This study investigated the combined association of physical activity and diet with the risk of Alzheimer disease (AD). The study followed 1880 community-dwelling elders without dementia in New York from 1992 to 2006. Participants completed standardized neurological and neuropsychological assessments every 1.5 years. Physical activity was measured using the Godin Leisure Time Exercise Questionnaire, while diet was assessed using the Willett Semi-quantitative Food Frequency Questionnaire. Both diet and physical activity were evaluated using standardized scores, and their combined effect on AD risk was analyzed. The study found that higher adherence to a Mediterranean-type diet and higher physical activity levels were independently associated with lower risk of AD. When considered together, both factors were associated with a significant reduction in AD risk. Individuals who adhered to both a Mediterranean-type diet and engaged in high levels of physical activity had a 65% lower risk of developing AD compared to those who adhered to neither. The study also found that the combined effect of diet and physical activity was additive, with no evidence of a non-additive interaction. Adjusted models showed that higher physical activity and diet adherence were associated with lower AD risk, even after controlling for various confounding factors such as age, sex, education, and APOE genotype. The study highlights the importance of both diet and physical activity in reducing the risk of AD. While previous studies have shown mixed results, this study provides evidence that both factors independently contribute to lower AD risk. The findings suggest that a healthy lifestyle, including both physical activity and a Mediterranean-type diet, may be beneficial in preventing or delaying the onset of AD. However, the study acknowledges limitations, including potential measurement errors and the relatively short follow-up period. Despite these limitations, the study provides strong evidence that both diet and physical activity play a significant role in reducing the risk of AD.This study investigated the combined association of physical activity and diet with the risk of Alzheimer disease (AD). The study followed 1880 community-dwelling elders without dementia in New York from 1992 to 2006. Participants completed standardized neurological and neuropsychological assessments every 1.5 years. Physical activity was measured using the Godin Leisure Time Exercise Questionnaire, while diet was assessed using the Willett Semi-quantitative Food Frequency Questionnaire. Both diet and physical activity were evaluated using standardized scores, and their combined effect on AD risk was analyzed. The study found that higher adherence to a Mediterranean-type diet and higher physical activity levels were independently associated with lower risk of AD. When considered together, both factors were associated with a significant reduction in AD risk. Individuals who adhered to both a Mediterranean-type diet and engaged in high levels of physical activity had a 65% lower risk of developing AD compared to those who adhered to neither. The study also found that the combined effect of diet and physical activity was additive, with no evidence of a non-additive interaction. Adjusted models showed that higher physical activity and diet adherence were associated with lower AD risk, even after controlling for various confounding factors such as age, sex, education, and APOE genotype. The study highlights the importance of both diet and physical activity in reducing the risk of AD. While previous studies have shown mixed results, this study provides evidence that both factors independently contribute to lower AD risk. The findings suggest that a healthy lifestyle, including both physical activity and a Mediterranean-type diet, may be beneficial in preventing or delaying the onset of AD. However, the study acknowledges limitations, including potential measurement errors and the relatively short follow-up period. Despite these limitations, the study provides strong evidence that both diet and physical activity play a significant role in reducing the risk of AD.