Since there has been an association between TB, poverty and over-crowding, most observers assumed that during pre chemotherepeutic era, decline in mortality due to TB has been because of the improvement in social conditions alone. As per the records available from 1850, except during the world wars, mortality from TB has steadily declined. However, the possible effects of natural immunity acquired by successive generations in a process of natural selection and selective mortality of susceptible individuals or family are over looked in studies of historical TB rates. The aim of this study is to reinvestigate the association between changes in mortality from TB on the one hand and mortality from other poverty related diseases, socio-economic conditions and measures in Victorian England on the other. Mortality statistics for England and Wales from 1853 to 1910 (before world war) were obtained from the Registrar General Annual Reports. These publications included data on TB, cholera and dysentery. Infant mortality, total mortality rates, socio-economic measures, statistics on average real earnings were also taken from the same source. Data on other diseases over the same period of time were not as complete, hence not included for the comparison.

The results showed total mortality rates declined by 0.80 per year where as TB mortality declined by 1.71. The average annual declining for TB was therefore twice that for all causes. The infant mortality a closer indicator of improvement in social deprivation declined even more slowly by 0.58 per year. Secondly, while TB deaths showed a steadily improving trend over the 60 years, infant mortality improved only from 1900. The study showed that TB mortality declined at a much faster rate than any indicator of social deprivation improved for the period 1853 to 1910. It is therefore unlikely that social improvements alone were responsible for the remarkable steady decline in TB mortality. Other diseases such as diphtheria and cholera thought to be poverty related showed no similar decline. The decline in TB mortality far exceeded improvements in social conditions and other disease markers of poverty. Some other factors are likely therefore do have been playing a part, of which the most important is probably the process of natural selection.

The study tested the hypothesis that a life-organizational stress of significant proportions typically appears shortly before the onset of TB. The sample comprised of all persons employed at Firland Sanatorium from its establishment at the present location in Seattle, Washington, USA. One group of sanatorium employees who became ill with TB was compared with an individually matched group of employees who remained well. The matching included age, sex, marital status, education, time of employment, job classification, income, skin test reading, appearance of chest roentgenograms, and previous record of certain chronic conditions. Those who became ill had experienced a concentration of disturbances such as domestic strife, residential and occupational changes and, personal crises during the two years preceding the change in a series of quarterly chest films, leading to the determination of pulmonary TB. This concentration of disturbances or situational crises was significant in comparison with the experience of the group of subjects who were well. The TB group also evidenced a significant degree of psychoneurotic pathology and did not recognize or could not admit their personality deficit on questions in which this recognition was obvious. The conclusion appears reasonable that many of the employees who became ill did so in a situation of stress which would be conducive to lowered resistance. Within the acknowledged limitations of the test, the postulation of psychosocial crisis as one of the precipitant causes is tenable.