Lower Serum Cholesterol Levels as a Risk Factor for Critical Illness Polyneuropathy: A matched Case-Control Study

Abstract

Abstract Background: Critical illness polyneuropathy (CIP) is a frequent and underdiagnosed phenomenon among intensive care unit patients. The lipophilic nature of neuronal synapses may result in the association of low serum cholesterol levels with a higher rate of CIP development. We aimed to investigate this issue in critically ill patients. Methods: All cases diagnosed with CIP in our tertiary care hospital between 2013 and 2017 were 1:1 matched with controls without the condition by age, sex, and ICD diagnoses. The main risk factor examined was the difference between initial and minimum serum cholesterol levels. Other predictors were serum markers of acute inflammation. Results: We included 67 cases and 67 controls (134 critically ill patients, 49% female, 46% medical). Minimum serum cholesterol levels were lower in the cases (median difference: -24, 95% CI [-39, -9], mg/dl). A conditional logistic regression model controlling for the patients’ length of CCU stay showed a 2.2% increase in odds (odds ratio 1.022, 95% CI [1.006, 1.037], p=0.007) for the development of CIP for every 1 mg/dl decrease in serum cholesterol levels between the initial and lowest serum concentrations. Cholesterol levels decreased more profoundly in cases than controls (median: -74 (IQR -115 to -24) vs. ‑22 (IQR -53 to 0), median difference: -36, 95% CI [-59, -13]), mg/dl). We found significant median differences across matched pairs in maximum serum C-reactive protein (8.9, 95% CI [4.56, 13.24], mg/dl), minimum albumin (-4.2, 95% CI [-6.7, -1.7], g/l) and lowest cholinesterase levels (-0.72, 95% CI [-1.05, -0.39], U/l). Conclusion: Lower minimum cholesterol levels and more pronounced decreases in cholesterol levels during critical care unit hospitalizations may be a risk factor for CIP.