Seasonal Variation in Sudden Death among Japanese Workers: Why are There Peaks in Spring and Winter?: Tsutomu HOSHUYAMA, et al. Department of Environmental Epidemiology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health—These days particular attention is being paid to sudden death among Japanese workers, an issue requiring an urgent solution. This study describes the seasonal variation in sudden death, and examines the synchronization of death with workers' busy period. Questionnaires were sent to occupational health physicians belonging to a representative sample of large-scale working establishments in Japan. Inquired were cause, date, and other demographic information on sudden death cases that had occurred in each establishment from 1988 to 1992. The seasonal variation in sudden death was analyzed by age, cause of death, and industry, and synchronization of death with the period of settlement of accounts (SA) of the establishment was examined. Of 488 male sudden deaths reported, 362 were categorized as being of cardiovascular origin. Both the 488 cases and the 362 cardiac cases had two peaks of occurrence in March-April and in November-December with statistical significance (p<0.01). Of the 201 cases aged 45-54, 70 (35%) died within two months of the SA. The peak in March-April may be accounted for by an increased number of sudden deaths among workers aged 45-54, whereas the peak in November-December may be accounted for by an increased number of sudden deaths among the entire worker population studied. Because both peaks were associated with busier periods for workers in Japan, work environmental factors may affect the seasonal variation resulting in such a distinctive shape of the curve for sudden death among workers.