Is Smoking Good or Bad for Dementia Prevention?

Learn about the connection between smoking and the risk of developing Alzheimer’s disease and vascular dementia.

Paul is not the first to ask whether smoking prevents dementia or increases risk. Some widespread misinformation on this matter has clouded public understanding. The most authoritative answer is that smoking significantly increases the risk of developing dementia.

Smoking is still very common in the United States and around the world. According to recent statistics, about 8 out of every 100 United States adults older than 64 are current smokers. Strangely, this is lower than the rate of smokers among US adults age 45 to 64, which is twice as high: 16 percent.

Why are there fewer smokers among the older adult population? Cigarette smoking, which is the leading cause of preventable disease and death in the US, results in earlier death. Once deceased, the former smokers are no longer counted in the statistics.

Research Studies on Smoking and Alzheimer’s

Early Studies Were Biased

Smoking is linked with heart and lung disease, but what about the relationship between smoking and dementia? Early studies exploring the risk for dementia among smokers concluded that smoking actually decreased the likelihood of developing Alzheimer’s disease. Later reviews have suggested that these studies were biased, possibly because of researchers’ connections to the tobacco industry. If smoking reduces the risk of dementia in later years, it accomplishes this by shortening life…but that is not a very comforting thought.

Recent Research

Using reliable study approaches, recent research estimates that current smokers have a 30 percent to 75 percent greater risk for developing dementia when compared with nonsmokers. One analysis of this data suggests that 14 percent of Alzheimer’s disease cases can be attributed to smoking. This is good news, in a certain way, because smoking is a lifestyle choice and therefore considered a modifiable risk factor.

Why Does Smoking Increase Alzheimer’s Risk?

The dangerous brain consequences of smoking are probably linked with smoking’s effects on the brain’s blood vessels. Smoking increases circulating levels of a blood chemical called homocysteine, which is toxic to the arteries. Increased homocysteine levels have been linked with increased risk for stroke and dementia. Smokers’ arteries are damaged by atherosclerosis at an earlier age, and this is very dangerous to the brain, which relies upon blood flow for nutrients and oxygen.

Smoking, furthermore, is associated with increased oxidative stress, a damaging effect that results in increased inflammation and the death of brain cells. Smoking is considered an additive risk factor, contributing additional risk to that resulting from other health features. Individuals already at increased risk for dementia as a result of having the e4 version of the APOE gene face even greater risk if they are current smokers.

Researchers warn of an additional concern, the danger of exposure to second-hand smoke. Although not so damaging as direct exposure, one study evaluating the effect of second-hand smoke found that dementia risk was increased by more than 25 percent and that longer duration and greater frequency of exposure carried increased risk.

Approaches to Stop Smoking

Since smoking is a modifiable risk factor, smoking cessation is of potential benefit to brain health. The increased risk of developing dementia, particularly Alzheimer’s disease and vascular dementia, is linked with current smoking, and smoking cessation is a risk reducer.

There are many effective approaches to smoking cessation. Societal interventions have included the creation of smoke-free public places and workplaces, the widespread availability of tobacco cessation programs, the education of health care providers in effective cessation approaches such as the “brief advice” intervention, taxation of tobacco products, clear labeling indicating tobacco’s health hazards, and bans on tobacco advertising.

Interventions available for individuals include psychotherapy and peer-support services, medications to reduce craving (bupropion sustained release, varenicline), and nicotine replacement via lozenge, gum, patch, nasal spray, or inhaler. The majority of smokers express a wish to quit. At any age, cessation is beneficial to health, and the mortality rates of cigarette smokers who quit before age 35 are similar to those of people who never smoked.