The impact of a private sector living wage intervention on consumption and cardiovascular disease risk factors in a middle income country

Given the existence of a socioeconomic gradient for diseases including cardiovascular disease [1], one might expect that raising the income of those in poverty would improve health. The exception, however, may be in low and middle-income countries (LMIC) where inverse associations of socioeconomic status and cardiovascular risk factors have been found. For example, countries below $2500 per capita gross domestic product (GDP) tended to have higher rates of obesity among the wealthy, with the relationship reversed in countries with greater than $2500 per capita GDP [2]. In addition, the evaluation of interventions in Mexico and Columbia providing income to families via conditional cash transfer (CCT) programs have found that increased cash provided to the households was associated with increased risk for obesity in adults [3‐5].

While these findings suggest the potential for deleterious impacts of income on cardiovascular risk factors in LMIC, there are several reasons that this question requires further investigation. First, the small number of prior investigations of effects of increased income on obesity, blood pressure and nutritional consumption have been based on governmental sponsored CCT programs, and effects may differ by type (and amount) of income intervention. In high-income countries, minimum wage laws have been used to increase the wages of workers. A complementary approach to public sector minimum wage ordinances are private sector interventions [6]. This includes paying workers a living wage, defined as a minimum income standard – the wage necessary to procure basic goods and services, rather than an arbitrary minimum wage. Differences in effects on health related factors may reflect differences in the nature of the income intervention itself [7]. Secondly, CCT programs that have been evaluated involve a much smaller increase in income. For example the CCTs in Columbia and Mexico represented a 20-30% increase among the poor, while living wages can increase income by more than 10 times that amount. Thirdly, although more than a dozen CCT programs exist, examining impacts on risk factors for cardiovascular health is very uncommon [8]. Finally, CCTs by definition require specific behavior changes – i.e. the “conditions” associated with the cash award – and thus not just an income intervention.

Investigating the impacts of an increase in income is critical to the 6 billion people living in LMICs, where the majority of the world’s poor live. Within the population of people living in poverty, cardiovascular disease (CVD) has emerged as a threat to overall health; three-quarters of global deaths due to CVD are in LMICs [9, 10]. In an analysis of countries worldwide, death rates from chronic disease were 54% and 86% higher for men and women in LMICs than in high-income countries [11]. While deaths due to infectious disease are still of primary importance and result in substantial mortality, in particular early in life, the emergence of CVD is a threat that also must be addressed.

We examine the association of participating in a living wage intervention with obesity and cardiovascular risk factors. In two previously published papers, we have reported the positive effects of this living wage intervention on reducing depressive symptoms and improving self-reported health [12, 13]. Here we test whether these benefits extend to cardiovascular diseases or whether cardiovascular risk is increased. We examined BMI, waist circumference, systolic blood pressure, diastolic blood pressure and pulse. We also examined differences in consumption patterns in order to better understand the mechanisms through which changes in cardiovascular risk factors could occur.

We examined the impacts of a workplace intervention involving low-wage apparel workers in the Dominican Republic, who were paid a living wage of RD$18153 per month as compared to the prevailing minimum wage of RD$5400 per month, and the world bank poverty level equivalent of RD$1500 per month. We found no negative impacts on any of the measures of cardio-metabolic risk for the intervention versus the comparison workers. In terms of spending, we found that households in the intervention group were more likely to spend money on groceries (especially protein, dairy and, to a lesser extent, soda and juices), furniture and home appliances, computers and related technology, and on home repair.

The absence of differences in BMI and waist circumference between the groups is notable, and in contrast with prior literature on CCT programs. Given the greater expenditure on groceries and consumption of sodas, juices and sugars by the intervention workers and the positive association in LMICs between socioeconomic status and obesity, it is encouraging that the living wage workers did not show higher rates of obesity. That said, the effects of increased consumption of soda, juices and sugars may not emerge until later, beyond our 15-month follow-up period. The finding that there were even stronger differences in consumption of dairy products and protein suggests that the additional funds may have been used in a more balanced manner that did not promote excessive weight gain. It will be important, however, to monitor changes over time to determine if longer-term detrimental dietary patterns emerge and create health risks. The health of the workers may benefit from both local and national programs focused on improving dietary consumption in the context of economic development in order to optimize the overall benefits of living wage interventions in middle-income countries [25, 26].

Taken together with previously reported findings of a reduction of depressive symptoms and a significant increase in self-rated health among those employed in the intervention factory [25, 26], these findings are encouraging. The positive impacts on savings, protein and household consumption are similar to those found in prior studies of CCT programs [27, 28]. There are also, however, differences found as compared to other studies that demonstrate the context dependent nature of income based interventions [7], including differences in the effects on debt [27], and differences in the effects on fruit and vegetable consumption [28].

Analyzing the impact of a private sector living wage involves analytic challenges since workers are not randomly assigned to the living wage condition. However, several factors work against selection bias. First, workers did not know at the time they applied for employment that they would be paid a living wage; the hiring pool was thus very similar to that of the comparison factory. Secondly, we chose a comparison factory that was similar on key characteristics to the intervention factory. We also analytically matched on eight individual characteristics that occurred prior to the intervention and that could be related to cardiovascular disease risk.

Our study, however, is limited by the fact that this intervention took place in only one factory and the number of workers in this factory limited our statistical power. Low statistical power could account for the lack of detected differences in cardio-metabolic risk. It is important to emphasize that the evaluation of impacts is for 15 months, and it is unknown whether obesity will increase over longer periods of time. However, prior work in Mexico did find impacts on obesity after just 23 months, and the fact that in this study no adverse impacts were found among women who were not yet overweight at baseline suggests that the lower prevalence of overweight individuals in our population at the time of intervention could be important for explaining the difference in findings [4]. Finally, this intervention took place in one LMIC, the Dominican Republic (gross national income per capita is approximately $6,000). LMICs are extremely diverse socially and economically. How and why living wage interventions diminish or exacerbate cardiovascular disease must be understood in each different context [29].

The findings of this study are encouraging in terms of overall positive effects of efforts to pay a living wage to workers. Workers receiving a higher wage saved more and invested more in goods (e.g. computers, furniture and appliances and home repair), which could raise their standard of living in a more sustained way. They also spent more in grocery markets and had greater intake of protein and dairy products. Greater consumption of protein and dairy can have positive impacts on health, although future work should examine the specific sources of protein consumption given the potential for negative health and environmental consequences of animal based protein [30]. In addition, we found higher levels of spending on sodas, juices and sugars in the living wage factory. The association with cardiovascular risk, whether measured as a continuous variable or in terms of clinically-meaningful cut-offs, were not statistically significant. However, we did observe a greater consumption of sodas/juices and sugar.

It is important to emphasize that while we do not observe differences in cardiovascular risk between the treatment and control factories, these differences may emerge over a longer period of time. Considering our results on higher levels of soda/juice and sugar consumption in the living wage factory, our study suggests the need for policies to promote healthier diets in conjunction with increases wages. While countries at all income levels need to address the increasing incidence of obesity and diabetes in their populations, this may be of the greatest importance in countries undergoing increases in wages, or in locations where living wages are implemented [31, 32]. Several types of interventions may be of use, including approaches that focus on availability of types of food as well as food prices and taxation [33‐35]. Given the fact that our living wage intervention was employer based, an additional actionable approach could involve workplace-based changes to address specific aspects of dietary intake [36, 37].

Conditional cash transfer programs in low and middle income countries have shown benefits for some health outcomes, but several studies have shown that there are increases in obesity. No previous research has examined the effects of a living wage intervention in a low or middle income country on dietary consumption and cardio-metabolic risk factors, including obesity. We found that following the implementation of the living wage policy at the factory, there was increased consumption of protein, dairy, soda and juice and sugars, but not with cardiovascular risk factors. In consideration with other beneficial impacts of the living wage, it suggests that there is an overall benefit on health and development, but with potential harm for long term cardio-metabolic health from increased soda, juice and sugar consumption.