Abdominal obesity may be a key determinant in the link between metabolic syndrome and impaired lung function, according to findings from a population analysis.
In an analysis of the health information for 121,965 men and women examined at a large French medical center between 1999 and 2006, Dr. Nathalie Leone of the University of Paris 7-Denis Diderot in France and colleagues observed a positive, independent relationship between impaired lung function and metabolic syndrome in both sexes. Waist circumference was the strongest predictor of the respiratory disturbance (Am. J. Respir. Crit. Care Med. 2009;179:509–16).
Based on the new evidence, the measurement of waist circumference should be routine practice before spirometry tests, Dr. Paul Enright of the University of Arizona in Tucson suggested in an accompanying editorial.
“Abdominal obesity could then be highlighted on the printed report so that the physician interpreting the report could take the effect of obesity into account,” Dr. Enright noted (Am. J. Respir. Crit. Care Med. 2009;179:432–3).
Previous studies have linked impaired lung function with an increased risk of cardiovascular morbidity and mortality, but the mechanisms underlying the association have not been identified, the authors wrote.
Hypothesizing that metabolic syndrome or specific combinations of its components might play an important role in the relationship, the investigators evaluated the risk for impaired lung function according to metabolic syndrome traits using a logistic regression model adjusted for age, sex, education, smoking status, alcohol, BMI, physical activity, and cardiovascular disease history.
Lung function measures included forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). Impaired lung function was defined as an FEV1 or FVC less than the lower limit of normal, the authors wrote. Metabolic syndrome was assessed according to American Heart Association and National Heart, Lung, and Blood Institute guidelines.
In the logistic regression model, impaired FEV1 and FVC were independently associated with metabolic syndrome, with odds ratios of 1.28 and 1.41, respectively. Similar results were observed in women and men, the authors reported.
Metabolic syndrome variables identified three factors independently associated with impaired lung function: low high-density lipoprotein cholesterol level/high triglyceride level, high fasting glucose level/high blood pressure, and waist circumference greater than 35 inches for women and greater than 40 inches for men.
Abdominal obesity showed the strongest association with lung function. The relationship was not significantly modified by smoking status or BMI category, and it persisted after the exclusion of individuals with a history of cardiovascular or respiratory diseases.
Given that abdominal obesity has been associated in recent studies with a higher risk of respiratory death regardless of BMI, “our study raises potential concerns about how the possible impact of the increase in [waist circumference] reported in the United States and, to a lesser extent, in France on future adverse health outcomes should be considered when assigning resources in respiratory care,” the authors wrote.
“Prospective studies are needed to determine the temporal relationship between lung function impairment and metabolic syndrome, including abdominal adiposity in particular,” they said.
Mechanistic studies are warranted to clarify the underlying physiopathological pathways, the investigators added.
The authors of the study and the editorial reported having no relevant financial conflicts of interest.