Historical declines in tuberculosis in England and Wales: Improving socialconditions or natural selection?

OBJECTIVES: A reinvestigation of the relationship between the decline of tu berculosis and improvement in social conditions in England and Wales during Victorian times. DESIGN: A retrospective study using data published in the annual reports of the Registrar General from 1853 to 1910. MEASURES ASSESSED: The diseases studied, in addition to tuberculosis were d ysentery and cholera, including their total and infant mortality. Social co nditions were evaluated from earnings and population density per house. RESULTS: Tuberculosis mortality declined at an annual average rate of 1.71% (95% confidence interval [CI] 0.77-2.63), whereas total mortality, infant mortality and mortality from cholera and dysentery and house population den sity showed no statistically significant decline over the same period. Real earnings increased by 1.05% (95% CI 0.29-1.81). CONCLUSION: Improving social conditions do not provide the total explanatio n for the decline in tuberculosis during Victorian times. Other factors, pr incipally natural selection, probably played a role. Part of the current in crease in tuberculosis may be caused by effective drug therapy eliminating natural selection.