Aim: to test the hypothesis that there is no association between seasonal cold and the circadian responses of blood pressure, deep-body temperature and physical activity in healthy young and elderly men. Methods: 25 healthy elderly (aged 70±82 years) and 21 young volunteers (aged 20±30 years) participated in a 3-year prospective cross-seasonal study. Results: ambulatory day-time blood pressures in the older men were higher in the winter than in the summer and higher in both seasons than in the

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... oung people. The seasonally related differences were associated with lower outdoor and indoor temperatures, lower body temperature and higher activity levels in the elderly group in the winter. The older but not the younger group had higher blood pressure and levels of physical activity at certain times of the day in the winter compared with the summer. Conclusion: time-of-day winter increases in blood pressure in older people may be related to increased activity as well as to levels of ambient temperature. Although it is generally advantageous for older people to be physically active in order to prevent circulatory disease, there may be a rationale for advising that that they should avoid intense activity at certain times of the day, especially in the winter.