Abstract Body (Do not enter title and authors here): Background: More than 50% of US young adults are estimated to have low-density lipoprotein cholesterol (LDL-C) ≥100 mg/dL. Compared to older adults, young adults are less likely to be screened and have lower rates of treatment and control for elevated LDL-C.

Research Questions: Among young adults, what are the patterns of follow-up lipid testing and timing of statin initiation after an initial LDL-C ≥100 mg/dL? What are the temporal trends of lipid testing and statin initiation over 13 years?

Methods: We identified members of Kaiser Permanente Southern California aged 18-39 years with their first elevated LDL-C (≥100 mg/dL) measurement (index) between 2008-2020. We examined statin initiation within 1, 2 and 5 years after the index test by high 10-year (≥7.5%) or 30-year (≥20%) estimated atherosclerotic cardiovascular disease (ASCVD) risk and further stratified by index LDL-C level. We calculated the proportion of young adults with a follow-up LDL-C test within 1, 2 and 5 years by index LDL-C level. We also assessed the temporal trends of follow-up testing and statin initiation within 1 year of an elevated LDL-C measure from 2008 to 2020 among 2 high risk subgroups: 1) LDL-C ≥190 mg/dL, and 2) LDL-C 160-189 mg/dL and a high 10- or 30-year ASCVD risk.

Results: Among 771,681 young adults, 66%, 25%, 7% and 2% had an index LDL-C 100-129, 130-159, 160-189, and ≥190 mg/dL, respectively. Among young adults with LDL-C ≥190 mg/dL, 28.4%, 33.5%, and 45.7% initiated a statin within 1, 2 and 5 years, respectively. Among those with high 10- or 30-year ASCVD risk, 15.2%, 20.5% and 34.4% initiated a statin within 1, 2 and 5 years, respectively, among those with index LDL-C 100-129 mg/dL, while 43.5%, 49.4% and 60.7% initiated a statin within 1, 2 and 5 years among those with index LDL-C LDL ≥190 mg/dL. The proportion of young adults receiving a follow-up lipid test declined between 2008 and 2019, from 47.8% to 38.4% among those with LDL-C ≥190 mg/dL, and from 52.1% to 27.5% among those with LDL-C 160–189 mg/dL and high 10- or 30-year risk (Figure). Statin initiation also declined in both high-risk subgroups from 32.3% and 33.4% in 2008 to 19.3% and 14.1% in 2020, respectively.

Conclusion: These findings suggest persistent care gaps in lipid management of young adults, particularly during a critical window for early intervention. Addressing these gaps may help reduce cumulative LDL-C exposure and prevent future ASCVD events.