Early onset of age-related diseases may be caused by the stresses of living in extreme poverty, and can take years off the lives of the urban poor, no matter their ethnicity.
In a new study, researchers measured telomere length of poor and moderate-income whites, African-Americans, and people of Mexican descent in Detroit neighborhoods to determine the impact of living conditions on health.
Telomeres cap the ends of chromosomes to maintain their integrity but shorten each time the cell divides. They have been compared to the plastic tips on the ends of shoelaces, as they protect the chromosomes from falling apart and from sticking to one another.
Scars and the City
The new research is said to be the first to associate telomere length specifically to detailed measures of life conditions among the disadvantaged—and casts doubt on the validity of previous research that suggests telomere length is based solely on race and ethnicity.
Arline Geronimus, public health professor at University of Michigan and a research professor at the Institute for Social Research, said:
“Currently, residents of Detroit are struggling—whether they are white, black, or of Mexican descent—in ways that measurably impact their health negatively, including at the cellular level.
Our findings suggest that any group subject to extremely difficult life conditions and contexts will bear physiological scars.
These findings are consistent with the view that social inequality can affect group health by placing members of different groups in more or less adverse economic, political, social psychological, and physical environmental contexts.”
Earlier research had confirmed the “weathering hypothesis” first named in 1992, which says those with chronic exposure to stress and limited access to coping resources face early onset of chronic disease.
The current study, published in the Journal of Health and Social Behavior, suggests telomere length is a biological indicator of that accelerated aging process.
A growing body of research has focused on using telomere length as a measure of biological rather than chronological age. Telomeres shorten to the point where chromosomes become functionally impaired, threatening health through cellular aging.
Telomeres have also been shown to be shortened by factors including smoking, stress, and obesity. These factors were controlled in the Detroit study.
Additional studies have concluded that some racial and ethnic groups have shorter or longer telomeres than others.
Psychosocial Stress and Coping
In the new study, telomere length comparisons between poor and nonpoor were inconsistent across groups, which the authors say is further evidence that differences between socioeconomic groups involve psychosocial stress and coping.
In particular, the difference between poor and nonpoor whites was dramatic, with the poor showing significantly shorter telomere length.
With African-Americans, the telomere length was not much different between the two groups. Among the Mexican population, the telomere actually was longer for the poor than for the nonpoor.
The detailed aspects of socioeconomic disadvantage controlled in the study explained much of the difference across groups.
“The reasons some demographic groups have more health problems than others may stem from inequitable exposure to environmental challenges and difficult life conditions,” Geronimus says.
For example, she noted that both groups of blacks have similar telomere length because often the poor and nonpoor live in close proximity and are exposed to similar stressors.
As for the Mexican poor having longer telomeres than the nonpoor, Geronimus notes that many of the poorest of this group are new to this country and live together in supportive enclaves. The nonpoor people of Mexican descent, however, often are those who were born in the United States, and may struggle with their stereotyped or stigmatized identity.
“Residents of distressed urban areas suffer early aging-related disease and excess mortality. Using a community-based participatory research approach in a collaboration between social researchers and cellular biologists, we collected a unique data set of 239 black, white, or Mexican adults from a stratified, multistage probability sample of three Detroit neighborhoods. We drew venous blood and measured telomere length (TL), an indicator of stress-mediated biological aging, linking respondents’ TL to their community survey responses.
We regressed TL on socioeconomic, psychosocial, neighborhood, and behavioral stressors, hypothesizing and finding an interaction between poverty and racial-ethnic group. Poor whites had shorter TL than nonpoor whites; poor and nonpoor blacks had equivalent TL; and poor Mexicans had longer TL than nonpoor Mexicans. Findings suggest unobserved heterogeneity bias is an important threat to the validity of estimates of TL differences by race-ethnicity. They point to health impacts of social identity as contingent, the products of structurally rooted biopsychosocial processes.”