Changes in the seasonality of mortality in Germany from 1946 to 1995: the role of temperature.

Based on records from the Federal Bureau for Statistics of Germany, the seasonality of mortality was investigated for the period 1946-1995. Lowest mortality rates were found during summer (August or September) while highest values were found in winter (January through March). Non-linear regression of all monthly mortality data with the average monthly temperatures in Germany revealed a significant negative relationship (r = -0.739; n = 600; P < 0.0001). The fact that the differences between the long-range monthly temperatures and the individual monthly temperatures also showed a distinct relationship to the mortality rates speaks against a mere coincidence of both parameters. The amplitude of this seasonal rhythm declined steadily within the observation period. It is concluded that low temperatures cause an increase in mortality rates and that this effect has become less important during recent decades due to the increased use of central heating and because of improvements in the public health system.