Relationship of hyperlipidemia to comorbidities and lung function in COPD: Results of the COSYCONET cohort

Abstract

Although hyperlipidemia is common in COPD, its relationship to comorbidities, risk factors and lung function in COPD has not been studied in detail. Using the baseline data of the COSYCONET cohort we addressed this question. Data from 1746 COPD patients (GOLD stage 1-4; mean age 64.6 y, mean FEV1%pred 57%) were evaluated, focusing on the comorbidities hyperlipidemia, diabetes and cardiovascular complex (CVC; including arterial hypertension, cardiac failure, ischemic heart disease). Risk factors comprised age, gender, BMI, and packyears of smoking. The results of linear and logistic regression analyses were implemented into a path analysis model describing the multiple relationships between parameters. Hyperlipidemia (prevalence 42.9%) was associated with lower intrathoracic gas volume (ITGV) and higher forced expiratory volume in 1 second (FEV1) when adjusting for its multiple relationships to risk factors and other comorbidities. These findings were robust in various statistical analyses. The associations between comorbidities and risk factors were in accordance with previous findings, thereby underlining the validity of our data. In conclusion, hyperlipidemia was associated with less hyperinflation and airway obstruction in patients with COPD. This surprising result might be due to different COPD phenotypes in these patients or related to effects of medication.

Fig 1. Adjusted effects of hyperlipidemia on lung function.

The figure shows the differences between patients with and without hyperlipidemia for three selected lung function parameters representing airway obstruction, lung volume and alveolar gas exchange. These differences are based on multivariate regression analyses adjusting for age, gender, BMI and packyears, as major confounders some of which were different between groups. The circles represent mean values and the vertical bars 95% confidence intervals, showing that even after adjustment there were significant (p<0.05) differences in FEV₁ and ITGV.

Fig 2. Prevalence of hyperlipidemia versus diabetes and cardiovascular complex.

Diabetes and cardiovascular complex were associated with hyperlipidemia. Significant differences (p<0.001) were marked with (*).

Fig 3. Results of path analysis.

Final path analysis model comprising three layers: risk factors, comorbidities and lung function parameters. The structure only contains relationships which turned out to be statistically significant (p<0.05 each). Error terms of dependent variables have been omitted for the sake of clarity. Correlations between the independent variables are indicated by arched arrows.