Taking long daytime naps — rather than being excessively sleepy during day hours but not napping — appeared to be linked to a two-times higher risk of Parkinson’s disease in older men in a long-term study.
The study, “Excessive daytime sleepiness, objective napping and 11-year risk of Parkinson’s disease in older men,” was published in the International Journal of Epidemiology.
About half of all Parkinson’s patients report with some form of disturbed sleep and feeling disagreeably sleepy during waking hours. While this is a common non-motor symptom of the disease, it is still unclear if daytime sleepiness could be an early factor — or a risk factor — for Parkinson’s disease.
University of California researchers conducted an 11-year prospective study to understand the association between daytime excessive sleepiness and napping, and the risk of developing Parkinson’s.
They evaluated daytime sleeping patterns in 2,920 men, mean age 76.3 years, who did not have a history of Parkinson’s. Participants reported their sleeping routines and wore a small device on their wrist that objectively recorded their activity and napping habits.
Among the study group, 7.4% of participants reported excessive daytime sleepiness but taking naps for less than one hour during the day. Another 28.1% did not report excessive sleepiness but napped for more than one hour each day.
About 5% reported being both sleepy during daytime hours and taking spending considerable time napping — more one hour each day. These men were found to be older, overweight, showed depressive symptoms, lower cognitive function, and were more likely to have a medical history of stroke, coronary heart disease, hypertension, or diabetes.
The remaining men — 59.5% — reported neither excessive daytime sleepiness nor a habit of daily napping.
During the 11 years of follow-up, 106 of these men were diagnosed with Parkinson’s disease.
Men with excessive daytime sleepiness who also napped for more than one hour a day were 2.52 times more likely to develop Parkinson’s than those who neither took daytime naps or felt extremely sleepy during the day. Men who took long daily naps — but without expressing excessive daytime sleepiness — had a 1.96 increased risk of developing the disease. No link was found between daytime sleepiness alone and Parkinson’s, the study reported.
Rather, longer times spent napping each day, rather than excessive daytime sleepiness, were linked to a higher risk of developing Parkinson’s. “Men with a napping duration of at least 1 h per day were more than twice as likely to develop Parkinson’s compared with those who napped for less than 30 min per day,” the researchers wrote.
Although they lacked information on exactly when a participant developed Parkinson’s, their results suggest that “napping precedes PD diagnosis by at least 2 years,” the researchers wrote.
“Objective measures of napping might be a potentially useful early marker of future risk for Parkinson’s disease,” they added.
Additional studies are needed to further investigate the predictive value of long napping in addition to established risk predictors for the disease, the researchers said.
But they thought their results “might open up new avenues for the early detection of Parkinson’s in the elderly,” and contributed to treatment strategies that may “be critical for better management of Parkinson’s disease in the long run,” they concluded.