Diabetes Linked to Earlier Death, Including From Cancer

Diabetes is associated with a significantly increased risk of premature death not only due to cardiovascular complications but also as a result of cancer and other serious diseases, the results of a large Spanish study reveal.

In a pooled analysis of over 55,000 individuals, the team found that diabetes patients had an increased risk of premature death from liver, colorectal, and lung cancer, as well as liver and kidney disease, in addition to the more well-known cardiovascular complications, such as myocardial infarction and stroke.

The study was published online by Diabetes Care on August 4.

The findings support those of previous studies showing that although overall diabetes mortality has reduced in recent years, patients with diabetes still have a reduced life expectancy and spend more time with disability than people without diabetes.

The association between diabetes and cardiovascular death has been demonstrated many times. However, senior author María Grau, MD, PhD, REGICOR Study Group–Cardiovascular Epidemiology and Genetics, Hospital del Mar Research Institute, Barcelona, Spain, pointed out that the link with cancer mortality is not as well described in the literature.
Speaking to Medscape Medical News, she noted: "I think this is the main finding of the study, because we know that cardiovascular complications are common in diabetes."

She said that, as a result, "we should highlight this problem and implement screening programs for cancer, particularly colorectal cancer and liver cancer, in this population."

To tackle the high mortality rates among diabetes patients, the researchers call for "more efficient preventive activities to reduce the incidence of this disease and its related complications."
They note that previous studies have shown that the course of diabetes can be altered by changes in health-promotion activities, in clinical management, in health systems, and in society as a whole, such as through smoking bans.

However, Dr Grau explained that there is still much room for improvement: "We need more research; in parallel we need more investment in health-services resources, such as multifunctional units in primary care to attend to these people, because the complications of diabetes are multisystemic."

She also noted that the diabetes epidemic has been growing and will continue to grow for the foreseeable future. Consequently, "we need to share best practices between countries" to help preventive activities.

Diabetes More Than Doubles Risk of Death

To examine the association between diabetes and the risk of cause-specific death, the researchers pooled individual patient data from 12 population cohorts in seven regions in Spain studied using similar methods between 1991 and 2005.

All of the participants were randomly selected from the general population, were aged 35 to 79 years, and did not have previous symptoms or a diagnosis of cardiovascular disease at baseline. Diabetes was self-reported or defined as glycemia >125 mg/dL.

Dr Grau pointed out that the majority of people in the study would have had type 2 diabetes: "In Spain, the prevalence of type 1 diabetes is around 1% or less, so the results are largely due to type 2 diabetes."

The individuals were followed up for a median of 10 years, and their medical records were reviewed and linked to the official death registry to determine their vital status and causes of death.

A total of 55,292 individuals from across Spain were included, of whom 15.6% had diabetes. Individuals with diabetes were significantly older; less likely to smoke; and had a higher body mass index (BMI), systolic blood pressure, triglycerides, and blood glucose than those without diabetes.

Over the 10-year follow-up, there were 1710 (3.8%) deaths among participants without diabetes and 781 (9.1%) among those with diabetes. No cause of death was available for 220 and 85 deaths, respectively.

Diabetes Significantly Increases Many Causes of Death

A multivariate model that incorporated smoking status, BMI, systolic blood pressure, and total and HDL cholesterol showed that diabetes significantly increased the risk of cardiovascular, cancer, noncardiovascular, noncancer, and overall death in both sexes compared with the general population.

The team assessed the mortality risk in two statistical ways — as the cause-specific hazard (CSH) and the proportional subdistribution hazard (PSH), with the former providing a direct measure of the association of diabetes with a single cause of death, while the latter includes competing risks.

Diabetes was associated with an increased risk of cardiovascular death, at a CSH of 2.03 and a PSH of 1.99 in men and a CSH of 2.28 and PSH of 2.23 in women, which was largely attributable to myocardial infarction, stroke, and heart failure.

The risk of cancer death was also increased among individuals with diabetes, at a CSH of 1.37 and a PSH of 1.35 in men and a CSH of 1.68 and a PSH of 1.66 in women. The results indicated that the primary causes of cancer-related death were liver, colorectal, and lung cancer.

The researchers also found that the risk of noncardiovascular and noncancer death was increased in diabetic individuals, at a CSH of 1.53 and PSH of 1.50 in men and a CSH of 1.89 and a PSH of 1.84 in women, with the majority of deaths associated with infections, chronic obstructive pulmonary disease, and liver and kidney disease.

This work was supported by MARATO TV3, Instituto de Salud Carlos III – Fondo Europeo de Desarrollo Regional – European Regions Development Funds, the Agency for Management of University and Research Grants, Consortium for Biomedical Research in Epidemiology and Public Health, and Consortium for Biomedical Research in Obesity and Nutrition. Dr Grau was supported by the Instituto de Salud Carlos III – Fondo Europeo de Desarrollo Regional – European Regions Development Fund FEDER. The authors report no relevant financial relationships.

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