Harmful impact of blood lead on the prevalence of Alzheimer's disease among middle‐aged and older adults and the modifying role of physical activity: Evidence from the National Health and Nutrition Examination Survey (NHANES) study

INTRODUCTION: Alzheimer's disease (AD) is a major public health challenge. This study aims to explore the combined effects of blood lead levels (BLL) and physical activity (PA) on AD prevalence among middle-aged and older adults. METHODS: A total of 13,426 middle-aged and older adults (57.8% over 60 years old; 49.7% males) were included. Firth's penalized logistic regression models were used for statistical analysis. RESULTS: High blood lead level (High-BLL) was associated with an 86.7% increase in AD prevalence. For PA levels, engaging in sufficiently active PA was associated with a 72% reduction in AD prevalence. In addition, the combination of sufficiently active PA with high-BLL, moderate blood lead level (Moderate-BLL), or low blood lead level (Low-BLL) was associated with an 83.9%, 65.9%, or 76.5% reduction in AD prevalence, respectively. DISCUSSION: Although higher BLL is associated with increased AD prevalence, engaging in PA can reduce the AD prevalence caused by BLL, with greater benefits observed from sufficiently active PA. HIGHLIGHTS: Higher blood lead levels (BLL) are associated with an increased prevalence of Alzheimer's disease (AD), whereas engaging in physical activity (PA) is associated with a reduced prevalence. Furthermore, engaging in sufficient occupational PA and sufficient leisure-time PA are both associated with a lower prevalence of AD. Engaging in PA can reduce the AD prevalence caused by BLL, with greater benefits observed from engaging in sufficiently active PA. The combined effects of BLL and PA levels on AD prevalence may vary among populations with different gender, marital status, socioeconomic status, or smoking status.