High birth rates in developing nations are fueling the world's baby boom, while women in dozens of richer countries are not producing enough children to keep population levels there, according to figures released on Friday.
A global view of birth, death and disease rates that evaluated thousands of data sets per country also found that heart disease was now the leading cause of death worldwide.
The Institute for Metrics and Health Assessment (IHME), established at the University of Washington by the Bill and Melinda Gates Foundation, used more than 8,000 data sources, more than 600 of them new, to compile one of the most detailed images . in global public health.
His sources included research in the country, social networks and open source material.
He found that while the world's population soared from 2,600 million in 1950 to 7,600 million last year, that growth was profoundly unequal by region and income.
According to the IHME study, ninety-one nations, mainly in Europe and North and North America, were not producing enough children to support their current populations.
But in Africa and Asia fertility rates continued to grow, and the average woman in Niger had seven children during her lifetime.
Ali Mokdad, a professor of health sciences at the IHME, told AFP that the most important factor in determining population growth was education.
"It's about socioeconomic factors, but it's a function of women's education," he said. "The more a woman is educated, the more years she spends in school, delays her pregnancies and will have fewer babies."
The IHME discovered that Cyprus was the least fertile nation on Earth, with an average woman giving birth only once in her life.
In contrast, women in Mali, Chad and Afghanistan have on average more than six babies.
– Less mortality, more disability & # 39; –
The United Nations predicts that there will be more than 10 billion human beings on the planet by the middle of the century, in line with the projection of IHME.
This raises the question of how many people can support our world, known as "carrying capacity" of the Earth.
Mokdad said that while populations in developing countries continue to grow, their economies are generally growing.
This typically has a knock-on effect on fertility rates over time.
"In Asia and Africa, the population continues to increase and people are moving from poverty to better income, unless there are wars or riots," he said.
"It is expected that countries do better economically and fertility is more likely to decrease and level off."
Not only are there billions more of us than 70 years ago, but we also live longer than ever.
The study, published in the medical journal The Lancet, showed that male life expectancy had increased to 71 years from 48 in 1950. Women are now expected to live up to 76, compared with 53 in 1950.
Living longer involves your own health problems, as we get older, we deteriorate and put more burdens on our health systems.
The IHME said that heart disease was now the leading cause of death worldwide. Just in 1990, neonatal disorders were the biggest killer, followed by lung disease and diarrhea.
Uzbekistan, Ukraine and Azerbaijan had the highest death rates from heart disease, while South Korea, Japan and France had the lowest.
"You see less mortality from infectious diseases as countries get richer, but there is also more disability as people live longer," Mokdad said.
He noted that although deaths from infectious diseases such as malaria and tuberculosis have declined significantly since 1990, new noncommunicable killers have emerged.
"There are certain behaviors that lead to an increase in cardiovascular disease and cancer, obesity is number one, it's increasing every year and our behavior contributes to that."
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