Middle aged people who are regular heavy smokers have over double the risk of developing Alzheimer’s disease and various forms of dementia later in life, Finnish researchers report in an article published today in the peer-reviewed medical journal Archives of Internal Medicine. The authors explain that smoking, and in this case specifically heavy smoking (at least two packs per day) has another addition to its long list of illnesses.

Prior studies had linked regular smoking to a lower risk of developing some neurodegenerative conditions, including Parkinson’s disease.

The authors wrote:

The link between smoking and risk of Alzheimer’s disease, the most common subtype of dementia, has been somewhat controversial, with some studies suggesting that smoking reduces the risk of cognitive impairment.

Minna Rusanen, M.D., of University of Eastern Finland and team examined information from a 1978-1985 health care system survey consisting of 21,123 participants. They were all aged between 50 and 60 years old. They were monitored for Alzheimer’s disease and vascular dementia from the beginning of 1994 to July 31, 2008.

Over an average follow-up period of 23 years, 25.4% (5,367) of them were diagnosed with dementia, of which 416 had vascular dementia and 1,136 had Alzheimer’s disease. Individuals who smoked more than 40 cigarettes per day had an overall higher risk of developing dementia, as well as an elevated risk for Alzheimer’s disease and vascular dementia, when compared to lifetime non-smokers and ex-smokers.

The researchers add that according to their findings, ex-smokers as well as moderate smokers – less than half a pack per day – did not have a higher risk compared to lifetime non-smokers.

The heavy smoking link was the same for all ethnic groups and both sexes.

The authors add that smoking has been proven to be a risk factor for stroke, and may raise vascular dementia risk via similar mechanisms. Oxidative stress and inflammation are exacerbated by smoking – two key factors in the development of Alzheimer’s disease.

They wrote:

It is possible that smoking affects the development of dementia via vascular and neurodegenerative pathways.

(conclusion) To our knowledge, this is the first study evaluating the amount of midlife smoking on long-term risk of dementia and dementia subtypes in a large multiethnic cohort,” they conclude. “Our study suggests that heavy smoking in middle age increases the risk of both Alzheimer’s disease and vascular dementia for men and women across different race groups. The large detrimental impact that smoking already has on public health has the potential to become even greater as the population worldwide ages and dementia prevalence increases.

“Heavy Smoking in Midlife and Long-term Risk of Alzheimer Disease and Vascular Dementia”
Minna Rusanen, MD; Miia Kivipelto, MD, PhD; Charles P. Quesenberry Jr, PhD; Jufen Zhou, MS; Rachel A. Whitmer, PhD
Arch Intern Med. Published online October 25, 2010. doi:10.1001/archinternmed.2010.393
Written by Christian Nordqvist