People who often feel lonely are more likely to contract Parkinson’s disease independently of clinical depression and other risk factors such as genetics, a new study has found.

American and British researchers published the study Monday in JAMA Neurology. They followed 491,603 British patients between the ages of 38 and 73 for up to 15 years, from March 2006 to October 2021.

Researchers found that participants who said they “often feel lonely” were 37% more likely to be diagnosed with Parkinson’s over the period than those who did not. The study defined loneliness as a “distressing subjective feeling that arises from the discrepancy between one’s desired and perceived social relationships.”

Parkinson’s is a brain disease that causes uncontrollable shaking, stiffness, physical imbalance and lack of coordination that can gradually inhibit walking and talking.

The study is the first large-scale effort to explore the link between the disorder and loneliness. It also adds Parkinson’s to a growing body of medical evidence that loneliness is a “substantial psychosocial determinant of health,” the researchers noted.

Antonio Terracciano, a co-author of the study and professor of geriatrics at Florida State University College of Medicine, said the findings are significant because previous studies with the same British sample produced similar results for U.S. adults.

While it’s possible that Parkinson’s makes some people lonely rather than vice-versa, follow-up analyses five and 10 years into the study appeared to rule that out, Mr. Terracciano added.

“Taken together, the more likely explanation is that being lonely increases [Parkinson’s] risk,” Mr. Terracciano told The Washington Times.

In the study, participants did not have Parkinson’s when researchers first assessed their feelings of loneliness between 2006 and 2010. During the 15 years of follow-up assessments, 2,822 of them developed it.

The study found that those who contracted the disease were more likely to be older men who were former smokers, overweight and suffering from other afflictions such as diabetes or hypertension. They were also less likely to have a college degree and more likely to have seen a psychiatrist for anxiety or depression.

Earlier studies have shown that men are more likely than women to develop Parkinson’s, which has no known cause. Research suggests that a combination of genetics and environmental factors, including exposure to chemical toxins, may play a role.

• Sean Salai can be reached at ssalai@washingtontimes.com.