Unhealthy Midlife Leads to Brain Shrinkage, Dementia Later On

The research taps into the well-known Framingham Heart Study, which has followed residents of Framingham, Mass., and now their offspring, for more than 60 years. Led by Charles DeCarli of the University of California at Davis, researchers examined just a subset of this massive study group, approximately 1,400 people in their 50s who did not have dementia or history of stroke at the beginning of the analysis.

What they found was enough to trigger a midlife crisis. Within a decade, many subjects began experiencing cognitive decline and excessive brain shrinkage, as revealed through brainteaser tests and routine MRI scans. Each of the risk factors — hypertension, diabetes, smoking and obesity — was associated with a different element of cognitive impairment. [10 Ways to Keep Your Mind Sharp ]

For example, people with high blood pressure developed vascular damage in their brain's white matter at a faster rate than those with normal blood pressure. White matter contains the neural highways connecting various regions of gray matter, where sensory perception and higher thought takes place.

Diabetics lost brain volume in the hippocampus, which, among other functions, converts short-term memory into long-term memory. This is one of the first regions to suffer damage in Alzheimer's disease. Smokers were worst off, losing brain volume overall and in the hippocampus at a faster rate than nonsmokers. Smokers also had the same white matter vascular damage seen among subjects with hypertension.

Obesity led to brain shrinkage, ironically despite overall body enlargement. Obese subjects were more likely to experience declines in test scores for various brain tasks, such as memory and abstract thinking.

This Framingham brain study, the largest of its kind to date, offers insight into the connection between the rise of chronic disease and the rise of Alzheimer's disease and other forms of dementia. The study also supports research from disparate investigators, including recent work from Boston University on a different subset of Framingham subjects. That group found that the fatter the body (particularly in the midsection), the greater the brain shrinkage and the greater the risk of dementia. Similarly, Australian researchers found a strong connection between smoking and brain damage, published in the journal NeuroImage in April 2011. [5 Ways Obesity Affects the Brain]

In light of these recent findings, a companion to the aphorism "sound mind, sound body" may very well be "when it rains, it pours." Or, you can interpret carpe diem, seize the day, anyway you like.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears regularly on Live Science.