Socioeconomic differences in childhood BMI trajectories in Belarus.

OBJECTIVE: To examine associations of parental socioeconomic position with early-life offspring body mass index (BMI) trajectories in a middle-income country. SUBJECTS: Overall, 12,385 Belarusian children born 1996-97 and enrolled in a randomised breastfeeding promotion trial at birth, with 3-14 measurements of BMI from birth to 7 years. METHODS: Cohort analysis in which exposures were parental education (common secondary or less; advanced secondary or partial university; completed university) and occupation (manual; non-manual) at birth, and the outcome was BMI z-score trajectories estimated using multilevel linear spline models, controlling for trial arm, location, parental BMI, maternal smoking status and number of older siblings. RESULTS: Infants born to university-educated mothers were heavier at birth than those born to secondary school-educated mothers [by 0.13 BMI z-score units (95% confidence interval, CI: 0.07, 0.19) for girls and 0.11 (95% CI: 0.05, 0.17) for boys; equivalent for an infant of average birth length to 43 and 38 g, respectively]. Between the ages of 3-7 years children of the most educated mothers had larger BMI increases than children of the least educated mothers. At age 7 years, after controlling for trial arm and location,  children of university-educated mothers had higher BMIs than those born to secondary school-educated mothers by 0.11 z-score (95% CI: 0.03, 0.19) among girls and 0.18 (95% CI: 0.1, 0.27) among boys, equivalent to differences in BMI for a child of average height of 0.19 and 0.26 kg/m2, respectively. After further controlling for parental BMI, these differences attenuated to 0.08 z-score (95% CI: 0, 0.16) and 0.16 z-score (95% CI: 0.07, 0.24), respectively, but changed very little after additional adjustment for number of older siblings and mother's smoking status. Associations were similar when based on paternal educational attainment and highest household occupation. CONCLUSIONS: In Belarus, consistent with some middle-income countries, higher socioeconomic position was associated with greater BMI trajectories from age 3 onwards.

Competition, coinfection and strain replacement in models of Bordetella pertussis.

Pertussis, or whooping cough, is an important respiratory infection causing considerable infant mortality worldwide. Recently, incidence has risen in countries with strong vaccine programmes and there are concerns about antigenic shift resulting in vaccine evasion. Interactions between pertussis and non-vaccine-preventable strains will play an important role in the evolution and population dynamics of pertussis. In particular, if we are to understand the role strain replacement plays in vaccinated settings, it will be essential to understand how strains or variants of pertussis interact. Here we explore under what conditions we would expect strain replacement to be of concern in pertussis. We develop a dynamic transmission model that allows for coinfection between Bordetella pertussis (the main causative agent of pertussis) and a strain or variant unaffected by the vaccine. We incorporate both neutrality (in the sense of ecological/population genetic neutrality) and immunity into the model, leaving the specificity of the immune response flexible. We find that strain replacement may be considerable when immunity is non-specific. This is in contrast to previous findings where neutrality was not considered. We conclude that the extent to which models reflect ecological neutrality can have a large impact on conclusions regarding strain replacement. This will likely have onward consequences for estimates of vaccine efficacy and cost-effectiveness.

Socioeconomic differences in childhood length/height trajectories in a middle-income country: a cohort study.

BACKGROUND: Socioeconomic disadvantage is associated with shorter adult stature. Few studies have examined socioeconomic differences in stature from birth to childhood and the mechanisms involved, particularly in middle-income former Soviet settings. METHODS: The sample included 12,463 Belarusian children (73% of the original cohort) born in 1996-1997, with up to 14 stature measurements from birth to 7 years. Linear spline multi-level models with 3 knots at 3, 12 and 34 months were used to analyse birth length and growth velocity during four age-periods by parental educational achievement (up to secondary school, advanced secondary/partial university, completed university) and occupation (manual, non-manual). RESULTS: Girls born to the most (versus least) educated mothers were 0.43 cm (95% confidence interval (CI): 0.28, 0.58) longer at birth; for boys, the corresponding difference was 0.30 cm (95% CI: 0.15, 0.46). Similarly, children of the most educated mothers grew faster from birth-3 months and 12-34 months (p-values for trend ≤ 0.08), such that, by age 7 years, girls with the most (versus least) educated mothers were 1.92 cm (95% CI: 1.47, 2.36) taller; after controlling for urban/rural and East/West area of residence, this difference remained at 1.86 cm (95% CI: 1.42, 2.31), but after additionally controlling for mid-parental height, attenuated to 1.10 cm (95% CI: 0.69, 1.52). Among boys, these differences were 1.95 cm (95% CI: 1.53, 2.37), 1.89 cm (95% CI: 1.47, 2.31) and 1.16 cm (95% CI: 0.77, 1.55), respectively. Additionally controlling for breastfeeding, maternal smoking and older siblings did not substantively alter these findings. There was no evidence that the association of maternal educational attainment with growth differed in girls compared to boys (p for interaction = 0.45). Results were similar for those born to the most (versus least) educated fathers, or who had a parent with a non-manual (versus manual) occupation. CONCLUSIONS: In Belarus, a middle-income former Soviet country, socioeconomic differences in offspring growth commence in the pre-natal period and generate up to approximately 2 cm difference in height at age 7 years. These associations are partly explained by genetic or other factors influencing parental stature. TRIAL REGISTRATION: Current Controlled Trials: NCT01352247 assigned 9 Sept 2005; ClinicalTrials.gov. Identifier: NCT01561612 received 20 Mar 2012.

Relationships between rhinitis symptoms, respiratory viral infections and nasopharyngeal colonization with Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus in children attending daycare.

BACKGROUND: Nasal bacterial colonization is often dubbed "asymptomatic." We hypothesized that rhinitis, common in preschool children, is associated with bacterial colonization and that respiratory viruses, which cause rhinitis, interact with bacteria in ways which promote transmission. METHODS: Five hundred eighty-five children (4.2-73.6 months) attending daycare had clinical information, a rhinitis score and nasal swabs collected in February 2009. Swabs in soya tryptone glucose glycerine broth were cultured for Streptococcus pneumoniae (Sp), Haemophilus influenzae (Hi) and Staphylococcus aureus and analyzed by real-time polymerase chain reaction for respiratory viruses, both semiquantitatively. RESULTS: Rhinitis symptoms, carriage of Sp and Hi and viral detection fell, whereas S. aureus carriage rates rose with age. Significant, age-independent associations between rhinitis symptoms and detection of Hi (P < 0.033) and Hi colonization density (P < 0.027) were observed. Of the 42% with detected viruses, most (78%) had picornavirus detection. There was a significant age-independent association between viral detection (and viral load, picornavirus detection and picorn aviral load) and detection of Sp (P = 0.020, 0.035, 0.005, 0.014) and between viral detection and viral load and Sp colonization density (P = 0.024, 0.028) [corrected]. CONCLUSIONS: Hi may promote its own transmission by inducing or ampli¬fying rhinitis in children. There isa close quantitative relationship between respiratory viral detection, including picornavirus detection and Spcoloni¬zation. These findings have implications for understanding disease patho¬genesis and formulating prevention strategies using vaccines [corrected].

Influenza and RSV make a modest contribution to invasive pneumococcal disease incidence in the UK.

OBJECTIVES: The common seasonality of incidence of invasive pneumococcal disease (IPD) and viral respiratory infections has long been recognized, however, the extent to which this affects the association between the pathogens is unknown. We have analysed weekly surveillance data of IPD, influenza and respiratory syncytial virus (RSV), using ambient temperature and hours of sunshine as measures of seasonality. METHODS: Reported cases of influenza, IPD and RSV, were collected in England and Wales, from week 1 (January) 1996 to week 23 (June) 2009. The associations between IPD and respiratory viral infections were analysed using several statistical methods, including correlation coefficients and both additive and multiplicative regression models. RESULTS: 6-7.5% of cases of IPD are attributable to influenza and 3-4% attributable to RSV. Correlation coefficients reported considerably stronger associations between IPD and the viral infections compared to regression models. CONCLUSIONS: A small but potentially important percentage of IPD may be attributable to influenza and RSV when adjusted for seasonality by temperature. Jointly these viral infections may lead to over 10% of IPD cases. Therefore, prevention of viral respiratory infections may offer some additional benefit in reducing invasive pneumococcal infections.

Associations of growth trajectories in infancy and early childhood with later childhood outcomes.

BACKGROUND: Weight and length at birth (which represent fetal growth) and weight and length or height gain during childhood (which potentially represent catch-up growth) may be related to later health outcomes. However, methods for the assessment of such relations are complex and underdeveloped. OBJECTIVES: We aimed to describe childhood weight and length or height trajectories and to relate these to later outcomes by using rash at age 6.5 y as an example. DESIGN: The data came from a prospective cohort study in Belarus in 10,494 children born in 31 hospitals that participated in a cluster randomized trial of breastfeeding promotion. Weight and length or height were measured at birth, at scheduled clinic visits up to 1 y, and at 6.5 y; intermediate measures were obtained from routine child health records. Linear spline multilevel models for weight and length or height were used to estimate each child's deviance from average birth weight, birth length, weight, and length or height gain velocity in each time period. Logistic regression was used to relate the outcome (parental report of rash at 6.5 y) to these weight and length or height estimates. RESULTS: The best-fitting splines for length or height and weight had knots at 3 and 12 mo, with another knot at 34 mo for height. The only relation between weight and length or height and reported rash was a positive association with weight gain velocity between 12 and 34 mo (odds ratio per SD increase in weight gain velocity: 1.11; 95% CI: 1.01, 1.22). CONCLUSION: Advantages of multilevel models include no restriction to measures at arbitrary times or to individuals with complete data and allowance for measurement error. This trial was registered at isrctn.org as ISRCTN37687716.