Falling asleep: the determinants of sleep latency.

BACKGROUND: Difficulty falling asleep (prolonged sleep latency) is a frequently reported problem in school-aged children. AIMS: This study aimed to describe the distribution of sleep latency and factors that influence its duration. METHODS: 871 children of European mothers were recruited at birth. 591 (67.9%) children took part in the follow-up at 7 years of age. Sleep and daytime activity were measured objectively by an actigraph worn for 24 h. RESULTS: Complete sleep data were available for 519 children (87.8%) with a mean age of 7.3 years (SD 0.2). Median sleep latency was 26 minutes (interquartile range 13-42). Higher mean daytime activity counts were associated with a decrease in sleep latency (-1.2 minutes per 102 movement count per minute, p = 0.05). Time spent in sedentary activity was associated with an increase in sleep latency (3.1 minutes per hour of sedentary activity, p = 0.01). CONCLUSIONS: These findings emphasise the importance of physical activity for children, not only for fitness, cardiovascular health and weight control, but also for promoting good sleep.

Risk factors for asthma at 3.5 and 7 years of age.

BACKGROUND: It has been suggested that factors in early life including exposure to allergens and microbes may influence the development of asthma. OBJECTIVE: To identify risk factors for asthma in early childhood. Methods Eight-hundred and seventy-one children of European mothers were enrolled at birth, of whom 385 (44.2%) were born small for gestational age (SGA) and 486 were appropriate for gestational age (AGA). Data were collected at birth, 12 months, 3.5 years of age (y) and 7 y. The outcome of interest (current wheeze) was defined as a positive response to the question: 'Has your child had wheezing or whistling in the chest in the last 12 months?' RESULTS: Participation rate was 85.4% at 1 y, 63.1% at 3.5 y and 68.0% at 7 y. The prevalence of asthma was 23.8% at 3.5 y and 18.1% at 7 y. Antibiotic use in the first year of life and day care in the first year of life were associated with increased risk of wheeze at 7 y [odds ratio (OR)=4.3 95% confidence interval (CI) (1.8-10.1) and OR=2.8 95% CI (1.2-6.5), respectively], but not at 3.5 y. Exposure to dogs was a risk factor for asthma at both ages [OR=2.1 95% CI (1.1-3.8)] as was sleeping on a used cot mattress in the first year of life [OR=1.8 95% CI (1.0-3.2)]. CONCLUSIONS: There was a significant association between antibiotic use and day care in the first year of life and wheezing at 7 y but not at 3.5 y. This strengthens the argument that these factors increase the risk of asthma. We have also made the novel observation that sleeping on a used mattress in the first year of life is a risk factor for wheezing at 3.5 and 7 y. Capsule summary This prospective study of 871 children made the novel observation that sleeping on a used mattress in the first year of life was a risk factor for wheezing at 3.5 and 7 y.

Breastfeeding and intelligence of preschool children.

AIM: To investigate whether breastfeeding during infancy is a determinant of intelligence at 3.5 y. METHODS: Five hundred and fifty European children enrolled at birth in the Auckland Birthweight Collaborative Study were assessed at 3.5 y of age. Approximately half were small for gestational age (SGA < or =10th percentile) at birth and half were appropriate for gestational age (AGA >10th percentile). Duration of breastfeeding was recorded at maternal interview, and the intelligence of children was assessed using the Stanford Binet Intelligence Scale. Regression analysis was used to calculate estimates of difference in intelligence scores between breastfeeding groups for the total sample and the group of SGA children. Analyses of the total sample were weighted to account for the disproportionate sampling of SGA children. RESULTS: Breastfeeding was not significantly related to intelligence scores in the total sample despite a trend for longer periods of breastfeeding to be associated with higher intelligence scores. However, in the SGA group, breastfeeding was significantly related to IQ at 3.5 y. Small for gestational age children who were breastfed for longer than 12 mo had adjusted scores 6.0 points higher than those who were not breastfed (p=0.06). CONCLUSION: Breastfeeding may be particularly important for the cognitive development of preschool children born small for gestational age.

Maternal stress, social support and preschool children's intelligence.

BACKGROUND: Despite some research suggesting maternal stress may be associated with cognitive impairment in preschool children, there has been little direct investigation of the association between maternal stress, social support and children's intelligence. AIM: To determine whether maternal stress and social support during pregnancy and during the child's early years of life are associated with the intelligence test performance of preschool children. STUDY DESIGN: Five hundred and fifty European mothers and children enrolled in the Auckland Birthweight Collaborative Study at birth were interviewed when the child was 3 1/2 years of age. SUBJECTS: All children were full term gestation and approximately half the sample were small for gestational age at birth (SGA = birthweight < or = 10th percentile). OUTCOME MEASURE: The cognitive ability of children aged 3 1/2 years was assessed using the Stanford Binet Intelligence Scale 4th Edition. RESULTS: In the total sample, maternal stress and lack of social support during pregnancy were significantly associated with lower intelligence test scores of children. In the group of SGA children, maternal stress post pregnancy was significantly associated with lower intelligence test scores in children. There is evidence that for some children the presence of good social support for mothers may reduce the negative effects of maternal stress on children's cognitive development. CONCLUSION: Maternal stress and lack of social support appear to be associated with lower intelligence test scores of preschool children. Social support may attenuate some of the negative effects of maternal stress on intelligence in children born small for gestational age.

Maternal nutritional risk factors for small for gestational age babies in a developed country: a case-control study.

AIMS: To assess the effect of maternal diet during pregnancy on the risk of delivering a baby who is small for gestational age (SGA). METHODS: Case-control study of 844 cases (SGA) and 870 controls (appropriate size for gestational age (AGA)). Only term (37+ completed weeks of gestation) infants were included. Retrospective food frequency questionnaires were completed at birth on the diet at the time of conception and in the last month of pregnancy. RESULTS: At the time of conception, mothers of AGA infants ate significantly more servings of carbohydrate rich food and fruit, and were more likely to have taken folate and vitamin supplements than mothers of SGA infants. There was some evidence that mothers of AGA infants also ate more servings of dairy products, meat, and fish (0.05 < p < 0.1). However, after adjustment for maternal ethnicity, smoking, height, weight, hypertension, and occupation, fish intake (p = 0.04), carbohydrate-rich foods (p = 0.04), and folate supplementation (p = 0.02) were associated with a reduced risk of SGA. In the last month of pregnancy, only iron supplementation was associated with a reduced risk of SGA (p = 0.05) after adjustment for potential confounders. CONCLUSIONS: This study suggests that small variations in maternal diets within the normal range during pregnancy in developed countries are associated with differences in birth weight.

Stress and lack of social support as risk factors for small-for-gestational-age birth.

AIM: To determine the contributions of social support and perceived stress to the risk of small-for-gestational-age birth. METHODS: The investigation was a case-control study of mothers of infants born at 37 or more completed weeks of gestation. Cases weighed less than the sex-specific 10th percentile for gestational age at birth (small for gestational age (SGA), n = 836), and controls (appropriate for gestational age (AGA), n = 870) comprised a random selection of heavier babies. RESULTS: In univariate analyses measures of informal social support, but not perceived stress or formal social support, were associated with SGA birth. It was found that Asian mothers are less likely to receive support from families and friends. After adjustment for ethnicity, informal social support was not associated with SGA. CONCLUSIONS: Support appears to reduce the risk of SGA births, but after adjustment for ethnicity this is no longer the case. Stress during pregnancy was not associated with SGA birth.

Smoking, nicotine and tar and risk of small for gestational age babies.

AIMS: To assess the effect of maternal smoking and environmental tobacco smoke (ETS) on risk of small for gestational age infants (SGA). METHODS: Case-control study of 844 cases and 870 controls. RESULTS: Maternal smoking in pregnancy was associated with an increased risk of SGA (adjusted odds ratio (OR)= 2.41; 95% confidence interval (CI) = 1.78, 3.28). We could not detect an increased risk of SGA with paternal smoking, or with other household smokers when the mother was a non-smoker, but did find an increased risk with exposure to ETS in the workplace or while socializing. Infants of mothers who ceased smoking during pregnancy were not at increased risk of SGA, but those who decreased but did not stop remained at risk of SGA. There was no evidence that the concentration of nicotine and tar in the cigarettes influenced the risk of SGA. CONCLUSIONS: Maternal smoking in pregnancy is a major risk factor for SGA. This study suggests that mothers should be advised to cease smoking completely during pregnancy, and that a reduction in the number of cigarettes smoked or smoking low tar or nicotine concentration cigarettes does not reduce the risk of SGA.

The epidemiology of placental infarction at term.

The incidence and associations of placental infarction at term were investigated as part of a population based case-control study of small for gestational age (SGA) infants. 509 placentas from women delivering SGA infants (SGAP) and 529 placentas from women delivering infants with birthweights appropriate for gestational age (AGAP) were examined using fixed protocols for macroscopic identification and microscopic confirmation of infarction. Other information was obtained by maternal interview and from an obstetric database. Infarcts were found in 17.3 per cent of SGAP and 11.7 per cent of AGAP. This difference was in placentas with multiple infarcts not involving the placental margin and was significant in multivariate analysis (OR 1.66; 95 per cent CI 1.12,2.47). Multivariate analysis showed significant associations between the presence of any infarct and maternal hypertension in both SGAP (OR=4.00; 95 per cent CI 1.96,8.16) and AGAP (OR 2.99; 95 per cent CI 1.23,7.32); maternal smoking, associated with a lesser risk in SGAP only (OR=0.31; 95 per cent CI 0.13,0.73); maternal age at first pregnancy in a linear relationship with AGAP only (beta co-efficient 0.09, P=0.0034); and between some ethnic groups. We conclude that at least five factors have independent associations with the incidence of placental infarction and these associations differ by site and age of infarcts.