Why quitting smoking in midlife could save your brain later.

I hate smoking. I hate seeing other people smoke, especially young people. Smoking kills. The toxins contribute to heart disease and cancer and stroke.

It also affects our brains.

We all see the messages about why smoking is bad for us. Yet, despite many of us expressing a wish not to smoke, the choice of not smoking remains still too hard for many who prefer to carry on, despite the knowledge that yes they may have an increased risk of lung and throat cancer. And it is frustrating that you are continue to meet people who have lived to a ripe old age who have smoked several packets a day all their lives who will brightly tell you that it hasn’t done them any harm. There are always going to be those who dodge the bullet. But not everyone does.

Does the thought that smoking increases your risk of developing dementia make you think any harder about why it is a good idea to stop?

Heavy smoking in middle age increases the risk of Alzheimer’s disease and vascular dementia in men and women across different age groups. Their risk is doubled for developing a form of dementia within a twenty year period. This was the finding of a study from Finland recently published in JAMA, Archives of Internal Medicine. They analysed the data from over 21000 multiethnic participants who took part in a survey conducted between 1978 and 1985 when aged between 50 to 60 years. Then from 1994 to 2008 when the average age of this cohort was 72 years, they tracked the number of diagnoses of dementia, Alzheimer’s disease and vascular dementia in the group.

Over the 23-year follow up of these 21,000 people, 25% were subsequently diagnosed with dementia. The heaviest smokers had the greatest risk. Compared to non-smokers, those smokers who averaged two packs a day had a greater risk of dementia overall and also of the various forms of dementia. i.e. Alzheimer’s disease and vascular dementia. Those who had given up smoking and those who smoked less than half a packet a day did not appear to be at increased risk. There was a no difference in the rates by race or sex.

The relevance of this study is that smoking is a double-edged sword. Smoking has long been a well-recognised risk factor for stroke and contributer to vascular dementia. Now it appears that smoking by its contribution to oxidative stress and inflammation, is of significance in the development of Alzheimer’s disease. Smoking through vascular and neurodegenerative pathways can contribute to different forms of dementia.

This is the first study to evaluate the amount of long-term smoking on long-term risk of dementia in all of its forms. As the world braces itself for the rising tide of dementia from ageing alone, the detrimental effect of smoking is going to become even more relevant.

Convinced yet?

Minna Rusanen; Miia Kivipelto; Charles P. Quesenberry, Jr; Jufen Zhou; Rachel A. Whitmer. Heavy Smoking in Midlife and Long-term Risk of Alzheimer Disease and Vascular Dementia. Archives of Internal Medicine, 2010; DOI: 10.1001/archinternmed.2010.393