Factors influencing sex differences in mortality from respiratory tuberculosis in England and Wales.

In Great Britain, men and women die from respiratory tuberculosis at very different rates. After due allowance is made for variations in age structure, the death rate for men is much higher than for women. Even more striking is the difference between the curves exhibiting age-specific death rates in the two sexes. The male curve is now characterized by a slow rise from early adult life to a peak at about 60 years and then a decline to old age. The female curve, in contrast, rises steeply to a high peak between 20 and 30 years and then falls away almost as rapidly. The aim of this paper is to examine some of the many factors which may be responsible for these different mortality patterns. Investigation has been confined to the examination of existing records, all of which have been taken from various volumes of the Registrar-General's Statistical Review of England and Wales, and from his Decennial Supplement for 1931. From these tables, numbers of deaths from respiratory tuberculosis by age, sex, social class, and occupation have been extracted for different years. The populations of each group were obtained from the same source. Age-specific death rates were calculated from these figures in various population groups. In a few instances the calculation had already been made by the Registrar-General. The usefulness of this method of study is limited by the fact that mortality records are the only indices of respiratory tuberculosis used. Death is the terminal event in a disease which may have been going on for many years. A description of the circumstances which are associated at death may bear little or no relation to those which set the morbid process in motion. This is particularly true of circumstances leading to the primary infection with the tubercle bacillus. Tuberculin testing surveys have shown that no significant difference exists between the percentage of male and female reactors (McDougall, 1949a). This fact suggests that mortality differences may be attributed either to some inherent difference between the sexes, to unequal chances of reinfection, or to other environmental inequalities. HISTORICAL TRENDS.-Tuberculosis mortality has been falling for at least a century, and consideration of Fig. 1 gives evidence of the very considerable improvement which has taken place during the past 50 years. The standardized mortality per million for the years 1851-60 was 2,694 for men and 2,854 for women. By 1939 these rates had dropped to 556 and 404 (Registrar General, 1947), a reduction to one-fifth of the male rate and to one-seventh of the female rate.