Over 422 million people worldwide have diabetes and the global cost of this disease currently stands at $825 billion (€727 billion) per year, a major new study has revealed.

According to the largest study ever undertaken into global diabetes levels, if current trends continue, over 700 million people will have developed diabetes by 2025.

The study compared diabetes levels among adults worldwide from 1980 to 2014. It included data on almost 4.4 million people. No differentiation was made between type 1 and type 2 diabetes, although the researchers noted that 85-90% of diabetes cases are type 2.

The findings revealed that in 1980, 108 million people had diabetes, but by 2014, this had quadrupled to 422 million.

The incidence of the disease has more than doubled among men - from 4.3% in 1980 to 9% in 2014, while in women, it rose from 5% in 1980 to 7.9% in 2014.

Globally, low-income and middle-income countries saw the biggest increases in incidence. The highest prevalence was found in Polynesia and Micronesia, where at least one in five adults has the disease.

In Europe, the prevalence of diabetes was lowest in Switzerland, Austria, Denmark, Belgium and the Netherlands.

The researchers calculated the annual cost of diabetes to be $825 billion per year, which included costs related to treatment and managing complications, such as amputations. However, they pointed out that they had not included the cost of work days lost due to diabetes, and added that the overall costs would be much higher if these were also incorporated.

"This is the first time we have had such a complete global picture about diabetes and the data reveals the disease has reached levels that can bankrupt some countries' health systems. The enormous cost of this disease - to both governments and individuals - could otherwise go towards life essentials such as food and education," commented the study's lead author, Prof Majid Ezzati, of Imperial College London in the UK.

The researchers noted that the biggest risk factor for type 2 diabetes is obesity, yet obesity levels ‘are soaring out of control'.

However, they also noted that genetics and foetal and early-life conditions may also have a role to play.

"There is increasing evidence that the interaction of genes and the environment plays a role in diabetes. For example, certain genotypes may increase the risk of diabetes especially in people with unhealthy lifestyles. In addition, inadequate nutrition during pregnancy and in early life may increase the risk of diabetes later in life. Therefore, long-term diabetes prevention should address nutrition in every stage of life," commented the study's co-lead author, Prof Goodarz Danaei, of the Harvard T.H. Chan School of Public Health in the US.

Details of these findings are published in the journal, The Lancet.