142 1. Introduction Infant sleep problems are significant disturbance in the first year of life, with prevalence rates raging from 14 to 46% (Hiscock and Wake, 2001; Martin, Hiscock, Hardy, Davey e Wake, 2007). Early reports have pointed a tendency to sleep problems persist over time (Gregory and O’Connor, 2002). Futhermore, sleep difficulties could also shape affect, attention, cognitive and language development (Dahl, 1996; Dearing, McCartney, Marshal and Warner, 2001; Tronik and Reck, 2009), and have been found to forecast behavior problems (Gregory and O’Connor, 2002). Maternal post-natal depression is a modifiable risk factor for the development of sleep problems in the child (Bayer, Hiscock, Hampton and Wake, 2007). Moreover, depressed mothers have been seem to spend less time positively interacting with their children and to show more inconsistent and ineffective child management strategies than non-depressed parents (Cicchetti and Toth, 1995; Field, 2010). Therefore, as the depressive symptoms worsen and persist, a greater impact over the child sleep is expected. We report here the prevalence rates for sleep problems at 12 months of life, with emphasis in the impact of chronicity and severity of maternal depressive symptoms over their child’s sleep. 2. Methods A cohort study was conduct with a representative sample of mothers enrolled in the Brazilian National System of Public Health from the city of Pelotas, southern Brazil. Between July and December 2007, we randomly selected 397 pregnant women engaged in the Antenatal Health Program (SIS – pré-natal), which represents 40% of all deliveries of the period.
143 Mothers were visited after 9-12 weeks postpartum and 12 months after delivery. The Edinburgh Postpartum Depression Scale (EPDS) in its validated Portuguese version (Santos et al., 2007) was applied to detect mother’s depressive symptoms. Severity of maternal depression was based on EPDS scores as follow: mild depression (from 10 to 12) and severe depression (13 or more). Chronic cases were determined by the presence of depressive disorder in both assessments. For the assessment of sleep problems in the babies as 4-item self-rating questionnaire was applied in both mothers and fathers, asking about the following dysfunctional sleep behavior observed in the last week: (1) sleep more than 12h per day or less than 12h per day, naps included; (2) nighttime awakenings; (3) absence of sleep routine and (4) sleep terror. We considered sleep problems when two or more of these behaviors were consistently present in both reports. The following variables were considered as potential confounders: maternal age, socioeconomic status (according to the Economic Classification for Brazil of the Association of Population Survey Companies, in which the highest-income level is “A”, middle class is “C” and the lowest is “E”), maternal years of schooling, living with partner, working outside the home, birthweight, gender, prematurity, troubles at birth, number of sickness period in the last month, number of medical consults in the first year of life, breastfeeding and paternal depression (assessed with EPDS). In order to control for maternal mood-related sleep symptoms, we used the question 7 of EPDS (EPDS7), which states: “I have been so unhappy that I have had difficulty sleeping”. Data entry used EpiInfo 6.4 software with dual keying-in and subsequent consistency check. Statistical analyses was performed with Stata 9 software and SPSS 10.0 for windows. Univariate analysis was used to assess sample’s characteristics. Associations between sleep problems and the independent variables were verified with the Pearson chi-square test, with