Overall Mortality Drops in Diabetes, But Data Raise Concerns

Miriam E Tucker

May 05, 2016

While overall death rates have declined in people with diabetes over the past decade, their cancer-mortality rates haven't changed, and younger diabetes patients may not be seeing the same life-expectancy gains, a large Australian study finds.

Results from the analysis of over one million people with linked data from the National Diabetes Service Scheme (NDSS) and the National Death Index (NDI) for 2000–2011 were published online April 26 in Diabetes Care by Jessica L Harding, PhD, of the Baker IDI Heart and Diabetes Institute, Melbourne, Australia, and colleagues.

The study is the first to analyze both cause-specific and age-specific absolute mortality rates in people with diabetes and to examine type 1 and type 2 diabetes death rates separately. Decreases were seen for all-cause, cardiovascular, and diabetes-related deaths, but not for cancer overall, nor for people younger than 40 years.

"The decline in [mortality] rates among older people may be attributed to improvements in risk factors and treatment among people with diabetes. But we are not seeing this same decline in rates among younger populations. We are not sure why this is, but it may be due to emergence of other risk factors among these young populations and a lack of a targeted approach for these groups," Dr Harding told Medscape Medical News.

And the absence of a decline in cancer-mortality rates among people with diabetes suggests that the mortality burden of cancer is likely to increase over time, she noted.

"This may be due to a range of reasons, including a rise in cancer incidence, later presentations and diagnosis, and poorer responses to therapy among people with diabetes. Clinicians need to be vigilant in ensuring that people with diabetes are being routinely screened for cancer according to standard screening protocols for the general population."

And she pointed out that the finding of increased all-cause and cancer mortality among people with type 2 diabetes younger than 40 years of age is particularly worrisome, given that the incidence of young-onset type 2 diabetes is rising and may be associated with even greater morbidity and mortality than type 1 diabetes.

The data suggest "an urgent need for [type 2] diabetes prevention efforts to be targeted toward youth," she stressed.

Largest Declines in Mortality Among Elderly With Type 1 Diabetes

Data were collected for 1,189,049 people with diabetes — including 7.3% with type 1 — who were registered during 2000–2011 in the NDSS, a product and information service that captures 80% to 90% of all Australians with known diabetes. Those data were linked with the NDI, in which cause of death was classified via ICD-10 codes.

Mean age at diabetes diagnosis was 20.1 years for type 1 and 58.5 years for type 2, and median follow-up times were 15.2 and 7.2 years, respectively.

Of the 87,047 people with type 1 diabetes, a total of 5578 deaths occurred during 825,777 person-years (PY) of follow-up over the 10-year period. The age-standardized mortality rate (ASMR) was 16.2 per 1000 PY.

In the total population with type 1 diabetes, all-cause, CVD, and diabetes ASMRs significantly decreased each year by 0.61, 0.35, and 0.14 per 1000 PY, respectively (P trend < 0.05), while the rate for cancer remained unchanged.

Significant decreases in all-cause, CVD, and diabetes mortality rates were seen in all age groups, except for diabetes mortality in those aged 0 to 40 years. No declines in cancer-mortality rates were seen in any age group.

The largest declines in mortality rates were found consistently in the 60–80-year age groups, with declines per year of 0.08, 0.11, and 0.10 per 1000 PY for all-cause, CVD, and diabetes deaths, respectively. Similar patterns were found in men and women.

No Declines in Mortality Among Under-40s With Type 2 Diabetes

Among 1,102,002 people with type 2 diabetes, there were a total 206,974 deaths during 7,309,921 PY of follow-up, with an ASMR of 8.6 per 1000 PY.

In the total population with type 2 diabetes, all-cause, CVD, and diabetes ASMRs significantly decreased per year by 0.18, 0.15, and 0.03 per 1000 PY, respectively, over the 10-year period, while cancer ASMRs remained unchanged.

By age, significant decreases in all-cause, CVD, diabetes, and cancer-mortality rates occurred in all age groups except for 0 to 40 years. In that group, there were significant increases in mortality from all causes and cancer and no changes for CVD or diabetes-specific mortality.

The largest declines in mortality rates were consistently observed in the 40–60-year age groups, with annual rate declines of 0.02, 0.05, 0.05, and 0.03 per 1000 PY for all-cause, CVD, diabetes, and cancer mortality, respectively.

Similar patterns were observed in men and women, although the mortality numbers for women aged 0 to 40 were too small to derive trend information.

Dr Harding explained that although the NDSS includes all people in Australia with diagnosed diabetes — including those of differing races and socioeconomic status — it is known to underrepresent indigenous Australians with diabetes.

While the overall findings are likely to be generalizable to other similar developed nations, "the extent to which race, socioeconomic status, etc, impacts our findings is currently unknown due to the lack of information on these factors collected within the NDSS, so extrapolations need to be treated cautiously."

Other recently published studies have shown life expectancy is still lower among those with diabetes, compared with the general population, including data showing a 12-year gap for those with type 1 diabetes. In addition, patients with both types of diabetes spend more time living with disability than people without diabetes.

The study authors have no relevant financial relationships.

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Diabetes Care. Published online April 26, 2016. Abstract

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