If you want to ward off crippling diseases, of both the physical and mental variety, you may want to make an investment in your present day health, as the longest study to-date, examining the effects of five key lifestyle factors, has found that dementia is most effectively prevented through regular exercise.

As a precursor for mental decline, a sedentary lifestyle is all but sweeping the American, and indeed, international landscape. Data from the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) show that, stateside, obesity has risen in prevalence to 35.7 percent of the population. Worldwide, the numbers are no more hopeful. In 2008, more than 1.4 billion adults over the age of 20 were overweight. Meanwhile, researchers speculate dementia cases will triple by 2050. Taken together, these two trends are sobering: Unless people start moving, their mental processes will eventually grind to a halt.

Scientists have thought for some time that dementia could be fended off with adequate exercise. But longitudinal studies are costly and (obviously) time-consuming. As such, they’re also immensely important for understanding long-term consequences of certain behaviors. One of these consequences is mental health.

Aside from exercise, the present 35-year study included among its factors: smoking, diet, alcohol use, and body weight. Researchers from Cardiff University tracked 2,235 men beginning in 1979 and monitored them for each lifestyle factor, checking in on measures of diabetes, heart disease, cancer, and death along the way. In 2004, cognitive states were assessed. Ultimately, not even one percent of participants followed all five behaviors. Roughly five percent followed at least four.

Benefits among those adhering to the behaviors were stark. People who followed at least four of them saw a 60 percent reduction in dementia and overall cognitive decline, with exercise being the strongest predictive factor. Diabetes, heart disease, and stroke fell by 70 percent compared to people who followed none of the prescribed lifestyle choices.

"The size of reduction in the instance of disease owing to these simple healthy steps has really amazed us and is of enormous importance in an aging population," lead researcher Professor Peter Elwood from Cardiff University’s School of Medicine said in a statement. "What the research shows is that following a healthy lifestyle confers surprisingly large benefits to health — healthy behaviors have a far more beneficial effect than any medical treatment or preventative procedure.”

Much has changed since the study began in 1979. Smoking, one of the deadliest lifestyle behaviors, has actually declined in prevalence, as has alcohol. But where thin smokers once dominated the realm of poor health, obese couch potatoes have now taken their place. And it’s less their lungs paying the price, so much as their brains.

"We have known for some time that what is good for your heart is also good for your head,” said director of research and development at the Alzheimer’s Society, Dr. Doug Brown, in the statement, “and this study provides more evidence to show that healthy living could significantly reduce the chances of developing dementia.”

The term “dementia” functions as a kind of umbrella for a range of degenerative mental illnesses, most popularly Alzheimer’s disease, but also includes vascular dementia, frontotemporal dementia, and semantic dementia. Sufferers lose their ability to recall names and dates, recognize faces, recall life experiences, and identify who they are.

Sadly, for much of the 20th century dementia was recognized as a normal side-effect of aging. But now emerging research confirms the disease is preventable, much like physical ailments, such as obesity. Prior studies, for instance, have all conferred the benefits of olive oil, bilingualism, rising early, and retiring later in life for reducing a person’s risk of dementia. Now the new study adds exercise into the mix, confirming what mothers have known anecdotally for years, that being active doesn’t only make the body strong; it makes the mind strong, too.

"This large study further underlines the importance of a healthy lifestyle and provides yet more evidence to indicate that healthy living could lower the risk of dementia,” said Rebecca Wood, chief executive of Alzheimer’s Research UK, in the release. “We still need more research to understand how to prevent dementia…but it’s encouraging for people to know there are simple steps they can take now to reduce their risk of this devastating condition.”

Source: Elwood P, Galante J, Pickering J. Healthy Lifestyles Reduce the Incidence of Chronic Diseases and Dementia: Evidence from the Caerphilly Cohort Study. PLOS ONE. 2013.