Lenie van Rossem

Cohort profile: The Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort

The Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort was set up in The Netherlands with two main aims: to investigate the effect of mite-allergen avoidance on the incidence of childhood asthma (Intervention study) and to assess lifestyle and environmental risk factors for childhood asthma (Natural History study). The baseline study population consisted of 3963 children born in 1996– 1997. Questionnaires were completed by parents during pregnancy, when the child was 3 months old, then annually from 1 up to 8 years and by parents as well as children at 11 and 14 years. Data were obtained on child and family characteristics, a wide range of environmental and lifestyle exposures and on asthma and other allergic and respiratory outcomes. Home visits and clinical examinations were conducted in sub-groups at the ages of 1, 4, 8 and 12 years to obtain objective measures. These included anthropometric measures, measurements of lung function, bronchial hyper-responsiveness and blood pressure, house dust and blood samples, which were used to determine total and specific IgEs, cholesterol and HbA1c and to extract DNA.

Breast-feeding and growth in children until the age of 3 years: the Generation R Study

Breast-feeding has been suggested to be associated with lower risks of obesity in older children and adults. We assessed whether the duration and exclusiveness of breast-feeding are associated with early postnatal growth rates and the risks of overweight and obesity in preschool children. The present study was embedded in a population-based prospective cohort study from early fetal life onwards, among 5047 children and their mothers in The Netherlands. Compared with children who were breast-fed, those who were never breast-fed had a lower weight at birth (difference 134 (95 % CI - 190, - 77) g). No associations between breast-feeding duration and exclusivity with growth rates before the age of 3 months were observed. Shorter breast-feeding duration was associated with an increased gain in age- and sex-adjusted standard deviation scores for length, weight and BMI (P for trend < 0·05) between 3 and 6 months of age. Similar tendencies were observed for the associations of breast-feeding exclusivity with change in length, weight and BMI. Breast-feeding duration and exclusivity were not consistently associated with the risks of overweight and obesity at the ages of 1, 2 and 3 years. In conclusion, shorter breast-feeding duration and exclusivity during the first 6 months tended to be associated with increased growth rates for length, weight and BMI between the age of 3 and 6 months but not with the risks of overweight and obesity until the age of 3 years.

Traffic-related air pollution and noise and children’s blood pressure: Results from the PIAMA birth cohort study

Aims Elevation of a child’s blood pressure may cause possible health risks in later life. There is evidence for adverse effects of exposure to air pollution and noise on blood pressure in adults. Little is known about these associations in children. We investigated the associations of air pollution and noise exposure with blood pressure in 12-year-olds. Methods Blood pressure was measured at age 12 years in 1432 participants of the PIAMA birth cohort study. Annual average exposure to traffic-related air pollution [NO2, mass concentrations of particulate matter with diameters of less than 2.5 µm (PM2.5) and less than 10 µm (PM10), and PM2.5 absorbance] at the participants’ home and school addresses at the time of blood pressure measurements was estimated by land-use regression models. Air pollution exposure on the days preceding blood pressure measurements was estimated from routine air monitoring data. Long-term noise exposure was assessed by linking addresses to modelled equivalent road traffic noise levels. Associations of exposures with blood pressure were analysed by linear regression. Effects are presented for an interquartile range increase in exposure. Results Long-term exposure to NO2 and PM2.5 absorbance were associated with increased diastolic blood pressure, in children who lived at the same address since birth [adjusted mean difference (95% confidence interval) [mmHg] 0.83 (0.06 to 1.61) and 0.75 (−0.08 to 1.58), respectively], but not with systolic blood pressure. We found no association of blood pressure with short-term air pollution or noise exposure. Conclusions Long-term exposure to traffic-related air pollution may increase diastolic blood pressure in children.

Particulate matter composition and respiratory health : the PIAMA birth cohort study

Background: Ambient particulate matter (PM) exposure is associated with children’s respiratory health. Little is known about the importance of different PM constituents. We investigated the effects of PM constituents on asthma, allergy, and lung function until the age of 11–12 years. Methods: For 3,702 participants of a prospective birth cohort study, questionnaire-reported asthma and hay fever and measurements of allergic sensitization and lung function were linked with annual average concentrations of copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc in particles with diameters of less than 2.5 and 10 &mgr;m (PM2.5 and PM10) at birth addresses and current addresses from land-use regression models. Exposure–health relations were analyzed by multiple (repeated measures) logistic and linear regressions. Results: Asthma incidence and prevalence of asthma symptoms and rhinitis were positively associated with zinc in PM10 at the birth address (odds ratio [95% confidence interval] per interquartile range increase in exposure 1.13 [1.02, 1.25], 1.08 [1.00, 1.17], and 1.16 [1.04, 1.30], respectively). Moreover, asthma symptoms were positively associated with copper in PM10 at the current address (1.06 [1.00, 1.12]). Allergic sensitization was positively associated with copper and iron in PM10 at the birth address (relative risk [95% confidence interval] 1.07 [1.01, 1.14] and 1.10 [1.03, 1.18]) and current address. Forced expiratory volume in 1 second was negatively associated with copper and iron in PM2.5 (change [95% confidence interval] -2.1% [-1.1, -0.1%] and -1.0% [-2.0, -0.0%]) and FEF75–50 with copper in PM10 at the current address (-2.3% [-4.3, -0.3%]). Conclusion: PM constituents, in particular iron, copper, and zinc, reflecting poorly regulated non-tailpipe road traffic emissions, may increase the risk of asthma and allergy in schoolchildren.

Behavioral risk factors for overweight in early childhood; the ‘Be active, eat right’ study

BackgroundThe lifestyle-related behaviors having breakfast, drinking sweet beverages, playing outside and watching TV have been indicated to have an association with childhood overweight, but research among young children (below 6 years old) is limited. The aim of the present study was to assess the associations between these four behaviors and overweight among young children.MethodsThis cross-sectional study used baseline data on 5-year-old children (n = 7505) collected for the study ‘Be active, eat right’. Age and sex-specific cut-off points for body mass index of the International Obesity Task Force were used to assess overweight/obesity. Multivariable logistic regression analyses were applied.ResultsFor children whom had breakfast <7 days/week and watched TV >2 hours/day, the odds ratio (OR) for having overweight (obesity included) was, respectively, 1.49 (95% confidence interval (CI): 1.13-1.95), and 1.25 (95% CI: 1.03-1.51). There was a positive association between the number of risk behaviors present and the risk for having overweight. For children with 3 or all of the risk behaviors having breakfast <7 days/week, drinking sweet beverages >2 glasses/day, playing outside <1 h/day, watching TV >2 hs/day, the OR for overweight was 1.73 (95% CI: 1.11-2.71) (all models adjusted for children’s sex and sociodemographic characteristics).ConclusionGiven the positive association between the number of behavioral risk factors and overweight, further studies are needed to evaluate the effectiveness of behavioral counseling of parents of toddlers in preventing childhood overweight. In the meantime we recommend physicians to target all four behaviors for counseling during well-child visits.

Is the association of breastfeeding with child obesity explained by infant weight change

OBJECTIVE Breastfeeding and infant weight change are both associated with adiposity. We examined the extent to which infant weight change mediates the association between breastfeeding and adiposity at age 3 years. METHODS We studied 884 children in a prospective cohort study. We determined breastfeeding status in the first 6 months. Our primary outcomes at 3 years were body mass index (BMI) z score and the sum of subscapular and triceps skinfold thicknesses (SS + TR); we also assessed obesity. We defined infant weight change as change in weight-for-age z score between birth and 6 months. We performed multivariable regression analyses. RESULTS At age 6 months, 25.0% of infants were fully breastfed. At age 3 years, mean (standard deviation) BMI z score was 0.45 (1.03). In linear regression analyses adjusted for mothers educational level, race/ethnicity, smoking, BMI, pregnancy weight gain and birth weight (adjusted for gestational age), the BMI z score of fully breastfed children was 0.17 (95% CI: -0.43, 0.09) units lower than never breastfed children. After additional adjustment for infant weight change, the estimate was attenuated (-0.03, 95% CI: -0.27, 0.20). Adjustment for infant weight change only modestly attenuated estimates for SS + TR (from -1.48 mm [95% CI: -2.52, -0.44] to -1.16 mm [95% CI: -2.18, -0.14]), and for the odds of being obese (from 0.21 [95% CI: 0.07, 0.68] to 0.29 [95% CI: 0.08, 1.05]). CONCLUSION Infant weight change between birth and 6 months mediates associations of breastfeeding with BMI, but only partially with indicators of child adiposity.

An observational study on socio-economic and ethnic differences in indicators of sedentary behavior and physical activity in preschool children

OBJECTIVE We studied associations between social disadvantage and indicators of sedentary behavior and physical activity at preschool age. METHODS Data from 4688 children enrolled in a birth cohort in Rotterdam, the Netherlands, between 2002 and 2006 were analyzed. Indicators of sedentary behavior (watching television ≥ 2 h/day and sitting in a buggy ≥ 0.5 h/day) and physical inactivity (playing outside < 3 h/day) were measured by a parent-reported questionnaire at age 3. Adjustments were made for social circumstances and indicators of health behaviors. Logistic regression was used to obtain odds ratios (OR) and 95% confidence intervals (CI). RESULTS Children with low-educated mothers (OR: 3.27, 95% CI 2.12-5.05) and non-Dutch children (OR(nonWestern): 2.67, 95% CI 2.04-3.49, OR(Western): 2.09, 95% CI 1.42-3.0) were more likely to watch television for at least 2 h/day. Similar results were seen for sitting in a buggy for at least 0.5h/day. Non western children were more likely to play outside for less than 3 h/day (OR: 1.95, 95% CI: 1.39-2.73) than native Dutch children, while no differences were seen for other western children or children from mothers with a low educational level. CONCLUSIONS Socio-economic status and ethnicity are already associated with indicators of sedentary lifestyles at preschool age.

Socioeconomic Status is not Inversely Associated with Overweight in Preschool Children

OBJECTIVE To assess whether socioeconomic inequalities were already present in preschool children. STUDY DESIGN We used data from 2954 Dutch children participating in a longitudinal birth cohort study. Indicators of socioeconomic status were mothers educational level and household income. Body mass index (BMI)-for-age standard deviation scores were derived from a national reference. Overweight was defined at 24 and 36 months according to age- and sex-specific cut-off points for BMI. Multivariable regression analyses were performed. RESULTS Relative to children from mothers with the highest educational level, mean BMI standard deviation scores was lower at age 24 months in children from mothers with the low, mid-low, and mid-high educational level, and in the mid-low group at 36 months (P < .001). Prevalence of overweight was lower in children from mothers with the mid-low educational level at age 24 and 36 months (adjusted odds ratio at 24 months: 0.61; 95% confidence interval: 0.43-0.87 and at 36 months: 0.65; 95% confidence interval: 0.44-0.96) but was not significantly different for the other educational levels. There were no significant differences in childhood overweight by income level. CONCLUSIONS The inverse association between socioeconomic status and childhood overweight presumably emerges after age 3 years. Before this age, the gradient may be the reverse.

Time in bed, sleep quality and associations with cardiometabolic markers in children : the Prevention and Incidence of Asthma and Mite Allergy birth cohort study

We investigated associations of time in bed and multiple sleep quality characteristics with cardiometabolic markers in children. Data from the prevention and incidence of asthma and mite allergy study, a population‐based prospective birth‐cohort study started in 1996–1997 in the Netherlands, were analysed. In total 1481 children aged 11–12 years completed a questionnaire (including questions on sleep) and underwent a medical examination. We measured body mass index, waist circumference, total‐ and high‐density lipoprotein cholesterol, blood pressure and glycated haemoglobin. Results showed that in girls, some sleep characteristics were related to anthropometrics (body mass index, waist circumference) and cholesterol. Girls who had a long time in bed (11–12.5 h) had 0.16 lower body mass index z‐score (95% confidence interval −0.31; −0.01) and 0.99 cm smaller waist circumference (95% confidence interval −2.01; −0.13) compared with girls who spent 10–10.5 h in bed. Girls who went to bed late and rose early had 0.16 mm higher total cholesterol (95% confidence interval 0.01; 0.31) and 0.08 mm higher high‐density lipoprotein cholesterol (95% confidence interval 0.01; 0.14) than ‘early to bed/early rise’ girls. Girls with night‐time awakenings had 0.14 mm higher total cholesterol (95% confidence interval 0.03; 0.25) than girls without night‐time awakenings. Girls who felt sleepy/tired ≥1 day per week had 0.10 mm lower high‐density lipoprotein cholesterol (95% confidence interval −0.16; −0.04) and 0.17 mm higher total cholesterol/high‐density lipoprotein cholesterol ratio (95% confidence interval 0.02; 0.32) than girls who did not feel sleepy. No associations were found for boys. Sleep characteristics were not related to blood pressure and glycated haemoglobin, and effect sizes of the associations in girls were small. Therefore, we consider it premature to propose that improved sleep could reduce cardiovascular risk during childhood.

Children of low socioeconomic status show accelerated linear growth in early childhood; results from the Generation R Study.

Objectives People of low socioeconomic status are shorter than those of high socioeconomic status. The first two years of life being critical for height development, we hypothesized that a low socioeconomic status is associated with a slower linear growth in early childhood. We studied maternal educational level (high, mid-high, mid-low, and low) as a measure of socioeconomic status and its association with repeatedly measured height in children aged 0–2 years, and also examined to what extent known determinants of postnatal growth contribute to this association. Methods This study was based on data from 2972 mothers with a Dutch ethnicity, and their children participating in The Generation R Study, a population-based cohort study in Rotterdam, the Netherlands (participation rate 61%). All children were born between April 2002 and January 2006. Height was measured at 2 months (mid-90% range 1.0–3.9), 6 months (mid-90% range 5.6–11.4), 14 months (mid-90% range 13.7–17.9) and 25 months of age (mid-90% range 23.6–29.6). Results At 2 months, children in the lowest educational subgroup were shorter than those in the highest (difference: −0.87 cm; 95% CI: −1.16, −0.58). Between 1 and 18 months, they grew faster than their counterparts. By 14 months, children in the lowest educational subgroup were taller than those in the highest (difference at 14 months: 0.40 cm; 95% CI: 0.08,0.72). Adjustment for other determinants of postnatal growth did not explain the taller height. On the contrary, the differences became even larger (difference at 14 months: 0.61 cm; 95% CI: 0.26,0.95; and at 25 months: 1.00 cm; 95% CI: 0.57,1.43) Conclusions Compared with children of high socioeconomic status, those of low socioeconomic status show an accelerated linear growth until the18th month of life, leading to an overcompensation of their initial height deficit. The long-term consequences of these findings remain unclear and require further study.