In recent years, the total number of smokers around the world has increased to over 1.3 billion, with the vast majority of smokers living in developing or underdeveloped countries. Smoking is associated with a legion of health problems, including but not limited to cancer, heart disease, stroke, lung diseases, diabetes, and chronic lung diseases. Smoking is bad for you, it really is — and we’re still discovering new ways it’s bad for you.

In a new study presented at the American Stroke Association’s International Stroke Conference 2022, a team of researchers announced that smoking also seems to affect your cognitive abilities.

“A person who smokes cigarettes regularly yet is otherwise healthy, without Type 2 diabetes or high blood pressure, is still at risk for poor brain health,” said Neal S. Parikh, M.D., M.S., senior author of the study and an assistant professor of neurology and neuroscience in the clinical and translational neuroscience unit at the Feil Family Brain and Mind Research Institute and the department of neurology at Weill Cornell Medicine in New York City.

Essentially, the researchers wanted to see whether smoking impairs brain function by itself — and it does. Parikh told ZME Science:

“Cognitive impairment and dementia pose substantial public health burdens. Identifying modifiable risk factors – things we can intervene upon using existing interventions, is critical. This specific study was designed to ask: do people who smoke who also have other risk factors for poor brain health, specifically hypertension and diabetes, experience a compounded effect of smoking?”

“Serum cotinine, a blood marker of cigarette smoking and exposure, was associated with worse cognitive performance on select tests. This means that people with higher blood levels of a nicotine derivative had worse brain health. This was not impacted by whether the person has hypertension or diabetes. This was a significant finding.”

Parikh and colleagues looked at data collected by the U.S. National Health and Nutrition Examination Survey (NHANES) — a program of research surveys conducted by the National Center for Health Statistics (NCHS) to assess the health and nutritional status of Americans. The program has been ongoing since the early 1960s.

The researchers examined data from 3,244 participants (average age 69). Out of them, 23% smoke. The participants took four tests to measure various cognitive abilities, including tasks that involved word recall, fluency, working memory, and processing.

While higher cotinine levels were not associated with significant differences in scores that measured memory and language fluency, they were associated with significantly worse scores on the Digit Symbol Substitution Test (DSST), a test that reflects multiple aspects of cognition, such as processing speed, attention, and working memory. The difference persisted even after researchers corrected for other conditions that could affect cognitive abilities.

“We were surprised to find that smoking does not act synergistically with high blood pressure or Type 2 diabetes to impact cognitive performance. To us, these results suggest that smoking has a strong enough influence on brain health independent of other health conditions. This means that smoking is bad for brain health even in people who don’t have other health conditions typically linked with poor brain health,” Parikh said.

Researchers say this is yet another argument to stop smoking, regardless of age. Smoking is a known modifiable risk for a number of conditions, but it’s not clear how people’s cognitive abilities would be affected after people stop smoking.

Researchers also emphasize that this is a correlational study and it didn’t establish a cause-effect relationship, although there are plausible mechanisms through which smoking could affect cognitive ability.

“We did not analyze causal pathways, but it is reasonable to speculate that vascular disease, such as stroke and other forms of silent brain vascular disease like silent strokes, may connect smoking to poor brain health.”

Next up, researchers want to focus on how to best target smoking in people at risk of dementia.

The study was presented at the American Stroke Association’s International Stroke Conference 2022.