Weight-adjusted waist index (WWI)—a relatively novel anthropometric index—was first proposed as a dose-response association with cardiometabolic risk. WWI has previously indicated to be involved in disease onset and progression in clinical studies, including in associations with asthma, onset of asthma, and duration of asthma; however, there have been no studies that specifically explored associations between mortality in asthma populations and WWI. Authors of a study published in Heart & Lung examined those potential associations between WWI and mortality in adult patients with asthma, and whether WWI can serve as a relatively novel prognostic factor in this population.
The population-based study utilized the public database National Health and Nutrition Examination Survey (NHANES). A total of 3223 eligible patients from the database were included in the study, all of whom had asthma. The diagnosis of asthma was determined depending on patients’ responses to specific questions (eg, “Has a doctor or other health care professional ever told you that you have asthma?” and “Do you still have asthma?”), with affirmative responses indicating the presence of current asthma in patients.
Additionally, WWI is a measurement that considered both the waist circumference (WC) in combination with weight. Any mortality data was obtained by following up the included baseline asthma patients and matching them to the National Death Index database. The follow-up end point was outcome occurrence or until December 31, 2019, with mortality outcomes including all-cause, cardiovascular disease (CVD), cancer, and respiratory disease-related mortality.
Further, several covariates that may influence the associations were also selected, including sociodemographic factors (eg, age, race, gender, education level), lifestyle (eg, smoking, alcohol consumption, and physical activity), medical comorbidities (eg, diabetes, hypertension, and CVD), and family history of asthma (eg, self-reported asthma status of blood relatives). The investigators explored whether associations were consistent across subgroups based on the included covariates.
According to the results, the baseline population (N = 3223) was grouped according to WWI quartiles. Interquartile ranges of WWI were quartile 1 (Q1, 8.51–10.57), Q2 (10.57-11.20), Q3 (11.20-11.82), and Q4 (>11.82), and compared to the low WWI population, people with asthma who had higher WWI were older, had a lower poverty-income ratio (PIR), and were more likely to be Hispanic, former smokers, physically inactive, and never drink alcohol. Additionally, patients with a higher WWI were associated with higher prevalence of diabetes, hypertension, and CVD; however, the investigators observed no difference in the prevalence of family history of asthma in between groups. Further, at a median follow-up duration of 104 months (range: 58-160 months), approximately 12.8% (n = 565) of patients with asthma died, of which 164 (3.62%) of the baseline population were CVD-related deaths, 136 (2.79%) cancer-related, and 87 (2.13%) respiratory disease-related.
Key Takeaways
- Weight-Adjusted Waist Index as a Prognostic Factor for Asthma: The study found that weight-adjusted waist index (WWI) is significantly associated with all-cause mortality in adult patients with asthma. Higher WWI levels were observed to be linked to an increased risk of death, suggesting that WWI may serve as a novel prognostic factor for this population.
- Increased Mortality Risks: Patients with higher WWI were not only at greater risk for all-cause mortality, but also showed significantly higher risks of cardiovascular disease (CVD)-, cancer-, and respiratory disease-related deaths. This highlights the importance of considering WWI when managing health outcomes for patients who have asthma.
- Need for Further Research: The study's limitations, such as reliance on self-reported asthma diagnosis and lack of consideration for asthma-related medication, suggest that future research should explore these areas and compare WWI with other weight-related indicators, like body mass index, to better understand its impact on asthma-related mortality.
When the investigators assessed whether WWI was an independent prognostic factor for mortality in the asthmatic population, they observed that WWI was significantly and positively associated with all-cause mortality in people with asthma who were in both crude and partially adjusted models. Following adjustments made for age, sex, race, education, marital status, PIR, lifestyle, and medical comorbidities, the authors found that WWI remained positively associated with all-cause mortality (HR, 95% CI = 1.43 (1.25,1.64), p < .0001). Additionally, higher WWI was associated with an increased all-cause mortality in patients with asthma, and compared to those with WWI at Q1, those at Q2, Q3, and Q4 were observed to have an approximate 63% (HR = 1.63 [1.12, 2.35], p = .01), 120% (HR = 2.20 [1.50, 3.22], p < .0001), and 153% (HR = 2.53 [1.73, 3.71], p < .0001) increased risk of all-cause mortality, respectively.
Similarly, WWI was also found to be associated with CVD mortality (HR = 1.58 [1.25, 1.99], p < .001), and when used as a categorical variable, higher WWI was associated with a significant increase in CVD-related mortality in Q2 (HR = 3.74 [1.72, 8.14]), Q3 (HR = 3.42 [1.44, 8.16]), and Q4 (HR = 5.24 [2.15, 12.73]). In addition, WWI was also significantly and positively associated with cancer mortality (HR = 1.50 [1.19, 1.90], p < .001), with asthma populations at Q3 and Q4 demonstrating higher mortality (Q3: HR = 3.23 [1.43, 7.32]; and Q4: HR = 2.64 [1.24, 5.61]; p = .002). Mortality for respiratory disease also increased by about 154% and 346% in the patients with asthma and WWI at Q3 and Q4, respectively.
Limitations of the study include the diagnosis of asthma being based on self-reports, the impact of asthma-related medication use and its potential effects of WWI were not taken into consideration, and WWI was not compared with body mass index. The authors note that future research should include these areas while also considering different weight-related indicators to compare and evaluate differences.
REFERENCE
Wang S, Li D, Sun L. Weight-adjusted waist index is an independent predictor of all-cause and cause-specific mortality in patients with asthma. Heart & Lung. 2024;68:166–174. doi:10.1016/j.hrtlng.2024.07.002
