title: Age, period, and cohort effects in adult lifetime asthma prevalence in California: an application of hierarchical age-period-cohort analysis.
abstract: OBJECTIVE
  Using 27 years of survey data, the contributions of age, period, and cohort effects on the increase in adult lifetime asthma prevalence in California were examined.
  
  
  METHODS
  Lifetime asthma diagnosis for adults was assessed in 1984-1992 and 1995-2011 through the California Behavioral Risk Factor Surveillance System, an annual, cross-sectional, population-based survey (n = 144,100). Using date of survey and date of birth, we classified 18,305 adult respondents with lifetime asthma into 7 age groups, 6 periods, and 17 cohorts. Using hierarchical, cross-classified random effects models, birth cohort, period, and age patterns in adult lifetime asthma prevalence were analyzed.
  
  
  RESULTS
  After adjusting for sex, ethnicity, education, and smoking, age effects peak in young adulthood, flatten from 40 to 60 years old, and then decrease in older adulthood. A significant positive trend in asthma prevalence was observed in the two earliest survey periods (1984-1993; P value < .0001). Survey period trends appear to flatten beginning in 2004. Although the overall birth cohort effect was statistically significant, the magnitude of the effect for each birth cohort category was small (P value = .0005).
  
  
  CONCLUSIONS
  We observed that strong age and period effects have been driving the increase in lifetime asthma prevalence in California over the past 3 decades.
authors.affiliation: Survey Research Group, Public Health Institute, Sacramento, CA. Electronic address: sryan@s-r-g.org.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Ryan-Ibarra
authors.affiliation: Environmental Health Investigations Branch, California Department of Public Health, Richmond, CA.
authors.forename: Meredith
authors.initials: M
authors.lastname: Milet
authors.affiliation: California Breathing Program Impact Assessment, Inc., For the California Department of Public Health, Richmond, CA.
authors.forename: Liza
authors.initials: L
authors.lastname: Lutzker
authors.affiliation: Cancer Registry of Greater California, Public Health Institute, Sacramento, CA.
authors.forename: Danielle
authors.initials: D
authors.lastname: Rodriguez
authors.affiliation: Survey Research Group, Public Health Institute, Sacramento, CA; Cancer Registry of Greater California, Public Health Institute, Sacramento, CA.
authors.forename: Marta
authors.initials: M
authors.lastname: Induni
authors.affiliation: Division of Environmental and Occupational Disease Control, California Department of Public Health, Richmond, CA.
authors.forename: Rick
authors.initials: R
authors.lastname: Kreutzer
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001249:Asthma / Q000453:epidemiology*; D040343:Behavioral Risk Factor Surveillance System; D002140:California / Q000453:epidemiology; D015988:Cohort Effect; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012907:Smoking / Q000453:epidemiology; D012959:Socioeconomic Factors; D055815:Young Adult
keywords: Age-period-cohort analysis; California Behavioral Risk Factor Surveillance System; Hierarchical age-period-cohort model; Lifetime asthma prevalence