Serum Cholesterol and Incident Alzheimer's Disease: Findings from the Adult Changes in Thought Study.

OBJECTIVES: To evaluate associations between high-density lipoprotein cholesterol (HDL) and non-HDL-C levels at specific ages and subsequent Alzheimer's disease (AD) risk.

DESIGN: Prospective population-based cohort study.

SETTING: Adult Changes in Thought (ACT) Study.

PARTICIPANTS: Individuals aged 65 and older with no dementia at ACT Study entry. We identified separate, partially overlapping subcohorts of ACT participants who were eligible for each age band-specific analysis (50-59, n = 1,088; 60-69, n = 2,852; 70-79, n = 2,344; 80-89, n = 537).

MEASUREMENTS: Exposure consisted of clinical measures of total cholesterol (TC) and HDL-C from laboratory data during a given age band. Outcomes of incident AD were assessed post-age band using standard research diagnostic criteria. Statistical analyses used adjusted Cox proportional hazards regression models for each exposure and outcome pair within an age band. Cholesterol exposures were modeled using cubic splines.

RESULTS: For non-HDL-C, we found a statistically significant association with AD risk in the 60 to 69 (omnibus p = .005) and 70 to 79 (omnibus p = .04) age bands, suggesting a potential U-shaped relationship (greater risk at low and high levels). For example, in people aged 60 to 69, those with an average non-HDL-C level of 120 mg/DL had a 29% greater AD hazard (hazard ratio (HR)=1.29, 95% confidence interval (CI)=1.04-1.61) than those with an average non-HDL-C level of 160 mg/dL, whereas those with an average non-HDL-C level of 210 mg/dL had a 16% greater hazard (HR=1.16, 95% CI=1.01-1.33). We did not find a statistically significant association between HDL-C and AD risk.

CONCLUSION: People with low (120 mg/dL) and high (210 mg/dL) non-HDL-C levels during their 60s and 70s had modestly higher risk of AD than those with intermediate (160 mg/dL) levels. The extreme age bands (50s and 80s) had small sample sizes. J Am Geriatr Soc 66:2344-2352, 2018.