Breastfeeding has long been believed to protect against infection in infants, but protection against respiratory illnesses has not been consistently demonstrated in studies in developed countries. Between 1988 and 1992, the authors assessed the effect of breastfeeding on incidence and duration of respiratory illnesses during the first 6 months of life in a prospective study that actively tracked breastfeeding and respiratory illnesses. A cohort of 1,202 healthy infants, born in Albuquerque, New Mexico, between January 1, 1988 and June 30, 1990, from homes without smokers was enrolled. The daily occurrences of respiratory symptoms and breastfeeding status were reported by the mothers every 2 weeks. Illnesses were classified as lower respiratory illness (LRI) if wheezing or wet cough was reported; the remaining illnesses were classified as upper respiratory. The annualized incidence rates for LRI were 2.8, 2.6, and 2.1 during follow-up time with no, partial, or full breastfeeding, respectively, but the incidence rates for upper respiratory illness and lower respiratory illness combined were similar in the three categories. After adjustment for potential confounding factors, full breastfeeding was associated with a reduction in lower respiratory illness risk (odds ratio=0.81, 95% confidence interval 0.68-0.96). Median duration of all respiratory illnesses was 5 days for the fully breastfed infants during the first 6 months of life compared with a median of 6 days for not breastfed and partially breastfed infants. Multivariate analysis confirmed that breastfeeding significantly reduced the duration of respiratory illness. This pattern of reduced incidence of LRI and shorter duration of all respiratory illnesses suggests that breastfeeding reduces the severity of infant respiratory illnesses during the first 6 months of life.

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Nitrogen dioxide is an oxidant gas that contaminates outdoor air and indoor air in homes with unvented gas appliances. A prospective cohort study was carried out to test the hypothesis that residential exposure to NO2 increases incidence and severity of respiratory illnesses during the first 18 months of life. A cohort of 1,205 healthy infants from homes without smokers was enrolled. The daily occurrence of respiratory symptoms and illnesses was reported by the mothers every 2 wk. Illnesses with wheezing or wet cough were classified as lower respiratory tract. Indoor NO2 concentrations were serially measured with passive samplers place in the subjects' bedrooms. In stratified analyses, illness incidence rates did not consistently increase with exposure to NO2 or stove type. In multivariate analyses that adjusted for potential confounding factors, odds ratios were not significantly elevated for current or lagged NO2 exposures, or stove type. Illness duration, a measure of illness severity, was not associated with NO2 exposure. The findings can be extended to homes with gas stoves in regions of the United States where the outdoor air is not heavily polluted by NO2.

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S U M M A R Y Forty-nine children with complicated bacterial meningitis were studied. Thirteen had abnormalities on computed tomography compatible with the diagnosis of brain infarction; one had a brain biopsy with the histological appearance of infarction. Factors exist in childhood bacterial meningitis which are associated with the development of brain infarction.Although antibiotics have been successful in eradicating the infecting organtism in many cases of childhood bacterial meningitis, major neurological complications continue to occur.'-3 For many decades physicians have relied upon necropsy to determine the pathogenesis of 'these complications.46 Only limited help has been obtained from cerebral arteriography and pneumoencephalography.78 The complexity and risk of such procedures prevent wide use.9'10 Recent application of computed tomography of the brain (CT) has provided a unique and relatively simple noninvasive radiographic method for examining those children with bacterial meningitis who developed neurological complications. 11-14 CT has provided additional information concerning the pathogenesis of the neurologic complications.

In a cohort study of respiratory illnesses from birth through age 18 months, the investigators assessed the occurrence of illness by telephone reports of respiratory symptoms. To assess the comparability of illness events based on symptom reports with usual clinical modalities, a nurse practitioner examined children during illnesses, and office and clinic records of outpatient visits were reviewed. Respiratory illnesses were defined as symptom episodes of at least 2 days; lower respiratory illnesses included at least 1 day of either wet cough or wheeze. This report is based on 10,771 illnesses in the 1,315 subjects enrolled. Runny or stuffy nose was reported for most (93%) illnesses, wet cough in 33%, and wheeze in 6%. In comparison with the diagnoses made by a nurse practitioner, parent report of wet cough or wheeze was sensitive (93.4%) for detecting lower respiratory illnesses, but nonspecific with specificity of only 24.2%. The majority of the false-positive lower respiratory illnesses had the symptom of wet cough. The comparison of parent reports with outpatient records provided similar findings. Standardized reporting of respiratory illnesses can be achieved with a telephone surveillance system but classification of specific illnesses from the surveillance information may differ from diagnoses made by clinicians.

Toxicologic and epidemiologic studies have elevated concern that exposure to nitrogen dioxide (NO2) in outdoor and indoor air may increase the frequency and severity of respiratory infections. We have developed and implemented a prospective cohort study to test the hypothesis that exposure to NO2 increases the incidence and severity of respiratory infections during the first 18 mo of life. This study, which was based on extensive pilot research, was designed to address the potential limitations of misclassification, confounding, and inadequate power. Enrollment of 1,315 subjects has been completed. This paper reviews the methods used in the study, characteristics of the enrolled subjects, NO2 concentrations in the homes of study participants, and rates of illness occurrence.

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