Death rates among middle-aged people are higher when the economy is growing than when it is heading for recession, research has found.
Scientists say while long-term economic growth is associated with better health, cycles of "boom and bust" in developed nations resulted in increased death rates among those aged 40 and over.
Research published today shows there is not enough evidence to suggest work-related stress and unhealthy lifestyles - sometimes seen as symptoms of a good economy - explain the increased death rate.
The Leyden Academy on Vitality and Ageing in the Netherlands found that for every one percentage point increase in gross domestic product (GDP - the market value of goods and services produced within a country over a given period of time), death rates rose by 0.36% among 70-74-year-olds, and by 0.38% among 40-44-year-olds.
Herbert Rolden, economic researcher, said the results were "highly unexpected".
He said: "We were very surprised to see that there is also a movement between economic growth and mortality in the older population.
"Now that we found that retirees also have an increased mortality risk in good economic times, we are still in the dark on what really explains the association.
"Although we think that the lack of social support in good economic times might explain the counter-intuitive finding - as a good social network is highly beneficial for the survival of older people - this still remains to be studied."
The authors said they were undecided about the possible explanations for the figures. Unhealthy lifestyles are more prevalent when economies are in good health, but are unlikely to fully explain the trends, researchers said.
Changes in social support may exert some influence, they said, as higher employment could mean less time for informal care-giving to older people, and heightened stress among the carers.
The report, published in the Journal Of Epidemiology And Community Health, added: "The counter-intuitive association between macroeconomic cycles and cyclical variation in mortality needs further explanation.
"So far, the most plausible explanations have been labour-related, but these cannot explain the similar associations we found among older people. Higher levels of air pollution and lower levels of informal care and social support during good economic times could be major contributors to the association, but the evidence on the existence of such dynamics is scant.
"In times of economic turmoil and population ageing, further exploration of the effects the economic environment can have on the well-being of older people is of great importance."
Researchers used historical data from 1950 to 2008 across 19 developed countries, including the UK and Ireland.