title: Effect of reduction in household air pollution on childhood pneumonia in Guatemala (RESPIRE): a randomised controlled trial.
abstract: BACKGROUND
  Pneumonia causes more child deaths than does any other disease. Observational studies have indicated that smoke from household solid fuel is a significant risk factor that affects about half the world's children. We investigated whether an intervention to lower indoor wood smoke emissions would reduce pneumonia in children.
  
  
  METHODS
  We undertook a parallel randomised controlled trial in highland Guatemala, in a population using open indoor wood fires for cooking. We randomly assigned 534 households with a pregnant woman or young infant to receive a woodstove with chimney (n=269) or to remain as controls using open woodfires (n=265), by concealed permuted blocks of ten homes. Fieldworkers visited homes every week until children were aged 18 months to record the child's health status. Sick children with cough and fast breathing, or signs of severe illness were referred to study physicians, masked to intervention status, for clinical examination. The primary outcome was physician-diagnosed pneumonia, without use of a chest radiograph. Analysis was by intention to treat (ITT). Infant 48-h carbon monoxide measurements were used for exposure-response analysis after adjustment for covariates. This trial is registered, number ISRCTN29007941.
  
  
  RESULTS
  During 29,125 child-weeks of surveillance of 265 intervention and 253 control children, there were 124 physician-diagnosed pneumonia cases in intervention households and 139 in control households (rate ratio [RR] 0·84, 95% CI 0·63-1·13; p=0·257). After multiple imputation, there were 149 cases in intervention households and 180 in controls (0·78, 0·59-1·06, p=0·095; reduction 22%, 95% CI -6% to 41%). ITT analysis was undertaken for secondary outcomes: all and severe fieldworker-assessed pneumonia; severe (hypoxaemic) physician-diagnosed pneumonia; and radiologically confirmed, RSV-negative, and RSV-positive pneumonia, both total and severe. We recorded significant reductions in the intervention group for three severe outcomes-fieldworker-assessed, physician-diagnosed, and RSV-negative pneumonia--but not for others. We identified no adverse effects from the intervention. The chimney stove reduced exposure by 50% on average (from 2·2 to 1·1 ppm carbon monoxide), but exposure distributions for the two groups overlapped substantially. In exposure-response analysis, a 50% exposure reduction was significantly associated with physician-diagnosed pneumonia (RR 0·82, 0·70-0·98), the greater precision resulting from less exposure misclassification compared with use of stove type alone in ITT analysis.
  
  
  CONCLUSIONS
  In a population heavily exposed to wood smoke from cooking, a reduction in exposure achieved with chimney stoves did not significantly reduce physician-diagnosed pneumonia for children younger than 18 months. The significant reduction of a third in severe pneumonia, however, if confirmed, could have important implications for reduction of child mortality. The significant exposure-response associations contribute to causal inference and suggest that stove or fuel interventions producing lower average exposures than these chimney stoves might be needed to substantially reduce pneumonia in populations heavily exposed to biomass fuel air pollution.
  
  
  BACKGROUND
  US National Institute of Environmental Health Sciences and WHO.
authors.affiliation: Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA 94720-7360, USA. krksmith@berkeley.edu
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Smith
authors.forename: John P
authors.initials: JP
authors.lastname: McCracken
authors.forename: Martin W
authors.initials: MW
authors.lastname: Weber
authors.forename: Alan
authors.initials: A
authors.lastname: Hubbard
authors.forename: Alisa
authors.initials: A
authors.lastname: Jenny
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Thompson
authors.forename: John
authors.initials: J
authors.lastname: Balmes
authors.forename: Anaité
authors.initials: A
authors.lastname: Diaz
authors.forename: Byron
authors.initials: B
authors.lastname: Arana
authors.forename: Nigel
authors.initials: N
authors.lastname: Bruce
mesh_terms: D016902:Air Pollution, Indoor / Q000009:adverse effects* / Q000517:prevention & control; D002248:Carbon Monoxide / Q000032:analysis; D003296:Cooking; D004781:Environmental Exposure / Q000009:adverse effects; D005390:Fires; D006166:Guatemala / Q000453:epidemiology; D006801:Humans; D007223:Infant; D011014:Pneumonia / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D011159:Population Surveillance; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology; D012720:Severity of Illness Index; D012906:Smoke / Q000009:adverse effects; D014934:Wood
chemical_list: D012906:Smoke; D002248:Carbon Monoxide