Seasonal Variation in Vascular Dehydration Risk: Insights from the KOBE Study

Abstract Objectives Dehydration, a risk factor for ischemic cerebrovascular diseases, is common in summer; however, the incidence of ischemic diseases is not necessarily higher in summer. The phenomenon may be influenced by the differences in the susceptibility to vascular dehydration based on the season. Therefore, this study aimed to distinguish types of dehydration in colder and warmer seasons by analyzing serum osmolarity, hematocrit, and daily non-alcohol drink (NAD) intake. Methods Participants in the Kobe Orthopedic and Biomedical Epidemiologic (KOBE) Study, consisting of healthy individuals, were categorized into two groups based on the examination month: the warmer and colder seasons. Multivariate analyses were conducted to examine disparities in serum osmolarity, hematocrit, and NAD intake between these two groups. Results Participant ratios by age group and the seasons (warmer season/colder season) were as follows: Women under 50 (35/62), 50-60 (77/126), 60-70 (123/170), over 70 (58/52); Men under 50 (14/17), 50-60 (22/36), 60-70 (57/71), over 70 (55/34). The colder season was found to be negatively correlated with serum osmolarity and NAD intake, but positively correlated with hematocrit, even after adjusting for relevant factors. Age was independently associated with serum osmolarity, but not with hematocrit and NAD intake. Conclusions This study highlights that vascular dehydration is more likely in the colder season despite lower serum osmolarity than the warmer season. Age-related increases in serum osmolarity without a corresponding rise in water intake may contribute to this. These findings emphasize the importance of addressing dehydration in the colder season, particularly in older adults. Key messages • The colder season showed a negative correlation with serum osmolarity and NAD intake but a positive correlation with hematocrit. • Raising awareness about the importance of hydration during winter may be essential.