Nonlinear relationship associations between a lipid composite index and asthma in middle-aged women: a cross-sectional study from NHANES 2007-2016

Background Asthma demonstrates pronounced sex-based disparities, with adult females exhibiting a disproportionately higher disease burden. Although aberrant lipid metabolic profiles have been mechanistically linked to asthma pathogenesis, the specific association between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and asthma risk in women remains unclear. This study aims to investigate the relationship between NHHR and asthma risk in middle-aged women using a nationally representative U.S. population. Methods Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 2007-2016. A variety of statistical methods, such as multivariate logistic regression, smoothed curve fitting, threshold effects, and subgroup analyses, were applied to explore the relationship between NHHR and asthma risk. Results A total of 7,337 participants aged 30–65 years were included, with an asthma prevalence of 16.82%. After full adjustment for demographic, socioeconomic, lifestyle, and clinical factors, higher NHHR levels were positively associated with asthma risk (OR = 1.26, 95% CI: 1.01, 1.58). Smooth curve fitting demonstrated a nonlinear relationship with a threshold inflection point at Log10(NHHR) = 0.07 (corresponding to NHHR ≈ 1.17). Above this threshold, asthma risk increased significantly (OR = 1.78, 95% CI: 1.24–2.54). Subgroup analyses indicated a significant interaction by education level, with stronger associations observed among women with lower educational attainment. Conclusions Elevated NHHR is independently and nonlinearly associated with asthma risk in middle-aged women. The findings suggest that dysregulated lipid metabolism may contribute to asthma susceptibility, highlighting NHHR as a potential biomarker for metabolic-inflammatory crosstalk and in women’s respiratory health.