Association between the dietary index for gut microbiota (DI-GM) and all-cause mortality in older adults with COPD: Evidence from the NHANES.

Higher DI-GM scores were significantly associated with lower all-cause mortality risk in older adults with COPD.

• Compared with Q1, individuals in Q4 had a hazard ratio of 0.51 (95% CI: 0.37–0.70, P < .001) after full adjustment, representing a 35% lower mortality risk.
• During a median follow-up of 92 months, 304 deaths (32.1%) were recorded among 946 participants.
• Participants were categorized into quartiles (Q1–Q4) of DI-GM scores, with Q1 as the reference group.
• Cox proportional hazards models were used to evaluate the relationship between DI-GM and mortality risk.

Restricted cubic spline analysis revealed a linear inverse association between DI-GM scores and all-cause mortality risk.

• P-overall = .001 for the association between DI-GM and mortality.
• P-nonlinear > .05, indicating the relationship was linear rather than nonlinear.
• The linear inverse association suggests a dose-response relationship between diet quality for gut microbiota and mortality risk.

Subgroup analyses showed consistent associations across most strata, with stronger protective effects observed among participants with higher poverty-income ratios.

• A statistically significant interaction was found for poverty-income ratio (P for interaction = .021).
• Associations between DI-GM and mortality were consistent across most other subgroups tested.
• Subgroup analyses were performed to test the robustness of the associations.

The study included 946 older adults aged ≥65 years with COPD from the NHANES 2007–2018 dataset.

• Data were derived from the National Health and Nutrition Examination Survey (NHANES) 2007 to 2018.
• DI-GM scores were calculated using 24-hour dietary recalls based on 14 food and nutrient components reflecting favorable or unfavorable effects on gut microbiota.
• The primary outcome was all-cause mortality.
• Kaplan-Meier survival curves, Cox proportional hazards models, and restricted cubic spline analyses were used.

COPD is a major cause of death especially among older adults, and dietary patterns may affect COPD prognosis through the gut-lung axis by modulating inflammation and immune balance.

• The gut-lung axis is proposed as a biological mechanism linking diet quality to COPD outcomes.
• The DI-GM is a dietary index specifically designed to reflect dietary effects on gut microbiota composition.
• The index incorporates 14 food and nutrient components with favorable or unfavorable effects on gut microbiota.