Can we reduce the risk of Alzheimer’s?

Might physical activity, educational achievement, a healthy diet and an active social life reduce the risk of Alzheimer’s? Might smoking, obesity and depression increase the risk?

That’s what the Royal Society for Public Health (RSPH) concluded in August 2014. Here’s what our review of the evidence suggests:

There are different types of dementia

Each has its own causes and symptoms. Of the different types of dementia Alzheimer’s Disease is the most common, so is the one we’re focusing on here.

Is physical activity important?

The RSPH’s review of the evidence suggested physical inactivity was responsible for nearly 22% of cases. This is in line with studies that have shown an assocation between lower levels of physical activity and higher rates of Alzheimer's. However Alzheimer's Disease International (ADI) explains that most of these studies were conducted with older adults and it could simply be that as people get older or develop Alzheimer's they exercise less i.e. that low levels of physical activity may be a result of ageing or Alzheimer's rather than being responsible for Alzheimer's. 

At the same time ADI has identified that two of the factors for which there is the strongest evidence for possibly causing dementia (including Alzheimer's) are diabetes and hypertension (high blood pressure). A report by the Academy of Medical Royal Colleges suggests that regular exercise can reduce the risk of type 2 diabetes by at least 30%. And a number of studies have suggested that exercise (provided it isn't too intense) is likely to reduce the risk of hypertension. So there are possible indirect ways in which regular physical exercise might reduce the risk of Alzheimer's.

Whatever the case we can probably agree with Dr Louise Allan, of the British Geriatrics Association. She advises, ‘There’s now so much evidence for the general health benefits of keeping physically active, and so few health risks, that it seems sensible to recommend physical activity.’

And a recent study has suggested one way in which physical exercise may make a difference – by reducing shrinkage of the brain’s hippocampus. The hippocampus is important for memory and is particularly vulnerable to Alzheimer’s.

What about mental activity?

Alzheimer's Disease International identifies low levels of education in early life as one of the most likely causes of dementia. Similarly, the RSPH estimates that higher levels of educational achievement can reduce dementia rates by around 19%. Other forms of mental activity also seem to have a protective effect. 

One interpretation is that if we stay mentally active throughout our lives, by developing new interests and skills, then this develops some form of reserve in our brain which helps protect against or compensate for dementia. This is known as the Cognitive Reserve hypothesis. For example a nine year study of 602 older adults in Sweden, published in 2017, concluded that increased frequency of engagement in stimulating activities over the life course was associated with a progressively reduced risk of dementia.

One example of mental activity in practice is speaking several languages. Several studies suggest that being bilingual helps protect our mental ability. For example a study published in 2011 analyzed brain CT scans. It found that people who speak more than one language were able to absorb more brain damage than those who only spoke one language before they exhibited symptoms of Alzheimer's disease. Observational studies have suggested that bilingualism delays the onset of Alzheimer's symptoms by up to four and a half years, while a study of 85 patients, published in 2017, has suggested which aspects of the brain are strengthened by being bilingual.

And studies suggest that enriching your mind in later life can help protect your brain too. Even volunteering may help improve cognitive function (our ability to process thoughts).

Might diet make a difference?

We haven’t found as much evidence here. However, the RSPH reports there is evidence that a diet high in fruit and vegetables and low in saturated fat may protect against dementia. This is in line with the maxim that what is good for the heart is usually good for the brain. And a study of 932 people, over 4.5 years, published in 2015, concluded that following three healthy diets may reduce the risk of Alzheimer's.

And social life?

Low social participation, less frequent social contact and loneliness were associated with a greater likelyhood of developing dementia. That was the conclusion of a 2015 review of nineteen long term studies. The review concluded, 'The strength of the associations between poor social interaction and incident dementia is comparable with other well-established risk factors for dementia, including low educational attainment, physical inactivity and late-life depression.' So stay connected with your family and friends or get reconnected. Other options include joining a book club, sports club, volunteer group, continuing education class or community activity. 

What factors increase the risk of Alzheimer's?

Genetics - Less than 1% of people are at a particularly high inherited risk of dementia, which may occur earlier than usual in life. In such cases even a healthy lifestyle probably won't protect you- although the disease may skip a generation, appear seemingly from nowhere or not be passed on at all. A larger proportion have other 'risk genes' i.e. an increased risk but no certainty of developing dementia. In such cases the Alzheimer's Society advises you can reduce your overall risk by adopting a healthy lifestyle

Smoking – If we exclude those studies by researchers with tobacco industry affiliations the verdict seems to be that smoking is a significant risk factor for Alzheimer’s. This was one of the conclusions from the ADI review of the evidence mentioned earlier.

Obesity – This also appears to be a risk factor. However, the major risk seems to arise from being obese while middle aged (i.e under 65) rather than being obese when older.

Depression – Being depressed in later life is associated with an increased risk for all types of dementia, including Alzheimer's.

Medical advice should be sought if your depression continues. However, it is worth noting that physical exercise can help people with mild depression and may even stop them getting depressed in the first place.

Conclusions

  • Physical activity may help protect against Alzheimer’s – so consider activities like walking, swimming, dancing, cycling, aerobics, running, ball games or Tai Chi.
  • Mental activity is recommended, to help build your Cognitive Reserve –so consider activities like learning a new language or musical instrument, developing a new hobby or skill, board games or volunteering.
  • A healthy diet and social life are also likely to help reduce the risk.
  • Avoid known risk factors – so don’t smoke, don’t become obese and seek help if you suffer from depression. 

Originally published October 2014. Reviewed and updated by Christiane Hahn January 2017. Next Review Date December 2019  

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