Asthma and cognitive dysfunction in older adults: the mediating role of systemic immune-inflammation index

Asthma and cognitive dysfunction represent significant public health challenges. Our study aimed to investigate the relationship between asthma and cognitive dysfunction in adults aged ≥ 60 years, and explore the role of systemic immune inflammation index (SII) in asthma - cognitive dysfunction link. The retrospective cross-sectional study included 2,579 participants aged ≥ 60 years from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) cycles. Asthma diagnosis was confirmed using the MCQ010 questionnaire, cognitive function assessed through the Digit Symbol Substitution Test (DSST). SII was calculated using the formula: (platelet count × neutrophil count)/lymphocyte count. Controlling for demographic variables including sex, age, race and/ethnicity, poverty-to-income ratio (PIR) and education level, a negative association was found between asthma and DSST scores (β = -1.75, 95% CI: -3.38, -0.120, P = 0.037). This association persisted even after further adjustments for body mass index (BMI) and diabetes (β = -1.72, 95% CI: -3.38, -0.057, P = 0.043). Moreover, subgroup analysis showed no significant association of sex, age, race/ethnicity, BMI or diabetes with the relationship between asthma and cognitive function. Mediation analysis indicated SII was a mediator of asthma-induced cognitive impairment, a notable Average Causal Mediated Effect (ACME) (P = 0.004) between SII and cognitive dysfunction. Our investigation indicated that elderly asthma (aged ≥ 60 years) was predisposed to cognitive dysfunction, independent of sex, age, race/ethnicity, BMI and diabetes. Furthermore, mediation analysis suggested that asthma might contribute to cognitive dysfunction through the involvement of SII.