Doctor-assisted suicide does not cause more deaths among certain groups of terminally ill patients such as the poor or the elderly.
Critics quickly dismisssed the study, to be published in the October issue of the Journal of Medical Ethics, saying its leader failed to disclose she is a member of the advisory board of the Death With Dignity National Center, a nonprofit that defends the Oregon assisted suicide law and coordinates support for legalizing assisted suicide in other states.
The study leader, University of Utah bioethicist Margaret Battin, argued that three doctors and a public health researcher were co-authors and that her views are well known. She admitted she should have disclosed her board role.
The study analyzed nearly a decade of data from Oregon - the only U.S. state with an assisted suicide law - and 20 years in the Netherlands. The results contradict claims by opponents that allowing doctors to help terminally ill patients end their lives would result in a higher number of deaths among certain groups.
The study looked at 10 groups identified as vulnerable, including the elderly, the poor, women, minorities, the uninsured, children, the chronically ill, the less educated, AIDS patients and psychiatric patients.
Researchers found that in both Oregon and the Netherlands, the average age of patients who died with a doctor's assistance was 70 years old. Eighty percent of the patients suffered from cancer.
Only AIDS patients appeared to request assisted suicide at higher rates than the general population, researchers said. The higher rate among AIDS patients, however, was for homosexual men in the Netherlands between 1985 and 1995, before more effective drugs became available to control the disease, the study said.
"All the of the data involved are publicly available," Battin said. "It's not as if we hid cases or misinterpreted data. This is data anybody can inspect."
In Oregon, terminally ill patients must be assessed by at least two doctors who must agree the patient is mentally qualified to make the request and is not suffering from depression. The patient must also administer the lethal dose to himself or herself.
Federal courts repeatedly rejected legal claims by opponents that assisted suicide would lead to higher death rates. In 2006 the U.S. Supreme Court ruled it was up to the states to regulate medical practice, including assisted suicide.
Assisted suicide is still opposed by a number of major groups, including the American Medical Association and the Roman Catholic Church.
Kathy McReynolds, public policy director at the Christian Institute on Disability, did not dispute the study results. But she said the small number of patients who request assisted suicide is an argument against legalizing it across the United States.
In the first nine years after the Oregon law took effect in the mid-1990s, 292 people used the lethal dose to kill themselves, the report says.
And about 1.7 percent of the roughly 136,000 deaths per year in the Netherlands are by voluntary active euthanasia, the report says.