Associations between the planetary health diet index and multiple long-term conditions among women and men: A prospective cohort study

BACKGROUND & AIMS: The Planetary Health Diet Index (PHDI) quantifies adherence to the EAT-Lancet reference diet, a diet beneficial for human and environmental health. While higher PHDI scores have been linked to lower risk of individual diseases and mortality, associations with multiple long-term conditions (MLTCs) remain unexplored. METHODS: We examined associations between the PHDI and MLTCs in 113,209 UK Biobank participants with ≥2 valid 24-h dietary recalls. PHDI scores (range 0-140) were derived from the EAT-Lancet reference diet. MLTC was defined as ≥2 long-term conditions, excluding hypertension, diabetes, and obesity. Cox proportional hazards models estimated hazard ratios (HRs) for MLTC, complex MLTC (≥3 conditions), and 10 leading non-communicable diseases, adjusting for sociodemographic, lifestyle, and clinical covariates. RESULTS: Over a median 10·5 years, 28,052 MLTC cases occurred. Each 20-unit higher PHDI was associated with a lower risk of MLTC (HR [95%CI]; 0·93 [0·91, 0·95]), complex MLTC (0·92 [0·89, 0·94]), ischaemic heart disease (0·89 [0·85, 0·94]), chronic obstructive pulmonary disease (0·70 [0·65, 0·76]), kidney diseases (0·81 [0·76, 0·87]), cirrhosis and other chronic liver diseases (0·83 [0·70, 0·98]), and colorectal cancer (0·87 [0·79, 0·95]). No associations were observed for stroke, dementia, or upper gastrointestinal cancers. No sex differences were observed, but associations were overall stronger in younger (<60 years of age) and more deprived participants. CONCLUSIONS: Greater adherence to the planetary health diet is associated with a lower risk of MLTC. These findings support dietary policies that promote sustainable dietary patterns, consistent with the EAT-Lancet recommendations, to reduce disease burden and improve population health.