Background: Inflammatory response plays a crucial role in the development and deterioration of asthma. The aim of this study was to assess the association between Dietary Inflammatory Index (DII) score and all-cause mortality among patients with asthma in the United States (US).
Methods: We included participants aged ≥20 years and excluded those with no data relating to 24-hour dietary recall of dietary intake interview and asthma status. DII score was calculated based 25 food parameters. Multivariate Cox regression analysis was used to analyze the linear association between DII score and all-cause mortality, and a generalized additive model (GAM) with a spline smoothing function was used to analyze the nonlinear dose-response relationship.
Results: Among the 20,573 participants, 2,805 (13.63%) participants had a current or past diagnosis of asthma, and 17,768 (86.37%) participants had no history of asthma. DII score was associated with increased all-cause mortality among participants who had previously been diagnosed with asthma [hazard ratio (HR): 1.13; 95% confidence interval (CI): 1.04, 1.23; P=0.004] and participants who were currently diagnosed with asthma (HR: 1.13; 95% CI: 1.03, 1.24; P=0.010) after multivariable adjustment for age, sex, race, education, family income, body mass index, physical activity, smoking status, diabetes, hypertension, and coronary heart disease. When DII score was transformed into a categorical variable, participants with a current or past diagnosis of asthma who were in the DII score fifth quintile were associated with increased all-cause mortality when compared with participants in the lowest quintile (HR: 2.34; 95% CI: 1.34, 4.11). The association was stronger in these participants than in participants with no history of asthma (HR: 1.25; 95% CI: 1.04, 1.49). Furthermore, the GAM model showed a linear dose-response relationship, which indicated that increased DII score was associated with increased all-cause mortality among participants with a current or past diagnosis of asthma.
Conclusions: Our study is the first to provide evidence that DII score is associated with increased all-cause mortality among patients with asthma in the US. Due to potential bias and residual confounding, our findings require further investigation and confirmation in randomized controlled trials.
Keywords: Dietary Inflammatory Index (DII); National Health and Nutrition Examination Survey (NHANES); all-cause mortality; asthma.