Association between planetary health diet index and lung cancer risk in 106,542 participants: a prospective cohort...

The Planetary Health Diet Index (PHDI) is a validated tool for assessing adherence to the Planetary Health Diet (PHD)-a dietary pattern designed to address both human wellness and environmental sustainability. However, limited studies have specifically investigated the association between PHDI and lung cancer susceptibility-a leading global cancer mortality cause. Our study intends to explore this potential association.

Data for this analysis were derived from the prospective cohort of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The PHDI was calculated for each participant to quantify their adherence to the target dietary pattern. Cox proportional hazards regression models were applied to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between PHDI and the incidence of lung cancer and its distinct subtypes. Subgroup analyses were conducted to identify potential effect modifiers that might influence the observed association, while sensitivity analyses were performed to verify the robustness and stability of the study findings.

Over a follow-up period of 8.8 years, 1,846 lung cancer cases were identified among 106,542 participants. In the fully adjusted model, participants in the highest quartile (Quartile 4) of the PHDI had a 29% lower lung cancer risk compared to those in the lowest quartile (Quartile 1) (HR _{Quartile 4 vs Quartile 1}: 0.71, 95% CI: 0.62, 0.81; P _trend < 0.001). This inverse association was consistent across both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Restricted cubic spline plots revealed a non-linear inverse dose-response relationship between PHDI and lung cancer risk (P _non-linear: 0.043) as well as NSCLC risk (P _non-linear: 0.035), whereas a linear inverse association was observed for SCLC (P _non-linear: 0.956). No significant effect modification was detected in subgroup analyses, and the core findings remained stable and reliable following multiple sensitivity analyses.

Our findings suggest that higher PHDI is inversely associated with lung cancer risk and its subtypes (NSCLC and SCLC), supporting the potential of PHD as a dietary strategy for lung cancer prevention.