Combined effect of obstructive sleep apnea and chronic smoking on cognitive impairment

Little is known about combined effect of obstructive sleep apnea (OSA) and chronic smoking on cognitive impairment. We aimed to determine whether smoking synergizes with OSA in deteriorating cognitive function and whether smoking cessation contributes to cognitive benefits.

One hundred and eighteen male patients were enrolled in the study and asked to complete neurocognitive function tests including Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), clock drawing test (CDT), and verbal fluency test (VFT). Variables of those neurocognitive function tests were analyzed with two factors: OSA and smoking.

After adjustment of potential confounding factors, an OSA-by-smoking interaction was found in CDT-C scores and a main smoking effect were showed in MoCA scores. Smoking patients with OSA had the worst performance in the four tests compared with the other three groups (smoking patients without OSA, non-smoking patients with and without OSA). Ex-smokers with OSA tended to perform better than current smokers, but still worse than never-smokers with OSA in those tests.

The results suggested that the coexistence of OSA and chronic smoking resulted in more pronounced cognitive deficits than either factor along. Smoking cessation may benefit cognitive function to some extents in patients with OSA.