Dietary glycemic index is inversely associated with the risk of Parkinson's disease: a case-control study in Japan.
OBJECTIVE
High glycemic index (GI) or glycemic load (GL) carbohydrates might be expected to decrease the risk of Parkinson's disease (PD) by an insulin-induced increase in brain dopamine. We conducted a hospital-based case-control study in Japan to examine associations between dietary GI and GL and other dietary carbohydrate variables, including intake of available carbohydrate and dietary fiber, and PD.


METHODS
Patients with PD diagnosed using the U.K. Parkinson's Disease Society Brain Bank criteria (n=249) and controls without neurodegenerative diseases (n=368) were recruited. Dietary intake during the preceding month was assessed at the time of study recruitment using a validated, self-administered, semiquantitative, comprehensive diet history questionnaire.


RESULTS
After adjustment for potential dietary and non-dietary confounding factors, dietary GI was significantly inversely associated with the risk of PD. Multivariate odds ratios (95% confidence intervals) for PD in the first, second, third, and fourth quartiles of dietary GI were 1.00 (reference), 1.03 (0.64-1.66), 0.68 (0.41-1.15), and 0.61 (0.34-1.09), respectively (P for trend=0.04). Conversely, no significant association was observed for other dietary carbohydrates, including dietary GL (P for trend=0.77), available carbohydrate intake (P for trend=0.28), or dietary fiber intake (P for trend=0.73).


CONCLUSIONS
This preliminary case-control study based on current dietary habits found an independent inverse relation between dietary GI and PD. Considering the plausibility of the putative mechanism, further investigation using a case-control design with accurate assessment of past dietary habits or a prospective design is warranted.
Murakami
Kentaro
K
Department of Social and Preventive Epidemiology, School of Public Health, the University of Tokyo, Tokyo, Japan.
Miyake
Yoshihiro
Y
Sasaki
Satoshi
S
Tanaka
Keiko
K
Fukushima
Wakaba
W
Kiyohara
Chikako
C
Tsuboi
Yoshio
Y
Yamada
Tatsuo
T
Oeda
Tomoko
T
Miki
Takami
T
Kawamura
Nobutoshi
N
Sakae
Nobutaka
N
Fukuyama
Hidenao
H
Hirota
Yoshio
Y
Nagai
Masaki
M
D000368:Aged; D016022:Case-Control Studies; D004032:Diet; D015930:Diet Records; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004043:Dietary Fiber; D005260:Female; D038321:Glycemic Index; D006761:Hospitals; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010300:Parkinson Disease / Q000453:epidemiology*; D012307:Risk Factors; D011795:Surveys and Questionnaires
D004040:Dietary Carbohydrates; D004043:Dietary Fiber