Presence of a Synergistic Interaction Between Current Cigarette Smoking and Diabetes Mellitus on Development of Dementia in Older Adults

Article type: Research Article

Authors: Noguchi-Shinohara, Moeko^{a; b} | Hirako, Kohei^c | Fujiu, Makoto^d | Sagae, Masahiko^e | Samuta, Hikaru^e | Nakamura, Hiroyuki^f | Yamada, Masahito^{a; *}

Affiliations: [a] Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan | [b] Department of Preemptive Medicine for Dementia, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan | [c] Frontier Science and Social Co-creation Initiative, Kanazawa University, Kanazawa, Japan | [d] Faculty of Geosciences and Civil Engineering, Institute of Science and Engineering, Kanazawa University, Kanazawa, Japan | [e] Faculty of Economics and Management, Institute of Human and Social Sciences, Kanazawa University, Kanazawa, Japan | [f] Department of Environmental and Preventive Medicine, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan

Correspondence: [*] Correspondence to: Professor Masahito Yamada, MD, PhD, Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Sciences, 13-1 Takara-machi, Kanazawa 920 8640, Japan. Tel.: +81 76 265 2290; Fax: +81 76 265 4253; E-mail: m-yamada@med.kanazawa-u.ac.jp.

Abstract: Background:Both cigarette smoking and diabetes mellitus are well-established risk factors for development of dementia. However, the interaction between smoking and diabetes is yet unknown. Objective:In this study, we clarify association between smoking, diabetes, and dementia risk in older adults. Methods:Participants in this study included community residents aged 65 years and older who had participated in a health checkup in 2006, followed for 10 years (n = 9,403) and had long-term care insurance information data. Furthermore, the risk estimates of smoking status and diabetes diagnosis on dementia adjusted for the competing risk of death prior to dementia were analyzed. Results:During follow-up, 2,647 participants developed dementia. The smoking status–diabetes interaction on development of dementia was statistically significant (p≤0.001). Among those patients exposed to both factors, 17% of risk of development of dementia was attributable to the interaction of these factors. Current smokers with diabetes had significantly greater risks of development of dementia than never smokers without diabetes (reference): multivariable-adjusted risk of dementia in current smokers without diabetes (subdistribution hazard ratio [sHR], 1.25; 95% confidence interval [CI], 1.05–1.48); never smokers with diabetes (1.31, 1.16–1.47); and current smokers with diabetes (1.86, 1.39–2.48). However, no such association was noted for former smokers with and without diabetes. Conclusions:Current smoking, but not former smoking, was associated with increased risk of development of dementia in older adults with and without diabetes. Moreover, the synergistic effect of current smoking and diabetes on dementia was noted.

Keywords: Cigarette smoking, dementia, diabetes mellitus, insurance, long-term care

DOI: 10.3233/JAD-190340

Journal: Journal of Alzheimer's Disease, vol. 71, no. 3, pp. 833-840, 2019