Middle-aged men and women who are overweight may be at increased risk of developing Parkinson’s disease, a progressive, irreversible neurodegenerative disease, study shows.

In recent years, two studies looking at the association between obesity and the risk of Parkinson’s disease yielded “inconsistent” results, Dr. Gang Hu, of the National Public Health Institute, Helsinki, and colleagues note in the journal Neurology.

To further investigate, they examined the association between BMI and the risk of Parkinson’s disease in 22,367 Finnish men and 23,439 women between the ages of 25 and 59 years who were free of Parkinson’s at the outset.

Over an average of 18.8 years, 272 men and 254 women developed Parkinson’s disease. The overall incidence of Parkinson’s disease was higher in men than women, but Parkinson’s disease increased with age for both sexes.

After adjusting for potentially confounding factors, the risk of developing Parkinson’s disease increased with increasing body mass index (BMI) - a height to weight ratio used to determine how thin or fat an individual is.

Men in the study who were overweight with a BMI of 25.0 to 26.9 had a nearly two-fold higher risk of Parkinson’s disease. Men who were even heavier (BMI, 27 to 29.9) or obese (BMI 30 or greater) had a greater than two-fold risk of developing the disease.

Similar, albeit less pronounced, associations were evident in women.

The mechanisms behind the association between obesity and increased Parkinson’s risk are unclear, the authors note.

SOURCE: Neurology December, 2006.