Clinical Manifestations

Individuals with Down syndrome (DS) have a 90% lifetime risk for symptomatic Alzheimer's disease. Yet, there is a 20+ year age range in when individuals with DS reach PET amyloid-beta (Aβ) positivity (i.e., centiloid (CL) ≥18). There is a critical need to identify factors associated with resistance (i.e., less than expected Aβ for age) and resilience (i.e., better than expected cognitive function given Aβ) in the DS community.

262 adults with DS (M=43.93, SD=9.29) in the Alzheimer Biomarker Consortium-Down syndrome underwent MRI and amyloid PET scans with [11C] PiB or [18F] florbetapir. A study partner reported on health history. Systolic blood pressure and BMI were obtained. Using multiple regression models, we examined the best fit function for association between: 1) age and Aβ, and 2) Aβ and cognitive performance, adjusted for premorbid intellectual disability level. We than calculated each participant's residual (i.e., difference between observed versus predicted value) to assess resistance to Aβ (defined as less than predicted Aβ for age) and resilience to cognitive impairment (defined as better than predicted cognition for Aβ). The modified Cued Recall Test and Down Syndrome Mental Status Exam were used as cognitive scores. The cardiovascular composite was based on the original and no-lab Framingham Risk Score (BMI ≥ 30, systolic blood pressure ≥ 130, use of statins, and presence of hypertension, hyperlipidemia, and diabetes).

In partial correlations adjusted for age, there was a significant positive association between the cardiovascular composite (r = .156, p = .016) and resistance score; higher cardiovascular composite was associated with greater than expected Aβ for age. At the item level, hyperlipidemia was associated with a 1.8 x higher likelihood of greater than expected Aβ for age (OR = 1.83, p = .047). There was not a significant correlation between the cardiovascular composite and the resilience scores.

Cardiovascular conditions may alter resistance to DSAD, including an earlier age of Aβ accumulation, and be an important target for delaying or preventing DSAD.