Insulin Resistance & Chronic Inflammation

Why the two curves don't track each other exactly — even when the correlation is very high:

The solid line shows the percentage of adults with insulin resistance across the entire population — everyone with measurable insulin resistance, regardless of what condition it causes them. Because insulin resistance is the upstream root cause of many different diseases — type 2 diabetes, fatty liver, cardiovascular disease, cognitive decline and more — this curve rises relatively gradually as it reflects a burden shared across all of those outcomes.

The dotted line shows the estimated prevalence of adults with clinically significant chronic low-grade inflammation, defined as persistently elevated inflammatory biomarkers (hs-CRP >3 mg/L, elevated IL-6 or TNF-α) in the absence of acute infection. This curve tracks closely with insulin resistance because IR is a primary driver — but it also captures individuals with inflammatory conditions from other causes. Both lines have risen markedly since 1975, reflecting the same underlying shift in metabolic health.

The r value (e.g. r = 0.96) is a correlation coefficient. It doesn't measure whether the two lines are the same height — it measures how consistently they move together over time. An r of 0.96 means that 96% of the rise in chronic low-grade inflammation over the past five decades is statistically explained by the parallel rise in insulin resistance.

What the r value tells you:
0.50–0.70 — Modest connection. The two trends are related but other factors are involved.
0.70–0.90 — Strong connection. Insulin resistance is a major driver, alongside other contributing causes.
0.90 and above — Dominant connection. Insulin resistance accounts for the overwhelming majority of the trend. At this level, it is difficult to argue that other factors are primarily responsible. The values seen across these studies — consistently 0.90 to 0.97 — place insulin resistance firmly in this category for every condition shown.