A study by the national public health institute reveals alarming rates of type 2 diabetes among residents of France's overseas territories, where the chronic illness is two times as common as it is on the French mainland. What explains the disparity?
According to research published this week by Sante Publique France, the share of adults with diabetes on the Indian Ocean island of Reunion was 13.6 percent in 2021 - while in mainland France, the rate was last estimated at 5.7 percent in 2016.
The public health institute also found a high incidence of the disease on the Caribbean islands of Guadeloupe (12 percent) and Martinique (11.5 percent), as well as in French Guiana (11.6 percent), on the northern coast of South America.
Each of those rates is above the global average, which according to the International Diabetes Federation stood at 10.5 percent in 2021.
Most new cases of diabetes are type 2, which typically appears in adulthood and is associated with both family history and lifestyle factors: high body weight, lack of exercise and high cholesterol.
Marie-Helène Chopinet, president of AFD974, an association for diabetes patients in Reunion and part of the French Diabetics Federation, blames much of the problem on diet.
"Food products here are more sugary than on the mainland," she told RFI. "That's supposedly because people in Reunion are addicted to sugar."
Concern over rising rates of diet-related health problems like diabetes prompted the French parliament to pass a law in 2013 that banned companies from adding extra sugar to drinks and snacks sold in the overseas territories, which are now supposed to contain no more than products marketed in mainland France.
But the legislation has loopholes and isn't strictly enforced, with recent studies indicating that juices, yoghurts, biscuits and other products remain higher in sugar in overseas departments than in mainland France.
Meanwhile research also indicates that residents of overseas departments tend to consume more of such products, more frequently.
People in Guadeloupe and Martinique consume nearly three times as many sweetened beverages than people on the mainland, according to the French Research Institute for Development. In French Guiana it's almost double.
"Here in Reunion we have lots of what we call camions bars - food trucks, as you'd say. And there are loads of them, especially around schools," Chopinet said.
"They sell all sorts of sandwiches, greasy food, sweet things, and kids love that stuff. And they're risking their future health."
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The public health institute notes, however, that type 2 diabetes was also observed in some younger, slimmer people in Reunion and French Guiana - which suggests that there could be a genetic component at work.
The science still isn't clear on how genes might increase the risk of diabetes. But research outside France, where few statistics on race are available, consistently indicates that certain ethnic groups have a higher chance of developing type 2 diabetes from a younger age - including people of black African and Afro-Caribbean descent, who make up much of the population in French overseas territories.
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Studies also suggest that these differences are at least partly due to socioeconomic factors. Poverty and deprivation, experienced disproportionately by minority and marginalised groups, are associated with higher incidence of diabetes and worse health outcomes.
France's overseas departments are among the poorest in the country, with extreme poverty five to 15 times more frequent there than the mainland, according to national statistics agency Insee.
At the same time overseas departments have an outsized cost of living: Insee calculates that food is as much as 39 percent more expensive in French Guiana than the mainland, 40 percent in Martinique and 42 percent in Guadeloupe.
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While resources might affect how well people can afford to eat, Chopinet rejects the suggestion that diabetics in Reunion lack access to care.
"As far as healthcare goes, diabetes is well looked after here. Reunion has lots of facilities, the university hospitals all have diabetes services, there are diabetes specialists throughout the department, nurses also take a hand in educating people - so it's not a lack of healthcare in itself," she told RFI.
Instead, she reports seeing patients struggle to manage the disease the way they're advised to, whether by failing to take medication and submit to regular tests or having difficulty getting more exercise and changing their diet.
The result is complications, which should be avoidable and can be debilitating: failing eyesight, kidney damage, foot problems so severe they require amputation.
Like diabetes itself, such complications are more common in overseas departments, according to Sante Publique France.
Its research found that admissions to hospital for lower limb amputations were 1.3 and 1.5 times more frequent in Reunion and Martinique than France as a whole, while hospitalisation for chronic kidney failure was two times as common in Martinique, 1.7 times in Reunion, 1.6 times in French Guiana and 1.3 times in Guadeloupe.
Delays in getting treatment might explain some of this disparity.
"We found that around three or four percent of people we interviewed did not realise that they had diabetes," one of the study's authors, Sandrine Fosse-Edorh, told RFI.
"They told us that they didn't have diabetes, but that a doctor had told them they had 'mild diabetes', or not very serious diabetes.
"It reflects a kind of denial of the disease or a lack of understanding that they have diabetes, and as a result it sometimes means there's a long delay in them getting the treatment they need that would help prevent complications."
Chopinet points out, too, that diabetes is a "silent disease".
"Someone who is developing diabetes will start to feel very thirsty, which isn't something that alarms you - especially for us, living on an island where it's hot, we'll just drink a bit more without thinking much of it," she said.
Nor do other early symptoms such as needing to urinate more frequently and feeling tired necessarily ring alarm bells.
Often it's only with the development of more worrying signs, like rapid weight loss, blurred vision or a foot sore that won't go away, that people finally seek help, Chopinet said: "Lots of people don't go to the doctor. They wait until they're ill."
Much of her association's work is focused on awareness raising for this reason.
While events are taking place across Reunion for World Diabetes Day this week, AFD974 campaigns all year round, from offering screening for diabetes to organising nutrition workshops.
They target people of all ages, Chopinet says, going from old people's homes to nurseries.
"It's important to do prevention work throughout the year with all different types of people precisely so that we can in the long term, I hope, bring these figures down - but for now even just stabilise them."