Effects of dairy products intake on prodromal Parkinson's disease in Chinese adults aged 55 and above: A prospective cohort study

Background It has been reported that a high intake of dairy products might be associated with an increased risk of Parkinson's disease (PD) in foreign studies, but no such study has yet been conducted on prodromal Parkinson's disease (pPD) and the Chinese population.

Objective To investigate the prospective relationship between the intake of dairy products and pPD among people aged 55 and above in four provinces of China.

Methods The research data were obtained from the baseline 2018 and follow-up 2020 surveys of Community-based Cohort Study on Nervous System Disease. A total of 9984 residents were selected who participated in both waves of surveys and had complete data on demographics, dietary products intake, and risk factors for PD. We evaluated the risk level and the numbers of related risk/prodromal markers of pPD in the participants based on a criteria recommended by the International Parkinson and Movement Disorder Society (MDS). Food Frequency Questionnaire was used to obtain food consumption data in the past 12 months, and the intake of dairy products was calculated and divided into non-consumption and tertiles of consumption (T1, T2, and T3 from low to high). Multiple linear regression was used to analyze the association between baseline dairy intake and risk level of follow-up pPD. Poisson regression and multinomial logit regression models were used to analyze the relationship of baseline dairy products and the number of risk/prodromal markers of follow-up pPD in the population, and multiple logistic regression was used to analyze each risk/prodromal marker of follow-up pPD according to baseline levels of dairy products intake.

Results The percentage of residents without dairy products consumption was 58.02% in 2018, and the dairy products intakes were relatively high among residents being female, aged 55 to 74 years, with an education level of middle school and above, with a per capita monthly household income ≥ 1000 yuan, living in urban areas, and without active employment (P<0.05). The median risk level of pPD was 0.74% in 2020, and the proportion of residents with 3 to 5 markers was 66.74%. The multiple linear regression analysis results suggested no association between baseline dairy intake and follow-up risk level of pPD. The Poisson regression model showed that the high dairy products intake group at baseline (T3, median=250.00 g·d⁻¹) was found to be 1.159 (95%CI: 1.065~1.261, P_trend<0.001) times more likely to have the risk/prodromal markers of pPD at follow-up than non-consumers. When the number of markers was grouped, no statistically significant association was found by multiple logistic regression analysis.

Conclusion Although high dairy products intake levels might be associated with pPD risk/prodromal markers among people aged 55 and above in four provinces of China, no direct association is found between dairy products intake and pPD risk levels in this study.