A systematic review of gait perturbation paradigms for improving reactive stepping responses and falls risk among healthy older adults

Background

Falls are a leading cause of injury among older adults and most often occur during walking. While strength and balance training moderately improve falls risk, training reactive recovery responses following sudden perturbations during walking may be more task-specific for falls prevention. The aim of this review was to determine the variety, characteristics and effectiveness of gait perturbation paradigms that have been used for improving reactive recovery responses during walking and reducing falls among healthy older adults.

Methods

A systematic search was conducted in PubMed, Web of Science, MEDLINE and CINAHL databases in December 2015, repeated in May 2016, using sets of terms relating to gait, perturbations, adaptation and training, and ageing. Inclusion criteria: studies were conducted with healthy participants of 60 years or older; repeated, unpredictable, mechanical perturbations were applied during walking; and reactive recovery responses to gait perturbations or the incidence of laboratory or daily life falls were recorded. Results were narratively synthesised. The risk of bias for each study (PEDro Scale) and the levels of evidence for each perturbation type were determined.

Results

In the nine studies that met the inclusion criteria, moveable floor platforms, ground surface compliance changes, or treadmill belt accelerations or decelerations were used to perturb the gait of older adults. Eight studies used a single session of perturbations, with two studies using multiple sessions. Eight of the studies reported improvement in the reactive recovery response to the perturbations. Four studies reported a reduction in the percentage of laboratory falls from the pre- to post-perturbation experience measurement and two studies reported a reduction in daily life falls. As well as the range of perturbation types, the magnitude and frequency of the perturbations varied between the studies.

Conclusions

To date, a range of perturbation paradigms have been used successfully to perturb older adults’ gait and stimulate reactive response adaptations. Variation also exists in the number and magnitudes of applied perturbations. Future research should examine the effects of perturbation type, magnitude and number on the extent and retention of the reactive recovery response adaptations, as well as on falls, over longer time periods among older adults.

     

Husbands,wives, sons,and daughters: Fertility preferences and the demand for contraception in Ethiopia

Ethiopia, with nearly 65 millionpeople, is the second most populous country in sub-Saharan Africa. Fertility levels are among the highest in the world. Using the matched wife-husband sample from the 1990 National Family and Fertility Survey of Ethiopia we investigate the fertility desires of wives and husbands and the degree to which they are similar, including whether a preference for sons exists. We model the determinants of the desire to limit or space births, and estimate unmet need. Results indicate high levels of concurrence among husbands and wives on reproductive preferences. Where differences exist, husbands are more pronatalist than their wives. Both husbands and wives prefer to have sons and daughters, but more sons overall. Approximately 22% of wives and husbands desire to limit or space births but do not use contraception. More than half of wives and husbands with an unmet need for limiting are paired with a partner who has no such need. Three implications follow from these results: (1) differences in wives' and husbands' son and daughter preferences may help to explain discordant views among couples when it comes to the desire to limit or space births; (2) husbands' overall contribution to wives' unmet need can be substantial in African societies in the early stages of fertility transition; and (3) wives' preferences regarding children and contraception can result in unmet need on the part of husbands, even in highly gender-stratified societies where men are more pronatalist.     

Rural Out‐migration in the Drought Prone Areas of Ethiopia: A Multilevel Analysis1

This article presents a multilevel analysis of rural out‐migration in Ethiopia over the 1984–1994 period. Using a recent household survey carried out in the drought prone rural areas of Ethiopia, discrete‐time hazard models are used to examine the impact of individual, household and community factors on migration. Incorporating a life‐course and the “new economics of migration” perspectives, our findings suggest that rural out‐migration in these areas can be viewed as a function of individual, household and community characteristics. We find that mobility of people for schooling in the impoverished rural communities is minimal. Migration of both sexes was possible mainly through marriage, although females tend to depart their residences more than males. Our findings also reveal substantial period effects on out‐migration trends.     

Dynamic latent trait models with mixed hidden Markov structure for mixed longitudinal outcomes

We propose a general Bayesian joint modeling approach to model mixed longitudinal outcomes from the exponential family for taking into account any differential misclassification that may exist among categorical outcomes. Under this framework, outcomes observed without measurement error are related to latent trait variables through generalized linear mixed effect models. The misclassified outcomes are related to the latent class variables, which represent unobserved real states, using mixed hidden Markov models (MHMMs). In addition to enabling the estimation of parameters in prevalence, transition and misclassification probabilities, MHMMs capture cluster level heterogeneity. A transition modeling structure allows the latent trait and latent class variables to depend on observed predictors at the same time period and also on latent trait and latent class variables at previous time periods for each individual. Simulation studies are conducted to make comparisons with traditional models in order to illustrate the gains from the proposed approach. The new approach is applied to data from the Southern California Children Health Study to jointly model questionnaire-based asthma state and multiple lung function measurements in order to gain better insight about the underlying biological mechanism that governs the inter-relationship between asthma state and lung function development.     

Generalized additive models for longitudinal data

We introduce a class of models for longitudinal data by extending the generalized estimating equations approach of Liang and Zeger (1986) to incorporate the flexibility of nonparametric smoothing. The algorithm provides a unified estimation procedure for marginal distributions from the exponential family. We propose pointwise standard-error bands and approximate likelihood-ratio and score tests for inference. The algorithm is formally derived by using the penalized quasilikelihood framework. Convergence of the estimating equations and consistency of the resulting solutions are discussed. We illustrate the algorithm with data on the population dynamics of Colorado potato beetles on potato plants.     

The impact of infant and child death on subsequent fertility in Ethiopia

This paper uses hazard regression models to assess the impact of experienced infant and child mortality on the risk of subsequent conceptions in Ethiopia. The purpose of this paper is to test for the presence of a fertility response to an infant or child death, net of the effects of truncated breastfeeding on fecundity. Using retrospective birth history data from a national survey in Ethiopia, we find a significantly higher risk of a conception in the months following the death of an index child, even after controlling for postpartum amenorrhoea and breastfeeding status. The fertility response is strongest after the death of the fourth or fifth child, which is when most women in Ethiopia are at or near their desired family size. However, we find no evidence of a fertility response to the death of a nonindex child. We attribute the higher risk of a conception following an index child’s death to the intentional efforts of couples to reduce the waiting time to a next birth and thereby replace the deceased child. However, absent evidence of replacement fertility in response to the death of older nonindex children, we interpret the response to the death of an index child as an emotional response to child loss rather than a conscious strategy to meet a fertility target.