Biomass fuel use and ALRI in children under 5 in developing countries
| Study | Design | Case definition | Exposure | Confounding adjusted | Comments | OR (95% CI) |
| Rural South Africa (1980) Natal (Kossove)58 | Case control, 0–12 months, 132 cases, 18 controls | Outpatient cases: Wheezing, bronchiolitis & ALRI; Clinical + x ray. Controls: Non-respiratory problems | Asked: “Does the child stay in the smoke?” Prevalence = 33% | Routine data collection: • number of siblings • economic status Examined, not adjusted | Only 63% of 123x rayed had pneumonic changes. Control group was small. Exposure assessment was vague. | 4.8 (1.7 to 13.6) |
| Rural Nepal (1984–85) Kathmandu Valley (Pandeyet al)53 | Cohort, 0–23 months, 780 (study 1), 455 (study 2) | Two-weekly home visits: ARI grades I–IV (Goroka) Breathlessness | Asked mothers for average hours per day the child near fireplace. In study 1, same team asked about exposure and ARI > possible bias 77% exposed over 1 hour | Since homes were “homogeneous” confounding not taken into account | Dose response relationship found Exposure assessment not validated | 2.2 (1.6 to 3.0) |
| Rural Gambia (1987–88) Basse (Campbellet al)54 | Cohort, 0–11 months, 280 | Weekly surveillance. Mother's history of “difficulty with breathing” over subsequent 3 month period | Reported carriage of child on the mother's back Prevalence = 37% | Adjusted for • birth interval • parental ETS • crowding • socioeconomic score • nutritional indicators • vaccination status • no. of health centre visits • ethnic group • maternal education • other | Father's ETS only other significant factor. Cautious about interpretation, ability to deal with confounding, and to establish causation where exposure and incidence high | 2.8 (1.3 to 6.1) |
| Urban, Argentina (1984–87) Buenos Aires (Cerqueiro et al)67 | Case-control, 0–59 months Cases: 516 inpatients; 153 outpatients, Controls: 669 | Three hospitals: Cases: ALRI within previous 12 days Controls: well baby clinic or vaccination, matched by age, sex, nutritional status, socioeconomic level, date of visit, and residence. | Interview with mother: Household heating by charcoal; heating with any fuel; bottled gas for cooking | None, but success of matching verified. Multivariate analysis “currently underway” | No data available re charcoal heating in outpatient households. Chimney smoke nearby found to be associated (OR 2.5–2.7) with ARLI in both kinds of patients. ETS not significant for either | 9.9 (1.8 to 31.4) for charcoal heat for inpatients 1.6 (1.3 to 2.0) for any heating fuel in inpatients 2.2 (1.2 to 3.9) for gas cooking in outpatients |
| Rural Zimbabwe (?) Marondera (Collingset al)57 | Case control, 0–35 months, 244 cases, 500 controls | Hospital: Cases: Hosp ALRI, clinical and x ray. Controls: Local well baby clinic | (a) Questionnaire on cooking/exposure to woodsmoke (b) COHb (all) (c) TSP (2 h during cooking): 20 ALRI and 20 AURI cases 73% exposed to open fire | Questionnaire: • maternal ETS • overcrowding • housing conditions • school age sibs • paternal occupation not adjusted | Confounding: only difference was number of school age sibs, but not adjusted. COHb not different between ALRI and AURI. TSP means: ALRI (n=18) 1915 μg/m3 AURI (n=15) 546 μg/m3 | 2.2 (1.4 to 3.3) |
| Rural Gambia (?) Upper River Division (Armstrong and Campbell)56 | Cohort, 0–59 months, 500 (approx.) | Weekly home visits: ALRI clinical andx ray | Questionnaire: Carriage on mother's back while cooking | Questionnaire: • parental ETS • crowding • socioeconomic index • number of siblings • sharing bedroom • vitamin A intake • no. of wives • no. of clinic visits Adjusted in MLR | Boy/girl difference could be due to greater exposure. Report carriage on back quite a distinct behaviour so should define the two groups fairly clearly with low level of misclassification | Approach (1) (all episodes) M: 0.5 (0.2 to 1.2) F: 1.9 (1.0 to 3.9) Approach (2) (1st episode) M: 0.5 (0.2 to 1.3) F: 6.0 (1.1 to 34.2) |
| Urban Nigeria (1985–86) Ibadan (Johnson and Aderele)62 | Case control, n=103+103, 0–59 months | Cases: Hospitalised for ALRI (croup, bronchiolitis, pneumonia, empyema thoracis) based on clinical,x ray, and biolab workup. Controls: infant welfare clinic, age and sex matched, no respiratory disease | Interview Type of cooking fuel used at home (wood, kerosene, gas) | None | Age, nutritional status, ETS, crowding, and location of cooking area also not significant. | NS |
| Urban Nigeria (1985–86) Ibadan (Johnson and Aderele)62 | Case fatality, n=103, 0–59 months | Cases: Death in hospital among ALRI patients (see above) | Interview Type of cooking fuel used at home (79 = kerosene, gas = 5, wood = 16, other = 3) | None | Overall case fatality rate = 7.8%. 5 of 8 deaths were from wood burning homes; one additional death had partial exposure to wood smoke. Poor nutrition (1.8×), low income (1.5×), low maternal literacy (2.1×) were more frequent in wood burning homes. ETS rates were similar. Yet paternal income, maternal education, household crowding, ETS not related to case fatality rate | 12.2 (p<0.0005) for those exposed to wood smoke compared with those exposed to kerosene and gas |
| Rural Tanzania (1986–87) Bagamoyo District (Mtango et al)60 | Case-control Cases: ALRI deaths = 154 Other deaths = 456 Controls = 1160 0–59 months | Cases: Verbal autopsy certified by physician of all deaths in period. Controls: Multistage sampling (40 of 76 villages). Children with ALRI were excluded | Household interview; • Child sleeps in room where cooking is done • Cook with wood | Village, age, questionnaire respondent, maternal education, parity, water source, child eating habit, whether mother alone decides treatment. | About 95% of all groups cook with wood. No tendency to be different distances from road. Perhaps confusion of ALRI with other diseases (e.g. measles). Water not from tap had OR = 11.9 (5.5 to 25.7). Models with all deaths, pneumonia deaths, and non-pneumonia deaths all had same significant risk factors. No difference in source of treatment by location where child sleeps. Maternal education, religion, crowding, and ETS, not significant | All deaths: 2.8 (1.8 to 4.3) for sleeping in room with cooking. 4.3 for pneumonia only. 2.4 for other deaths |
| Rural Gambia Upper River Division (de Francisco et al)61 | Case-control Cases: 129 ALRI deaths Controls: 144 other deaths 270 live controls 0–23 months | Cases: Verbal autopsy confirmed by 2 of 3 physicians. Controls: Matched by age, sex, ethnic group, season of death, and geographic area | Indoor air pollution index based on location and type of stove, carrying of child while cooking, and parental ETS (details not provided) | Cases vs. live controls: Adjusted for significant factors in univariate analysis: socioeconomic score, crowding, parental ETS, and nutrition indicators plus maternal education. No significant factors for cases vs. dead controls. | Only other significant risk factor remaining after multiple conditional logistic regression was whether child ever visited welfare clinic OR = 0.14 (0.06 to 0.36) Misclassification of ALRI deaths (e.g. confusion with malaria) is possible reason for lack of significant difference between cases and dead controls. | 5.2 (1.7 to 15.9) for cases vs. live controls |
| Urban Brazil (1990) Porto Alegre (Victoraet al)64 | Case control, 0–23 months, 510 cases, 510 controls | Cases: ALRI admitted to hospital, clinical and X-ray. Controls: Age matched, neighborhood | Trained field worker interview: • Any source of indoor smoke (open fires, woodstoves, fireplaces) • Usually in kitchen while cooking | Interview: • cigarettes smoked • housing quality • other children in hh • income/education • day centre attendance • history of respiratory illness • (other) Hierarchical model/MLR | Only 6% of children exposed to indoor smoke. Urban population with relatively good access to health care. Not representative of other settings in developing countries | Indoor smoke: 1.1 (0.61 to 1.98) Usually in the kitchen: 0.97 (0.75 to 1.26) |
| Urban and rural India (1991) South Kerala-Trivandrum (Shah et al)63 | Case control, 2–60 months, 400 total | Hospital: Cases: Admitted for severe/very severe ARI (WHO definition). Controls: Outpatients with non-severe ARI | History taken, including • type of stove, with “smokeless” category • outdoor pollution | History: • smokers in house • number of siblings • house characteristics • socioeconomic conditions • education • birth weight etc. Adjusted in MLR | This is a study of the risk factors for increased severity, as the controls have ARI (non-severe). On MLR, only age, sharing a bedroom, and immunisation were significant. Exposure assessment was vague and invalidated | “Smokeless” stove: 0.82 (0.46 to 1.43). |
| Rural Gambia (1989–1991) Upper River Division (O'Dempsey et al)55 | Prospective case-control, n=80+159, 0–59 months | Attending clinic. Cases: if high respiratory rate, transported to Medical Research Council where physician diagnosed pneumonia after lab tests and x ray. Controls: selected randomly from neighbourhood of cases, matched by age | Household questionnaire: Mother carries child while cooking | Adjusted for mother's income, ETS, child's weight slope, recent illness, and significant illness in last six months. | No effect of bednets, crowding, wealth, parental education, paternal occupation, age of weaning, and nutritional status. ETS OR = 3.0 (1.1 to 8.1). Aetiological (preventive) fraction for eliminating maternal carriage while cooking = 39%; for eliminating ETS in house = 31%. May be reverse causality, i.e. sick children being more likely to be carried. | 2.5 (1.0 to 6.6) |
This list is confined to quantitative studies that have used internationally standardised criteria for diagnosing ALRI. There are additional studies that have noted a relationship with various respiratory symptoms including cough, runny nose, noisy respiration, and sore throat—for example, the study in Lucknow, India by Awasthiet al 68 which is discussed in the text.