A nationwide, retrospective, observational study

Abstract

Aims To investigate the population attributable risk of out-of-hospital cardiac arrest (OHCA) from non-optimal sunshine duration and the relative contribution of daily sunshine hours. Methods and results National registry data of all cases of OHCA occurred between 2005 and 2014 in the 47 Japanese prefectures were obtained. We examined the relationship between daily duration of sunshine and OHCA risk for each prefecture in Japan using a Poisson regression model combined with a distributed lag non-linear model, adjusting for confounding factors. The estimated associations for each prefecture were pooled at the nationwide level using a multivariate random-effects meta-analysis. A total of 658 742 cases of OHCA of presumed cardiac origin met our inclusion criteria. The minimum morbidity sunshine duration varied from the 21st percentile in Okayama to the 99th percentile in Hokkaido, Gifu, and Hyogo. Overall, 5.78% [95% empirical confidence interval (eCI): 3.57-7.16] of the OHCA cases were attributable to daily sunshine duration. The attributable fraction for short sunshine duration (below the minimum morbidity sunshine duration) was 4.18% (95% eCI: 2.64-5.38), whereas that for long sunshine duration (above the minimum morbidity sunshine duration) was 1.59% (95% eCI: 0.81-2.21). Conclusions Daily sunshine duration was responsible for OHCA burden, and a greater number of OHCA cases occurred in patients who were only exposed to sunshine for short periods of time each day. Our findings suggest that public health efforts to reduce OHCA burden should take sunshine level into account.