Post‐diagnosis smoking habit change and incident dementia in cancer survivors

Abstract

AbstractINTRODUCTIONMany individuals change their smoking habits after cancer diagnosis. We aimed to evaluate the association of post‐diagnosis smoking habit change with incident dementia in cancer survivors.METHODSWe identified 558,127 individuals who were diagnosed with cancer at age ≥ 20 and survived for ≥ 3 years. Participants were classified into four groups: (1) sustained non‐smokers, (2) initiators/relapsers, (3) quitters, and (4) continuing smokers. Dementia risk in each group was assessed using a cause‐specific Cox model.RESULTSAfter cancer diagnosis, 2.3% of pre‐diagnosis non‐smokers initiated/relapsed into smoking, while 51.7% of pre‐diagnosis smokers quit smoking. Compared to sustained non‐smokers, multivariable‐adjusted risk of dementia was 29% higher among initiators/relapsers, 11% higher among quitters, and 31% higher among continuing smokers. Compared to continuing smokers, the risk was 15% lower among quitters.DISCUSSIONIn cancer survivors, smoking initiation/relapse was associated with increased risk of dementia, whereas smoking cessation was associated with decreased risk of dementia.Highlights Approximately half of pre‐diagnosis smokers quit smoking after a cancer diagnosis. Smoking cessation was associated with a 15% reduced risk of dementia. More than 2% of pre‐diagnosis non‐smokers initiated or relapsed into smoking after a cancer diagnosis. Smoking initiation/relapse was associated with a 29% elevated risk of dementia.