Dementia risk among smokers: Quitting protective, smoking reduction harmful

Smoking cessation appears to lower the risk of dementia as opposed to sustained smoking intensity, according to a study. However, cutting down on smoking may do more harm than good, as this approach is associated with a risk increase.

The study drew data from the National Health Insurance Service database of Korea and included participants aged at least 40 years who underwent biennial health examinations and had data on current smoking status at the first health examination.

Researchers grouped the participants according to the change in smoking intensity from baseline, as follows: quitters (stopped smoking), reducers I (decreased number of cigarettes smoked per day by ≥50 percent), reducers II (decreased number of cigarettes smoked per day by 20 percent to 50 percent), sustainers (maintained number of cigarettes smoked per day [decreased or increased by <20 percent]), or increasers (increased number of cigarettes smoked per day by ≥20 percent). These changes were assessed in relation to the primary outcome of newly diagnosed dementia.

The analysis included 789,532 participants (mean age 52.2 years, 95.8 percent men). Over a median follow-up of 6.3 years, 11,912 participants were diagnosed with dementia. Of these dementia cases, 8,800 were Alzheimer disease and 1,889 were vascular dementia.

Multivariable Cox proportional hazards regression showed that compared with sustainers, quitters had a significantly lower risk of dementia overall (adjusted hazard ratio [aHR], 0.92, 95 percent confidence interval [CI], 0.87–0.97).

Conversely, the risk of dementia relative to sustainers was significantly higher among reducers I (aHR, 1.25, 95 percent CI, 1.18–1.33) and increasers (aHR, 1.12, 95 percent CI, 1.06–1.18).

Results for Alzheimer disease and vascular dementia were consistent with that of overall dementia.

The present data highlight the importance of promoting smoking cessation to reduce the disease burden of dementia.