(CNN) — Middle-age workers who tend to earn a low wage have an elevated mortality risk, especially when they experience unstable employment, according to a study published Tuesday in the medical journal JAMA.

Researchers from Columbia University's Mailman School of Public Health tracked employment and health metrics for about 4,000 workers in the US across a 12-year period, using data from the University of Michigan's Health and Retirement Study collected between 1992 and 2018. All participants were at least 50 years old at the beginning of the study period and in their 60s at the end.

Workers who had a sustained history of low wages — annual earnings below the poverty line for a family of four — were 38 percent more likely to die over the course of 12 years than those who had never experienced low-wage earnings.

The risk was more than twice as high for workers who had fluctuating employment along with sustained low wages.

Shifts in labor market composition and worker shortages in high-demand areas have helped push up US wages over the past two years.

However, by and large, those wage gains couldn't keep up with historically high price inflation.

Adjusting for inflation, wages and salaries declined 1.2 percent for the 12 months ending December, according to the Bureau of Labor Statistics' Employment Cost Index.

Lower- and middle-income workers — especially in industries such as leisure and hospitality — typically saw faster wage growth than higher earners, and some even eked out gains that surpassed inflation; however, household incomes remained uneven, and those groups continue to be disproportionately hurt by higher inflation, research shows.

The lion's share of low-income households' earnings goes toward necessities such as food, gas, and rent — categories with higher-than-average and stubbornly high inflation — and they lack the savings and wiggle room of wealthier households to buy in bulk or delay purchases, according to Federal Reserve Bank of Dallas researchers.

Additionally, the incidence of high inflation stress is higher for Black and Hispanic people than others, the Dallas Fed researchers wrote.

There are well-established links between socioeconomic status and health, and the authors of the new study said that focusing on wages adds an important perspective. Wages "capture aspects of both income and occupation that may impact health in distinct ways," they wrote. Workers with low wages are among the "most vulnerable in the workforce," as they disproportionately work jobs with the highest exposure to workplace hazards, job stress and other established health risks.

Data from this study showed that workers with sustained low wages were significantly more likely than others to report poor or fair health and elevated symptoms of depression, and to never have had health insurance covered by their employer.

The study authors also noted that wages are unique from many other social determinants of health in that there are actionable policy measures.

Wages are a "modifiable and an actionable risk factor for potentially improving health and, in particular, health inequalities" because Black, Hispanic and female workers are disproportionately represented in the low-wage workforce and most likely to benefit from higher wages.

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