Institute for Mathematical Behavioral Sciences

THE 1918 INFLUENZA epidemic was a major demographic event in the United States and worldwide. It is notable for its virulence (over 20 million deaths worldwide, approximately half a million in the United States); its maleness a difference between male and female age-standardized death rates of 174 per 100,0001 ); and its W-shaped mortality age profile (death rates having a mode in the 25–34-year age group, strange for influenza, which usually has a U-shaped profile). This study presents a new finding from reexamination of published statistics on death: the 1918 influenza had a strong and fairly long-lasting effect on differential mortality by sex, diminishing the earlier female advantage. The mechanism we posit is a selection effect, whereby those with tuberculosis (TB) in 1918 were more likely than others to die of influenza. This outcome affected males more than females because TB morbidity was disproportionately male. The reduction of the pool of male TB cases lowered the male TB death rate in the years following 1918, and brought males’ life expectancy closer to the longer female life expectancy. Before going into detail about our reexamination, we briefly review some of the salient features of the 1918 influenza epidemic, which, in spite of its enormity, has not been a major focus of studies by demographers.