Previous research has suggested that gout might be associated with diabetes, but the findings were restricted to one study of men at high risk of heart disease and stroke. The researchers wanted to know if the link existed in the general population, and also applied to women.
They searched the Health Improvement Network (THIN), an electronic database of the anonymised health records of almost 7.5 million patients registered with 477 general practices across the UK.
They included adults who were at least 20 years old, and whose details had been entered into the database for at least a year. The study period ran from January 1995 to May 2010.
Each of the 35,339 cases of newly diagnosed gout was compared with up to five people who did not have gout, but who had been enrolled into the database at the same time, adding up to 137,056 in total.
People in the comparison group were of the same gender, age, and weight (BMI) as obesity is a strong risk factor for both gout and type 2 diabetes.
The THIN database also included information on other potentially influential risk factors, such as alcohol consumption, smoking, GP visits, plus other underlying health problems and their treatment.
Almost three quarters of the newly diagnosed gout cases were in men (72%), whose average age was 62; women with gout tended to be older (67).
All those diagnosed with gout drank more alcohol, visited the doctor more frequently, had more health problems, and took steroids and diuretics more often than those who did not have gout.
The new case rate for diabetes was significantly higher among people with gout (9.6/1000 person years) than it was among the comparison group (6.7/1000 patient years).
But although the risk factors were more numerous in men, women had a higher case rate for diabetes: 10.1/1000 person years compared with 9.5/1000 person years. And this difference was evident across all age groups. This compares with equivalent figures of 5.6 for women and 7.2 for men per 1000 person years for the comparison group.
The difference in absolute risk was 4.5 cases of diabetes per 1000 person years among women compared with 2.3/1000 person years among men.
This disparity also emerged in relative risk: women were 71% more likely to develop diabetes if they had gout, whereas men were 22% more likely to do so.
This is an observational study so no definitive conclusions can be drawn about cause and effect, but this is the first study to show that there is a link between gout and diabetes in the general UK population, explain the authors.
The ongoing low level inflammation typical of gout may promote the development of diabetes, they suggest. Alternatively, the risk factors the two conditions share in common may help to explain the link.
Risk factors for diabetes in people with gout, particularly women, should be picked up and treated promptly, conclude the authors.