Scientists have determined that cigarette smoking - more than a lack of wealth - is responsible for a higher risk of premature death among poor men.
Social scientists have long known that men in lower socio-economic groups are at a greater risk of dying prematurely than men who are wealthier or better educated. The question has been why.
Prabhat Jha of the Center for Global Health at the University of Toronto and colleagues at Oxford University studied the 1996 deaths of a half million men, between the ages of 35 and 69, in the United States, Canada, England, Wales and Poland.
They found that poor men are two-times more likely to die in middle age than more affluent men.
"Of that two-fold difference, there as an absolute difference of something like 19 percent in the risk of death, of that, about 12 percent was attributable to smoking-related diseases," said Prabhat Jha.
Researchers used an indirect method of data collection to estimate mortality risk. The proportion of smoking-related deaths was calculated based on lung cancer rates in each socioeconomic group.
Jha says the finding - that smoking is responsible for about half of the difference in the risk of death between rich and poor - held in each country that was studied.
"Effective interventions are not reaching the lower social strata," he said.
An effective intervention, according to Jha, is one that has not been used much - an increase in cigarette taxes, which would make them more expensive and, therefore, less accessible to lower income smokers.
Jha notes that smoking cessation has contributed to declines in lung cancer, heart disease, and other smoking-related causes of deaths in western countries.
"To extend those benefits to the poorest, means much more aggressive tobacco control," noted Prabhat Jha. "And if there was widespread cessation, then we believe we could have the social inequalities [reduced] between rich and poor by reducing tobacco consumption considerably."
The study on mortality risk, smoking and class was published in the journal The Lancet.