Smoking in middle age linked to higher risk of dementia

If you were to ask 10 former smokers what motivated them to finally quit, you'd probably get 10 different answers. Perhaps it was the family hike cut short by their hacking cough. Or maybe it was seeing a friend with COPD struggling for breath. For my husband, the most persuasive factor turned out to be his growing disgust with big tobacco. He'd finally had enough when the tobacco CEOs testified before Congress that nicotine was not addictive. If you haven't yet found a personal motivation strong enough to help you quit (no easy feat), a new study suggests another health risk that may resonate: more than double the chance of dementia for those who smoke heavily in middle age.

Researchers have long wondered about a link between smoking and dementia, as inhaling cigarette smoke has wide-ranging effects on the body. Besides damaging your lungs and depriving your cells of oxygen, it also exposes your body to more than 4,000 chemicals, many of which are poisons.

Previous research has suggested that smoking may increase the risk of Alzheimer's disease and other forms of dementia. However, most studies have been too small or too short to reliably spot a difference in risk. And many have focused mainly on white men and women, despite the fact that dementia risk varies among ethnic groups.

Researchers have now done a large, long-term study looking at the risk of dementia among 21,123 ethnically diverse smokers and nonsmokers in the United States. The participants had medical exams and were interviewed about their health and health habits, including smoking, between 1978 and 1985, when they were 50 to 60 years old. Two decades later, the researchers checked whether they'd been diagnosed with dementia.

The link between smoking and dementia was equally strong for men and women, and people of different ethnic groups. But, notably, former smokers who'd quit before they reached middle age weren't any more likely to get dementia than lifelong nonsmokers.

This type of study can't show cause and effect, so we can't be certain that smoking was what increased people's risk of dementia. However, the researchers did take into account several other factors known to influence a person's chance of getting dementia, including their age, sex, education, race, body mass index (BMI), alcohol consumption, risk of stroke, and whether they had high blood pressure, high cholesterol, diabetes, or heart disease. This makes the link between smoking and dementia considerably stronger.

What you need to know. This study suggests yet another compelling reason to give up smoking, showing that people who smoke a half a pack or more a day in middle age are more likely to get dementia. But the good news is that those who stopped before middle age had no higher risk.

If you're ready to give up cigarettes, you can find extra support and motivation on November 18, this year's Great American Smokeout. The American Cancer Society provides details on this year's event, as well as tools and resources to help you stub out cigarettes for good. You can also read our ratings  (available to subscribers) on what treatments can boost your odds of success.

—Sophie Ramsey, patient editor, BMJ Group

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