Comparing the Characteristics of Type 2 Diabetes Patients in General Practices and Those in Randomized Controlled Trials


Cross-sectional comparative study of over 36,000 patients with diabetes found differences in the two groups, suggesting a need for broader patient criteria in trials.

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A study recently published in BMJ Open has identified differences in the characteristics of patients with type 2 diabetes mellitus in general practice versus those enrolled in randomized controlled clinical studies.1

According to the World Health Organization, the number of people with diabetes rose from 108 million in 1980 to 422 million in 2014. Between 2000 and 2019, there was a 3% increase in diabetes mortality rates by age. The disease is a major cause of blindness, kidney failure, and heart attacks.2

The study included 675 patients with type 2 diabetes mellitus as well as data from 23 randomized controlled trials, bringing the total number of patients analyzed to 36,059.

“We asked 45 general practitioners from three French Departments to identify the 15 patients with type 2 diabetes mellitus they most recently saw in consultation,” the authors wrote. “In parallel, we selected randomized controlled trials included in the Cochrane systematic review on which the clinical practice guidelines for type 2 diabetes mellitus were based.”

Results of the study showed differences in many of the major characteristics of patients with type 2 diabetes. General-practice patients were older than randomized controlled trial patients (mean [SD] 68.8 [1.1] vs 59.9 years) and had a higher body mass index (mean [SD] 31.5 [6.9] vs 28.2 kg/m2), but smoked less (11.0% vs 29.3%). General-practice patients also used antihypertensive drugs more frequently (82.1% vs 37.5%), but had lower rates of myocardial infarction (7.6% vs 23.1%).

The collected variables—which included sex, age, cardiovascular risk factors (smoking status, weight and body mass index [BMI], serum cholesterol and triglycerides levels, blood pressure), diabetes duration, glycosylated hemoglobin level, serum creatinine level, cardiovascular history, glucose-lowering medications (oral glucose-lowering drug and insulin) and cardiovascular medications (antihypertensive drugs, lipid-lowering drugs and aspirin—were the same for both groups of patients.

“We found substantial differences in characteristics between general-practice type 2 diabetes mellitus patients and those included in the randomized controlled trials on which the associated clinical guidelines are based,” the authors wrote of the results. “General-practice patients were older, had higher BMI, more frequently took anti-hypertensive and lipid-lowering drugs but had less cardiovascular history than randomized controlled trial patients.”

According to the authors, a major strength of the study was that it considered baseline characteristics of patients actually included in the trials, rather than just considering selection criteria; however, there were some limitations.

One limitation was that patient care has evolved since some of the reviewed studies took place. Cardiovascular risk in diabetes patients has decreased in recent years thanks to the introduction of therapies such as statins. Some other limitations included the sample of general practitioners, which were selected based off convenience and that data were missing from some of the trial reports.

“Randomized controlled trials of type 2 diabetes mellitus on which recommendations are based included participants that were not fully representative of general-practice patients,” the authors concluded. “There is a need for studies including a wider range of patients with type 2 diabetes mellitus such as older patients or those with polypharmacy to ensure a better generalizability of the results.”

1. Dugard A, Giraudeau B, Dibao-Dina C. Do patients with type 2 diabetes mellitus included in randomised clinical trials differ from general-practice patients? A cross-sectional comparative study. BMJ Open 2024;14:e077582. doi: 10.1136/bmjopen-2023-077582

2. Diabetes. World Health Organization. April 5, 2023. Accessed April 24, 2024.

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