Overdiagnosis of asthma in obese and nonobese adults.
BACKGROUND
It is unclear whether asthma is overdiagnosed in developed countries, particularly among obese individuals, who may be more likely than nonobese people to experience dyspnea.


METHODS
We conducted a longitudinal study involving nonobese (body mass index 20-25) and obese (body mass index >/= 30) individuals with asthma that had been diagnosed by a physician. Participants were recruited from 8 Canadian cities by means of random-digit dialing. A diagnosis of current asthma was excluded in those who did not have evidence of acute worsening of asthma symptoms, reversible airflow obstruction or bronchial hyperresponsiveness, despite being weaned off asthma medications. We stopped asthma medications in those in whom a diagnosis of asthma was excluded and assessed their clinical outcomes over 6 months.


RESULTS
Of 540 individuals with physician-diagnosed asthma who participated in the study, 496 (242 obese and 254 nonobese) could be conclusively assessed for a diagnosis of asthma. Asthma was ultimately excluded in 31.8% (95% confidence interval [CI] 26.3%-37.9%) in the obese group and in 28.7% (95% CI 23.5%-34.6%) in the nonobese group. Overdiagnosis of asthma was no more likely to occur among obese individuals than among nonobese individuals (p = 0.46). Of those in whom asthma was excluded, 65.5% did not need to take asthma medication or seek health care services because of asthma symptoms during a 6-month follow-up period.


CONCLUSIONS
About one-third of obese and nonobese individuals with physician-diagnosed asthma did not have asthma when objectively assessed. This finding suggests that, in developed countries such as Canada, asthma is overdiagnosed.
Aaron
Shawn D
SD
Ottawa Health Research Institute, Ottawa, Ont, USA. saaron@ohri.ca
Vandemheen
Katherine L
KL
Boulet
Louis-Philippe
LP
McIvor
R Andrew
RA
Fitzgerald
J Mark
JM
Hernandez
Paul
P
Lemiere
Catherine
C
Sharma
Sat
S
Field
Stephen K
SK
Alvarez
Gonzalo G
GG
Dales
Robert E
RE
Doucette
Steve
S
Fergusson
Dean
D
D000328:Adult; D017677:Age Distribution; D001249:Asthma / Q000175:diagnosis* / Q000453:epidemiology*; D015992:Body Mass Index; D001835:Body Weight; D002170:Canada / Q000453:epidemiology; D016001:Confidence Intervals; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D005260:Female; D005541:Forced Expiratory Volume; D006306:Health Surveys; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology*; D016017:Odds Ratio; D015995:Prevalence; D011336:Probability; D012016:Reference Values; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017678:Sex Distribution; D013147:Spirometry