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Age Limits on Trials in Type 1 Diabetes

Published: 2/28/09
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This issue’s TalkBack question comes from a reader who is interested in the rationale behind age limits on trials in type 1 diabetes. We sent her question to Dr. Jay Skyler, the chairman of Type 1 Diabetes TrialNet, for his answer.

Question:

Hello Kelly: A serious problem facing people with Type 1 diabetes is the exclusion of Type 1s from clinical trials based on age alone. The number of new-onset Type 1 in adults is two to three times that of childhood-onset Type 1, according to all scientific studies that use antibody testing. But we who are adult-onset Type 1s are excluded from clinical trials for Type 1. For example, in your most recent diaTribe issue 13, the clinical trial for new-onset Type 1s (using adult stem cells) is only for those aged 18-30. Now, I can understand excluding children, due to risk and consent issues, but why exclude the 50% or more new-onset Type 1s who are over age 30? For example, Amy Tenderich (DiabetesMine) would have been excluded from such a clinical trial because she was diagnosed at age 37, and I would have been excluded because I was diagnosed at age 35. I would greatly appreciate it if you could investigate this.

Answer from Dr. Jay Skyler:

The entry criteria for any clinical trial are established for a variety of reasons, and vary from trial to trial. In Type 1 Diabetes TrialNet, the NIH-sponsored clinical trials network looking at new interventions for type 1 diabetes, we have stipulated various age ranges depending on a number of factors. Many studies limit the lower age until safety is established in older individuals. Other studies, particularly smaller ones, try to limit the number of older individuals because the rate of decline of beta cell function is slower in older individuals. This means that potential beneficial treatment effects are more difficult to detect in older individuals, and if they are included one would need either a larger sample size or longer duration of follow-up to establish whether or not there is any treatment effect. Thus, many considerations are given in establishing eligibility criteria for any given trial.

Two other points to make.

First, the peak age of onset of type 1 diabetes is 11 to 14 years, and the incidence rate of development of type 1 diabetes is growing most rapidly in children under age 10. Thus, it is incorrect to state that the number of new onset type 1 diabetes in adults is two-to-three times greater than in children and adolescents.

Second, although those of us conducting clinical trials seek as our research partners individuals with new onset type 1 diabetes, it must be appreciated that the interventions being evaluated may or may not offer benefit. Indeed, the reason for conducting the trials is to establish both the benefits and the risks of any given intervention. Thus, individuals who are excluded from trials by not meeting the eligibility criteria should not feel that they have been denied some new beneficial treatment. It is unknown whether the treatment will have benefit at all, or whether the benefit will outweigh the risk.

Dr. Jay S. Skyler, MD, MACP Chairman, NIDDK Type 1 Diabetes TrialNet

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