Despite evidence suggesting that physical activity and body mass index (BMI) have an impact on the risk for Parkinson disease (PD), a large prospective study published in Neurology shows that there is no significant association between prolonged sitting/inactivity or obesity and PD risk.
Investigators prospectively assessed participants from the Swedish National March Cohort (N=41,638) from 1997 to 2010 to evaluate the association between BMI and time spent sitting per day and risk for PD. Participants reported spending <6 hours per day (n=26,960) or ≥6 hours per day (n=13,834) sitting/inactive.
Participants were also categorized and analyzed according to BMI (<25 kg/m2 [n=23,776] vs 25 kg/m2 to <30 kg/m2 [n=13,054] vs ≥30 [n=2907]). All participants were followed to the 2010 follow-up period, a primary or secondary diagnosis of PD, emigration, or death, whichever came first.
Sitting for ≥6 hours per day vs <6 hours per day increased participants’ PD risk by only 6% (95% CI, -24% to 47%). Additionally, having a baseline BMI ≥30 vs <25 increased the risk for PD by 13% (95% CI, -40% to 112%). During follow-up, a total of 286 incident cases of PD were identified.
A multivariable-adjusted analysis found no significant association between baseline BMI of ≥30 vs <25 kg/m2 (hazard ratio 1.13; 95% CI, 0.60-2.12; P =.849) or sitting time of ≥6 vs <6 hours per day (hazard ratio 1.06; 95% CI, 0.76-1.47; P =.727). Investigators stratified patients by sex, smoking status, and age at baseline evaluation and found no significant associations between BMI or sitting time and PD risk.
Limitations of this analysis include the reliance on self-reported data and the inclusion of an exclusively Swedish patient population.
The study may likely facilitate future studies that “should focus on environmental factors other than obesity and sedentary time in efforts to disentangle the complex causation of PD.”
Roos E, Grotta A, Yang F, et al. Body mass index, sitting time, and risk of Parkinson disease. Neurology. 2018;90(16):e1413-e1417.