Prevalence of asthma among adults in metropolitan versus nonmetropolitan areas in Montana, 2008.

Introduction: Most US studies on asthma prevalence have been conducted in urban areas, and few have assessed the prevalence of asthma among residents of rural areas versus urban areas. The objective of this study was to compare the prevalence of asthma among adults living in metropolitan versus nonmetropolitan counties in Montana.

Methods: We analyzed data from 6,846 adult Montanans who completed the Behavioral Risk Factor Surveillance System survey in 2008. We used Rural-Urban Continuum Codes to categorize respondents' county of residence as metropolitan (Metro), nonmetropolitan and adjacent to a metropolitan county (NMA), and nonmetropolitan and nonadjacent to a metropolitan county (NMNA). We compared the prevalence of current self-reported asthma among respondents in the 3 areas, overall and by selected characteristics, and conducted multivariable logistic regression analyses to identify factors independently associated with current self-reported asthma.

Results: No differences in the prevalence of self-reported asthma were found between residents of Metro and NMA or NMNA counties, overall or by age, sex, race, years of education, health insurance status, annual household income, or body mass index. Respondents aged 65 years or older (adjusted odds ratio [AOR], 0.7; 95% confidence interval [CI], 0.5-0.9) and men (AOR, 0.6; 95% CI, 0.5-0.8) were less likely to report current asthma than younger respondents and women, respectively. Obese respondents were more likely (AOR, 1.9; 95% CI, 1.4-2.7) to report asthma than were respondents who were not obese. Metropolitan county of residence was not independently associated with self-reported current asthma.

Conclusion: The prevalence of self-reported current asthma is similar in metropolitan and nonmetropolitan counties in Montana, but other sociodemographic differences exist. Our findings highlight the need to conduct regional and state surveillance of asthma to understand the demographic risk factors associated with it and to determine the potential geographic variation of asthma prevalence in the United States.