We can help prevent Alzheimer’s disease. Research shows that Alzheimer’s disease starts altering the structure of the brain years or even decades before the first behavioral symptoms appear. During this “preclinical phase”, amyloid plaques are building up on neurons, but the load is not yet sufficient to kill neurons and cause memory or behavioral problems to appear. As worrying as this sounds, the flip side means that we have a “window of opportunity” to act in order to prevent or defer a diagnosis. Numerous studies have shown that it is in this mid-life preclinical phase that our actions matter most, before the long term accumulation of plaques and neurofibrillary tangles.
Risk factors for dementia
Age is the number one risk factor for Alzheimer’s disease: the older you get, the greater your chance of being diagnosed with Alzheimer’s. Genetics are also a factor: a gene variant known as APOE-e4 is thought to play a role in up to one quarter of Alzheimer’s cases. We can’t control our age or our genes; but there are other established risk factors that we can control. High blood pressure, high cholesterol, diabetes, obesity, smoking, and physical inactivity all increase a person’s chance of developing Alzheimer’s disease. These are ‘modifiable factors’, that is, conditions that are within our power to change or modify.
It is no coincidence that the Alzheimer’s risk factors listed above also contribute to cardiovascular disease. Our brain function relies heavily upon healthy blood vessels and hormone balance. As we shall see in this article, these modifiable risk factors are often linked (one causes another), and so taking action to reduce one of them will have a positive effect on all the rest.
How we can prevent Alzheimer’s: High cholesterol and high blood pressure
Especially during mid-life, high cholesterol levels and high blood pressure can increase your chances of developing Alzheimer’s disease. Studies have found that people who had raised systolic blood pressure (⩾160 mm Hg) or high serum cholesterol concentration (⩾6.5 mmol/l) in mid-life had a significantly higher risk of Alzheimer’s disease in later life. People who had both of these risk factors in mid-life had a significantly higher risk of developing Alzheimer’s disease than those who had only one of these risk factors.
High LDL Cholesterol causes a build-up of plaque and subsequent hardening of the arteries. This causes the arteries to narrow, forcing the heart to strain harder to push blood through. The resulting high blood pressure damages the tiny blood vessels of the brain. Abnormally high cholesterol can be caused by being overweight, lack of exercise, and having type 2 diabetes. Both high cholesterol and high blood pressure can be reduced by:
• eating a healthier diet,
• losing weight, and
• exercising
How we can prevent Alzheimer’s: Type 2 diabetes
Research consistently shows that people who have mid-life type 2 diabetes are, on average, twice as likely to develop dementia as people without diabetes. Impaired insulin secretion, insulin resistance and glucose intolerance are also associated with an increased risk of dementia. Longer duration and greater severity of diabetes may further increase the risk of dementia. Over time, untreated diabetes can lead to blood vessel disease. Diabetes may also contribute to the build-up of plaques and tangles in the brain, inflammation in the brain, and oxidation in brain cells, all of which increase the risk of dementia. Type 2 diabetes is also linked to high cholesterol. Even if blood sugar control is good, people with diabetes tend to have increased triglycerides, decreased HDL, and sometimes increased LDL. This increases the likelihood of developing narrowing in the arteries and high blood pressure. More than 80% of people diagnosed with type 2 diabetes are obese. A decrease in the effects of type 2 diabetes can be achieved by:
• eating a healthier diet,
• losing weight, and
• exercising
How we can prevent Alzheimer’s: Smoking cigarettes
Cigarette smoking has been linked to cardiovascular disease and diabetes. Smoking accelerates the onset of every single diabetes complication. The evidence is strong and consistent that smokers (vs. non-smokers or ex-smokers) are at a 45% higher risk of developing Alzheimer’s disease. Ex-smokers reduce their risk by not smoking. This is an encouraging finding for dementia prevention, suggesting, as with other adverse impacts of smoking, that the increased risk of dementia can be avoided by quitting smoking.
How we can prevent Alzheimer’s: Obesity
Central obesity, having a large waist, has been particularly associated with a higher dementia risk in recent studies. Obesity is closely linked to high blood pressure, high cholesterol and diabetes, all of which increase the risk of dementia. Adipose tissue (fat) secretes hormones that might directly affect the health of the brain and may increase the production of the plaques that are thought to cause Alzheimer’s disease.
How we can prevent Alzheimer’s: Inactivity
Exercise reduces the risk of cardiovascular disease (including high cholesterol and high blood pressure). In terms of brain health, physical exercise is essential for maintaining good blood flow to the brain and increasing chemicals that protect the brain, as well as for encouraging the growth of new brain cells. Exercise also increases neural efficiency and stimulates the growth of new connections between brain cells. Two studies by a team in Finland and Sweden found that exercising at least twice a week in midlife lowers one’s chance of getting dementia more than 20 years later. A study in the UK estimated physical inactivity accounted for 21.8% of the risk of developing Alzheimer’s in the UK. Another way of saying this is that if nobody was inactive, the risk of Alzheimer’s in the UK population could reduce by 21.8%.
How much exercise do we need?
There is growing evidence that physical exercise does not have to be strenuous or require a major time commitment to help prevent Alzheimer’s disease. It is largely thought that 150 minutes of moderate exercise per week, taken even in 10 minute segments, is enough to improve brain health. In a study published in 2013 in the Journal of Alzheimer’s Research, researchers found that just 150 minutes of moderate exercise every week could significantly improve memory performance after just 12 weeks. Another long-term study of people averaging 78 years old found that participants who walked 72 city blocks per week had increased grey matter volume 9 years later. Greater gray matter volume due to walking reduced the risk for cognitive impairment 2-fold.
There is some evidence that surpassing the 150 minutes per week of moderate exercise will provide even greater benefits, however, findings are conflicted. If all other modifiable risk factors are under control, meeting the 150 minutes per week may be all that is needed.
For the moment, our imperfect knowledge of the causes of Alzheimer’s leaves us with two safe weapons to prevent or push off a diagnosis: eating well and exercise.
