['Physical activity is thought to facilitate cognitive performance and to slow down the rate of age-related cognitive decline. This study aimed to investigate the association between the time spent on physical activity as well as the average intensity of these activities and cognitive function.', 'Cross-sectional analysis.', 'Our study population comprised of 1927 healthy men and women aged 45-70 years in the Netherlands, examined from 1995 until 2000. Physical activity was assessed with an extensive questionnaire, and cognitive function by a neuropsychological test battery.', 'Multivariate linear regression analysis showed that intensity of weekly physical activities is significantly positively associated with processing speed, memory, mental flexibility and overall cognitive function. No significant associations were observed between the time spent weekly on physical activities and the various cognitive domains. At the same time, variation in activities was significantly positively associated with speed, memory, mental flexibility and overall cognitive function.'] Is intensity , but not duration , of physical activities related to cognitive function?