My takehome message from this is that even in your middle age, stopping smoking is good for you. It's not too late.
The study presented 4 key findings, the group writes.
First, smoking in middle age was associated with memory deficit and decline in reasoning abilities. At phase 5, after adjustment for sex, age, socioeconomic differences, health behaviors, and health measures, current smokers vs participants who had never smoked had a 37% greater risk of being in the lowest quintile of cognitive function (odds ratio, 1.37; 95% confidence interval [CI], 1.10 - 1.73).
Second, compared with smokers, long-term ex-smokers (those who had stopped smoking before the beginning of the study) had a 30% lower risk for poor vocabulary and low verbal fluency.
Third, giving up smoking in midlife was accompanied by improvement in health habits such as drinking less alcohol, being more active, and eating more fruits and vegetables.
Fourth, compared with nonsmokers, smokers were more likely to die by phase 7 (an average 17.1 years of follow-up) or not to participate in cognitive tests, suggesting that nonparticipants had cognitive deficits and that, thus, the association between smoking and cognition in late midlife could be underestimated.
These findings are important because other research suggests that individuals with mild cognitive impairment progress to clinically diagnosed dementia at an accelerated rate, the group writes.