Despite everything we know about the risk of smoking, it still remains a habit that many Canadians can't quit. Smoking has been shown to increase the risk of a myriad of diseases, with it being responsible for several million deaths worldwide. In addition, there are increases in cardiovascular and cancer-associated mortality.

This week in the Archives of Internal Medicine, a study looks at the risk of smoking and cognitive impairments such as Alzheimer's and vascular dementias.

Dementias typically have a long development time before there is a clinical diagnosis. If risk factors can be identified, then it allows us a way to intervene and remove the risk factor.

This study looks at smoking in early life and the possibility of developing dementia in later life. The goal of this study was to look at the association between the amount of mid-life smoking and long-term risk of all-cause dementia, Alzheimer's disease (AD) and vascular dementia (VD) two to three decades later in a large multi-ethnic cohort of health plan members.

The participants entered the study from 1978 through 1985, at ages 50 to 60. Dementia diagnosis was then tracked from 1994 to 2008, when the participants were about 72 year old or so.

What was found was 25.4% were diagnosed with dementia. Overall, they were older, had fewer years of education, and were more likely to be women. African Americans were more likely to have dementias and Asians were less likely. As well, a higher percentage of divorced, widowed or separated persons had dementias, as did never drinkers. But what about smoking?

Those who smoked more than two packs per day in middle age had an elevated risk of dementia overall and also of each subtype compared to non-smokers. The risks were dose-dependent, meaning the more they smoked the higher the risk.

The good news is that FORMER smokers or those who smoked less than half a pack a day did not appear to be at increased risk. These findings held for both sexes and race.

Smoking increases inflammation and oxidative stress, which are thought to be causative mechanisms in dementia. Smoking can impact on both the vascular and neurodegenerative pathways in the brain.

This is a modifiable risk factor. As the population ages, we will see more cases of dementia based on numbers entering the at-risk period. Here is a way for smokers to decrease their risks!