Researchers from the University of Pennsylvania have identified a link between smoking and brain shrinkage, with indications that this change may raise the risk of dementia. The work appeared in the medRxiv preprint archive and was considered preliminary until it underwent formal peer review in a trusted journal.
Earlier studies consistently observed that smokers present smaller brain volumes than non-smokers. Yet a lingering question persisted: does smoking drive brain loss, or are individuals with naturally smaller brains more prone to smoke? In the latest study, scientists offered convincing evidence that smoking contributes to brain volume reduction, rather than the reverse.
The investigation involved more than 28,000 participants. Researchers drew on magnetic resonance imaging data from a large repository of genetic and medical information gathered in the United Kingdom, and then examined how smoking status related to brain measurements across the cohort.
The findings showed that smokers, on average, have reduced brain volumes compared with non-smokers. Moreover, for each additional pack smoked per year, there was an associated slight decline in gray matter volume of about 0.15 cubic centimeters. This pattern aligns with a dose response, suggesting a causal link between smoking intensity and brain shrinking.
Additional analyses indicated that individuals who stopped smoking a longer time ago tended to retain a bit more gray matter than those who quit more recently. In one year after quitting, gray matter volume appeared to rise by roughly 0.09 cubic centimeters, indicating potential, though partial, reversal of brain decline after cessation.
Reduced brain size has been connected to several neurological conditions, including Alzheimer’s disease. The study’s outcomes imply that smoking can directly raise the odds of developing dementia, a point echoed by the researchers as well as subsequent reviews of brain aging and cognitive health. The implications emphasize the importance of smoking cessation for those seeking to preserve brain integrity as they age in North America and beyond [Citation: University of Pennsylvania research team].