MIDDLE-AGED people can reduce their risk of developing dementia and Alzhei-mer's later in life by remaining physically active, according to a study.

Researchers found people who exercised at least twice a week in sessions lasting 20 minutes reduced their risk of developing Alzheimer's by 60 per cent, compared with those who did a small amount of training.

The active group also lowered their odds of having dementia by 50 per cent, reports the Lancet Neurology.

Dr Miia Kivipelto, from the Ageing Research Centre at the Karolinska Institutet in Sweden, who led the study, said: "These findings may have wide implications for preventive healthcare.

"If an individual adopts an active lifestyle in youth and at mid-life, this may increase their probability of enjoying both physically and cognitively vital years later in life."

The researchers randomly selected 1,449 people, aged 65 to 79, who had been surveyed about their leisure-time physical activity in 1972, 1977, 1982 and 1987, to take part in the study.

The scientists also found that in individuals who were genetically susceptible to Alzheimer's, physical activity had more pronounced effects against developing the condition or dementia.