According to a study published in the December 19, 2007 online issue of "Neurology," the medical journal of the American Academy of Neurology, people 65 and older who get moderate amounts of exercise appear to significantly lower their risk of developing vascular dementia.
Vascular dementia is the second most common form of dementia after Alzheimer's disease. Unlike some studies, this report didn't find that exercise reduced the risk of Alzheimer's disease, but that is the nature of studies. It generally takes many studies to determine a truth - and as we all know, that "truth" can change in a millisecond if another study is conducted.
This particular study involved 749 men and women in Italy who were over 65. What I find interesting and important to most of us isn't the numbers. It's the fact that you don't have to belong to a gym or run marathons to benefit from exercise. The physical activities measured energy expended while walking, climbing stairs, doing house and yard work, gardening, and light carpentry.
Most people who are in reasonable health are going to be doing some of these things. It isn't a stretch to start thinking about, when possible, climbing a couple of flights of stairs rather than taking an elevator, or walking a few blocks rather than driving your car (I'm a champ at the first, and plead guilty when it comes to driving. Always in a hurry, you know).
The element of the study that I find most useful and hopeful for the majority of elders and boomers who want to avoid memory disorders, is that, like many other studies, this one showed that moderate activity like walking provided "the same cognitive benefits as other, more demanding activities."
Most of us know people who have been very active during their lives, but who still develop vascular dementia. Like the studies that showed education levels influencing the development of Alzheimer's (less education equaled more Alzheimer's) and the speed of decline once Alzheimer's was detected (more education equaled faster decline), this study will likely confuse some issues for those with vascular dementia and Alzheimer's. And it will seem patently untrue for those who have a loved one with an active background, who now has vascular dementia.
Studies are needed for scientific research. Often we, the public, will be cautioned to "wait for more research" before taking some sort of action - say taking an extra vitamin. At least with this study, few of us will be told to "avoid walking until further studies are done." At least one would hope so.
But then, my hair curling brush, in the cautions section, said, "do not use while sleeping," so in our world of "cautions" I've learned to expect nearly anything. So, see your doctor first, but, assuming he or she says it is okay, go ahead and walk. Climb stairs too, unless there's a reason you shouldn't. And planting a flower rarely hurt anyone.

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