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Study sees world of longer lives but more disabilities


David Brown
Friday 14 December 2012 09:13 GMT
Study shows we're living longer but with an increase in disabilities
Study shows we're living longer but with an increase in disabilities (Getty Images)

The health of most of the planet's population is rapidly coming to resemble that of the United States, where death in childhood is rare, too much food is a bigger problem than too little, and life is long and often darkened by disability.

High blood pressure is now the leading "risk factor" for disease around the world. Alcohol use is third. Low-back pain now causes more disability than childbirth complications or anemia.

"We are in transition to a world where disability is the dominant concern as opposed to premature death," said Christopher J.L. Murray, who headed the Global Burden of Disease Study, published Thursday. "The pace of change is such that we are ill prepared to deal with what the burden of disease is now in most places."

Produced over five years by 486 researchers at 302 institutions in 50 countries, the study is the most detailed look at health on the population level ever attempted.

It charts 235 causes of death, including AIDS, alcoholism, bladder cancer and animal bites. It examines the effects of 67 "risk factors" — as diverse as not enough fruit in the diet and childhood sexual abuse — that can lead to illness.

The calculations are made for two points in time — 1990 and 2010. As a consequence, the study reveals how the world's health has changed over two decades and provides a trajectory of where it may be headed. The purpose is to give governments, international agencies, donors and researchers an idea of what to plan for.

The study provides both a broad-brush portrait of 7 billion people and a detailed etching of what's happening in 187 individual nations.

Heart disease and stroke were the leading and second-leading causes of death in 1990 and remained so in 2010. But over that two-decade period, malnutrition dropped from the 11th to the 21st cause of death. Diabetes, car accidents and lung cancer all rose in the rankings.

Africa remains the one place where afflictions of the poor — AIDS, malaria, childhood infections, malnutrition, childbirth calamities — remain hugely important. They account for three-quarters of all premature deaths.

The study also reveals many highly localized variations in health.

As a consequence of the earthquake in Haiti in 2010, Haitian men that year had the globe's lowest life expectancy: 33 years. Egypt has the highest rate of cirrhosis of any country, caused by hepatitis C unwittingly transmitted to millions of people through unclean needles used in public health campaigns against the tropical infection schistosomiasis. Ethiopian men gained 13 years of "healthy life expectancy" between 1990 and 2010, the most of any group in the world. There's a "homicide belt" in Latin America and a "suicide belt" in Asia.

The package of seven papers totaling 196 pages is being published in the Lancet. It is the first time an entire issue of the journal has been given over to one research study.

Although population aging, declining poverty and smaller family size have been the major forces changing the world's health profile over the two decades, improvements in medicine and public health have also made a huge difference. Measles tells the story.

In 1990, 631,000 people died from that childhood infection, which was the world's 19th-leading cause of death. In 2010, only 125,000 people died from measles, which had fallen to the No. 62 cause.

"There have been very, very big payoffs in all the investments made to improve child survival," said Alan Lopez, the dean of the school of population health at the University of Queensland in Australia, who with Murray led the project.

Those investments include vaccines, vitamin A and zinc supplements, antibiotics for children with pneumonia, insecticide-treated mosquito nets for children to sleep under in malaria zones, and better obstetrical care.

The risk of dying prematurely from many "adult" diseases (such as heart attacks and cancer) has also fallen because of better treatment and prevention. As a result, the average age of the world's population is getting older. Soon after 2015, for the first time in history, there will be more people older than 65 than younger than 5.

That has had two consequences.

More people are surviving to die of diseases that occur only in old age. These include Alzheimer's disease, deaths from which tripled from 1990 to 2010, and Parkinson's disease, whose deaths doubled. At the same time, people are living with conditions that don't kill them but that affect their health.

"These are things like mental disorders, substance abuse, musculoskeletal pain, vision loss, hearing loss . . . that cause a huge amount of disability but not a whole lot of death," said Murray, who heads the Institute for Health Metrics and Evaluation at the University of Washington.

People are living longer lives, but the time they are gaining isn't entirely time with good health. For every year of life expectancy added since 1990, about 9 1/2 months is time in good health. The rest is time in a diminished state — in pain, immobility, mental incapacity or medical support such as dialysis. For people who survive to age 50, the added time is "discounted" even further. For every added year they get, only seven months are healthy.

"Progress in reducing disability just hasn't kept pace with progress in reducing mortality," said Joshua Salomon of the Harvard School of Public Health, one of the project leaders.

The trend of adding increasing amounts of bad health to life is known as the "expansion of morbidity." It is likely to be the biggest challenge to patients, doctors and people who pay for medical care for the next few centuries.

Mental illness (including addiction) is now responsible for 23 percent of "years lived with disability." Low-back pain is responsible for 11 percent. Those conditions are a lot harder to treat, or prevent, than childhood infections and malnutrition.

"We may or we may not know the ways we can reduce those problems," Salomon said. "But the study should prompt us to think hard about what are the major causes of disability today, and what are the possible solutions that can accelerate progress against them."

There are also regional problems that will require their own solutions.

Globally, homicide is the 27th-leading cause of early death and disability. But in the region that includes Mexico, Central America and Colombia, it is No. 1. In the region just to the south (Brazil and Paraguay), it is No. 2. Men ages 20 to 24 alone suffered 654,000 "years of life lost" because of violence in 2010.

Suicide is the 18th-leading cause of early death and disability worldwide, but in the "high-income Asia Pacific" region (Brunei, Japan, Singapore and South Korea) it is No. 5. In Eastern Europe, including Russia, it is No. 6.

The Global Burden of Disease researchers uncovered a number of surprises, some of which are likely to be questioned by other epidemiologists and biostatisticians.

As a cause of death and disability, lung cancer is rising, but emphysema and chronic bronchitis — which are also caused by smoking — are declining. The reason appears to be a huge reduction in indoor air pollution from cook stoves (which can also cause emphysema and bronchitis) in China and India.

In charting risk factors, the researchers found that diets low in fruit were responsible for more disease than obesity or physical inactivity. That conclusion was reached through analysis of the health effects of various components of diet and the number of people consuming diets high or low in those components.

"We were very surprised," Murray said of the fruit finding. "I'm a pretty profound diet skeptic. But the evidence on diet is as convincing as on obesity."

Murray and Lopez did a similar but smaller Global Burden of Disease in 1996 that described causes of death and risk factors for the world in 1990. The new study recalculated those findings using new data and methods in addition to providing a picture of the world in 2010.

The Bill and Melinda Gates Foundation provided $12 million for the project, which cost more than $20 million.

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