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Midlife Experience and Alzheimer's Disease

Dear Readers: I rarely run guest posts, however this offer was too good to pass up. Dr. Michael Mullan of the Roskamp Institute is a biomedical researcher in the field of neurodegenerative disorders and CEO & President of the Roskamp Institute in Sarasota, FL., a non-profit research center whose main goal is to discover new and effective treatments for Alzheimer's disease. Read on to learn more about lifestyle and Alzheimer’s:

Although AD is regarded largely as a disease of the elderly, in fact, the seeds of the disorder can be sown quite early in life. We now know that a wide variety of influences during midlife can influence our subsequent risk for the disease. In some cases, the link between midlife activities and medical conditions and late-life Alzheimer's are obscure but, in other cases, the underlying biological reasons for these associations are being established.

Broadly, late-life risks for AD determined by midlife experiences can be divided into four categories:  midlife medical conditions; midlife mental activity; midlife diet; and physical activity. Under the category of midlife medical conditions, it's now well established that midlife diabetes, hypertension and obesity are all risks for late-life AD. To be clear, it is not a diagnosis of hypertension per se that increases risk of late onset AD, but, rather, uncontrolled high blood pressure. Thus in several large population based studies including the Honolulu Asia aging study and the Kuopio study in Finland raised diastolic (above 95 mm Hg) and systolic (greater than 160 mm Hg) were associated with late-life risk for dementia.


Interestingly, higher blood pressure in late-life is not necessarily associated with dementia and, in fact, decreases in blood pressure have been noted as risk for dementia in late life. Increased midlife blood pressure has also been associated with reduced cognitive abilities, even in the absence of dementia in the elderly. High blood pressure may predispose the brain to damage and subsequent dementia via many mechanisms, not least of all small bleeds and/or clotting, which can obscure blood delivery to parts of the brain. So called white matter changes or white matter hyperintensities have been previously related to reduced cognition in normal, elderly subjects and these are clearly related to high blood pressure in midlife. Similarly, several studies have suggested that midlife diabetes or tendency to diabetes is a risk for late-life AD.

In one large Swedish study, men who showed low insulin secretion capacity in their 50s were subsequently at increased risk for Alzheimer's in later life. Similarly, women are at increased risk for cognitive impairment and dementia if they are diabetic. In general, poorly controlled diabetes is much more of a risk for AD and related dementias than is well controlled diabetes. Body Mass Index (BMI) in midlife of greater than 25 doubles the risk for AD and vascular dementia in late life. If BMI is greater than 30 during midlife then, there is over a three-times increased risk for the development of AD in late life and a five-fold increase in risk for developing vascular dementia in late life. Obviously, diet and physical exercise interact with these three common medical conditions of hypertension, diabetes, and obesity.

Diets rich in polysaturated fat in midlife contribute to cerebral vascular damage and cardiovascular damage which can contribute to mini strokes caused by clots or bleeds in the brain. We know that damage to the vascular delivery of glucose and oxygen and other nutrients to the brain is highly detrimental in and of itself and interacts very negatively with AD. Poor diet and lack of exercise in midlife are therefore associated with increased risk of developing late-life AD and other dementias. In addition, multiple studies suggest that education and professional occupations that require the use of mental faculties protect us in later life against AD. Thus, individuals with higher educational achievements and ongoing requirement for the engagement of the brain in mentally challenging tasks are at reduced risk for AD compared to individuals who have less mentally challenging occupations.

In summary, although we consider AD to be a disease of old age and late old age, multiple large population studies suggest that we predispose ourselves or protect ourselves from AD depending on lifestyle choices and medical conditions in mid life. The need to control body weight, take diets with low tendency to form atherosclerosis (in vessels either in the brain or the rest of the body) and to exercise in midlife is emphasized by the reduction in risk for individuals who do so compared to those who don't. Similarly, the aggressive control of midlife hypertension and diabetes is a prerequisite to reducing our risk of AD and related dementias much later in life. The medical, societal, and economic benefits of programs which promote healthy diets, an active lifestyle, and attention to potentially detrimental medical conditions are clear in relation to their ability to reduce our risk for AD in later life.

More on Dr. Michael Mullan and Roskamp Institute

 

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