Sam Watson’s journal round-up for 19th September 2016

Every Monday our authors provide a round-up of some of the most recently published peer reviewed articles from the field. We don’t cover everything, or even what’s most important – just a few papers that have interested the author. Visit our Resources page for links to more journals or follow the HealthEconBot. If you’d like to write one of our weekly journal round-ups, get in touch.

Health losses at the end of life: a Bayesian mixed beta regression approach. Journal of the Royal Statistical Society Series A Published 2nd September 2016

The growth in healthcare expenditure is and has long been a concern for policy makers worldwide. Many factors contribute to this increase, for example it may be a consequence of economic growth, but perhaps the most widely cited determinant is an ageing population. A growing literature is questioning the simplicity of this assumption though: is it age per se that leads to increased healthcare costs or is it proximity to death? This study presents a new analysis of this question. More specifically, the authors propose that the observed decline in health related quality of life (HRQoL) associated with age is due to the increased age-specific mortality and the lower HRQoL associated with being close to death, and not age itself. The implication of this is that increased longevity is unlikely to have a large effect on overall healthcare expenditure. To examine this empirically the authors use longitudinal data on HRQoL from 356 individuals over 16 years. Issues such as the skewness of the outcome measure and it being bounded between zero and one, along with the correlation within individuals over time and the relationship between the mean and variance are accommodated using a Bayesian beta regression. Estimation using MCMC methods provides great flexibility in terms of complex models that may be intractable using classical maximum likelihood methods, and the inclusion of previous evidence through the prior reduces uncertainty that may arise due to smaller sample sizes. A wide range of sensitivity analyses are also conducted. The authors’ key finding is that when time to death is included as a variable the effect of age is almost negligible. This journal round-up author’s interest in Bayesian methods has grown exponentially over the last few years and most of his analyses are now in the Bayesian paradigm. Articles such as this demonstrate the power and flexibility of such methods and, importantly, they show how the emphasis is on the estimation problem rather than arbitrary hypothesis testing and estimation of p-values.

Group-based microfinance for collective empowerment: a systematic review of health impacts. Bulletin of the World Health Organisation Published September 2016

Microfinance initiatives have become a popular method to promote development and a sizable empirical literature has grown around it. Indeed, the 2006 Nobel Peace Prize was awarded to a Bangladeshi microfinance program. Many microfinance schemes are founded on the principle of collective empowerment by providing capital to support female autonomy and entrepreneurship. As such, there is an increasing interest in whether these schemes can also improve health. However, the enthusiasm for microfinance initiatives is often said to outstrip evidence of their effectiveness. This systematic review considers the evidence for whether microfinance can improve health. The studies identified in this review provided evidence that microfinance schemes can reduce maternal and infant mortality, improve sexual health, and in some cases lower interpersonal violence. However, even in the higher quality studies, there was potential for bias and unfortunately publication bias was not assessed. Nevertheless, such a review of the effectiveness of microfinance has been long overdue.

The impact of changing economic conditions on overweight risk among children in California from 2008 to 2012. Journal of Epidemiology and Community Health [PubMedPublished September 2016

The relationship between economic conditions and population health has emerged into a huge research area in the last 20 years. We’ve previously discussed it in a number of blog posts. As the literature grows and understanding and knowledge expand, research moves from generalities to specifics. This article explores whether childhood obesity was affected by changing economic conditions during the last recession using a huge dataset of over 1.7 million children. The proportion of children who are obese is larger among low socioeconomic status groups than higher status groups, so it may be expected that a worsening of economic conditions, measured here as unemployment, would lead to an increase in childhood obesity. However, the authors theorise that the association is ambiguous, citing the typical economic argument that through income and substitution effects households may both change their consumption patterns and the amount of time devoted to health promoting activities, which could either improve or worsen health. Using an individual and county level fixed-effects linear probability model (the justification for using the linear probability model over a perhaps more appropriate nonlinear model is not given), a one percentage point increase (around 10-15% relative increase) in the county level unemployment rate is estimated to lead to a 1.4 percentage point increase in the risk of being obese (around 4% increase in risk). Of course, the results are statistically significant. The results seem reasonable, but I’m left struggling to interpret them properly having had the same issue with an aggregate treatment and individual level outcomes previously. The results are consistent with the idea that the increase in obesity occurred among individuals whose families increased their income over the period, for example. Simpson’s paradox often rears its head in the economic conditions and health literature, as we have previously seen with infant health.

Photo credit: Antony Theobald (CC BY-NC-ND 2.0)

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