ROME (Thomson Reuters Foundation) - Childhood hunger is costing Chad more than 575 billion CFA francs ($982 million) a year in health and education costs and lower productivity in adult life, the African Union and U.N. agencies said in a joint study launched on Wednesday.

This is equivalent to 9.5 percent of Chad's gross domestic product (GDP), the Cost of Hunger in Africa (COHA) study said.

More than 56 percent of Chad's adults - some 3.4 million people - suffered from stunting as children, and as a result are unable to achieve their full potential, according to the study.

Stunting, which leads to children being short for their age, is a sign of chronic undernourishment and occurs when children lack the calories and proteins - and sometimes vitamins and minerals - they need to grow.

"The study provides us with compelling evidence of the consequences of child undernutrition as well as the justification to increase investment in nutrition," said the World Food Programme's Chad country director, Mary-Ellen McGroarty.

It also provides evidence of the "potential economic returns if we are to take aggressive measures toward eliminating stunting", she said in a statement.

Stunting among Chadian children under the age of five fell to 39 percent in 2010 from 45 percent in 2004, according to the 2016 Global Nutrition Report.

More than 183,000 children in Chad died from undernutrition in the last five years, the COHA study said.

Chad is one of 12 African countries carrying out a COHA study. Studies completed to date have concluded that African economies are losing the equivalent of between 1.9 and 16 percent of GDP due to child undernutrition.

The studies are an initiative led by the African Union, with the support of the U.N. Economic Commission for Africa, and WFP.

(Reporting by Alex Whiting, Editing by Katie Nguyen.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit http://news.trust.org)