Up to 35 percent of dementia cases could be prevented if people ate better and got regular exercise in mid-life and didn't smoke or cut themselves off from others later in life. Those are the implications of a study published Thursday in The Lancet.
The Lancet Commission on Dementia Prevention and Care, a group of 24 international experts who systematically reviewed existing research on dementia, acknowledges that age is the greatest risk factor for dementia. But it says it identified nine other risk factors. They include less education in early life; hypertension, obesity and hearing loss between the ages of 45 and 65; and smoking, depression, physical inactivity, social isolation and diabetes after age 65.
The researchers say there's good evidence that treating hypertension reduces dementia incidence. They say efforts to address the major risk factors – such as increasing early education, reducing hypertension, hearing loss and obesity in midlife; and stopping smoking, treating depression, managing diabetes and increasing physical activity and social contact in late life - are safe, affordable and provide other public health benefits as well.
Interventions could include ensuring children are motivated to stay in school and taxing sugar-sweetened beverages, says Dr. Lon Schneider, director of the USC California Alzheimer's Disease Center and one of the authors of the report.
"Many of these interventions are relatively cheap and the payoff is some several decades later, there being so much less Alzheimer's disease that the cost of care is decreased," Schneider says.
The experts point out that such efforts will not postpone, prevent or cure all dementia cases, but could delay the onset of many. Dementia prevalence would be halved if its onset were delayed by five years, they say.
"Of course, not everyone will be able to make changes; some changes will not make a difference and some risks of dementia are genetic and not currently modifiable," they write. "Nonetheless, delaying dementia for some years for even a small percentage of people would be an enormous achievement and would enable many people to reach the end of life without developing dementia."
The researchers say they didn't incorporate other potential risk factors, including diet, alcohol, living near major roads or sleep into their modeling, so "the potentially preventable fraction of dementia might be underestimated in our figures."
About 47 million people were living with dementia in 2014; that number is expected to triple by 2050, according to the report. It says the 2015 global cost of dementia was estimated to be $818 billion.