Effect seen across ethnicities
The stress of living in extreme poverty may cause the early onset of age-related diseases and can take years off the lives of the urban poor, regardless of ethnicity.
For 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.
The new research is believed to be the first to link 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.
“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,” says Arline Geronimus, a professor of public health at University of Michigan and a research professor at the Institute for Social Research.
“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.”
Previous research has substantiated 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.
In the new study, telomere length comparisons between poor and non-poor 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 non-poor 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 non-poor.
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, noting, for example, that both groups of blacks have similar telomere length because often the poor and non-poor live in close proximity and are exposed to similar stressors.
As for the Mexican poor having longer telomeres than the non-poor, Geronimus notes that many of the poorest of this group are new to this country and live together in supportive enclaves. The non-poor people of Mexican descent, however, often are those who were born in the United States, and may struggle with their stereotyped or stigmatized identity.