Meta-analysis finds inverse dose-response link between activity and PD risk
Moderate and vigorous physical activity was tied to a lower risk of Parkinson’s disease (PD) in men, a meta-analysis found.
In studies that collectively included more than 500,000 people, an inverse dose-response link emerged between physical activity and PD risk among men, reported Fudi Wang, MD, PhD, of Zhejiang University School of Medicine in Hangzhou, China, and colleagues in JAMA Network Open.
“Physical activity has long been known to reduce the risk of a wide range of diseases, including cardiovascular disease, stroke, and diabetes,” Wang told MedPage Today. “A growing body of studies investigated the association between physical activity and PD risk, but with mixed results, due to limited sample size, differential ethnicity, and other different characteristics.”
The connection between physical activity and Parkinson’s risk was significant among males and did not apply to light intensity exercise, he added. “Specifically, only moderate or vigorous activities were found to be significantly associated with the decreased risk for PD.”
In this systematic review and meta-analysis, Wang and co-authors evaluated eight prospective studies that had a total of 544,336 people — including 2,192 PD cases — who were followed for a median of 12 years. Although each study used different cutoffs for high versus low activity levels, the researchers quantified data for six studies that had detailed information about physical activity into metabolic equivalent of tasks (METs), a measure of exercise intensity.
The results showed a significantly reduced risk of PD tied to the highest levels of either total physical activity (RR 0.79; 95% CI 0.68-0.91) or moderate-to-vigorous physical activity (RR 0.71; 95% CI 0.58-0.87), with stronger associations among men than women. Light physical activity was not tied to PD risk (RR 0.86; 95% CI 0.60-1.23).
For each 10 MET-hours/week increase in either total or moderate-to-vigorous physical activity, the risk of PD among men decreased by 10% and 17%, respectively. There was no linear dose-response association between physical activity and PD risk in women (RR 0.95; 95% CI 0.87-1.04).
To adjust for possible reverse causation, the researchers conducted a time-lag meta-analysis excluding the first 4 to 10 years of follow-up, and found similar results.
The study is “an excellent example showing meta-analysis in its best role,” noted Lorene M. Nelson, PhD, MS, of Stanford University School of Medicine, in an accompanying editorial.
“Among the eight studies, only one study found a statistically significant reduced PD risk when comparing the highest with the lowest category of physical activity; however, when analyzed together, a significantly reduced risk of PD was observed with the highest level of total physical activity compared with the lowest level.”
More recent research has found similar results, Nelson pointed out. The Veterans Exercise Testing Study, a cohort study of 7,347 male veterans that measured physical fitness objectively by maximal exercise testing, reported a strong inverse association between physical activity and PD: men who had a high (>12 METs) versus low (<8 METs) level of fitness had a 76% reduction in the incidence of PD. “This study adds evidence that objectively measured physical fitness in men, not just self-reported moderate and vigorous physical activity, is inversely associated with PD in a dose-response fashion.”
The meta-analysis has several limitations, Wang and co-authors said. A limited amount of empirical data was appropriate to be included. Residual confounding could be a factor; the researchers used risk estimates derived from fully adjusted models for the pooled analysis to reduce potential confounding factors. Most studies used self-reported information, which may be subject to error. It also was possible that preclinical or undiagnosed PD may have manifested as a lower level of physical activity, although the time-lag analysis suggested this was unlikely.
The editorial also pointed out that conclusions about physical activity and risk of PD for women could not really be made as the number of women in the included studies was small.
Link Original: https://www.medpagetoday.com/neurology/parkinsonsdisease/75249?xid=nl_mpt_DHE_2018-09-22&eun=g1052537d0r&pos=&utm_source=Sailthru&utm_medium=email&utm_campaign=Daily%20Headlines%202018-09-22&utm_term=Daily%20Headlines%20-%20Active%20User%20-%20180%20days