A recent Swedish study found that both abdominal and general obesity were independently associated with respiratory illnesses, including asthma and self-reported chronic obstructive pulmonary disease (COPD).

Relationships between respiratory conditions with characterized obesity types in adults were assessed using self-report surveys from participants originally enrolled in the European Community Respiratory Health Survey (ECRHS) investigating asthma, allergy, and risk factors. The Respiratory Health in Northern Europe (RHINE) III, provides a second follow-up substudy of ECRHS focused on two forms of obesity associated with respiratory illnesses.

Obesity is a characteristic risk factor linked to respiratory ailments such as asthma and COPD. High body mass index (BMI) and waist circumference (WC) provide quantitative measurements for defining conditions of comprehensive general and abdominal obesity, respectively.

Although both types of obesity have been associated with asthma incidence, studies on their independent impact on this disease have been limited. Previous reports on abdominal obesity associated with asthma have been inconsistent when considering sexes in the analysis. Additionally, COPD and related outcomes differed between abdominal and general obesity indicating a need to discover whether self-reported WC abdominal obesity and BMI-based general obesity are independently associated with respiratory symptoms, early and late-onset asthma, COPD, chronic bronchitis, rhinitis, and sex, Marta A. Kisiel, MD, PhD, of the Department of Environmental and Occupational Medicine, Uppsala, Sweden, and colleagues write.

In a prospective study published in the journal Respiratory Medicine, the researchers report on a cross-sectional investigation of responses to a questionnaire similar to one utilized 10 years earlier in the RHINE II study. Questions required simple yes/no responses that covered asthma, respiratory symptoms, allergic rhinitis, chronic bronchitis, and COPD. Additional requested information included age of asthma onset, potential confounding variables of age, smoking, physical activity, and highest education level, weight and height for BMI calculation, and WC measurement with instructions and a provided tape measure.

The population of the RHINE III study conducted from 2010-2012 was composed of 12,290 participants (53% response frequency) obtained from a total of seven research centers located in five northern European countries. Obesity categorization classified 1837 (6.7%) participants as generally obese based on a high BMI ≥ 30 kg/m2 and 4261 (34.7%) as abdominal obese by WC measurements of ≥ 102 cm for men and ≥ 88 cm for women. Of the 4261 total participants, 1669 met both general and abdominal obesity criteria. Mean age was in the low 50s range and the obese population consisted of more women than men.

Simple linear regression revealed that BMI and WC were highly correlated, and both were associated with tested respiratory conditions when adjusted for confounding variables. Differences with respect to WC and BMI were independently associated with most of the examined respiratory conditions when WC was adjusted for BMI and vice versa. Neither early onset asthma nor allergic rhinitis were associated with WC, BMI, or abdominal or general obesity.

A significantly high proportion of individuals with general and abdominal obesity experienced a variety of defined respiratory symptoms, had asthma, chronic bronchitis, or COPD. An independent association of abdominal obesity (with or without general obesity) was found to occur with respiratory symptoms, asthma, late-onset asthma, and chronic bronchitis.

Adjusting for abdominal obesity, general obesity showed an independent and significant association with respiratory symptoms, asthma, adult-onset asthma, and COPD. An analysis stratified by sex indicated a significant association of abdominal and general obesity with asthma in women presented as an odds ratio (OR) of 1.56 (95% CI, 1.30 – 1.87) and 1.95 (95% CI, 1.56 – 2.43), respectively, compared with men, with an OR of 1.22 (95% CI, 0.97 – 3.17) and 1.28 (95% CI, 0.97 – 1.68), respectively. The association of abdominal and general obesity with COPD was also stronger in women compared with men.

The researchers conclude that “both general and abdominal obesity [were] independent of each other associated with respiratory symptoms in adults.” There is also a distinct difference between women and men for the association of self-reported asthma and COPD with abdominal and general obesity.

The large randomly selected sample size of participants from research centers located in five northern European countries was considered a major strength of this study as it permitted simultaneous adjustment for multiple potential confounders. Several limitations were acknowledged, including absence of data on obstructive respiratory disease severity, WC measurements not being performed by trained staff, and self-reported height and weight measurements.

The authors have disclosed no relevant financial relationships.

Respiratory Medicine. 2023;211:107213. Full text

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