Dementia: Genetic or Environmental?

By Natasha

Think of your fondest memory. Now imagine being stripped away of your ability to hold on to that moment. Alzheimer’s (the most common type of dementia), is an irreversible, progressive brain disorder that slowly destroys your memory, your ability to think and, eventually, your ability to carry out the simplest tasks. Alzheimer’s disease was beautifully depicted in Still Alice, a Hollywood movie released in 2014. Cinema is an extremely powerful tool which triggers interest in the most obscure topics. However, the portrayal of scientific topics can often be highly inaccurate. The movie portrayed a very rare type of Alzheimer’s which occurs due to genetic predisposition.

Genetics vs. Environment?

Is this entirely true? Although genetic factors are the main cause of rare cases of Alzheimer’s, environmental factors play an equally important role. In fact, the interplay between genetics and environment is still not fully understood by the scientific community. The field of epigenetics studies exactly that – how environmental factors (e.g. exposure to chemicals, smoking, lifestyle choices) can switch our genes ON or OFF. Could it be that we may be able to alter our genes by making simple lifestyle changes? Could it be that lifestyle choices could prevent dementia?

Social Isolation and Alzheimer’s

An overwhelming number of studies suggest that isolation is a big risk factor for Alzheimer’s. The largest study followed the journey of 12,000 participants over 10 years and confirmed the heavy toll that loneliness can take on your health: It increases your risk of dementia by 40%. The study also highlights that the individuals who felt lonely were likely to have a higher risk for other diseases too, including diabetes, hypertension and depression. They are less likely to be physically active and more likely to smoke. Even in mice, it has been repeatedly demonstrated that social isolation triggers memory deficit.

The Science Behind This…

One possible explanation is the reduced levels of BDNF, a molecule that produces many beneficial effects on brain functions. Reduced levels of BDNF have been found in postmortem Alzheimer’s brain samples. Another study with 3294 participants, showed that people with more companionship had higher serum BDNF level and a reduced risk for dementia.

Aerobic Exercise and Alzheimer’s

The strong correlation between exercise and Alzheimer’s has also been long known. For example, a study showed that people with lower fitness levels experience faster deterioration of vital nerve fibres in the brain. Research in mice has shown similar results!

An exciting new study examined the effects of aerobic exercise in 70 adults aged 55 or over who had beta-amyloid accumulation in the brain. Beta-amyloid is a protein that acts as a indicator of Alzheimer’s when it builds up to toxic levels. One group did aerobic exercise (at least a half-hour workout four to five times weekly), and another group did only flexibility training. Patients that did only flexibility training showed a larger reduction in the size and volume of their hippocampus – a memory-related brain region. Doctors are able to detect beta-amyloid levels early in some cases. However, at this point in time – there is little a doctor can do to stop dementia from progressing as there are no treatments available. If this research is replicated in larger trials it would suggest that giving these high-risk patients an exercise plan would be beneficial.

A Final Note

Alzheimer’s has risen exponentially in prevalence since it was first described in the early 1900s. Research still drives to understand the causes and effective treatments. But what we do know, is that there are modifiable risk factors, such as simple lifestyle choices which are very likely to contribute to this debilitating disease. Stay mentally active and exercise regularly if you want to hold on to those fond memories until your very last breath.

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