Alzheimer’s - is it a result of high body weight(obesity)!!!

Fig-1: retrieved from https://www.neura.edu.au/health-area/dementia-ageing/

Hello guys and welcome to med talks India, where we talk about interesting medical facts in simpler ways. So without wasting time let’s talk.

Today’s topic is memory loss and its relation to obesity

Now before going in detail of this topic, let’s discuss about some medical terms that we are going to use

First one is obesity: it is a disorder of excessive body fat as we all know

Second one is dementia: it is a disorder of brain that results in limited social skills, bizarre thinking and forgetfulness or memory loss. Alzheimer’s disease accounts for around 70-80% of all dementia patients which is mostly seen in older ages

Third one is body mass index or simply BMI which is presentation of body weight in relation to height. It has a formula BMI= weight in kg divided by square of height in meter. Normal range of BMI is 20-25. People lying in 25-30 range are called overweight, between 30-35 are mild obesity, 35-40 are moderate obesity and more than 40 are severe obesity also called as morbid or deadly obesity.

I believe everyone is more or less aware about the fact that obesity is associated with many chronic life-threatening diseases which includes diabetes, Heart attack, brain stroke etc. to name few. But the matter to worry is that this list is continuously expanding and the most recent member to be included in it is dementia. In a recent study it was found that around 10 crore children and 60 crore adults are obese worldwide. At the same time around 1 crore people are affected with dementia every year in India only.

Here the point to note is, while obesity is a potentially reversible condition, dementia is neither reversible nor treatable.

But the question is, how obesity is related to dementia?

In a study undertaken in Israel where 9000 men between the ages of 40-70 years were observed for a period of around 30 years. At the end of this study it was found that the tendency of developing dementia was higher in people with either very low or very high BMI. [1]

To confirm and re-evaluate the results of this research many studies were undertaken latter. But the results of one of the biggest studies among them were shockingly unbelievable. That study was undertaken on around 20 lakh middle aged people and they were observed for around 9-10 years. The researchers found that people with very low BMI had a 34% higher risk of developing dementia. But the risk goes on decreasing with increase of BMI with 29% risk reduction in very obese people which was completely contradicting the previous finding. [2]

Hence a large scale study was designed which included around 13 lakh people. But the specialty of this study was, those people were distributed in 39 different groups called cohorts in different countries of USA, Europe and Asia. These people were observed for around 20-30 years. The results not only confirmed the findings of the first study to be true, but also explained the errors of the second one. What they found was, with every 5 units rise in BMI beyond normal limits, there was 16-33% increased risk of dementia development. But at the same time they concluded that, obese people are more prone to developing metabolic diseases like diabetes which may result in rapid loss of body weight and hence low BMI. Hence the chance of including these low BMI people in the list of dementia patients increased, who were obese in their middle ages. This error was due to relatively shorter period of observation which was less than 10 years in second study. And this was contributed by the fact that obese people have a shorter life-span due to diseases they develop giving them less chance to live long enough for dementia.

Scientists named this as reverse-causation phenomenon and the paper was published in a reputed journal in the year 2017. [3]

Finally the conclusion can be summarized as:

1. High BMI or simply obesity increases the chance of dementia development in older ages

2. With every 5 units increase in BMI in Middle Ages there is 20-30% more chance of future dementia

3. Associated metabolic disorders like diabetes, hypertension etc. can be contributory to dementia development

So I would like to appeal to all young and middle aged people to try and maintain a healthy body weight so that the BMI will come in the range of 20 to 25 kg per meter square, as obesity is a far more dangerous devil than it is thought to be. Thank you and be healthy

References:

1.       Ravona-Springer R, Schnaider-Beeri M, Goldbourt U. Body weight variability in midlife and risk for dementia in old age. Neurology. 2013;80(18):1677-1683.

2.       Qizilbash N, Gregson J, Johnson M, Pearce N, Douglas I, Wing K et al. BMI and risk of dementia in two million people over two decades: a retrospective cohort study. 2017.

3.       Kivimäki M, Luukkonen R, Batty G, Ferrie J, Pentti J, Nyberg S et al. Body mass index and risk of dementia: Analysis of individual-level data from 1.3 million individuals. Alzheimer's & Dementia. 2017;.