Forskningsartikler

Background
Smoking is considered a risk factor for dementia. Nevertheless, uncertainty regarding the associations with dementia subtypes and the effects of quitting remains. In this large longitudinal population-based cohort study, we investigated smoking as an independent risk factor for all-cause dementia. Second, we investigated the associations with dementia subtypes.

Methods
We included participants from the Trøndelag Health Study (HUNT) and collected their smoking status at baseline (HUNT2, 1995-97). We assessed cognitive status at follow-up two decades later (HUNT4 70+, 2017-19, N = 8,532) and collected pack-years. We handled missing data with multiple imputations and estimated relative risks (RRs) with Poisson regression after adjustment for covariates and stratification by age and sex.

Results
Current smokers had a 31% increased dementia risk (RR 1.31, 95% confidence interval (CI) 1.12–1.52), women <85 at follow-up had a 54% increased risk (RR 1.54, 95% CI 1.20–1.98), and men <85 had a 36% increased risk (RR 1.36, 95% CI 1.01–1.82). We found no associations in persons 85+. Current smokers had an increased risk for vascular dementia but not for Alzheimer’s dementia. Pack-years were not associated with increased dementia risk, and former smoking was only associated with vascular dementia in men.

Conclusions
Current smoking was associated with an increased risk of dementia. Among those 85+ at follow-up, being a smoker 20+ years earlier was not associated with an increased risk of dementia, probably because death was a competing risk. In former smokers, there were no significant associations with dementia. Our results add to the literature an optimism about the effects of changing smoking habits and may encourage smoking cessation.

Christian Myrstad, Marie Larssen, Bo Engdahl & Geir Selbæk

Abstarct:

The prevalence of Alzheimer’s disease neuropathological changes (ADNCs), the leading cause of cognitive impairment, remains uncertain. Recent blood-based biomarkers enable scalable assessment of ADNCs¹. Here we measured phosphorylated tau at threonine 217 in 11,486 plasma samples from a Norwegian population-based cohort of individuals over 57 years of age as a surrogate marker for ADNCs. The estimated prevalence of ADNCs increased with age, from less than 8% in people 58–69.9 years of age to 65.2% in those over 90 years of age. Among participants aged 70 years or older, 10% had preclinical Alzheimer’s disease, 10.4% had prodromal Alzheimer’s disease and 9.8% had Alzheimer’s disease dementia. Furthermore, among those 70 years of age or older, ADNCs were present in 60% of people with dementia, in 32.6% of those with mild cognitive impairment and in 23.5% of the cognitively unimpaired group. Our findings suggest a higher prevalence of Alzheimer’s disease dementia in older individuals and a lower prevalence of preclinical Alzheimer’s disease in younger groups than previously estimated.

Dag Aarsland, Anita Lenora Sunde, Diego A. Tovar-Rios, Antoine Leuzy, Tormod Fladby, Henrik Zetterberg, Kaj Blennow, Kübra Tan, Giovanni De Santis, Yara Yakoub, Burak Arslan, Hanna Huber, Ilaria Pola, Lana Grötschel, Guglielmo Di Molfetta, Håvard K. Skjellegrind, Geir Selbaek & Nicholas J. Ashton