Mendelian randomization study on the causal association of dairy smoothie intake with Alzheimer’s disease

ABSTRACT Background: Observational studies have shown that dairy smoothie intake may be involved in Alzheimer’s disease (AD) pathogenesis. Objectives: The present two-sample Mendelian randomization study aims to identify the causal link between dairy smoothie intake and AD. Methods: Dairy smoothie intake-associated genetic variants were chosen from the largest genome-wide association study (GWAS) ( n = 64,941 participants from European ancestry). Weighted median and inverse variance weighted (IVW) were used to evaluate the causal effect of dairy smoothie intake-associated instrumental variants (IVs) on AD with the largest AD GWAS (71,880 cases and 383,378 controls from European ancestry). Results: We found no significant pleiotropy or heterogeneity of all three selected dairy smoothie intake genetic IVs in AD GWAS. Interestingly, we found that as dairy smoothie intake genetic changes increased, the risk of AD was increased using weighted median (Beta = 0.258, 95% CI for beta: 0.053 ~ 0.463, odds ratio [OR] =1.294, 95% CI for OR: 1.055 ~ 1.588, P = 0.013) and IVW (Beta = 0.260, 95% CI for beta: 0.089–0.430, OR = 1.296, 95% CI for OR: 1.093–1.537, P = 0.003). Conclusion: Our analysis suggested a potential causal association between genetically increased dairy smoothie intake and increased risk of AD. Thus, dairy smoothie intake may be a potential risk factor for AD.