Physical activity recommended to reduce the risk of dementia. Dementia, including Alzheimer's disease, affects some 50 million people worldwide, with about 10 million new cases annually. The annual cost of caring for those with dementia is expected to rise to $2 trillion by 2030. To address the concerns raised by these figures, the World Health Organization (WHO) has issued Risk Reduction of Cognitive Decline and Dementia: WHO Guidelines (http://www.who.int/mental_health/neurology/dementia/guidelines_risk_reduction/en). The guidelines strongly recommend physical activity for "adults with normal cognition to reduce the risks of cognitive decline," while stating that physical activity may also be useful for adults with mild cognitive impairment. The guidelines also evaluate tobacco and alcohol use, nutrition, and other interventions.