Statin Initiation and Dementia Incidence in a Large Health Care System From 1997 to 2020: A Target Trial Emulation Study.

Abstract

Background and objectives: Previous research of associations between statins and Alzheimer disease and Alzheimer disease-related dementias (AD/ADRDs) has been limited by short follow-up, small samples, and confounding. We aimed to estimate the association between the 1st statin prescription and incident AD/ADRD among members of a large population-based cohort of older adults.

Methods: We used a cohort study design emulating a target trial using data from Kaiser Permanente Northern California (KPNC), an integrated health care delivery system. Participants were born before 1951 and KPNC members for 4+ years during 1997-2010. Embedded subsamples included sociodemographic and genetic data. Statin initiators were matched at first prescription ("baseline") with up to 5 "noninitiators" based on age and low-density lipoprotein cholesterol (LDL-C). Participants with extreme propensity scores were excluded. The outcome was time to incident AD/ADRD diagnosis, censoring, or the administrative end of study (December 31, 2020). Cox proportional hazard models were used to estimate hazard ratios for statin initiation on AD/ADRD incidence. Follow-up time was divided at the first year of follow-up to account for increased AD/ADRD detection in the first year due to increased interaction with the health care system after a statin prescription.

Results: Among eligible participants (n = 705,061), 264,294 individuals (37.5% of eligible participants) initiated any statin during 2001-2010 ("initiators"), of whom 249,613 (94.4%) were matched with 255,937 unique noninitiators to create the analytic sample (322,358 unique participants; mean age at baseline = 67.4 years; 55.1% female). The average follow-up was 11.8 years. In the first year after initiating statins, AD/ADRD diagnoses were elevated by 46% (hazard ratio [HR] = 1.46, 95% CI 1.42-1.53) compared with noninitiators. After 1 year, statin initiators experienced no difference in AD/ADRD incidence (full sample: HR = 1.00, 95% CI 0.99-1.01; subsample with survey covariates: HR = 1.01, 95% CI 0.98-1.06; subsample with survey and genetic covariates: HR = 0.97, 95% CI 0.91-1.07). Adjustment for sociodemographic covariates and apolipoprotein E e4 allele count did not materially change the findings.

Discussion: In this large emulated target trial, statin initiation was inconsistent with more than a 3% increase or decrease in the hazard of AD/ADRD after the first year of follow-up. This intent-to-treat analysis does not directly quantify effects of long-term exposure to statins. Associations in the first year likely reflect increased medical observation immediately after statin initiation.

Classification of evidence: This emulated trial provides Class II evidence that statin initiation is not associated with AD/ADRD or AD incidence after the first year of follow-up.