Breast feeding and resilience against psychosocial stress

BACKGROUND: Some early life exposures may result in a well controlled stress response, which can reduce stress related anxiety. Breast feeding may be a marker of some relevant exposures. AIMS: To assess whether breast feeding is associated with modification of the relation between parental divorce and anxiety. METHODS: Observational study using longitudinal birth cohort data. Linear regression was used to assess whether breast feeding modifies the association of parental divorce/separation with anxiety using stratification and interaction testing. Data were obtained from the 1970 British Cohort Study, which is following the lives of those born in one week in 1970 and living in Great Britain. This study uses information collected at birth and at ages 5 and 10 years for 8958 subjects. Class teachers answered a question on anxiety among 10 year olds using an analogue scale (range 0–50) that was log transformed to minimise skewness. RESULTS: Among 5672 non‐breast fed subjects, parental divorce/separation was associated with a statistically significantly raised risk of anxiety, with a regression coefficient (95% CI) of 9.4 (6.1 to 12.8). Among the breast fed group this association was much lower: 2.2 (−2.6 to 7.0). Interaction testing confirmed statistically significant effect modification by breast feeding, independent of simultaneous adjustment for multiple potential confounding factors, producing an interaction coefficient of −7.0 (−12.8 to −1.2), indicating a 7% reduction in anxiety after adjustment. CONCLUSIONS: Breast feeding is associated with resilience against the psychosocial stress linked with parental divorce/separation. This could be because breast feeding is a marker of exposures related to maternal characteristics and parent–child interaction

Labour force sequences, unemployment spells and their effect on subjective well-being set points

Drawingupon recent psychological literature, we examine the effect of employment statuses pre- and post-unemployment on levels of subjective well-being (SWB),and the return to pre-unemployment levels, i.e. set points. Data came from the British Household Panel Survey. SWB was measured using the GHQ-12 and a question on life satisfaction; Employment status was self-reported. Multilevel, jointed, piecewise, growth curve regression models were used to explore associations by gender, specifically whether different labour force sequences produced different growth curves and rates of adaptation. Overall, there was a tendency for men and women to return to well-being set points for both outcomes. However, findings showed differences by labour force sequence and SWB measure. Women who experienced unemployment between spells of employment returned to their SWB setpoint at a faster rate of return for GHQ than for life satisfaction, while for men, the rates of return were similar to each other. Women who were employed prior to unemployment and then became economically inactive showed a return to their GHQ set point, but there was no return to their life satisfaction setpoint. Economically inactive participants pre-unemployment, who then gained employment, also showed a return to their well-being set point. After economic inactivity and then unemployment, only men experienced a significant increase in life satisfaction upon return to economic inactivity. The findings showed that following unemployment, return to subjective well-being setpoint was quicker for people who became employed than for people who became economically inactive. There were also differences in the return to SWB setpoint by type of economic inactivity upon exiting unemployment

Periodic solutions of a nonlinear second order differential equation

M.S.John A. Nohe

A Case Study of the Application of a Multilevel Growth Curve Model and the Prediction of Health Trajectories

This case study provides guidance on the application of a multilevel growth curve model and the prediction of health trajectories. Using our secondary data analysis as an example, we introduce definitions of the multilevel growth curve model, random intercept and slope, and the intraclass correlation coefficient. We discuss time centering and time metrics, marginal effects for drawing frailty trajectories, as well as multiple imputation for handling missing values

Missing Data in Longitudinal Surveys: A Comparison of Performance of Modern Techniques

Using a simulation study, the performance of complete case analysis, full information maximum likelihood, multivariate normal imputation, multiple imputation by chained equations and two-fold fully conditional specification to handle missing data were compared in longitudinal surveys with continuous and binary outcomes, missing covariates, and an interaction term

Basin of Attraction of Periodic Orbits of Maps on the Real Line

We prove a conjecture by Elaydi and Yakubu which states that the basin of attraction of an attracting 2 k -cycle of the Ricker\u27s map is where E is the set of all eventually 2 r -periodic points. The result is then extended to a more general class of continuous maps on the real line

Periodic Difference Equations, Population Biology and the Cushing-Henson Conjectures

We show that for a k-periodic difference equation, if a periodic orbit of period r is globally asymptotically stable (GAS), then r must be a divisor of k. Moreover, if r divides k we construct a non-autonomous dynamical system having minimum period k and which has a GAS periodic orbit with minimum period r. Our method uses the technique of skew-product dynamical systems. Our methods are then applied to prove two conjectures of J. Cushing and S. Henson concerning a non-autonomous Beverton-Holt equation which arises in the study of the response of a population to a periodically fluctuating environmental force such as seasonal fluctuations in carrying capacity or demographic parameters like birth or death rates. We show that the periodic fluctuations in the carrying capacity always have a deleterious effect on the average population, thus answering in the affirmative the second of the conjectures. Independently Ryusuke Kon [9], [10] discovered a solution to the second conjecture and in fact proved the result for a wider class of difference equations including the Beverton-Holt equation. The work of Davydova, Diekmann and van Gils, [6] should also be noted. There they study nonlinear Leslie matrix models describing the population dynamics of an age-structured semelparous species, a species whose individuals reproduce only once and die afterwards. See also the work of N.V. Davydova, [5] where the notion of families of single year class maps is introduced

Nonautonomous Beverton-Holt Equations and the Cushing-Henson Conjectures

In [3] Jim Cushing and Shandelle Henson published two conjectures (see Section 3) related to the Beverton-Holt difference equation (with growth parameter exceeding one), which said that the B-H equation with periodically varying coefficients (a) will have a globally asymptotically stable periodic solution and (b) the average of the state variable along the periodic orbit will be strictly less than the average of the carrying capacities of the individual maps. They had previously [2] proved both statements for period 2