We already know that regular smoking can develop neurodegenerative conditions like Parkinson’s disease, but active middle-aged smokers are twice as much prone to the risk of developing Alzheimer’s disease and various forms of dementia later in their lives, Medical News quoted Finnish researchers.

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

Examining information for a period from 1994 to 2008, from a 1978-1985 health care system survey consisting of 21,123 participants, all aged between 50 and 60 years old, Minna Rusanen, M.D., of University of Eastern Finland and team came up with a few conclusions.

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. Researchers noted that those 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.

Smoking has also 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.

The research concluded that smoking therefore has the potential to become even greater as the population worldwide ages and dementia prevalence increases.