title: Environmental risks for nontuberculous mycobacteria. Individual exposures and climatic factors in the cystic fibrosis population.
abstract: BACKGROUND
  Persons with cystic fibrosis are at high risk of pulmonary nontuberculous mycobacterial infection, with a national prevalence estimated at 13%. The risk of nontuberculous mycobacteria associated with specific environmental exposures, and the correlation with climatic conditions in this population has not been described.
  
  
  OBJECTIVE
  To describe the association of pulmonary nontuberculous mycobacteria with individual exposures to water and soil aerosols, and the population associations of these infections with climatic factors.
  
  
  METHODS
  We conducted a nested case-control study within a cohort study of pulmonary nontuberculous mycobacteria prevalence at 21 geographically diverse national cystic fibrosis centers. Incident nontuberculous mycobacterial infection cases (at least one prior negative culture followed by one positive culture) were age- and sex-matched to culture-negative controls. Exposures to water and soil were assessed by administering a standardized questionnaire. Cohort prevalence at each of the 21 centers was correlated with climatic conditions in the same area through linear regression modeling.
  
  
  RESULTS
  Overall, 48 cases and 85 control subjects were enrolled. Indoor swimming was associated with incident infection (adjusted odds ratio, 5.9, 95% confidence interval, 1.3-26.1), although only nine cases (19%) and five control subjects (6%) reported indoor swimming in the 4 months prior to infection. Exposure to showering and municipal water supply was common among both cases and control subjects: 77% of cases and 76% of control subjects reported showering at least daily. In linear regression, average annual atmospheric water vapor content was significantly predictive of center prevalence (P = 0.0019), with R(2) = 0.40.
  
  
  CONCLUSIONS
  Atmospheric conditions explain more of the variation in disease prevalence than individual behaviors. The risk of specific exposures may vary by geographic region due to differences in conditions favoring mycobacterial growth and survival. However, because exposure to these organisms is ubiquitous and behaviors are similar among persons with and without pulmonary nontuberculous mycobacteria, genetic susceptibility beyond cystic fibrosis is likely to be important for disease development. Common individual risk factors in high-risk populations remain to be identified.
authors: 1 Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland.
authors: D Rebecca
authors: DR
authors: Prevots
authors: Jennifer
authors: J
authors: Adjemian
authors: Aisling G
authors: AG
authors: Fernandez
authors: Michael R
authors: MR
authors: Knowles
authors: Kenneth N
authors: KN
authors: Olivier
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002980:Climate; D015331:Cohort Studies; D016001:Confidence Intervals; D003550:Cystic Fibrosis / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology*; D004777:Environment; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009165:Mycobacterium Infections, Nontuberculous / Q000453:epidemiology* / Q000209:etiology; D009170:Nontuberculous Mycobacteria / Q000302:isolation & purification*; D016017:Odds Ratio; D015995:Prevalence; D018570:Risk Assessment; D012720:Severity of Illness Index; D014481:United States / Q000453:epidemiology
keywords: cystic fibrosis; environmental; epidemiology; nontuberculous mycobacteria