You’re probably tired of hearing about all the health problems that simply having diabetes increases your risk of, including heart disease, kidney problems, lower limb amputations, and even erectile dysfunction in men. Sorry to burden you with more bad news, but it also appears that diabetes increases your risk of mental dysfunction, too. In fact, just having diabetes gives you a greatly enhanced risk of developing mental declines that range from mild memory loss to more severe dementia to full-blown Alzheimer’s disease.
What causes this increased risk? Let’s take a look at what the worst of these disorders entails to understand it better. Alzheimer’s disease is a devastating disorder of the brain that leads to memory loss, alterations in behavior and personality, inability to think appropriately, and loss of physical function. Since first being described nearly a century ago, it has long been associated with the presence of something called amyloid plaques (as well as neurofibrillary tangles) in the brain. Currently, it is believed that, along with other factors, overproduction of a particular type of these plaques called beta-amyloid (Abeta) largely contributes to the development of Alzheimer’s.
Systemic inflammation has also been implicated as a factor in its onset, possibly also through Abeta accumulation, but this low-level inflammation is also related to the development of other diabetes-related complications. Elevated levels of insulin (that doesn’t work well in your body) results in this inflammatory state – which is the case for many people with type 2 diabetes. Recent research studies have shown that even in elderly individuals (ages 65 years and older) who don’t have diabetes, higher-than-normal insulin levels increase their risk of Alzheimer’s disease and memory deficits, likely resulting from this inflammatory process.
In the near future, Alzheimer’s disease may actually prove to be another form of diabetes (coined “type 3” diabetes), according to some researchers. Brain cells can apparently make some of their own insulin, but this insulin disappears early and dramatically in people with Alzheimer’s. The discovery that your brain produces insulin at all is a recent one, as is the additional finding that levels of brain insulin fall below normal levels in people with Alzheimer’s, particularly as the disease progresses, thus resulting in a sort of insulin resistance in the brain similar to what you find in other parts of the body like muscle and fat. In the brain, this state of insulin resistance appears to result in a decreased clearance of Abeta, which in turn results in Alzheimer’s disease.
No one knows for certain yet if insulin resistance in your brain occurs only locally or results from decreased insulin action in the rest of your body as well. All we know at this point is that diabetes – particularly when poorly controlled – increases your risk of cognitive impairment and likely AD. Moreover, it appears that the ability of insulin to lower your overall blood glucose involves the brain’s response. There is hope, though, because you can apparently improve your mental status by achieving reasonable control over your diabetes using medications like insulin sensitizers. People in a recent study experienced improvements in their working memory when their fasting blood glucose levels went down.
The health of your cardiovascular system is also very important to the vitality of your brain, and your risk of developing Alzheimer’s disease increases with the number of vascular risk factors that you have (for example, insulin resistance, diabetes, smoking, hypertension, and heart disease, among others). As you already know, diabetes by itself confers a greatly exaggerated risk of vascular complications.
So, what can you do to keep your mind healthy? If you’ve read any of my columns before, you know that exercise has to figure in somewhere…so here it comes! Believe it or not, almost all forms of physical activity improve insulin sensitivity and simultaneously decrease your risk of vascular complications while improving your blood sugar control – even without drastic changes in your body weight or percent body fat. For example, women with type 2 diabetes have experienced acute improvements in their insulin action whether they engaged in low-intensity or high-intensity walking as long as the two forms of exercise used up the same number of total calories. Moreover, in other people with type 2 diabetes, insulin sensitivity can improve by 48% after 4 to 6 weeks of moderate-intensity resistance training with minimal changes in body fat or muscle and no change in overall fitness levels. However, exercise must be regular to have a sustained effect.
In addition, regular physical activity can (not surprisingly – to me, anyway) markedly decrease your risk of developing dementia and Alzheimer’s disease. More than one study has found that participation in leisure physical activities reduces your risk of dementia, and it appears that all levels of exercise participation may prevent or delay the onset of dementia and Alzheimer’s. If you’re already suffering from some mental changes, don’t despair; a meta-analysis (that is, a compilation of all relevant studies done to date) of studies done from 1970 to 2003 also found that exercise training increases mental functioning and positive behavior in people who have already developed some level of dementia and other related cognitive impairments. For people who are already impaired, physical activities like walking and stationary cycling are still possible – and beneficial – in most cases.
The only thing I can’t tell you for certain about exercise’s benefits yet is whether regular physical activity done by someone with diabetes offsets all or just some of the increased risk of dementia and Alzheimer’s disease that comes from having diabetes. At present I am doing some research on that exact topic, and once I find out for sure, I’ll let you know. In the meantime, dust off those walking shoes and start using them regularly – for the sake of your mind this time!