An Interpretation of the Decline of Mortality in England and Wales during the Twentieth Century
Citation: McKeown, T., Record, Turner (1975) An Interpretation of the Decline of Mortality in England and Wales during the Twentieth Century.
Except for a short interruption in the male death rate during WWII, mortality in both sexes declined continuously in England and Wales between 1901 and 1971. Approximately ? of the decline was associated with infectious diseases and the remainder with conditions not attributable to micro-organisms. Except for a few diseases, associated with streptococcus (scarlet fever, nephritis, and rheumatic fever), most diseases did not change in character/lethality over this time period. Therefore, a change in the character of diseases cannot be accepted as the explanation for the large and prolonged reduction of mortality from mortality infections.
Air-borne infectious diseases were responsible for nearly half (45%) of the mortality decline. Most of this improvement occurred before the introduction of effective medical measures and even after that time they were certainly not the only, and probably not the main reason for the further decrease in deaths. Reduction in exposure is unlikely to have had a substantial effect on the trend of mortality from the air-borne infections, except in the case of TB where the risk or re-infection was lowered by treatment and segregation of infectious cases. We conclude that the main influence on the air-borne infections was an improvement in nutrition. This influence was of great importance in TB and measles, and it is probably true of all air-borne infections that even when nutritional state has little effect on infection rates, it has a large effect on the response to infection and on the likelihood of death. Medical treatment had little to do with the decline of the water- and food-borne diseases (diarrhea and dysentery, non-respiratory TB and enteric fever), which accounted for about 16% of the mortality reduction. This trend was due mainly to reduced exposure brought about by hygienic measures improvements in water, sewage, and refuse disposal, food handling, milk supplies, and infant feeding. However, the decline also owed something to better nutrition.
Of the disease not spread by air, water, or food, it is more difficult to determine the reasons for their reduction. Treatment such as immunization and therapy was probably the main influence on such diseases as syphilis, appendicitis, and peritonitis. It also contributed to the decline of puerperal fever as did a reduction in exposure to infection. But most of the mortality from this miscellaneous group was due either to conditions which individually caused relatively few deaths, or which were certified by unsatisfactory terms; therefore, it is possible that these diseases were better identified and classified differently as time went on. Much of the decrease in these deaths occurred before the introduction of effective therapy and was probably caused by less frequent exposure and improved nutrition.
Since these 3 classes of disease were responsible nearly half, one-sixth, and one-tenth, respectively, of the mortality decline, it is probably that the advance in nutrition was the major influence.
The remaining quarter of the reduction in mortality was associated with conditions not attributable to micro-organisms. The fall in the death rate in this class was greatly reduced, particularly among males, by the increase in deaths from lung cancer and heart disease. The decline in mortality in this category (in diseases other than lung cancer and heart disease) was related to specific medical measures but was also influenced by general improvements in standards of living, particularly in respect of infant feeding and care.