title: Age-related seasonal patterns of emergency department visits for acute asthma in an urban environment.
abstract: OBJECTIVE
  Asthma morbidity is greater in younger patients. The reasons are not fully understood, although identifying demographic patterns of seasonality may help determine causes and potential prevention. The objective of this study is to determine the relationship between age and seasonal asthma periodicity in patients presenting to the emergency department (ED).
  
  
  METHODS
  We conducted a retrospective study of ED visits from 1991 to 2000 in 11 municipal hospitals in New York City, with 911 receiving facilities. There were 673,141 patients who presented to the ED during the study period and had a primary diagnosis of acute asthma.
  
  
  RESULTS
  Distinct seasonal patterns were observed, with the highest number of visits occurring in the fall and the fewest in the summer. Seasonal fluctuations of ED visits were highest in children aged 13 years or younger (coefficient of variation [CV] 37.8%; 95% confidence interval [CI] 37.5% to 38.1%), with a peak in CV occurring at approximately age 7 years (CV 43.3%; 95% CI 43.0% to 43.6%). Less variability was noted with increasing age, and the population aged 30 years and older appeared to be the least susceptible to seasonal influences (CV 11.7%; 95% CI 11.3% to 12.1%). Although the total number of asthma visits decreased by more than 30% from 1991 to 2000, the CVs for each year remained within a relatively narrow range of 24.2% to 30.5%.
  
  
  CONCLUSIONS
  In an urban population, seasonal variability of asthma episodes requiring ED visits are closely linked to age, which may be important in understanding the causes of asthma and developing disease-management strategies for the prevention of asthma episodes.
authors.affiliation: Department of Emergency Medicine, Long Island Jewish Medical Center, New Hyde Park, New York, NY 11040, USA. aresilv@aol.com
authors.forename: Robert A
authors.initials: RA
authors.lastname: Silverman
authors.forename: Lori
authors.initials: L
authors.lastname: Stevenson
authors.forename: Harold M
authors.initials: HM
authors.lastname: Hastings
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000367:Age Factors; D001249:Asthma / Q000628:therapy*; D002648:Child; D002675:Child, Preschool; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006773:Hospitals, Municipal; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009519:New York City; D012189:Retrospective Studies; D012621:Seasons; D014505:Urban Population