Scientists have known for years that people living in poverty have poorer health and shorter life spans than the more affluent. Now, Cornell researchers have identified several key mechanisms in 13-year-olds that may help explain how low socio-economic status takes its toll on health.

In the first longitudinal study on the physiological effects of poverty in young children, the Cornell researchers report that the longer 13-year-olds have lived in poverty, the less efficient their bodies become in handling environmental demands.

"We think that these mechanisms may be related to the fact that children who grow up in poverty have a [steeper] life trajectory of premature health problems than other children, regardless of their socio-economic status in adulthood," said Gary Evans, the Elizabeth Lee Vincent Professor of Human Ecology and professor of human development and of design and environmental analysis in Cornell's College of Human Ecology.

His study, co-authored with graduate student Pilyoung Kim, is published in the November issue of Psychological Science.

"These muted responses of stress regulatory mechanisms, which are part of the cardiovascular system, not only compromise the ability of the adolescents' bodies to respond to such stressors as noise, poor housing and family turmoil but also indicate they are suffering from more stress-induced physiological strain on their organs and tissues than other young people," said Evans.

"People need to understand that not leveling the playing field when it comes to poverty costs everyone money," said Evans. "It's very costly to society that low-income children end up getting sick prematurely and die younger than other people."

Many researchers over the years have shown that childhood poverty affects long-term morbidity (frequency of illnesses and diseases) and mortality, yet no one knows why.

The researchers assessed the neuroendocrine and cardiovascular markers of stress regulatory systems by measuring overnight levels of a stress hormone (cortisol) and blood pressure reactivity and recovery after an acute stressor (being asked unexpectedly to do mental math problems) in 217 low- and middle-income white adolescents -- at age 9 and then again at age 13 -- in rural areas of upstate New York. They assessed cumulative physical and social risk exposure by measuring crowding, noise and housing quality in conjunction with maternal and youth reports of family turmoil, youth separation from family and exposure to violence.

"The study provides yet another piece of evidence that poverty and other chronic risk factors induce physiological changes that appear to be related to long-term health problems," said Evans, who will summarize his findings with policy recommendations before the planning committee of the Robert W. Johnson Foundation Commission to Build a Healthier America, Oct. 17.