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Up to 40% of all dementia cases may be preventable, primarily by treating or acting on well-established cardiovascular risk factors such as diabetes, hypertension, smoking, and physical inactivity. Whether physical inactivity is associated with risk of non-Alzheimer's dementia – a disease influenced by cardiovascular risk factors – and whether a given association differs for physical activity in leisure time and at work remains unknown. We conducted a prospective cohort study including 117,616 individuals from the Copenhagen General Population Study and the Copenhagen City Heart Study with up to 43 years of follow-up. Multifactorially adjusted hazard ratios for low versus high physical activity at leisure time was 1.60 (95% confidence interval 1.40–1.83) for non-Alzheimer's dementia and 0.94 (0.80–1.11) for Alzheimer's disease. Corresponding values for non-Alzheimer's dementia after additional adjustment for physical activity at work or apolipoprotein E (APOE) genotype were 1.60 (1.40–1.83) and 1.82 (1.34–2.15). Multifactorially and APOE adjusted hazard ratios for high versus low physical activity at work were 1.50 (1.10–2.05) for non-Alzheimer's dementia and 1.62 (1.14–2.31) for Alzheimer's disease. When combining the two types of physical activity, physical activity in leisure time had the strongest relationship with risk of non-Alzheimer's dementia. Physical inactivity in leisure time was associated with increased risk of non-Alzheimer's dementia, independent of modifiable risk factors and physical activity at work. The present study thus provides evidence for public health advice on physical activity in leisure time for the vascular part of dementia. [Display omitted] • Prospective study including 117,616 individuals from the general Danish population. • Up to 43 years of follow-up with no losses to follow-up. • Low leisure physical activity associates with high risk of non-Alzheimer's dementia. • Leisure versus work physical activity is superior in predicting risk. • Public health advice on physical activity may prevent non-Alzheimer's dementia. [ABSTRACT FROM AUTHOR]

Introduction: We tested the hypothesis that low plasma complement C3 is observationally and genetically associated with high risk of Alzheimer's disease (AD). Methods: We studied 95,442 individuals enrolled in the Copenhagen General Population Study. In genetic analyses, we further included 8367 individuals from the Copenhagen City Heart Study. In the two studies, 1189 and 35 developed AD during median 8 years follow‐up. Results: The multifactorially adjusted hazard ratio for risk of AD for a one standard deviation lower levels of complement C3 was 1.11 (95% confidence interval: 1.04–1.19) in all individuals and 1.66 (1.33–2.07) in APOE ε44 carriers. In Mendelian randomization, the corresponding genetic estimates were 1.66 (1.05–2.63) overall and 1.99 (0.52–7.65) in APOE ε44 carriers. Discussion: Low baseline levels of complement C3 were associated with high risk of AD. The risk was amplified in APOE ε44 highly susceptible individuals, and these findings were substantiated by a Mendelian randomization approach, potentially implying causality. Based on these findings, we present and thoroughly discuss an updated Alzheimer hypothesis incorporating low complement C3 levels. [ABSTRACT FROM AUTHOR]

Dementia is one of the major causes of disability in later life, and ischemic heart disease is a leading cause of morbidity and mortality. Apolipoprotein E (apoE) plays a pivotal role in lipoprotein metabolism in the brain and in the periphery, and is implicated in both dementia and ischemic heart disease. Peripherally, liver-derived apoE is the main source of plasma apoE. Approximately half of plasma apoE is associated with triglyceride-rich lipoproteins, where apoE serves as the main ligand for the low density lipoprotein (LDL) receptor and the LDL receptor Related Protein (LRP). In the brain, apoE is produced mainly by astrocytes. Astrocyte-derived apoE is pivotal for cerebral cholesterol metabolism and clearance of β-amyloid, a major pathological hallmark of Alzheimer disease. Plasma levels of apoE and other lipids and lipoproteins are under strong genetic influence by the APOE polymorphism, and the ε4 allele is a strong genetic risk factor for Alzheimer disease. The characteristics of the APOE polymorphism thus suggest the qualitative importance of apoE, whereas studies of familial absolute apoE deficiency suggest a quantitative importance of plasma apoE levels in lipid metabolism. Whether plasma levels of apoE are associated with increased risk of dementia and ischemic heart disease, and whether these associations are independent of the APOE polymorphism and of lipids and lipoproteins has only recently been established. The aim of this review is to summarize and discuss the current epidemiological and biological evidence for an association of plasma levels of apoE with risk of dementia and ischemic heart disease. [ABSTRACT FROM AUTHOR]