People in the British study are in their 50s, far too young to know if the memory decline will translate into dementia when they're elderly.
But testing so far suggests that heavy smokers who survive smoking's bigger threats — lung cancer and heart disease — into old age may be at risk of serious cognitive decline, the researchers report Thursday in the American Journal of Public Health.
Other research already has labeled smoking a risk factor for dementia. One cause of dementia is restricted blood flow in the brain, and smoking is linked to narrowed arteries and silent mini-strokes that choke that blood supply.
The latest study is part of a broader tracking of the health of thousands of people born in Britain in 1946. A sample of the study participants underwent tests of memory, concentration and visual speed at age 43 and again at age 53.
Heavy smoking — more than 20 cigarettes a day — was associated with faster declines in verbal memory and visual speed, although the declines were small, concluded researchers from University College London.
They will continue tracking the study participants to see how their brains fare as they age.