Friday, December 19, 2014

One note on the global revolution in longevity

A recent Bloomberg article, Dani Bloomfield's "It’s the Best Time to Be Born as Life Expectancy Tops 70", caught my eye.

These are good times to be a baby. A child born last year will live six years longer on average than one born in 1990, the first time in history that life expectancy worldwide extends past age 70.

Much of the gain has come from poor countries, where better health infrastructure has helped people live dramatically longer lives, according to a paper published today in the journal Lancet. In rich countries, new drugs and other advances are stretching lifetimes, the study’s authors said.

Eastern sub-Saharan Africans saw a 9.2-year gain in life expectancy between 1990 and 2013, the biggest increase of any region. In some countries, such as Rwanda, Nepal, Niger and Iran, the outlook increased by more than 12 years.

“Outside of Southern Africa there’s been quite substantial improvement in life expectancy everywhere,” said Christopher Murray, the study’s lead author and a professor at the University of Washington, in Seattle. Except for 1993, when the worldwide estimate was hurt by genocide in Rwanda, “you can see that global life expectancy, particularly since 2000, has been going up 0.3 of a year, every single year.”

Worldwide, the expected length of life for an infant born last year grew 6.2 years, to 71.5 years old, according to the study, which was sponsored by the Bill & Melinda Gates Foundation.

The paper in question, "Global, regional, and national age–sex specific all-cause and cause-specific mortality for 240 causes of death, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013", is available in its entirety online.

Global life expectancy for both sexes increased from 65·3 years (UI 65·0–65·6) in 1990, to 71·5 years (UI 71·0–71·9) in 2013, while the number of deaths increased from 47·5 million (UI 46·8–48·2) to 54·9 million (UI 53·6–56·3) over the same interval. Global progress masked variation by age and sex: for children, average absolute differences between countries decreased but relative differences increased. For women aged 25–39 years and older than 75 years and for men aged 20–49 years and 65 years and older, both absolute and relative differences increased. Decomposition of global and regional life expectancy showed the prominent role of reductions in age-standardised death rates for cardiovascular diseases and cancers in high-income regions, and reductions in child deaths from diarrhoea, lower respiratory infections, and neonatal causes in low-income regions. HIV/AIDS reduced life expectancy in southern sub-Saharan Africa. For most communicable causes of death both numbers of deaths and age-standardised death rates fell whereas for most non-communicable causes, demographic shifts have increased numbers of deaths but decreased age-standardised death rates. Global deaths from injury increased by 10·7%, from 4·3 million deaths in 1990 to 4·8 million in 2013; but age-standardised rates declined over the same period by 21%. For some causes of more than 100 000 deaths per year in 2013, age-standardised death rates increased between 1990 and 2013, including HIV/AIDS, pancreatic cancer, atrial fibrillation and flutter, drug use disorders, diabetes, chronic kidney disease, and sickle-cell anaemias. Diarrhoeal diseases, lower respiratory infections, neonatal causes, and malaria are still in the top five causes of death in children younger than 5 years. The most important pathogens are rotavirus for diarrhoea and pneumococcus for lower respiratory infections. Country-specific probabilities of death over three phases of life were substantially varied between and within regions.

Causes of mortality, the authors suggest, are shifting globally away from communicable diseases towards non-communicable diseases and injuries.

This news item put me in mind of a 2010 post I made about the grim demographics of the Roman Empire, and by extension almost all other pre-modern societies of note. Mortality was by our contemporary standards terrifyingly high, especially high in the early lives of human beings, to an extent that even the least developed societies in our 21st century world would have difficulty comprehending. That world life expectancy is now comparable to that of Canada in the 1960s is a remarkable transformation without precedent, and something quite worth watching.

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