Association between the atherogenic index of plasma and time to onset of chronic lung disease: a nine-year prospective cohort study in China

Systemic inflammation and lipid metabolic disorders are increasingly recognized as key contributors to the pathogenesis of chronic lung disease (CLD). The atherogenic index of plasma (AIP), a marker of lipid imbalance, has been strongly linked to cardiovascular risk, yet its association with CLD remains underexplored. This study aimed to investigate the association between AIP and time to CLD onset using a prospective dataset ( n = 3,639) from the China Health and Retirement Longitudinal Study (2011–2020). Weighted Kaplan–Meier (KM) curves, accelerated failure time (AFT) models, and restricted cubic spline (RCS) analysis were used. Sensitivity analyses were conducted to assess the stability of the findings. During the follow-up period, 830 participants developed CLD. Weighted KM curves did not differ significantly across AIP tertiles ( p = 0.101). In Model 3, several factors were associated with shorter time to CLD onset (time ratios [TRs] < 1.00, p values < 0.05): smoking, retired status, treated dyslipidemia, and an elevated white blood cell count (> 10 × 10 9 /L). Conversely, high household income and high peak expiratory flow (PEF) were associated with longer time to CLD onset (TRs > 1.00, p values < 0.05). RCS analysis showed a U-shaped association with time to CLD onset (Model 3: p for overall = 0.027; p for nonlinearity = 0.007). The high AIP group had a shorter time to CLD onset than the low group (Model 3: TR = 0.95, 95% CI: 0.92–0.98, p < 0.001), with consistent findings in sensitivity analyses; the very high group did not differ significantly from the low group. The high, but not the very high, AIP group was associated with shorter time to CLD onset than the low group. The nonlinear pattern warrants independent validation. Not applicable.