Dietary inflammatory index and body shape index and mortality risk in early-stage cardiovascular–kidney–metabolic syndrome: evidence from NHANES

Abstract Background Cardiovascular-kidney-metabolic (CKM) syndrome is a newly recognized multisystem disorder encompassing metabolic dysfunction, chronic kidney disease, and cardiovascular disease, with most individuals remaining in early stages (0–3). Chronic inflammation and abnormal adipose tissue distribution are central to CKM pathogenesis; however, the prognostic relevance of diet-related inflammatory exposure in combination with body shape–derived central adiposity during this early stage remains unclear. Methods Data were derived from the National Health and Nutrition Examination Survey (NHANES) 2001–2018, including 32,976 adults with early-stage CKM syndrome. Dietary inflammatory potential was assessed using the Dietary Inflammatory Index (DII), calculated from dietary intake collected during the first 24-hour dietary recall in the primary analysis. In the sensitivity analysis restricted to participants from the 2003–2018 survey cycles with two valid 24-hour dietary recalls, the mean of the Day 1 and Day 2 recall-specific DII scores was used. Central adiposity was evaluated using A Body Shape Index (ABSI). All-cause mortality was the primary outcome, and cardiovascular disease (CVD) mortality was the secondary outcome. Multivariable Cox proportional hazards models were applied to examine independent and joint associations, with subgroup and sensitivity analyses conducted to assess robustness. Results During a mean follow-up of 102.5 months, 3,690 deaths occurred, including 1,004 due to CVD. Higher DII and ABSI were independently associated with increased all-cause mortality, while ABSI was also positively associated with CVD mortality. Notably, individuals with a dual high-risk profile—characterized by concomitantly high DII and high ABSI—exhibited the highest risks of both all-cause and CVD mortality. These associations appeared to be more pronounced among older adults, women, individuals with obesity, non-Hispanic White participants, and those with hypertension. In the repeated-recall sensitivity analysis, concomitantly high DII and high ABSI remained significantly associated with both all-cause and cardiovascular mortality, whereas high DII was significantly associated with cardiovascular mortality but not with all-cause mortality. Conclusions This study provides novel population-based evidence that concomitantly high dietary inflammatory potential and central adiposity are associated with increased risks of both all-cause and cardiovascular mortality among adults with early-stage CKM syndrome, with these joint associations remaining statistically significant in the repeated-recall analysis. Although the DII-specific association with all-cause mortality was less consistent across dietary assessment approaches, the joint assessment of DII and ABSI may provide complementary information for mortality risk stratification in early-stage CKM syndrome.