We're all living longer, but longevity increases not benefitting everybody

December 14, 2012

Global lifespans have risen dramatically in the past 40 years, but the increased life expectancy is not benefitting everybody equally, say University of Toronto researchers. In particular, adult males from low- and middle-income countries are losing ground.

People are living longer on average than they were in 1970, and those extra years of life are being achieved at lower cost, the researchers, led by U of T Chemical Engineering PhD candidate Ryan Hum, say in a paper published in the open access science journal eLife this month.

However, the costs for an extra year of life among adult males in lower-income countries are rising, Hum and his colleagues say, while the costs for an extra year of life among children worldwide and for adults in high-income countries continues to drop.

Hum, who is also a member of U of T's Centre for Global Engineering, co-wrote the paper with Professors Yu-Ling Cheng, director of the Centre, Prabhat Jha of the Dalla Lana School of Public Health and Anita McGahan of the Rotman School of Management.

The researchers made the discovery when they took the Michaelis-Menten (MM) equation – a well-known mathematical model first used to analyze enzyme kinetics in 1913 – and applied it to adult and child mortality at different incomes. They reasoned that just as chemical catalysts affect enzyme velocity; the public health catalysts react with income to affect .

"We noticed the similarity in the curvature and became fascinated with the beauty of the analogy," said Hum. The MM equation is standard curriculum for biochemistry, biology and most chemical engineering undergraduate students and we knew there could be added knowledge that we could decipher purely from the math."

"Over the past few decades, research and development of new technologies (drugs, vaccines, policies) have focused mostly on childhood and infectious disease, with fewer worldwide investments for adult ," the U of T researchers suggest. "Increasing coverage of inexpensive health interventions such as immunization, insecticide-treated nets, and case management of childhood infections could be contributing to decline in critical income for child survival."

Hum and his colleagues conclude by recommending that society invest in research and treatment of adult chronic disease, most notably the control of smoking and other risk factors for chronic diseases, and low-cost, widely useful treatments for these diseases.

In the paper, "Global divergence in critical income for adult and childhood survival: analyses of mortality using Michaelis-Menten", the authors expand on the analogy between enzymes and incomes: "Income directly enables certain technologies, immunization programs, epidemiological knowledge, education, and sanitation systems and other areas, which may themselves be interpreted as 'catalysts' – agents that accelerate the rate of a reaction without being fully consumed in the process," they write.

They came up with a new parameter, critical income, which they define as the level of income needed to achieve half of the maximal overall life expectancy found in high-income countries. For example, in 1970, the critical income for overall life expectancy (in inflation adjusted 2005 dollars) was $1.48 per day. By the year 2007, the critical income had fallen to $1.21 per day. In other words, a lower national income is needed to achieve a higher life expectancy now, compared to 40 years ago.

However, that good news is due mostly to improvements in children's health and to increased life expectancy in high-income countries, the researchers say. For adults (aged 15 to 59) in lower-income countries, critical income has actually risen since 1970. In other words, adults in low- and middle-income countries need to have higher incomes on average in order to add an extra year of life. Adult males in these countries are especially affected, though adult females also suffer.

"Under the current conditions, an approximate national income per capita of $2.20 per day would be required in 2007 to attain the same achievable adult male survival rate with $1.25 per day in 1970. Moreover, should the critical income costs for adults continue to rise (in line with current trends)," they warn.

Hum and his colleagues noted that increases in smoking, especially among , and HIV prevalence are responsible for part of the life expectancy gap. By contrast, worldwide attention to childhood health including much research on new technologies, vaccines and political attention mean a rosier future for children – it's becoming less expensive to give children the chance for longer lives.

Explore further: Obesity linked to economic status in developing countries

Related Stories

Obesity linked to economic status in developing countries

July 18, 2012
(HealthDay) -- In low- and middle-income developing countries, socioeconomic status (SES) plays an important role in the development of obesity, particularly in women, according to research published online July 5 in Obesity ...

World population gains more than a decade's life expectancy since 1970

December 13, 2012
In the first Global Burden of Disease Study 2010 paper, published in The Lancet, the authors present new estimates of life expectancy for the last four decades in 187 different countries. While overall life expectancy is ...

Sexually transmitted infections in adolescents in countries of all incomes remain great concern

April 24, 2012
In a Comment linked to The Lancet Series on Adolescent Health, Professor Robert W Blum (Chair of the Department of Population, Family, and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD) ...

Canada should play a role in addressing the global cancer epidemic: researchers

April 10, 2012
Cancer is a growing health concern in low- and middle-income countries, and there is an opportunity for Canada to make a significant contribution to help tackle the disease, states an analysis in CMAJ (Canadian Medical Association ...

Product regulatory systems in low-and middle-income countries must be strengthened

October 23, 2012
When regulatory systems for medical products in low-and middle-income countries work, people live but when such systems fail, people die, according to experts from the US Food and Drug Administration (FDA) writing in this ...

Mental disorders impair economic success in developed countries

July 31, 2012
Mental disorders that emerge in childhood and adolescence, including attention-deficit disorder, depression, anxiety and substance abuse, constitute significant challenges to cognitive, emotional, and social development. ...

Recommended for you

Dulled taste may prompt more calories on path to obesity

July 28, 2017
Cornell University food scientists have found that people with a diminished ability to taste food choose sweeter - and likely higher-calorie - fare. This could put people on the path to gaining weight.

Artificial light from digital devices lessens sleep quality

July 28, 2017
There's no doubt we love our digital devices at all hours, including after the sun goes down. Who hasn't snuggled up with a smart phone, tablet or watched their flat screen TV from the comfort of bed? A new study by researchers ...

Study finds walnuts may promote health by changing gut bacteria

July 28, 2017
Research led by Lauri Byerley, PhD, RD, Research Associate Professor of Physiology at LSU Health New Orleans School of Medicine, has found that walnuts in the diet change the makeup of bacteria in the gut, which suggests ...

Sugar not so sweet for mental health

July 27, 2017
Sugar may be bad not only for your teeth and your waistline, but also your mental health, claimed a study Thursday that was met with scepticism by other experts.

Could insufficient sleep be adding centimeters to your waistline?

July 27, 2017
Adults in the UK who have poor sleep patterns are more likely to be overweight and obese and have poorer metabolic health, according to a new study.

Vitamin E-deficient embryos are cognitively impaired even after diet improves

July 27, 2017
Zebrafish deficient in vitamin E produce offspring beset by behavioral impairment and metabolic problems, new research at Oregon State University shows.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.