More than 350 million people in the world now have diabetes, an international study has revealed. The analysis, published online by the Lancet on Saturday, adds several tens of millions to the previous estimate of the number of diabetics and indicates that the disease has become a major global health problem.
Diabetics have inadequate blood sugar control, a condition that can lead to heart disease and strokes, as well as damage to kidneys, nerves and the retina. About three million deaths a year are attributed to diabetes and associated conditions in which blood sugar levels are disrupted.
The dramatic and disturbing increase is blamed by scientists on the spread of a western-style diet to developing nations, which is causing rising levels of obesity. Researchers also say that increased life expectancy is playing a major role.
Type 2 is the most common type of diabetes, accounting for about 85-95% of cases, and is often tied to obesity. It develops when the body fails to produce enough insulin to break down glucose, inflating blood sugar levels. Type 1 diabetes is a separate auto-immune disorder.
"Diabetes is one of the biggest causes of mortality worldwide, and our study has shown that it is becoming more common almost everywhere. It is set to become the single largest burden on world health care systems," one of the study's main authors, Professor Majid Ezzati, of Imperial College London, told the Observer. "Many nations are going to find it very difficult to cope with the consequences."
This point was backed by Martin Tobias of the ministry of health in New Zealand in an accompanying editorial for the Lancet. As he states, there is "no worldwide surveillance network for diabetes, as there is for communicable diseases such as influenza". Given the inexorable rise in case numbers that is now occurring, there was now "an urgent need" to establish proper monitoring of the disease, he added.
The study – funded by the World Health Organisation and the Gates Foundation – analysed blood from 2.7 million participants aged 25 and over from across the world over a three-year period. Doctors measured levels of glucose in their blood after they had fasted for 12 to 14 hours – blood sugar rises after a meal.
If their glucose level fell below 5.6 millimoles per litre, they were considered healthy. If their reading topped 7, they were diagnosed as having diabetes, while a result that ranged between 5.6 and 7 indicated that a person was in a pre-diabetic state. Crucially, the study found that the average global level of glucose measured this way had risen for men and women.
The team then used advanced statistical methods to estimate prevalence rates among the participants. It was estimated that the number of adults with diabetes was 347 million, more than double the 153 million estimated in 1980 and considerably higher even than a 2009 study that put the number at 285 million. "We are not saying the previous study was a bad one," said Ezzati. "It is just that we have refined our methods a little more."
In percentage terms, the prevalence of male adult diabetics worldwide rose from 8.3% to 9.8% in that period, with adult females increasing from 7.5% to 9.2%. As to the causes, the team attribute 70% to ageing and 30% to the increased prevalence of other factors, with obesity and body mass the most important.
It was found that in the US glucose levels had risen at more than twice the rate of western Europe over the past three decades. In wealthy nations, diabetes and glucose levels were highest in the US, Malta, New Zealand and Spain, and lowest in the Netherlands, Austria and France. Despite its obesity epidemic, the UK's diabetes prevalence was lower than that of most other high-income countries. In a league of 27 western high-income countries, British men had the fifth lowest diabetes rates, while British women were eighth lowest.
Other badly affected countries included many Pacific island nations. As Ezzati put it: "There has been an explosion of cases there." In the Marshall Islands, for example, one in three women and one in four men has diabetes. Saudi Arabia was also reported to have very high rates. Glucose levels were also particularly high in south Asia, Latin America, the Caribbean, central Asia, north Africa and the Middle East. The region with the lowest glucose levels was sub-Saharan Africa, followed by east and south-east Asia. Eastern Europe's diabetes prevalence, while not low, also changed little over the three-decade period.
"Diabetes is a condition that is linked to long-term disability and we need to monitor how it is spreading very carefully or face the consequences."
The Lancet article comes after scientists said type 2 diabetes could be reversed in as little as seven days if sufferers went on a crash diet. Adherence to a strict 600 calorie-a-day diet causes fat levels in the pancreas to plummet, restoring normal function. Professor Roy Taylor, of Newcastle University, called the discovery a "radical change" in understanding type 2 diabetes.
• This article was amended on Saturday 25 June to make clear the distinction between type 2 diabetes, which accounts for between 85-95% of cases and has been linked to lifestyle, and type 1 diabetes, which is a separate auto-immune disorder