Conclusion
cognitive decline, dementia
BLIND
In summary, although not all participants achieved the intended improvement in physical activity, the tailored intervention was easily accessible and well appreciated in a group of elderly with low levels of physical activity. The ITT analyses did not show intervention effects on physical fitness or cognition. Responder analyses suggest benefits on physical fitness and cognition for those who managed to achieve an increase in physical activity ≥ 35% over 9 months. In light of the potential benefits of physical activity on physical fitness and cognitive functioning, we highly recommend an ambitious approach towards the prevention of cognitive decline and dementia by stimulating sustained engagement in moderate to high levels of physical activity, over the course of the lifetime. Future studies could optimize intervention potential by aiming at a sustained increase in physical activity of  ≥ 35% in a population of “at risk” individuals defined by various health parameters including age, level of physical activity, and genetic susceptibility. This study also reveals several difficulties in physical activity trials, which are difficult to blind for participants and researchers. Intervention potential could be further enhanced by replacing the active control condition with a no-contact or waitlist control condition and further standardization of the assessment of physical activity by means of actigraphy or accelerometry.