Body Mass Index and Asthma Severity Among Adults Presenting

Author: Support TCHCM December 16, 2014 0 Comments

The association between BMI and asthma severity was examined using x² test, analysis of variance, or Kruskal-Wallis test, as appropriate. Stratified analyses and multivariate linear and logistic regression models were performed. Factors associated with BMI (or with the outcome of interest) at p < 0.10 in univariate analysis were evaluated for inclusion in multivariate regression models. All odds ratios (ORs) are presented with 95% CIs. All p values are two sided, with p < 0.05 considered statistically significant.

Materials and Methods

This prospective cohort study was performed during November 2000 to May 2001 as part of the Multicenter Airway Research Collaboration (MARC). Using a standardized protocol, investigators at 26 EDs in 15 US states and 1 Canadian province provided 24-h per day coverage for a median of 2 weeks. All patients were managed at the discretion of the treating physician. Inclusion criteria were physician diagnosis of acute asthma, age 18 to 54 years, and ability to give informed consent. Repeat visits by individual subjects were excluded. Five hundred seventy-two of 590 enrolled adults (97%) reported their weight and height and were included in the current analysis. The institutional review board at each of the 26 participating hospitals approved the study.

Data Collection

The ED interview assessed demographic characteristics, asthma history, and details of the current asthma exacerbation. Data on ED management and disposition were obtained by chart review. All forms were reviewed by site investigators before submission to the MARC Coordinating Center in Boston, where they underwent further review by trained personnel and then double-data entry.

Results

The 572 patients had a mean age of 37 ± 10 years, and 66% (95% CI, 62 to 70) were women. As expected in this urban population, most subjects were black (44%) or Hispanic (26%), with only 30% white. The smoking status of these ED patients was never smoker (38%), former smoker (26%), and current smoker (36%). Only 3% reported comorbid COPD and the exclusion of these patients from analyses did not materially change any results (data not shown).

Figure 1 shows the BMI classification of these patients, with three of every four patients either overweight (30%) or obese (44%). The high prevalence of BMI > 25.0 did not materially differ by socioeconomic status. For example, the prevalence of overweight or obesity was comparable among those who had and had not graduated from high school (74% vs 73%, p = 0.83) and across quartiles of median household income (74%, 74%, 77%, and 73%, respectively; p = 0.83).

The obesity prevalence in this cohort of adults presenting to the ED with acute asthma was significantly greater than the prevalence among adults from the general population using either of the obesity prevalence estimates: 44% vs 27% (p < 0.001) in 1999 national survey, and 44% vs 20% (p < 0.001) in 2000 BRFSS. The national prevalence of obesity would have to rise to 41% for this difference to become nonsignificant. By contrast, the overweight prevalence in our sample of asthmatic patients did not differ from the National Health and Nutrition Examination Survey III estimate (30% vs 34%, p = 0.93), but did differ significantly from the BRFSS estimate (30% vs 37%, p < 0.001).

Comparisons of the three BMI groups are shown in Table 1. As previously noted, obese patients were significantly more likely to be female. Although the total with BMI > 25 did not differ between the 196 men and 376 women (70% vs 76%, p = 0.10), the distribution within BMI categories did (p < 0.001): women were less often overweight (40% vs 24%) and more often obese (30% vs 52%). Overall, men had a mean BMI of 28.4 ± 5.8 while women had a mean BMI of 32.1 ± 9.3 (p < 0.001). Obese participants were slightly older, but did not differ according to several other important sociodemographic factors.

Canadian Health Care Mall: Chronic asthma factors

1. Obese individuals did not differ by several markers of chronic asthma severity, such as history of asthma medication use, health-care utilization, and smoking status. In all groups, these factors pointed toward a very “real” asthma with a likely classification of patients as having moderate-to-severe persistent asthma.

Acute asthma presentation and ED course are shown in Table 2. Compared to normal/underweight and overweight individuals, the obese groups had a significantly higher initial PEF (48% vs 53%, p < 0.04), despite a trend toward more severe subjective symptoms (76% vs 81%, p = 0.15) and more inhaled (3-agonist puffs within 6 h of presenting to the ED (four puffs vs six puffs, p = 0.03). Although nonobese subjects had a shorter duration of symptoms than their obese counterparts (duration < 24 h, 38% vs 47%; p = 0.05), obese participants did not differ by ED management or clinical response (eg, change in PEF, hospital admission).

Because women were almost twice as common as men, and comprised 77% of the obese group (Table 1), we paid particular attention to potential confounding or interaction by sex in all subsequent analyses. We first explored potential sex differences in the major asthma factors. Compared to men, women reported more severe symptoms (71% vs 81%, p = 0.007) despite a higher PEF (45% vs 53%, p < 0.001). Other important factors (eg, median number of inhaled (3-agonist puffs within 6 h of presenting to the ED, hospital admission, ED length of stay, and the composite admission measure) did not differ by sex (data not shown).