JIM LEHRER: Next tonight: the connections between childhood illnesses and intelligence. That's the subject of Ray Suarez and our Global Health Unit's third and final report from Mozambique.
RAY SUAREZ: At the Chibuto Hospital in rural Mozambique, the pediatric ward is always busy. Children here battle deadly diseases, like malaria, HIV, and conditions like diarrhea, and often lose the fight.
In Mozambique, one in 11 children dies within the first year of life. One in seven dies within five years. The numbers are even higher in rural areas like Chibuto.
Nineteen-month-old Dadesdores Orlando (ph) has malaria.
WOMAN (through translator): She had seizures and a fever.
RAY SUAREZ: The family has already suffered one loss from the disease.
WOMAN (through translator): I have three living children. My fourth died of malaria at just seven months old.
RAY SUAREZ: Adrian Agusto Ndlate (ph) is 1 year and three months old, but he weighs just under nine pounds. He is severely malnourished.
Dr. Gilberto Luciano Lucas says it's the baby's second time here, and, if he continues on this path, he may not make it to age 5. Dr. Lucas is one of two physicians caring for 200,000 people.
DR. GILBERTO LUCIANO LUCAS, Chibuto Hospital: They are in danger throughout their childhood, but the first five years are definitely the most terrible, the most difficult.
RAY SUAREZ: Now a new study suggests the babies who do survive face an additional lifelong challenge: lower intelligence. The study concludes that babies who use their body's energy to fight disease will not have enough energy left to fully develop their brains.
Christopher Eppig, a graduate student at the University of New Mexico, authored the study.
CHRISTOPHER EPPIG, University of New Mexico: I like to think of this in terms of sort of economics. So, the body has a finite amount of physical energy that it can spend in a limited number of areas.
As a child at a younger age than 5, one estimate shows the brain occupying more than half of the body's entire energy budget. And at newborn -- as a newborn, that number may be as high as 87 percent. And another expensive thing that the body does is fights off infectious disease. And so, like any kind of budget, if you have a limited amount of funds, if you take money out of one area, it has to come from somewhere.
RAY SUAREZ: Eppig found that countries with the highest levels of infectious disease also had the lowest average I.Q.s. Researchers matched I.Q. estimates of 192 countries against 28 infectious diseases listed by the World Health Organization. Mozambique, which ranks at the bottom of I.Q. scores, also tops the charts in disease burden.
CHRISTOPHER EPPIG: The structure and the size of our brain is what gives us our intelligence. And, so, exposure to disease early in childhood can affect the way the brain is built, the way it's structured. And throughout your adult life, you can be left with a brain that wasn't built quite correctly.
RAY SUAREZ: So, multiply thousands of stories, like those in Chibuto Hospital's pediatric ward, and the economic potential of an entire country comes into question.
The study immediately caught the eye of Dr. Emanuele Capobianco, chief of health and nutrition for UNICEF in Mozambique.
DR. EMANUELE CAPOBIANCO, chief of health and nutrition, UNICEF, Mozambique: The study basically says that, if you fight infectious disease, that you will raise I.Q. of a nation.
If this proposition is true, by fighting infectious diseases, you bring up the I.Q. of a nation, which means the productivity of a nation, is a very strong argument for investing in health, in fighting infectious diseases. It's an economic argument that can be extremely strong and powerful for a policy-maker who will have to decide how to prioritize their investment.
RAY SUAREZ: Mozambique receives millions in foreign aid every year, and still ranks among the world's poorest countries.
Would we think about development in a different way, would we think about medicine in a different way, if lifting the disease burden in the worst-off countries wasn't just seen as a humanitarian gesture, but as something with a direct connection to the economic future of a country?
RAY SUAREZ: Paulo Ivo Garrido is the former health minister of Mozambique.
PAULO IVO GARRIDO, former health minister, Mozambique: You cannot have development in the Third World with the present state of affairs in what concerns disease. So, investing to combat diseases in Africa or generally in what is called the Third World is investing in development. And investing in development is investing in peace, stability for the whole world.
RAY SUAREZ: The study controlled for other potential factors in a nation's average I.Q. factors like quality and access to education, annual income levels, and even climate. And while those factors play a role, researchers found infectious disease to be the most powerful predictor of I.Q.
CHRISTOPHER EPPIG: What we found is that infectious disease has the largest independent ability to predict average I.Q. across the world, when we consider it simultaneously with these other factors.
RAY SUAREZ: More obvious is the effect of sickness on children who continue to suffer into their primary school years.
Jamie Madumene is principal of Chibuto's school.
JAMIE MADUMENE, principal (through translator): There is a difference between a child who is healthy and one who is not. There is a different level of understanding, not only on tests, but in how the child progresses.
RAY SUAREZ: Not surprisingly, the I.Q. study has been controversial.
These are difficult waters to be swimming in. Whenever a scientist asks questions about intelligence, national origin, you can face a backlash. Have you?
CHRISTOPHER EPPIG: A little bit. People can look at our research and say, you know, well, they're showing why some people are less intelligent. And, if those people have a racist ideology, then they could look at that and say, this isn't in line with what I believe.
If they're interested in changing the world, if they're interested in reducing inequality in the world, they can look at our research and say, they have given us a tool to achieve our goals of reducing the inequality in the world.
RAY SUAREZ: And in rural Chibuto, Mozambique, any tools that help fight inequality will be welcomed.