Women who developed type 1 diabetes before the age of 10 years die an average of nearly 18 years earlier than women who do not have diabetes. Men in the corresponding situation lose almost 14 years of life. The lives of patients diagnosed at age 26-30 years are shortened by an average of 10 years.
“These are disappointing and previously unknown figures. The study suggests that we must make an even greater effort to aggressively treat patients diagnosed at an early age to reduce the risk of complications and premature death,” says Araz Rawshani, researcher at the department of internal medicine, Sahlgrenska Academy, and the Swedish National Diabetes Registry.
The research is based on extensive material from the registry which has monitored 27,195 individuals with type 1 diabetes for an average of ten years. The group was compared with 135,178 controls from the general population who did not have diabetes, maintaining the same distribution regarding gender, age and county of residence.
While researchers already knew that type 1 diabetes is associated with a lower life expectancy, until now it was unclear whether and how much gender and age at onset of illness affect both life expectancy and the risk of cardiovascular disease.
The probability of severe cardiovascular disease generally proved to be 30 times higher for those who developed type 1 diabetes before the age of ten years than for controls. With a diagnosis of diabetes at the age of 26-30 years, the corresponding risk increased by a factor of six.
One of the highest increases in risk noted in the study involved heart attacks in women who developed type 1 diabetes before the age of ten years. The risk for these women is 90 times higher than for controls without diabetes.
“The study opens up the potential for individualized care. We know with certainty that if we maintain good blood sugar control in these patients, we can lower the risk of cardiovascular damage. This makes it important to carefully consider both evidence-based medications and modern technological aids for blood sugar measurements and insulin administration in patients diagnosed with type 1 diabetes at an early age,” says Rawshani.
“At the same time the study must also be viewed in the light of the tremendous progress that has been made in the past few decades. Management of type 1 diabetes is nowadays highly sophisticated, with modern tools for glucose monitoring, delivery of insulin and management of cardiovascular risk factors. Those who live with diabetes today, and those who will acquire the disease, will enjoy longer and healthier lives in the years to come,” says Rawshani.
Type 1 diabetes is one of the most common chronic diseases that affect children in Sweden. The majority are diagnosed between the ages of 10 and 14 years. The number of diagnoses among children is increasing and the percentage is among the highest in the world; Sweden is second after Finland. Between 50,000 and 60,000 people in Sweden suffer from the disease.
“From the patient perspective this study is tremendously important. Suddenly we can answer questions about complications and life expectancy that we were previously unable to answer. Now there is robust evidence that survival largely depends on the age at which the patient develops the disease, and that there is a difference between men and women,” says Rawshani.
Background: People with type 1 diabetes are at elevated risk of mortality and cardiovascular disease, yet current guidelines do not consider age of onset as an important risk stratifier. We aimed to examine how age at diagnosis of type 1 diabetes relates to excess mortality and cardiovascular risk.
Methods: We did a nationwide, register-based cohort study of individuals with type 1 diabetes in the Swedish National Diabetes Register and matched controls from the general population. We included patients with at least one registration between Jan 1, 1998, and Dec 31, 2012. Using Cox regression, and with adjustment for diabetes duration, we estimated the excess risk of all-cause mortality, cardiovascular mortality, non-cardiovascular mortality, acute myocardial infarction, stroke, cardiovascular disease (a composite of acute myocardial infarction and stroke), coronary heart disease, heart failure, and atrial fibrillation. Individuals with type 1 diabetes were categorised into five groups, according to age at diagnosis: 0–10 years, 11–15 years, 16–20 years, 21–25 years, and 26–30 years.
Findings: 27 195 individuals with type 1 diabetes and 135 178 matched controls were selected for this study. 959 individuals with type 1 diabetes and 1501 controls died during follow-up (median follow-up was 10 years). Patients who developed type 1 diabetes at 0–10 years of age had hazard ratios of 4·11 (95% CI 3·24–5·22) for all-cause mortality, 7·38 (3·65–14·94) for cardiovascular mortality, 3·96 (3·06–5·11) for non-cardiovascular mortality, 11·44 (7·95–16·44) for cardiovascular disease, 30·50 (19·98–46·57) for coronary heart disease, 30·95 (17·59–54·45) for acute myocardial infarction, 6·45 (4·04–10·31) for stroke, 12·90 (7·39–22·51) for heart failure, and 1·17 (0·62–2·20) for atrial fibrillation. Corresponding hazard ratios for individuals who developed type 1 diabetes aged 26–30 years were 2·83 (95% CI 2·38–3·37) for all-cause mortality, 3·64 (2·34–5·66) for cardiovascular mortality, 2·78 (2·29–3·38) for non-cardiovascular mortality, 3·85 (3·05–4·87) for cardiovascular disease, 6·08 (4·71–7·84) for coronary heart disease, 5·77 (4·08–8·16) for acute myocardial infarction, 3·22 (2·35–4·42) for stroke, 5·07 (3·55–7·22) for heart failure, and 1·18 (0·79–1·77) for atrial fibrillation; hence the excess risk differed by up to five times across the diagnosis age groups. The highest overall incidence rate, noted for all-cause mortality, was 1·9 (95% CI 1·71–2·11) per 100 000 person-years for people with type 1 diabetes. Development of type 1 diabetes before 10 years of age resulted in a loss of 17·7 life-years (95% CI 14·5–20·4) for women and 14·2 life-years (12·1–18·2) for men.
Interpretation: Age at onset of type 1 diabetes is an important determinant of survival, as well as all cardiovascular outcomes, with highest excess risk in women. Greater focus on cardioprotection might be warranted in people with early-onset type 1 diabetes.
Araz Rawshani, Naveed Sattar, Stefan Franzén, Aidin Rawshani, Andrew T Hattersley, Ann-Marie Svensson, Björn Eliasson, Soffia Gudbjörnsdottir