Because educational level is attained at an earlier age than adult occupational class, the study provides novel evidence that lifetime socioeconomic position – including after educational attainment – influences adult health. The results appear in the July 26, 2005, issue of the Public Library of Science Medicine, (www.plosmedicine.org).
Studying the health status of twins as adults, particularly identical twins, can provide unique insights to the issue of the influence of adult experiences, above and beyond early environment and genetics, to health outcomes later in life. Identical twins share not only similar genetics but the same environment while in childhood. Comparing the health of identical twins who have the same versus different educational level and adult occupational class can help answer the question of how much adult socioeconomic conditions affect adult health.
Participants for this study were selected from the Kaiser Permanente Women Twins Study Examination II. The researchers gathered information on 308 twin pairs (178 identical twin pairs and 130 fraternal twin pairs) who lived together until at least the age of 14, via questionnaires to assess childhood and adult occupational status and physical examinations to assess health measures such as blood pressure, cholesterol levels, body mass index (BMI) and physical activity. The twins' adult occupational position was categorized as either working class (non-supervisory employee) or professional/non-working class (owned a business, self-employed, employed or supervised others).
The researchers found that identical twins who had different adult occupational position had very different health outcomes, compared to twins in the study who had similar adult occupational position. Working class twins compared to their professional/non-working class sibling had significantly higher blood pressure, higher diastolic blood pressure, higher BMI and higher levels of low-density lipoprotein cholesterol. Additionally, identical twin pairs who had different adult occupational class were nearly 4 times more likely to rate their health differently, compared to twins with the same adult occupational class.
"The debate about what influences an adult's health status has been going on for quite some time," said Krieger. "Is it only childhood living conditions or education level or does occupational position later in life also matter? In this study we found that among identical women twins, their adult occupational position as an adult was an important predictor of health status as an adult, regardless of the environment they grew up in." She continued, "These findings have important policy implications with regard to directing resources to improving health for both children and adults, since they underscore the need for improving socioeconomic conditions across the lifecourse."
The research was supported by a grant from the National Heart, Lung and Blood Institute.
Harvard School of Public Health is dedicated to advancing the public's health through learning, discovery, and communication. More than 300 faculty members are engaged in teaching and training the 900-plus student body in a broad spectrum of disciplines crucial to the health and well being of individuals and populations around the world. Programs and projects range from the molecular biology of AIDS vaccines to the epidemiology of cancer; from risk analysis to violence prevention; from maternal and children's health to quality of care measurement; from health care management to international health and human rights. For more information on the school visit: www.hsph.harvard.edu
Journal
PLoS Medicine