The Great Depression had a silver lining: During that hard time, U.S. life expectancy actually increased by 6.2 years, according to a University of Michigan study published in the current issue of the Proceedings of the National Academy of Sciences.

Life expectancy rose from 57.1 in 1929 to 63.3 years in 1932, according to the analysis by U-M researchers José A. Tapia Granados and Ana Diez Roux. The increase occurred for both men and women, and for whites and non-whites.

"The finding is strong and counterintuitive," said Tapia Granados, the lead author of the study and a researcher at the U-M Institute for Social Research (ISR). "Most people assume that periods of high unemployment are harmful to health."

For the study, researchers used historical life expectancy and mortality data to examine associations between economic growth and population health for 1920 to 1940. They found that while population health generally improved during the four years of the Great Depression and during recessions in 1921 and 1938, mortality increased and life expectancy declined during periods of strong economic expansion, such as 1923, 1926, 1929, and 1936-1937.

The researchers analyzed age-specific mortality rates and rates due to six causes of death that composed about two-thirds of total mortality in the 1930s: cardiovascular and renal diseases, cancer, influenza and pneumonia, tuberculosis, motor vehicle traffic injuries, and suicide. The association between improving health and economic slowdowns was true for all ages, and for every major cause of death except one: suicide.

Although the research did not include analyses of possible causes for the pattern, Tapia Granados and Diez Roux offer some possible explanations about why population health tends to improve during recessions but not expansions.

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"Working conditions are very different during expansions and recessions," Tapia Granados said. "During expansions, firms are very busy, and they typically demand a lot of effort from employees, who are required to work a lot of overtime, and to work at a fast pace. This can create stress, which is associated with more drinking and smoking.

"Also, new workers may be hired who are inexperienced, so injuries are likely to be more common. And people who are working a lot may also sleep less which is known to have implications for health. Other health-related behaviors such as diet may also change for the worse during expansions."

In recessions, Tapia Granados noted, there is less work to do, so employees can work at a slower pace. There is more time to sleep, and because people have less money, they are less likely to spend as much on alcohol and tobacco.

In addition, economic expansions are also associated with increases in atmospheric pollution which has well-documented short-term effects on cardiovascular and respiratory mortality. Other reasons that periods of economic expansion may be bad for health could include increases in social isolation and decreases in social support that typically occur when people are working more.

The researchers noted that their study examined the relation between recessions and mortality for the population as a whole, and not the effect of becoming unemployed on an individual person. In fact, their results show that downturns in economic activity may have overall beneficial effects on the population, even if becoming unemployed has adverse health consequences for a given person.

"Social science is not physics," Tapia Granados said. "But regularities in the past allow us at least some confidence in forecasting the future. Historical experience tells us that no particular deterioration of mortality is to be expected as a consequence of a recession beyond an increase in suicides which, although clearly important, is of small magnitude compared to the reduced number of fatalities from other causes."

Other studies suggest that the relationship between population health and business cycles may be weakening, at least in the U.S. and in Japan, where the phenomenon of karoshi—sudden death from overwork among Japanese salarymen—dramatically illustrates the dangers of life in economic boom times.

Still, Tapia Granados hopes that a better understanding of the beneficial effects of recessions on health may perhaps contribute to the development of economic policies that enhance health and minimize or buffer adverse impacts of economic expansions. And he cautions that the findings also suggest that suicide prevention services—often the casualties of budget cuts during economic downturns—are more important during bad times than ever.