Unsupervised Learning Analysis of Triglycerides, Inflammation, Cholesterol, and the Risks of Incident Cardiovascular...

Traditional cardiovascular risk assessment entails investigator-defined exposure levels and individual risk markers in multivariable analysis. We sought to determine whether an alternative unbiased learning analysis might provide further insights into vascular risk.

We conducted an unsupervised learning (k-means cluster) analysis in the Women's Health Study (N=26 443) using baseline levels of triglycerides, high-sensitivity C-reactive protein, and low-density lipoprotein cholesterol to form novel exposures. We then evaluated cluster-based risk of incident coronary, cerebrovascular, and limb events using the Kaplan-Meier method and multivariable Cox models, followed by comparison with established clinical biomarker thresholds. Finally, we illustrated clinical applicability to a nonvascular outcome (type 2 diabetes).

Four clusters emerged and were named according to aggregate biomarker profiles: Cluster 1 ("healthy," n=12 101), cluster 2 ("hypercholesterolemic," n=7424), cluster 3 ("inflammatory," n=5056), and cluster 4 ("triglyceride-rich," n=1862). Triglyceride-rich cluster identity conferred the highest risk of future cardiovascular events (adjusted hazard ratio [HR_adj], 2.24 [95% CI, 1.93-2.60]) compared with those in the healthy cluster (reference group). Risk was intermediate in the hypercholesterolemic (predominantly elevated low-density lipoprotein cholesterol) and inflammatory (predominantly elevated high-sensitivity C-reactive protein) clusters (HR_adj, 1.44 [95% CI, 1.28-1.61]; and 1.54 [95% CI, 1.35-1.75], respectively). Clustering yielded stronger total cardiovascular disease risk associations than traditionally defined mixed dyslipidemia with modest improvement in reclassification statistics. Cluster identities also predicted incident type 2 diabetes, with the greatest risk among the triglyceride-rich cluster (HR_adj, 3.78 [95% CI, 3.29-4.35]).

Unsupervised learning analyses demonstrated associations that may be useful when refining cardiovascular risk and may inform atherosclerosis development in healthy individuals better than traditional classification methods.

URL: https://clinicaltrials.gov; Unique identifier: NCT00000479.