Lack of health coverage may contribute to about as many deaths in the United States as kidney disease does, researchers estimate.

The researchers, at the Harvard Medical School and the Cambridge Health Alliance, Cambridge, Mass., have published that estimate in a paper in the American Journal of Public Health.

The researchers followed up on studies released by the Institute of Medicine, Washington, that looked at the correlation between lack of health coverage on mortality. Like the earlier researchers, the authors of the new paper drew on survey data gathered by the U.S. Centers for Disease Control and Prevention.

Many people who lack health coverage also have low incomes, and some believe they may be more likely to have unhealthy lifestyles. But, even after taking into account factors such as education, income and smoking, it appears that lack of health coverage may cause about 45,000 U.S. deaths each year, the researchers estimate.

Uninsured, working-age U.S. residents are about 40% more likely to die in a given year than otherwise comparable, privately insured U.S. residents are, the researchers estimate. In 1993, the researchers report, the gap between mortality for insured and uninsured working-age U.S. residents was just 25%.

“Deaths associated with lack of health insurance now exceed those caused by many common killers such as kidney disease,” according to the Cambridge Health Alliance.