Alzheimer disease (AD) is a complex disorder with a strong heritable component. Amyloid pathology, vascular factors, and inflammation are postulated to be involved in its pathogenesis, but causality has not been established unequivocally.
To identify heritable traits in middle age that contribute to AD.
We used a proven family design, comparing middle-aged offspring with and without a parental history of AD. In such a design, the offspring under study are enriched for risk factors of AD but do not yet have the disease.
Two hundred six offspring of 92 families with a parental history of late-onset AD and 200 offspring of 97 families without a parental history of AD.
Main Outcome Measures
The APOE ε4 genotype, vascular factors, production capacity of pro- and anti-inflammatory cytokines upon stimulation with lipopolysaccharide, and circulating markers of inflammation. All outcome measures were assessed in the offspring only and not in the parental generation.
More offspring with a parental history of AD carried APOE ε4 than those without a parental history of the disease (47% vs 21%, P < .001). Those with a parental history of AD also had higher systolic blood pressures (P = .006), higher diastolic blood pressures (P < .001), and lower ankle brachial indices (P = .005) when compared with offspring without a family history of dementia. Production capacity of pro-inflammatory cytokines in offspring with a parental history of AD was also different, with higher levels of IL-1β (interleukin 1β) (P < .001), IL-1β to IL-1ra ratio (P < .001), tumor necrosis factor α (P = .008), IL-6 (P = .04), and interferon γ (P = .01). All of these positive associations were independent of APOE ε4 genotype.
Hypertension and the expression of an innate pro-inflammatory cytokine profile in middle age are early risk factors of AD in old age. For the offspring of affected families, it provides clues for screening and preventive strategies, of which blood pressure control can be implemented directly.