Assessment and 2-year follow-up of some factors associated with severity of respiratory infections in early childhood.

Objective. To assess the effect of some factors on the severity of acute respiratory infection (ARI) in children. Design. In a case control study, children with pneumonia were matched with controls who had upper respiratory infection. They were compared in respect of nutrition, household crowding and smoke pollution, and the presence of current viral respiratory infection. Both cohorts were followed up for 18 - 24 months to determine if there was a difference in subsequent respiratory sequelae. Setting. Primary health care-based cohorts of peri-urban township children. Participants. Forty-eight children < 3 years of age with pneumonia (index cases) were matched by age and presentation time with controls who suffered only from upper respiratory infection. All came from underprivileged communities. Index cases were selected as they presented and the study was conducted between February 1988 and June 1991. Main outcome measure. Any difference between index cases and controls in respect of the four factors listed under 'Design'. Follow-up home visits determined whether subsequent sequelae of the two grades of ARI were different. Results. The presence of current viral infection at entry to the study was evident in 21 of those with pneumonia and 12 controls (difference between groups = 19.15%, 95% confidence intervals 0.25 - 38.05, P = 0.052). Overcrowding in the home was comparable. Index homes were occupied by a mean of 3.57 (SD 1.54) children and 5.26 (SD 4.84) adults, control homes by 3.51 (SD 1.80) children and 4.36 (SD 2.02) adults. Occupancy of the room in which the child slept was also not significantly different : index group mean 4.23 (SD 1.55) and controls 4.02 (SD 1.38) (mean difference 0.21, 95% CI 0.378 - 0.798, P = 0.485). Correlation of bedroom crowding with young age (< 1 year) or weight-for-age centiles was not significant in either cohort (r < 0.3 in all). The prevalence of viral infection was not increased by degree of crowding in either group (P = 0.636). Domestic smoke pollution was similar : cigarette smoking occurred in 75% of index homes and 69% of control homes. Wood or coal fires were used in 19% of index and 14% of control homes. The nutritional status of both groups proved to be similar. Fifteen per cent of index children and 12% of controls had weight-for-age centiles ≤ 10th centile (difference = 3.26%, 95% CI -10.72 - 17.24, P = 0.649). Two-year home follow-up visits were completed in 75% of the index and 69% of the control group. The balance were followed up for 18 months. There was no difference between index and control children in the recurrence of respiratory symptoms (P = 0.664) or need to visit a health facility (P = 0.302). Conclusions. Factors shown elsewhere to contribute to the acquisition or severity of ARI could not be demonstrated as important in this study. The children with pneumonia and their matched controls with upper respiratory infections came from equally overcrowded and smoke-filled homes, had comparable nutritional status which was not markedly poor, and had an equal incidence of current viral infection. Subsequent ill-health was not found to be greater in the pneumonia group.