What is Alzheimer’s Dementia and how can I prevent it?
As a neurologist I often get asked: How can I prevent myself from getting Alzheimer’s? My normal answer is to increase your physical and mental activity and keep yourself healthy and you will keep your brain healthy. I will explain the reasoning below along with some basic information regarding Alzheimer’s dementia (AD)
What is Alzheimer’s Dementia?
Alzheimer’s dementia is the most common cause of dementia. Dementia by definition is a progressive decline in cognitive functioning. It is a decline in thinking, remembering and reasoning to an extent that it interferes with a person’s daily life and activities. Per estimates from the Alzheimer’s Association, 5.3 million Americans have AD. This number is estimated to triple in the next 40 years as the population continues to age and live longer.
How do you diagnosis AD?
Currently doctors can only diagnosis AD clinically, based on symptoms and excluding other causes of dementia that can be treated (vitamin deficiencies, hydrocephalus, tumors, depression etc). Unfortunately, the only way to confirm the diagnosis AD is by autopsy of your brain. The pathological changes that are seen in the brains of patients of AD include amyloid plaques (abnormal clumps of amyloid proteins) and neurofibrillary tangles (abnormal bundles of fibers). It is unclear how or why these plaques and tangles form. Once they are there, neurons in the brain lose their ability to function and communicate with each other. Over time the neurons eventually die causing brain atrophy (shrinking of the brain). This process is thought to start up to 30 years before clinical symptoms develop.
What causes AD?
Scientists are not sure what causes AD. It is most likely due to a combination of genetic, environmental and lifestyle factors. We do know some of the risk factors that can increase your risk of develop AD. The more risk factors you have the more likely you are to develop AD.
What are the Risk Factors for Dementia?
- The biggest risk factor for developing AD is age. Currently the risk of AD doubles every 5 years after age of 65.
- Genetics: Genetics plays a big part in what is called “familial AD” which is a young onset AD (typically onset in the 40-50s). This type is autosomal dominant and has strong connection to genetics. This type of AD, however, only accounts for 5% of all AD. The most common type of AD, “late onset AD” may be linked to an abnormal gene: the apolipoprotein E. The linkage is not however 100%. Thus not everyone who has this abnormal gene gets AD, and you may still get AD even if you don’t have the abnormal ApO E gene.
- Diabetes (DM): Studies have shown that people with DM are twice as likely to develop AD. The good news is that people who are at risk for diabetes who changed their lifestyles could reduce their risk of DM by 58% over a 3 year period, thus possibly decreasing their risk for developing AD. There may be several different reasons why people with diabetes are at an increased risk of dementia.
- First of all they have an increased risk of having a stroke which itself increases the risk of dementia.
- DM itself also causes micro-vascular disease which decreases blood flow into the brain thus increasing risk for dementia.
- AD could be from a problem with the way the brain uses insulin. Nerve cells require a lot of energy; they get this energy from glucose and oxygen. With diabetes cells lose their ability to respond to insulin, and brain is not able to use glucose properly. (Think of it as DM of the brain).
- Insulin also is known to regulate the metabolism of beta-amyloid and tau (the building blocks of the AD pathology) in the brain.
- Depression: A meta-analysis of 13 studies showed that people with a history of depression had almost a two times increased risk of dementia compared to controls without depression.
- Cardiovascular disease:
- Hypertension: Studies have shown people who have uncontrolled high blood pressure in midlife, are more likely to develop AD. Hypertension also increases the risk for stroke.
- High cholesterol: Cholesterol is felt to drive the production of beta amyloid.
- Increased risk of stroke, patients with DM, hypertension, and high cholesterol are all associated with an increase of having strokes. Having a stroke is felt to double your risk for dementia.
- Belly fat: Obesity has been associated with an increase risk of dementia. The association between dementia and body weight appears to be most associated with a larger “waist to height” ratios than “body-mass index”. The association is also greater for obesity during midlife instead of late life obesity. A 2008 study in the journal “Neurology” found that people in their 40’s who have the highest amount of abdominal fat were more likely to have dementia when they reached their 70s. They found that those with the highest amount of belly fat were nearly 3 times more likely to develop dementia than those with the lowest amount of belly fat.
- Head injury: The best data to date show that people who have had moderate to severe traumatic brain injury have a 2-4 fold increase risk of dementia. There is unclear association with mild head injuries or concussions. More and more evidence is emerging regarding the risk of dementia after multiple head injuries as seen in boxers and professional football players (what is described in the literature as “chronic traumatic encephalopathy”)
- Physical inactivity: A meta-analysis of 16 prospective studies and a systemic review of 24 longitudinal studies show that the lowest physical activity groups are associated with higher risks of developing AD. The good news is that the risks of AD can be decreased with higher levels of physical activity as shown in a study reported in 2012. Exercise has been shown to improve memory and to increase the size of the hippocampus (the area in the brain that works with memory), by 2% thus reversing age related volume loss by 1-2 years.
- Cognitive inactivity and low education levels: Multiple studies have showed that the risk for dementia is lower in people who have higher education levels, intelligence, occupational attainment, and mentally stimulating leisure activities. These studies are supported by randomized control studies, which reported cognitive interventions in healthy older adults are associated with improvement in cognitive function.
What can I do to prevent AD?
Dr. Deborah Barnes from University of California, San Francisco looked at seven potentially modifiable risk factors for AD: diabetes, midlife hypertension, midlife obesity, smoking, depression, cognitive inactivity, and physical inactivity. She estimates that up to a half of all the AD cases worldwide might be attributable to these risk factors. She states that if risk factors prevalence were decreased by 25% then prevalence of AD could potentially be lowered by over 3 million cases worldwide.
Out all of the risk factors, the one that has the largest impact on AD prevention in the US is physical inactivity. It is estimated that if 25% of sedentary people start exercising, potentially 230,000 cases of AD in the US could be avoided. Low education potentially contributed to the largest proportion of AD cases worldwide; thus with a 25% reduction in low education and cognitive inactivity could potentially lower AD prevalence by 1.375 million worldwide and 91,000 cases in US.
Are there any medical treatments to prevent AD?
Currently there are NO medications that have been shown to decrease your risk for AD. There are 4 medications that have been approved by the FDA to treat AD: Aricept, Exelon, Razadyne, and Namenda. These medications provide modest benefit in slowing the rate of cognitive decline, but they do not change the underlying disease process.
“So how can I prevent AD from occurring?”
The corner stone of dementia prevention, until disease-modifying agents are available, is risk factor modification. Thus you should try to decrease the bad things that may increase your risk for dementia: midlife obesity, midlife high blood pressure, diabetes, strokes, and tobacco use. Then you need to work on improving the things that have been shown to decrease your risk for dementia: increasing mental activity, regular exercise, remaining socially active, and have a healthy diet.
This site is purely informative and should not be considered medical advice. It is not intended to be used to diagnosis or treat any disease. Please consult your physician before starting any fitness program or new supplement.
Amen, D. Use Your Brain to Change your Age.
Barnes, D. E. (2011). The projected effect of risk factor reduction on Alzheimer’s disease prevalence. Lancet Neurology , 819-828.
Buchman, A. B. (2012). Total daily physical activity and the risk of AD and cognitive decline in older adults. Neurology , 13231329.
Desai, A. K. (2010). Healthy Brain Aging: A Road Map. Clinical Geriatric Medicine , 1-16.
Erickson, K. I. (2011). Exercise training increases size of hippocampus and improves memory. Proceeding of the National Academy of Sciences , 3017-3022.
Paturel, A. (2009, July/August). Your Heart, Your Belly and Alzheimer’s: People with so-called metabolic syndrome may be at a higher risk of developing Alzheimer’s dementia. Neurology Now , pp. 18-25.