What does smoking do to your brain as you age?

Smoking increases the risk of dementia. Large global burden-of-disease studies (GBD 2019) recognise smoking as a modifiable risk factor for dementia, alongside high blood sugar and excess weight. Projections show that the number of people living with dementia worldwide will rise from 57 million in 2019 to 153 million in 2050, and smoking is one of the factors driving that increase.

On MRI scans, the brains of smokers look older than they actually are. A large British study of more than 31,000 participants showed that people with diabetes who also smoked had the most accelerated brain ageing. Those who quit smoking, drank less alcohol and exercised more had significantly less of that extra brain ageing. Smoking therefore makes the brain more vulnerable, especially in combination with other risk factors.

There is one notable exception: Parkinson's disease. Multiple studies show an inverse association. Declining smoking rates in the population are linked to a higher burden of Parkinson's disease. Researchers cite this as one of the drivers behind the expected 'Parkinson's pandemic', with the number of patients worldwide projected to reach 17 million by 2040. This association is at present purely a statistical one, not evidence that smoking actually prevents Parkinson's disease. The harmful effects of smoking outweigh this paradoxical signal.

Quitting smoking is concretely supported as a brain-protective measure. Multiple large health organisations recommend stopping smoking as one of the most important steps against cognitive decline and dementia. Research drawing on epidemiological data, animal experiments and intervention studies consistently points in the same direction: those who quit protect their brains.