William H. Dow

Money, schooling, and health: Mechanisms and causal evidence

An association between higher educational attainment and better health status has been repeatedly reported in the literature. Similarly, thousands of studies have found a relationship between higher income and better health. However, whether these repeated observations amount to causality remains a challenge, not least because of the practical limitations of randomizing people to receive different amounts of money or schooling. In this essay, we review the potential causal mechanisms linking schooling and income to health, and discuss the twin challenges to causal inference in observational studies, in other words, reverse causation and omitted variable bias. We provide a survey of the empirical attempts to identify the causal effects of schooling and income on health, including natural experiments. There is evidence to suggest that schooling is causally related to improvements in health outcomes. Evidence also suggests that raising the incomes of the poor leads to improvement in their health outcomes. Much remains unknown beyond these crude findings, however; for example, what type of education matters for health, or whether there is a difference between the health impacts of temporary income shocks versus changes in long‐term income.

Incentivising Safe Sex : A Randomised Trial of Conditional Cash Transfers for HIV and Sexually Transmitted Infection Prevention in Rural Tanzania

Objective The authors evaluated the use of conditional cash transfers as an HIV and sexually transmitted infection prevention strategy to incentivise safe sex. Design An unblinded, individually randomised and controlled trial. Setting 10 villages within the Kilombero/Ulanga districts of the Ifakara Health and Demographic Surveillance System in rural south-west Tanzania. Participants The authors enrolled 2399 participants, aged 18–30 years, including adult spouses. Interventions Participants were randomly assigned to either a control arm (n=1124) or one of two intervention arms: low-value conditional cash transfer (eligible for

Choosing Between and Interpreting the Heckit and Two-Part Models for Corner Solutions

10 per testing round, n=660) and high-value conditional cash transfer (eligible for

Surprising SES Gradients in Mortality, Health, and Biomarkers in a Latin American Population of Adults

20 per testing round, n=615). The authors tested participants every 4 months over a 12-month period for the presence of common sexually transmitted infections. In the intervention arms, conditional cash transfer payments were tied to negative sexually transmitted infection test results. Anyone testing positive for a sexually transmitted infection was offered free treatment, and all received counselling. Main outcome measures The primary study end point was combined prevalence of the four sexually transmitted infections, which were tested and reported to subjects every 4 months: Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis and Mycoplasma genitalium. The authors also tested for HIV, herpes simplex virus 2 and syphilis at baseline and month 12. Results At the end of the 12-month period, for the combined prevalence of any of the four sexually transmitted infections, which were tested and reported every 4 months (C trachomatis, N gonorrhoeae, T vaginalis and M genitalium), unadjusted RR for the high-value conditional cash transfer arm compared to controls was 0.80 (95% CI 0.54 to 1.06) and the adjusted RR was 0.73 (95% CI 0.47 to 0.99). Unadjusted RR for the high-value conditional cash transfer arm compared to the low-value conditional cash transfer arm was 0.76 (95% CI 0.49 to 1.03) and the adjusted RR was 0.69 (95% CI 0.45 to 0.92). No harm was reported. Conclusions Conditional cash transfers used to incentivise safer sexual practices are a potentially promising new tool in HIV and sexually transmitted infections prevention. Additional larger study would be useful to clarify the effect size, to calibrate the size of the incentive and to determine whether the intervention can be delivered cost effectively. Trial registration number NCT00922038 ClinicalTrials.gov.

Did the distribution of health insurance in China continue to grow less equitable in the nineties? Results from a longitudinal survey

This article addresses certain poor practices commonly seen in the applied health economics literature regarding the use of the Heckit and the two-part model. First, many articles invoke the Heckit to solve a supposed selection problem associated with masses of zero values in continuous variables, despite the fact that it has been shown elsewhere that no such selection problem exists when modeling observed actual, as opposed to latent potential, outcomes. Second, many applications incorrectly formulate the marginal effect tests in the Heckit and two-part model, thus undermining central conclusions. Finally, many researchers use a t-test of the inverse Mills coefficient to choose between the Heckit and two-part models despite its poor performace; we propose instead an adapted empirical mean square error test.

Health insurance and child mortality in Costa Rica

Background To determine socioeconomic status (SES) gradients in the different dimensions of health among elderly Costa Ricans. Hypothesis: SES disparities in adult health are minimal in Costa Rican society. Methods Data from the Costa Rican Study on Longevity and Healthy Aging study: 8,000 elderly Costa Ricans to determine mortality in the period 2000–2007 and a subsample of 3,000 to determine prevalence of several health conditions and biomarkers from anthropometry and blood and urine specimens. Results The ultimate health indicator, mortality, as well as the metabolic syndrome, reveals that better educated and wealthier individuals are worse off. In contrast, quality of life–related measures such as functional and cognitive disabilities, physical frailty, and depression all clearly worsen with lower SES. Overall self-reported health (SRH) also shows a strong positive SES gradient. Traditional cardiovascular risk factors such as diabetes and cholesterol are not significantly related to SES, but hypertension and obesity are worse among high-SES individuals. Reflecting mixed SES gradients in behaviors, smoking and lack of exercise are more common among low SES, but high calorie diets are more common among high SES. Conclusions Negative modern behaviors among high-SES groups may be reversing cardiovascular risks across SES groups, hence reversing mortality risks. But negative SES gradients in healthy years of life persist.

Socioeconomic gradients in health in international and historical context.

This paper examines changes in the distribution of health insurance across socioeconomic groups in China over the 1989-1997 period. The analysis is based on the China Health and Nutrition Survey (CHNS), a unique micro-level longitudinal survey of households in eight Chinese provinces. Findings indicate that while aggregate insurance coverage rates in the sample changed little over this period, certain previously noted differences in coverage rates across socioeconomic groups narrowed significantly. These findings bring into question the presumption that continued market-oriented reform would lead to increased differences in coverage across those groups. The results, in fact, suggest exactly the opposite, that as the market oriented changes have occurred important disparities in health insurance coverage have been reduced. If these reductions are occurring there are important implications for policy. The groups normally targeted for equity reasons seem to be making progress over time but continued improvements are needed for these groups to reach the levels of coverage enjoyed by more fortunate subgroups.

Differences in the association of cardiovascular risk factors with education: a comparison of Costa Rica (CRELES) and the USA (NHANES)

This study uses a natural experiment approach to evaluate the effect of health insurance on infant and child mortality. In the 1970s Costa Rica adopted national health insurance, which expanded childrens insurance coverage from 42 percent in 1973 to 73 percent by 1984. Aggregate infant and child mortality rates dropped rapidly during this period, but this trend had begun prior to the insurance expansion, and may be related to other changes during this period. We use county-level vital statistics and census data to isolate the causal insurance effect on mortality using county fixed effects models. We find that insurance increases are strongly related to mortality decreases at the county level before controlling for other time-varying factors. However, after controlling for changes in other correlated maternal, household, and community characteristics, fixed effects models indicate that the insurance expansion could have explained only a small portion of the mortality change. These results question the proposition that health insurance can lead to large improvements in infant and child mortality, and that expanding insurance to the poor can substantially narrow socioeconomic differentials in mortality.

Patient choice in opt-in, active choice, and opt-out HIV screening: randomized clinical trial

This article places socioeconomic gradients in health into a broader international and historical context. The data we present supports the conclusion that current socioeconomic gradients in health within the United States are neither inevitable nor immutable. This literature reveals periods in the United States with substantially smaller gradients, and identifies many examples of other countries whose different social policy choices appear to have led to superior health levels and equity even with fewer aggregate resources. The article also sheds light on the potential importance of various hypothesized mechanisms in driving major shifts in U.S. population health patterns. While it is essential to carefully examine individual mechanisms contributing to health patterns, it is also illuminating to take a more holistic view of the set of factors changing in conjunction with major shifts in population health. In this article, we do so by focusing on the period of the 1980s, during which U.S. life expectancy gains slowed markedly relative to other developed countries, and U.S. health disparities substantially increased. A comparison with Canada suggests that exploring broad social policy differences, such as the weaker social safety net in the United States, may be a promising area for future investigation.

Longer leukocyte telomere length in Costa Rica's Nicoya Peninsula: a population-based study.

Background Despite different levels of economic development, Costa Rica and the USA have similar mortalities among adults. However, in the USA there are substantial differences in mortality by educational attainment, and in Costa Rica there are only minor differences. This contrast motivates an examination of behavioural and biological correlates underlying this difference. Methods The authors used data on adults aged 60 and above from the Costa Rican Longevity and Healthy Ageing Study (CRELES) (n=2827) and from the US National Health and Nutrition Examination Survey (NHANES) (n=5607) to analyse the cross-sectional association between educational level and the following risk factors for cardiovascular disease (CVD): ever smoked, current smoker, sedentary, high saturated fat, high carbohydrates, high calorie diet, obesity, severe obesity, large waist circumference, HDL cholesterol, LDL cholesterol, triglycerides, hemoglobin A1c, fasting glucose, C-reactive protein, systolic blood pressure and BMI. Results There were significantly fewer hazardous levels of risk biomarkers at higher levels of education for more than half (10 out of 17) of the risk factors in the USA, but for less than a third of the outcomes in Costa Rica (five out of 17). Conclusions These results are consistent with the context-specific nature of educational differences in risk factors for CVD and with a non-uniform nature of association of CVD risk factors with education within countries. Our results also demonstrate that social equity in mortality is achieved without uniform equity in all risk factors.