Relative and absolute disparities in preterm birth related to neighborhood education.

PURPOSE To evaluate relative and absolute relationships between preterm birth (PTB) and neighborhood education over time. METHODS Live births in Québec, Canada, were obtained for 1990-1995, 1996-2000, and 2001-2006. Mean maternal education and proportion of females with no high school diploma were expressed as continuous cumulative rank scores for 10,923 neighborhoods. We estimated the relative hazard of PTB (<37 gestational weeks) for neighborhood education in each period by using Cox proportional hazards regression, accounting for individual education, age, marital status, birthplace, language, parity, infant sex, rurality, neighborhood income, and area clustering. Adjusted absolute differences in the prevalence of PTB between the most and least educated neighborhoods were calculated. RESULTS PTB prevalence (6.1% overall) was greater in less-educated neighborhoods. Although PTB proportions increased over time in all neighborhoods, the increase was proportionately greater for less-educated areas. Hazards of PTB for neighborhood education were proportional over gestation. Depending on the indicator of neighborhood education and period, adjusted hazards of PTB were 10%-37% greater for the least relative to most educated neighborhoods, and prevalence percentage differences ranged from 0.6% to 1.9%. Associations persisted over time. CONCLUSIONS Relative and absolute neighborhood educational inequalities in PTB, independent of individual education, were present and persistent over time.