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Historical declines in tuberculosis in England and Wales: improving social conditions or natural selection?
R P Davies1, K Tocque, M A Bellis
1Tuberculosis Research Unit, Cardiothoracic Centre, Liverpool, United Kingdom. p.d.o.davies@liverpool.ac.uk
Objectives:
A reinvestigation of the relationship between the decline of tuberculosis 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 dysentery and cholera, including their total and infant mortality. Social conditions were evaluated from earnings and population density per house.
Results:
Tuberculosis mortality declined at an annual average rate of 1.71% (95% confidence interval [Cl] 0.77-2.63), whereas total mortality, infant mortality and mortality from cholera and dysentery and house population density 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 explanation for the decline in tuberculosis during Victorian times. Other factors, principally natural selection, probably played a role. Part of the current increase in tuberculosis may be caused by effective drug therapy eliminating natural selection.