WASHINGTON (AFP)--Major U.S., Canadian and U.K. life and health insurance companies have billions of dollars invested in tobacco companies, a study published Wednesday in the New England Journal of Medicine said.

Wesley Boyd, the study's lead author, found that at least $4.4 billion in insurance company funds are invested in companies whose affiliates produce cigarettes, cigars and chewing tobacco.

"Despite calls upon the insurance industry to get out of the tobacco business by physicians and others, insurers continue to put their profits above people's health," said Boyd, a faculty member of Harvard Medical School.

"It's clear their top priority is making money, not safeguarding people's well-being," he wrote.

Tobacco is considered the leading cause of lung cancer and a major risk factor for heart attack, stroke, pulmonary disease and cancer.

According to the World Health Organization, it is a contributing factor in 5.4 million deaths a year.

Researchers first revealed that health and life insurance companies had major investments in tobacco companies in 1995 in an article in the U.K. medical journal the Lancet.

"Although investing in tobacco while selling life or health insurance may seem self-defeating, insurance firms have figured out ways to profit from both," Boyd wrote.

"Insurers exclude smokers from coverage or, more commonly, charge them higher premiums. Insurers profit - and smokers lose - twice over."

According to the study, U.S. insurer Prudential Financial Inc. (PRU) has $264.3 million invested among three U.S. tobacco companies, including Reynolds America and Philip Morris.

Canadian insurer Sun Life Financial Inc. (SLF), which sells life, disability and health insurance, has a stock portfolio with more than $1 billion in two tobacco companies, including $890 million in Philip Morris.

Prudential PLC (PUK), which sells health and disability insurance, has $1.38 billion in two tobacco companies, including British American Tobacco (BTI).

The study also details the substantial tobacco investments of the U.S. firms Northwestern Mutual and Massachusetts Mutual Life, and the Scottish firm Standard Life PLC (SL.LN).