Life expectancy at birth for women increased by > 32 years from the beginning of the 20th century to the beginning of the 21st. Much of the improvement happened in a relatively short time—between 1900- 1950. Sanitation improved, bringing clean drinking water, and safe disposal of sewage, which reduced deaths due to infection and chronic diseases. Improved housing, better education, greater income, and reduced poverty also influenced the incidence of infectious diseases, and reduced contagion.
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Researchers from the CDC analyzed trends for all-cause unadjusted death rates from years 1900-2010 and computed age-adjusted all-cause death rates. But as changes in some environmental factors improved, life expectancy other changes decreased. Environmental influences fluctuated often. Cigarette smoking rose rapidly during the 1930s, peaked between 1965- 1975, then began to fall. Death rates for heart disease increased 97% in the first 5 decades, then declined by 71%. Death rates for cancer rose, then dropped. Stroke rates declined steadily. On the other hand, the researchers found a “dramatic rise” in mortality rates due to respiratory system cancers and chronic respiratory disease.
Rates for infectious diseases dropped the most. In 1900, the 5 major causes of death for females were pneumonia and influenza, tuberculosis, enteritis and diarrhea, heart disease, and stroke. Of those, only heart disease and stroke were among the 5 major causes in 2010.
The researchers found a “notable” lack of large increases in unintentional motor vehicle (UI-MV) deaths. Although the number of automobiles and highways increased exponentially, deaths per mile driven reached a low in 1930 and kept dropping thereafter, probably due to safety measures. Since 2007, drug-overdose deaths among women have risen rapidly and overtaken deaths from UI-MV.
Although some causes of death, particularly heart disease and stroke, decreased as a result of behavior change and better health care, the researchers say, decreases in mortality rates are slowing. They caution about the “persistent prevalence” of risky behaviors and underuse of preventive and medical services, especially in racial minority populations.