The theme of World Health Day this year is diabetes. To mark the occasion, a new study, published in the journal The Lancet, compared diabetes levels among adult men and women from 1980 to 2014.

The study found that, in the last 35 years, adjusting for the influence of aging worldwide, the proportion of men with diabetes globally has more than doubled - from 4.3 percent in 1980 to 9 percent in 2014. Meanwhile diabetes among women has risen from 5 percent in 1980 to 7.9 per cent in 2014. With growth in the size of populations worldwide, this has meant that the absolute number of people with diabetes has quadrupled from 1980 to 2014, and 422 million adults in the world now have diabetes.

Researchers at Emory University collaborated with the study leaders at Imperial College London, the Harvard T.H. Chan School of Public Health and the World Health Organization to compile data from 751 surveys and 4.4 million adults across the globe.

"This is the most comprehensive effort to track and quantify the diabetes epidemic worldwide over the past 35 years," says Mohammed K. Ali, MBChB, MSc, associate professor at Emory's Global Diabetes Research Center and one of the study's authors.

Diabetes occurs when a person is unable to regulate levels of sugar in the blood, resulting in an increase in the risk of heart and kidney disease, vision loss and amputations.

"The growth and sheer number of people affected has major implications for health care, health expenditures and health systems worldwide. Diabetes is a chronic condition requiring lifelong care, attention to lifestyle choices and adherence to medications – and these are challenging and costly to maintain," adds Ali.

The study also found variations in diabetes and growth of diabetes across the world. Diabetes has increased most dramatically in Pacific island nations and in the Middle East and North Africa, which now have the highest diabetes levels in the world. One half of the 422 million adults with diabetes in 2014 lived in five countries: China, India, USA, Brazil and Indonesia. Researchers believe that these geographic and ethnic variations could provide clues to developing more tailored diabetes prevention and care models for different parts of the world.

"In our own studies, patterns of diabetes emergence differ, and more innovative research will be important as we move forward, both to curb the growth in diabetes, but also to lower the cost burdens for those already affected," says Ali.

If current trends continue, over 700 million adults worldwide could be affected with diabetes by 2025.

The complete report is available online at: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(16)00618-8/abstract