Active elderly people live longer

Yet more evidence has emerged that staying active in old age is linked to prolonged survival. In a study of 302 elderly US adults, burning more energy was associated with a significantly lower risk of death over a mean follow-up of six years—every extra 1.2 MJ (287 kcal) a day cutting the risk by about 30%. The most active participants were substantially and significantly less likely to die during follow-up than the least active (hazard ratio comparing top and bottom thirds of energy expenditure, 0.33 (95% CI 0.15 to 0.74)) even accounting for age, sex, race, weight, height, percentage of body fat, sleep duration, smoking habit, education, and health.

The authors used doubly radiolabelled water to measure energy expenditure, then computed a figure for energy burnt during activity by subtracting the basal metabolic rate and allowing for the thermic effects of eating. The most active participants burnt 603 more “activity” calories a day than the least active. Less than half the difference was due to extra exercise. They burnt the rest simply moving around, fidgeting, and generally getting on with life.

Although these results are fairly striking, they don't translate easily into specific public health messages, writes a linked editorial (pp 216-8). Next time, researchers should try to record the intensity of people's activity too, preferably using an objective method such as accelerometry.

One per cent of children in a UK cohort have an autistic spectrum disorder

Twenty years ago, most people accepted that childhood autism was a rare developmental disorder with a prevalence of about four or five per 10 000 children. Japanese researchers were the first to notice an increase in the late 1980s. Europeans and Americans followed suit a decade later, and the prevalence has continued to rise since then, with 116 per 10 000, or more than 1%, of children having an autistic spectrum disorder in …