Hormones that are out-of-balance in poor and uneducated people may explain why they age faster and are more vulnerable to disease than their more affluent peers, a new study suggests.
It has long been known that less affluent folk die earlier and are "biologically older" than the rich, with those in the most affluent areas expected to live around eight years longer than those in the poorest regions, according to a report in Britain's Daily Telegraph.
Now, researchers at University College London (UCL) may have worked out why.
After monitoring a cohort of 1,880 British men and women since 1946, they have discovered that hormones critical to healthy ageing are significantly out of balance in poorer people by the time they reach 60-64.
Men with the lowest household income - defined by less than £6,000 (S$12,000) a year - had 10 per cent lower testosterone than men earning £30,000 a year or higher, reported the Telegraph.
Low testosterone has been linked to weight gain, loss of muscle, osteoporosis and depression.
In contrast, women whose parents were unskilled workers had testosterone levels 15 per cent higher than the daughters of professionals.
In women, too much testosterone is linked to early puberty, infertility and polycystic ovaries.
Those with the lowest education in both sexes also had depleted levels of insulin-like growth factor (IGF) which has been linked to poor cognitive function and an increased risk of cancer and cardiovascular mortality.
Women with no qualifications had 16 per less IGF than women who had degrees. For men the difference was 8 per cent less IGF, the Telegraph reported.
Low levels of cortisol, which can lead to heart palpitations, depression, pain and insomnia, was also seen in both men and women with the lowest education.
Professor Diana Kuh, of the Medical Research Council’s Unit for Lifelong Health and Ageing at UCL said the hormonal differences showed how societal factors literally "get under the skin" and affect health.
“We found that socioeconomic disadvantage across life, based on father’s social class and on the study member’s education, social class and income, was associated with an adverse hormone profile," she said, according to the Telegraph.
“These hormones are thought to work together to ensure healthy development and also have many different roles in regulating health in older age.
“So our findings suggest that these socioeconomic differences in hormone systems may play a role in explaining social inequalities in health as we age.
“Hormones may be affected by exposure across life to stress and adverse events, health problems and obesity, and unhealthy lifestyles such as physical inactivity, poor diet, and smoking.”
It is already known that socio-economic status has a major impact on health, with studies showing that being poor is associated with increased risks of cardiovascular, respiratory, rheumatic and psychiatric diseases, low birth weight and infant mortality.
Scientists believe psychological stresses of having a less secure future, being bossed around and having lower self-esteem and less access to social support networks cause an increased rate of molecular damage, said the Telegraph. Living in an area of high crime is also thought to accelerate ageing.
Dr David Bann, of the Institute of Education at UCL said: “Our study shows that people from a disadvantaged background are biologically different which could explain health inequalities.
“These hormone levels change with age, so it could potentially explain difference rates of ageing.”
But if the damage is being driven by an out-of-kilter hormone system, it may be possible to fix the disparities through better education and raising the standard of living.
Prof Di added: “We are examining the impact of these hormone differences in explaining inequalities in physical and mental functioning in older age.
“We are also looking at whether socioeconomic differences in other biological systems could help explain social inequalities in how fast we age.
“Our findings provide further evidence of the potentially harmful effects of social disadvantage on health, suggesting that reducing inequalities could have powerful benefits in improving the health of the population and reducing health-care expenditure.”
The research, which was based on data from the MRC National Survey of Health and Development was published in the journal Social Science and Medicine, the Telegraph said.