Poverty's negative impact on cognitive abilities strikes at a younger age than previously thought.
Due to a steady rise in socioeconomic inequality, many Americans are likely to experience poverty.
According to an Associated Press survey, a staggering 4 out of every 5 United States citizens will live near the poverty line at least once in their lives.
In 2015, an estimated 19.7 percent of American children under the age of 18 fell below the poverty line.
A problem of such size must be examined from every angle. The politics are, of course, a minefield, but the associated health issues are only slowly coming to light.
Earlier research has shown that exposure to poor socioeconomic environments in childhood, adulthood, or both, is associated with cognitive deficits later in life.
However, previous findings have come from studies focusing predominantly on older individuals. Little information has been gleaned about the effects of poverty on younger people's mental acuity.
Researchers from the Division of Epidemiology, Department of Public Health Sciences at the University of Miami set out to fill this gap in current understanding. Their results are published this week in the American Journal of Preventive Medicine.
"Income is dynamic and individuals are likely to experience income changes and mobility especially between young adulthood and midlife. Monitoring changes in income and financial difficulty over an extended period of time and how these influence cognitive health is of great public health interest."
Lead investigator Adina Zeki Al Hazzouri, Ph.D.
Studying poverty and the mind
With poverty at such a high rate, understanding all of its implications is vital for the successful management of public health today, and in the future. As Al Hazzouri says: "Maintaining cognitive abilities is a key component of health."
To answer questions about the cognitive effects of socioeconomic hardships, Al Hazzouri took data from an ongoing study - the Coronary Artery Risk Development in Young Adults (CARDIA) prospective cohort study.
The team used data from 3,400 black and white men and women. The participants were aged 18-30 at the start of the study in 1985-86. Information regarding household income was taken from the cohort six times between 1985-2010.
Poverty level was defined as the percentage of time that each participant's household income was under 200 percent of the federal poverty level; these annual income cut-offs amounted to:
- $26,718 in 1990
- $28,670 in 1992
- $31,138 in 1995
- $35,206 in 2000
- $39,942 in 2005
- $44,630 in 2010.
Participants were then split into four groups: never in poverty; in poverty less than one third of the time; from one third to 100 percent of the time, and always in poverty.
Cognitive testing uncovers deficits
In 2010, participants completed three psychological tests to assess their cognitive abilities. The tests were all standard psychological measures and considered reliable assessors of cognitive aging.
The Digit Symbol Substitution Test involves matching symbols to numbers; it tests memory and speed of mental processing. The Rey Auditory-Verbal Learning Test measures short-term auditory-verbal memory, rate of learning, and memory attention, among other skills. The Stroop Test assesses a number of cognitive skills including processing speed and selective attention.
Once the data was analyzed, a clear pattern emerged. There was a strong and graded association between time spent enduring economic hardship and a decline in cognitive function. Although the deficit was measured across all three test types, it was particularly pronounced in processing speed.
Even after adjusting for factors such as sex, race, marital status, smoking, and cholesterol levels, the effect remained. Participants in the "100 percent poverty" group performed significantly worse than those from the "no poverty" group. The researchers conclude that perceived hardship and poverty are contributors to cognitive aging.
This is the first time that such cognitive deficits have been measured in a younger population.
"Findings among this relatively young cohort place economic hardship as being on the pathway to cognitive aging and as an important contributor to premature aging among economically disadvantaged populations.
It is important to monitor how trends in income and other social and economic parameters influence health outcomes."
Adina Zeki Al Hazzouri, Ph.D.
The results are clear, as the authors conclude: "Sustained economic hardship over 20 years was associated with worse cognitive function among middle-aged adults."