Abstract
Human mortality widely differs in rate and seasonal variation from region to region in the world. A study in the seasonal variation of mortality in 18 countries reveals that there are three typical forms of seasonal variation in the 1060's. First, the seasonal variation is getting moderate in the North European countries in high latitudes and with severe cold and in North America (the United States and Canada) with a wide range of temperature changes in the year. Second, deaths still remain concentrated in the cold season in the comparatively warm zones, including Japan, England and the western and the southern parts of the European Continent. Third, what may be called an intermediate type of seasonal variation is seen in such countries as Germany and Switzerland.
It is also to be noted that these three types have been changing chronologically. At present the current tendency of moderation in seasonal variation is getting more conspicuous in the first countries, and that of the winter concentration in the second countries. Even among the countries with the same form of seasonal variation as, for instance, between Japan and England, there are various differences in chronological process and death rate.
These forms of seasonal variation appear to be ascribed, for the most part, to different methods of room heating, or varying types of artificial climate. In North Europe, Canada and the United States, for example, outside temperature drops far below zero in winter, so people cannot live in such environmental conditions without large-scale heating. Naturally, vigorous efforts are made to create and promote artificial climate through central heating, and this appears to have greatly contributed to the steady flattening of the winter death peak, or moderation in seasonal variation.
In such countries as Japan, England and Italy, on the other hand, it is comparatively warm in winter, so people are well able to make living even in the cold season without central heating. In other words, room temperature is usually kept at lower degrees, which appears to have checkmated the otherwise flattening of the winter peak. If central heating had been introduced earlier, the concentration of mortality in winter would have tapered off markedly in these countries as well. After all, it is now essential for these countries to reduce mortality in winter as they have already succeeded in flattening the summer peak.
From the foregoing, it might well be concluded that the steady slowing-down of seasonal variation with the very low death rate as seen in North Europe, Sweden in particular, is an ideal form of human mortality, which is no doubt a final outcome of large-scale central heating requiring huge costs of construction, highly-developed medical techniques, wide medical service, well-planned social security and so forth.
An extensive study by region, climatic and geographical, indicates that the recent moderation of seasonal variation is not at all universal in the United States, but that there are conspicuous differences from region to region. Generally speaking, the seasonal variation is getting particularly moderate in the industrialized regions and much less moderate in the backward states in the South, especially among the Nonwhites with very high infant mortality in winter and the high death rate (they still remain on the stage of winter death concentration). In striking contrast, infant mortality is considerably low in the cold northern regions because babies are protected by comfortable artificial climate.
The winter peak of mortality in the Black Belt is attributed, in final analysis, to the poverty of the Nonwhites (bad diet, unhealthy housing, etc.). Needless to emphasize, the Black Belt widely differs in death rate and seasonal variation from other parts of the United States, but chronological changes have occurred even there: the death rate is getting lower and the summer death rate has nearly disappeared.
