As part of a long-term study of possible effects of early-life otitis media on speech, language, cognitive, and psychosocial development, we set out to delineate the occurrence and course of otitis media during the first 2 years of life in a sociodemographically diverse population of infants, and to identify related risk factors. We enrolled healthy infants by age 2 months who presented for primary care at one of two urban hospitals or one of two small town/rural and four suburban private pediatric practices. We intensively monitored the infants' middle-ear status by pneumatic otoscopy, supplemented by tympanometry, throughout their first 2 years of life; we monitored the validity of the otoscopic observations on an ongoing basis; and we treated infants for otitis media according to specified guidelines. We followed 2253 infants until age 2 years. The proportions developing > or = 1 episode of middle-ear effusion (MEE) between age 61 days (the starting point for data analysis) and ages 6, 12, and 24 months, respectively, were 47.8%, 78.9%, and 91.1%. Overall, the mean cumulative proportion of days with MEE was 20.4% in the first year of life and 16.6% in the second year of life. Tympanostomy-tube placement was performed on 1.8% and 4.2% of the infants during the first and second years of life, respectively. By every measure, the occurrence of MEE was highest among urban infants and lowest among suburban infants; these differences were greatest in the earliest months of life. Overall, unadjusted mean cumulative proportions of days with MEE were higher among boys than girls, higher among black than white infants, and higher among Medicaid than private health insurance enrollees. Cumulative proportions of days with MEE varied directly with the number of smokers in the household and with the number of other children to whom infants were exposed, whether at home or in day care, and varied inversely with birth weight, maternal age, level of maternal education, a socioeconomic index, and duration of breastfeeding. After adjustment, using multivariate analysis, the only variables that each remained independently and significantly related to the cumulative proportion of days with MEE were: during the first year of life, study site grouping, sex, the socioeconomic index, breastfeeding for > or = 4 months, the number of smokers in the household, and an index rating the degree of exposure to other children at home or in day care; and during the second year of life, sex, the socioeconomic index, and the child exposure index. The duration of breastfeeding and the degree of exposure to tobacco smoke contributed little to the explained variance; most was attributable to differences in the socioeconomic index and the child exposure index. Contrary to findings in many previous reports, the prevalence of otitis media during the first 2 years of life among lower-socioeconomic-status black infants appears to be as high as, if not higher than among lower-socioeconomic-status white infants, and certainly higher than among middle-class white infants. Among middle-class white infants the prevalence may also be higher than commonly assumed. The most important sociodemographic risk factors for otitis media appear to be low socioeconomic status and repeated exposure to large numbers of other children, whether at home or in day care.
