Asthma and Obesity
According to a study by the CDC, obese adults were 66% more likely than
adults of normal weight to have asthma (1). Other studies have
found that women who gained weight after age 18 had an increased
risk of developing asthma (2) and that female reproductive hormones
may contribute to the onset of asthma among adult women (3).
Another study showed that while obesity is a risk factor for self-reported
asthma, many more obese than non-obese subjects were using bronchodilators
despite a lack of objective evidence for airflow obstruction
(e.g. pulmonary function tests). This suggests that causes other
than airflow obstruction are responsible for the onset of shortness
of breath in obesity, and that asthma might be overdiagnosed
in the obese population (4).
Childhood asthma and obesity have risen in tandem over the last 20 years,
but the nature of that relationship remains vague. A high, not
low, birth weight has been found to be a risk factor for increased
emergency visits for asthma during childhood (5). A large Canadian
study found there was no statistical association between obesity
and asthma among children age 4 to 11 years (6). In a study
of U.S. inner-city children with asthma, obese children used
more medicine, wheezed more, and a greater proportion had unscheduled
ED visits than thinner children (7).
Some potential explanations
for the apparent link between asthma and obesity that require
further research include: insulin resistance, gastroesophageal
reflux disease (GERD) as a result of obesity, physical inactivity
promoting both obesity and asthma, and diet. There may be no causal
connection between the two conditions, and more research is needed
to complete this complex puzzle.
(1) Risk factors for asthma in US adults: results from the 2000
Behavioral Risk Factor Surveillance System. Gwynn RC, J Asthma,
(2)Prospective Study of Body Mass Index, Weight Change, and Risk of Adult-onset
Asthma in Women. Camargo, CA et al, Arch Intern Med, 1999;159:2582-2588.
(3) Prospective Study of Postmenopausal Hormone Use and Newly Diagnosed
Asthma and Chronic
Obstructive Pulmonary Disease. Barr RG et
al , Arch Intern Med . 2004;164:379-386.
(4) Obesity is a risk factor for dyspnea but not for airflow obstruction.
Sin DD, et al, Arch Intern Med. 2002 Jul 8;162(13):1477-81.
(5) The relationship between birth weight and childhood asthma:
a population-based cohort study. Sin DD, et al, Arch Pediatr
Adolesc Med. 2004 Jan;158(1):60-4.
(6) Is obesity associated with asthma in young children? To T, et al, J Pediatr. 2004 Feb;144(2) :162-8.
(7) Do obese inner-city children
with asthma have more symptoms than nonobese children with asthma?
Belamarich PF et al, Pediatrics. 2000 Dec;106(6):1436-41.
From the Summer
2004 AIM newsletter, author: Michael Cabana, MD, MPH