As the White House and Congress continue debating how best to provide coverage to tens of millions of Americans currently without health insurance, a new study (PDF) is meant to offer a stark reminder of why lawmakers should continue to try. Researchers from Harvard Medical School say the lack of coverage can be tied to about 45,000 deaths a year in the United States — a toll that is greater than the number of people who die each year from kidney disease.

“If you extend coverage, you can save lives,” said Dr. Steffie Woolhandler, a professor of medicine at Harvard who is one of the study’s authors. The research is being published in the December issue of the American Journal of Public Health and was posted online Thursday.

The Harvard study found that people without health insurance had a 40 percent higher risk of death than those with private health insurance — as a result of being unable to obtain necessary medical care. The risk appears to have increased since 1993, when a similar study found the risk of death was 25 percent greater for the uninsured.

The increase in risk, according to the study, is likely to be a result of at least two factors. One is the greater difficulty the uninsured have today in finding care, as public hospitals have closed or cut back on services. The other is improvements in medical care for insured people with treatable chronic conditions like high blood pressure.

“As health care for the insured gets better, the gap between the insured and uninsured widens,” Dr. Woolhandler said.

The researchers also concluded that other ways of delivering care to the uninsured, like providing them with community health centers, are not adequate substitutes for health insurance. Individuals need the access to hospitals and specialists that comes only with adequate insurance coverage, Dr. Woolhander said.

Dr. Woolhandler said the study should prompt policymakers in Washington to consider the impact of scaling back any effort to provide truly universal coverage. She expressed concern about some lawmakers’ willingness to adopt a plan that could expand coverage to only a portion of the nearly 50 million people who are without health insurance. As a proponent for a single-payer system — something like Medicare for all — she said she was also disappointed in the current proposals before Congress.

Dr. Woolhandler, who has also conducted extensive research on medical-related bankruptcies, cautioned that expanding coverage would not be meaningful if the coverage is not generous enough. People might still not be able to afford care if they have to pay large deductibles or too great a share of their over all medical bills.

“Health insurance can only make you healthier if you have access to care,” she said.