(Reuters)—Virtually every U.S. doctor practicing in a high-risk specialty will face at least one malpractice claim during their career, and even physicians in low-risk areas have a 75% chance of facing a suit at some point, according to a new study.

At the same time, more than three-quarters of the claims do not result in any payments.

The study, published in the New England Journal of Medicine on Wednesday, was based on data from 40,916 U.S. physicians enrolled in a large nationwide professional liability insurance company from 1991 through 2005.

The study's overarching finding was that roughly seven of every 100 doctors insured by that company are the subject of a malpractice claim each year, but less than two of every 100 have a claim leading to payment.

By age 45, 36% of doctors in low-risk specialties had already faced their first malpractice claim. The rate was 88% in high-risk specialties. By age 65, the rates were 75% and 99%, respectively.

Amitabh Chandra of the Harvard Kennedy School, who headed the study, said the results show that doctors are correct when they say they face a constant threat of lawsuits, but that the direct cost tends to be lower than most think.

The threat of a suit does "generate emotional and hassle costs for doctors," he told Reuters Health. "Given that these suits take a long time—a typical suit takes five years to resolve—you spend your life in litigation."

The study looked at claims against doctors that prompted the insurance company to spend money. They did not necessarily evolve into a lawsuit.

Psychiatrists and pediatricians faced the lowest risk of a malpractice claim. Their rates were 2.6% and 3.1% per year, respectively. Brain surgeons and surgeons who operate on the chest or the heart faced the highest rates—19.1% and 18.9%, respectively.

"Specialties in which the largest proportion of physicians faced a claim were not necessarily those with the highest average payment size," the study said.

"Physicians in obstetrics and general surgery—both fields that are regarded as high-risk specialties—were substantially more likely to face a claim than pediatricians and pathologists, yet the average payments among pediatricians and pathologists were considerably greater."

Average payments ranged from $117,832 for dermatologists to $520,923 for pediatricians.

For all specialties combined, the average settlement was $274,887. Half of all settlements were for $112,000 or less.

Most specialties faced a 5%- to 10%-per-year risk of having a claim filed against a doctor. Specialists in the 10% to 15% range practiced orthopedic surgery, plastic surgery, gastroenterology, urology and obstetrics and gynecology. For general surgeons, the annual risk was 15.3%.

Fewer than 1% of awards exceeded $1 million. Eleven such awards were against obstetricians/gynecologists, 10 involved pathologists, seven involved anesthesiologists and seven involved pediatricians.

Over the past 20 to 30 years, "there's been some shifting" of which specialists face the highest risk of lawsuits, said Mr. Chandra. However, "in general the patterns are similar."

What this means for patients is not clear. Mr. Chandra and colleagues note that fear of malpractice claims may drive a large number of doctors to practice "defensive medicine," which can involve ordering lots of tests that a patient may not need or refusing to perform risky procedures.

The current study did not look at why a large proportion of claims do not lead to payments. A previous study cited by the authors, however, found that up to 40% of malpractice claims are not associated with medical errors. But the claims that are, are more likely to lead to compensation payments.

In an editorial recently in the Journal of the American Medical Association, Dr. Gianna Zuccotti and Dr. Luke Sato of the Harvard Medical Institutions in Boston said malpractice claims are only a proxy for mistakes in hospitals and clinics.

Malpractice claims, they said, represent only the tip of the iceberg for medical errors.