Consistently earning a low salary in midlife is associated with increased memory decline in older age, new research suggests.
In a new analysis of more than 3000 participants in the Health and Retirement Study, those who sustained low wages in midlife showed significantly faster memory decline than their peers who never earned low wages.
The findings could have implications for future public policy and research initiatives, the investigators note.
“Our findings, which suggest a pattern of sustained low wage earning is harmful for cognitive health, is broadly applicable to researchers across numerous health disciplines,” co-investigator Katrina Kezios, PhD, postdoctoral researcher, Department of Epidemiology, Mailman School of Public Health, Columbia University, New York City, told Medscape Medical News.
The findings were presented at the Alzheimer’s Association International Conference (AAIC) 2022.
Growing Number of Low-Wage Workers
Low-wage workers make up a growing share of the US labor market. Yet little research has examined the long-term relationship between earning low wages and memory decline.
The current investigators assessed 1992–2016 data from the Health and Retirement Study, a longitudinal survey of nationally representative samples of Americans aged 50 years and older. Study participants are interviewed every 2 years and provide, among other things, information on work-related factors, including hourly wages.
Memory function was measured at each visit from 2004 to 2016 using a memory composite score. The score included immediate and delayed word recall memory assessments. For those who became too impaired to complete cognitive assessment, memory tests by proxy informants were utilized.
On average, participants completed 4.8 memory assessments over the course of the study.
Researchers defined “low-wage” as an hourly wage lower than two thirds of the federal median wage for the corresponding year. They categorized low-wage exposure history as “never” or “intermittent” or “sustained” on the basis of wages earned from 1992 to 2004.
The current analysis included 3803 participants, 1913 of whom were men. All participants were born from 1936 to 1941. In 2004, the average age was 65 years, and the mean memory score was 1.15 standard units.
The investigators adjusted for factors that could confound the relationship between wages and cognition, including the participant’s education, parental education, household wealth, and marital status. Later, whether the participants’ occupation type was of low skill or not was also included.
The confounder-adjusted annual rate of memory decline among workers who never earned low wages was -0.12 standard units (95% CI, -0.14 to -0.10).
Compared with these workers, memory decline was significantly faster among participants with sustained low wage-earning during midlife (β for interaction between time and exposure group, -0.012; 95% CI, -0.02 to 0.01), corresponding to an annual rate of -0.13 standard units.
Put another way, the cognitive aging experienced by workers earning low wages over a 10-year period was equivalent to what workers who never earned low wages would experience over 11 years.
Although similar associations were found for men and women, it was stronger in magnitude for men ― a finding Kezios said was somewhat surprising. She noted that women are commonly more at risk for dementia than men.
However, she advises caution in interpreting this finding, as there were so few men in the sustained low-wage group. “Women disproportionately make up the group of workers earning low wages,” she said.
The negative low coefficient found for those who persistently earned low wages was also observed for those who intermittently earned low wages, but this was not statistically significant.
“We can speculate or hypothesize the cumulative effect of earning low wages at each exposure interval produces more cognitive harm than maybe earning low wages at some time points over that exposure period,” said Kezios.
A sensitivity analysis that examined wage earning at the same ages but in two different birth cohorts showed similar results for the two groups. When researchers removed self-employed workers from the study sample, the same association between sustained low wages and memory decline was found.
“Our findings held up, which gave us a little more reassurance that what we were seeing is at least signaling there might be something there,” said Kezios.
She described the study as a “first pass” for documenting the harmful cognitive effects of consistently earning low wages.
It would be interesting to now determine whether there’s a “dose effect” for having a low salary, she said. However, other studies with different designs would be needed to determine at what income level cognitive health starts to be protected and the impact of raising the minimum wage, she added.
Commenting for Medscape Medical News, Heather Snyder, PhD, vice president of medical and scientific relations, Alzheimer’s Association, said the study was unique.
“I don’t think we have seen anything like this before,” said Snyder.
The study, which links sustained low wage earning in midlife to later memory decline, “is looking beyond some of the other measures we’ve seen when we looked at socioeconomic status,” she noted.
The results “beg the question” of whether people who earn low wages have less access to healthcare, she added.
“We should think about how to ensure access and equity around healthcare and around potential ways that may address components of risk individuals have during their life course,” Snyder said.
She noted that the study provides a “start” at considering potential policies to address the impact of sustained low wages on overall health, particularly cognitive health, throughout life.
The study had no outside funding. Kezios has reported no relevant financial relationships.
Alzheimer’s Association International Conference (AAIC) 2022: Abstract 61298. Presented July 31, 2022.