Abdominal and general adiposity and level of asthma control in adults with uncontrolled asthma

Abstract

Rationale: Abdominal adiposity may be an important risk factor for uncontrolled asthma in adults, controlling for general obesity. Whether the relationship, if present, is explained by other factors (e.g., asthma onset age, sex, and/or coexisting conditions) is unclear.

Objectives: To examine whether clinically applicable anthropometric measures of abdominal adiposity--waist circumference and waist-to-height ratio (WHtR)--are related to poorer asthma control in adults with uncontrolled asthma controlling for body mass index (BMI), and whether the relationship (if present) is explained by gastroesophageal reflux disorder (GERD), sleep quality, or obstructive sleep apnea (OSA) or differs by age of asthma onset or sex.

Methods: Patients aged 18 to 70 years with uncontrolled asthma (n = 90) participated in a 6-month randomized clinical trial.

Measurements and main results: Baseline measures included sociodemographics, standardized anthropometrics, Asthma Control Test (ACT), GERD Symptom Assessment Scale, Pittsburgh Sleep Quality Index, and Berlin Questionnaire for Sleep Apnea. Participants (mean [SD] age, 52 [12] yr) were racially and ethnically diverse, 67% women, and 69% overweight or obese, and 71% reported their age of asthma onset was 12 years or older. Participants had uncontrolled asthma (mean [SD] ACT score, 14.9 [3.7]) and low GERD symptoms score (0.6 [0.4]); 67% reported poor sleep quality, and 42% had a high OSA risk. General linear regression results showed that worse ACT scores were significantly associated with every SD increase in waist circumference (β = -1.03; 95% confidence interval [CI], -1.96 to -0.16; P = 0.02) and waist-to-height ratio (β = -1.16; 95% CI, -2.00 to -0.33; P = 0.008), controlling for sociodemographics. Waist-to-height ratio remained correlated with ACT (β = -2.30; 95% CI, -4.16 to -0.45; P = 0.02) after further adjusting for BMI. The BMI-controlled relationship between WHtR and ACT did not differ by age of asthma onset or sex (P > 0.05 for interactions) and persisted after additional adjustment for GERD, sleep quality, or OSA scores. Poor sleep quality was associated with worse ACT scores (β = -0.87; 95% CI, -1.71 to -0.03; P = 0.045) controlling for waist-to-height ratio, BMI, and sociodemographics.

Conclusions: Abdominal adiposity by waist-to-height ratio and poor sleep quality correlated with poorer asthma control in adults with uncontrolled asthma, after controlling for BMI and sociodemographics. These results warrant replication in larger studies of diverse populations. Clinical trial registered with www.clinicaltrials.gov (NCT 01725945).

Trial registration: ClinicalTrials.gov NCT01725945.

Keywords: abdominal obesity; asthma; body mass index; gastroesophageal reflux; sleep.

Figure 1.

Associations between adiposity indices and Asthma Control Test (ACT) scores (range, 5–25; higher scores indicate better control). Graphs show unadjusted associations between raw values of adiposity indices and ACT scores. ^†Standardized as (raw value − mean)/SD and examined as a continuous variable in the regression model. ^‡Model 1 controlled for age, sex, race/ethnicity, education, income, and smoking status. ^§Model 2 controlled for all Model 1 covariates and body mass index (BMI). CI = confidence interval. P values in bold were statistically significant (<0.05).

Figure 2.

Associations of gastroesophageal reflux disorder (GERD) symptoms (range, 0–3; higher scores indicate more distress), sleep quality, and obstructive sleep apnea risk scores with Asthma Control Test (ACT) scores (range, 5–25; higher scores indicate better control). OSA = obstructive sleep apnea (range, 0–3; higher scores indicate higher risk); SQ = sleep quality (range, 0–21; higher scores indicate poorer quality); WHtR = waist-to-height ratio. Graphs show unadjusted associations of raw values of coexisting conditions with ACT scores. ^†Standardized as (raw value − mean)/SD and examined as a continuous variable in the regression model. ^‡Each adjusted model included WHtR and the coexisting condition (OSA, GERD, or sleep quality), controlling for age, sex, race/ethnicity, education, income, smoking status, and BMI. P values in bold were statistically significant (<0.05).