Association between low-density lipoprotein cholesterol and the risk of bronchial asthma: a case-control study

This study investigated the association between low-density lipoprotein cholesterol (LDL-C) and the risk of bronchial asthma. A retrospective case-control study was conducted, including 944 patients with asthma and 1,580 controls. Subjects were divided by median LDL-C into high and low groups. Propensity score matching (PSM 1:1) was performed for age, gender, body mass index (BMI), family history, smoking, alcohol use, and diabetes, yielding 1,043 participants in each LDL-C group. Multivariate binary logistic regression was used post-PSM to assess the independent association between LDL-C and asthma risk. Stratified and interaction analyses were performed by age, gender, and BMI. Restricted cubic splines (RCS) with logistic regression were used to evaluate non-linear relationships and identify exploratory turning points. After PSM, multivariate analysis indicated LDL-C was independently associated with asthma risk (OR: 1.75, 95% CI: 1.47-2.09). Stratified analysis showed LDL-C was significantly associated with asthma risk in individuals aged <60 years (OR: 2.61, 95% CI: 2.04-3.36) but not in those ≥60 years (OR: 1.16, 95% CI: 0.91-1.49). Interaction analysis confirmed a significant difference between age strata (p < 0.05). No significant interactions were found for gender or BMI (p > 0.05). RCS analysis suggested a non-linear relationship, with an exploratory turning point at 3.62 mmol/L. This non-linearity was also present in both age subgroups (p < 0.05). Higher LDL-C was independently associated with asthma risk, and the estimated association curve was initially relatively stable with rising LDL-C and then became steeper once LDL-C exceeded 3.62 mmol/L.