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More evidence links diabetes, Parkinson's disease

Last Updated: 2011-04-15 9:01:08 -0400 (Reuters Health)

NEW YORK (Reuters Health) - People with diabetes may be more likely to also develop Parkinson's disease - and this seems particularly true for younger patients, a new study suggests.

The findings, published online by the journal Diabetes Care, add to evidence linking diabetes and Parkinson's. One recent report said that U.S. adults with diabetes had a slightly higher risk of developing Parkinson's over a 15-year period, compared to nondiabetics.

Neither study, however, proves that diabetes itself causes Parkinson's.

Instead, researchers think it's more likely that the two disorders share some common underlying causes.

The new findings are from Denmark, where researchers compared close to 2,000 adults with Parkinson's disease and nearly 10,000 people the same age but without the disease (the "control" group).

Overall, 6.5 percent of the Parkinson's patients had diabetes for at least 2 years before they were diagnosed with the movement disorder. By comparison, just 5 percent of people in the control group had diabetes for at least 2 years.

Overall, the study found, having diabetes was linked to a roughly one-third higher risk of developing Parkinson's. That was after the researchers accounted for participants' age and sex, and any diagnoses of emphysema - which was considered a proxy for heavy smoking. (Studies have found cigarette smokers to be at lower risk of Parkinson's, for reasons that are not clear.)

In particular, diabetes was related to a higher risk of developing Parkinson's before the age of 60 -- which is about the average age at diagnosis.

Exactly what the findings mean is unclear, according to the researchers, who were led by Dr. Eva Schernhammer of Harvard Medical School in Boston.

But they say that for now, the "most plausible" explanation would be that diabetes and Parkinson's have some of the same biological underpinnings.

One possibility is continuous low-level inflammation throughout the body, which is suspected of contributing to a number of chronic diseases by damaging cells. There might also be a common genetic susceptibility.

However, even if people with diabetes have a relatively bigger risk of Parkinson's, that does not mean it is a high risk. For example, the recent U.S. study that tracked patients for 15 years involved nearly 289,000 older adults. The proportion of people who eventually developed Parkinson's disease was 0.8 percent among diabetics and 0.5 percent among nondiabetics - less than 1 percent in either case.

The researchers on that study said that people with diabetes should simply continue to do the things already recommended for their overall health -- eating a well-balanced diet and getting regular exercise.

More studies are needed, they said, to understand why diabetes is related to a higher Parkinson's risk, and what, if anything, can be done about it.

Diabetes arises when the body can no longer properly use the blood-sugar-regulating hormone insulin. Parkinson's occurs when movement-regulating cells in the brain die off or become disabled, leading to symptoms like tremors, rigidity in the joints, slowed movement and balance problems.

Researchers say it's possible that something about diabetes -- like a problem regulating insulin -- might somehow contribute to Parkinson's. But that remains unproven.

SOURCE: http://bit.ly/fWbB3u Diabetes Care, online March 16, 2011.