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A study recently published in JAMA indicates that life expectancy is considerably lower for people with type 1 diabetes. However, new data, also published in the journal, suggest that intensive blood glucose control may help patients with type 1 diabetes live longer.
“The outlook for people with type 1 diabetes continues to improve … These results show that by tightly controlling their blood glucose, people with type 1 diabetes can live longer,” Catherine Cowie, PhD, of the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), said in a press release.
Shorter Life Expectancy in Type 1 Diabetes
The first study, conducted in Scotland, evaluated life expectancy in a prospective cohort of all living people aged at least 20 years with type 1 diabetes in the country from 2008 to 2010 who were in a nationwide register. A total of 24,691 people were included, contributing 67,712 person-years and 1,043 deaths.
“Major advances in treatment of type 1 diabetes have occurred in the past 3 decades. Contemporary estimates of the effect of type 1 diabetes on life expectancy are needed,” the researchers wrote.
Results revealed that men with type 1 diabetes had an additional 46.2 years of life expectancy at an attained age of 20 years vs. 57.3 years among men without the disease, translating to a loss in life expectancy of 11.1 years (95% CI, 10.1-12.1) for those with type 1 diabetes.
For women, life expectancy at an attained age of 20 years was an additional 48.1 years for those with type 1 diabetes vs. 61.0 years for those without the disease, translating to an estimated loss in life expectancy of 12.9 years (95% CI, 11.7-14.1) for those with type 1 diabetes.
Further, the researchers found that life expectancy was decreased even among people with type 1 diabetes and estimated glomerular filtration rates (eGFRs) of 90 mL/min/1.73 m2 or greater (men, 49.0 years; women, 53.1 years). Estimated loss from age 20 years was 8.3 years (95% CI, 6.5-10.1) for men and 7.9 years (95% CI, 5.5-10.3) for women in this group.
According to the data, ischemic heart disease accounted for the largest percentage of estimated loss of life expectancy in people with type 1 diabetes (men, 36%; women, 31%). Death resulting from diabetic coma or ketoacidosis was linked to the largest percentage of estimated loss occurring before age 50 years (men 29.4%; women, 21.7%).
The researchers, however, noted that their results may not be globally representative.
“An important question is whether our findings are generalizable internationally. This cannot be directly assessed because there are no large contemporary or historical nationally representative studies from other countries,” the researchers wrote, noting that contemporary larger scale data from the United States and other countries would be of interest.
Benefit of Tight Glucose Control
The second study linking tight glucose control to lower mortality rates in type 1 diabetes described the latest data from the Diabetes Control and Complications Trial (DCCT) and its follow-up, the Epidemiology of Diabetes Control and Complications (EDIC) study.
Starting in 1983, the DCCT/EDIC study enrolled 1,441 healthy participants aged 13 to 39 years at baseline with 1 to 15 years of diabetes duration and no early microvascular complications. Participants were then randomly assigned to intensive therapy (n=711), with a goal of achieving glycemic levels as close to nondiabetic range as safely possible, or conventional therapy (n=730).
After a mean of 6.5 years, all participants were taught and recommended intensive therapy and resumed care with their personal physicians. The study concluded in 1993.
Over a mean 27 years of follow-up, 107 deaths occurred — 64 in the conventional therapy group and 43 in the intensive treatment group. Risk for all-cause mortality was significantly lower in the intensive therapy group, with an HR of 0.67 (95% CI, 0.46-0.99).
Cardiovascular disease (CVD) accounted for 22.4% of deaths, cancer for 19.6%, acute diabetes complications for 17.8% and accidents or suicide for 16.8%, according to the data.
The researchers also found that all-cause mortality was linked to higher HbA1c levels, with an HR of 1.56 per 10% relative increase in HbA1c (95% CI, 1.35-1.81). Higher HbA1c also appeared to be associated with albuminuria, with an HR of 2.20 (95% CI, 1.46-3.31).
“These results build on earlier studies, which suggested that increased protein in the urine largely accounts for shorter lifespans for people with type 1 diabetes,” lead study author Trevor Orchard, MD, of the University of Pittsburgh Graduate School of Public Health, said in the release.
“These results further emphasize the importance of good early glucose control, as this reduces the risk for increased protein in the urine in general, as well as diabetic kidney disease.”
Since publication of the DCCT findings in 1993, intensive treatment has become standard for patients with type 1 diabetes. These new findings appear to reaffirm that decreasing diabetes complications with tight glucose control may extend the life of patients with type 1 diabetes.
“Thanks to the findings over the years from the landmark DCCT/EDIC study, millions of people with diabetes may prevent or delay debilitating and often fatal complications from the disease,” NIDDK Director Griffin P. Rodgers, MD, said in the release.
“NIH’s mission is to help improve lives through biomedical research. These kinds of results provide hard evidence that what we do helps people live longer, healthier lives.”
More Information Needed
In an editorial that accompanied the two studies, Michelle Katz, MD, MPH, and Lori Laffel, MD, MPH, both from the Joslin Diabetes Center in Boston, noted that these results add to the knowledge regarding life expectancy in type 1 diabetes, but further research is still necessary.
“The search for genetic factors and biomarkers related to risk of diabetes complications generally and risk of diabetic nephropathy specifically needs to accelerate. There continues to be inadequate access to advanced diabetes technologies, education and support from health care professionals, and, at times, even family encouragement, which all need to improve,” they wrote.
“Patients, families, and the health care community await more steps forward. There is some reassurance for the present; efforts to improve glycemic control and therapies that provide renal protection and cardiovascular risk reduction can prevent or postpone complications and preserve the futures of persons with type 1 diabetes.”
