Associations between Seasonal Variation of Heart Rate Variability and Healthy Life Expectancy in Japan

—Although both summer heat and winter cold increase the risk of health problems, the effects could be modified by living environment and clothes. We investigated the relationship between regional differences in healthy life span (HALE) (HRV) that may reflect biological burden caused by heat and cold weather. Using the Allostatic State Mapping by Ambulatory ECG Repository (ALLSTAR) database, we analyzed the 24-h standard deviation of sinus-rhythm R-R intervals (SDNN) among 86,712 men and 108,771 women across Japan as a measure of HRV. Then, SDNN data were divided into 47 prefectures, averaged over 4 seasons, and associated with the prefectural averages of HALE reported by Japanese government. As the results, in both sexes, prefectural age-adjusted HALE negatively correlated with seasonal variation of prefectural age-adjusted SDNN, while it did not corelated significantly with prefectural age-adjusted SDNN of any seasons. Additionally, there was no significant correlation between prefectural age-adjusted average life expectancy and the seasonal variation of prefectural age-adjusted SDNN. Our observations support the hypothesis that the magnitude of the seasonal variation in biological burden might be a shortening factor for HALE.