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Predictors of mortality and survival in type 1 diabetes: a retrospective cohort study of type 1 diabetes mellitus (T1D) in the Wirral Peninsula
Akata, Eloho
Akata, Eloho
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2019-05
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Abstract
Background: The prevalence of T1D is rising, despite improvements in the management of
this condition. It presents a risk of premature and excess mortality, which impacts survival and
life expectancy.
Aim: The study aim was to assess mortality, identify predicting risk factors for mortality and
survival in T1D in the Wirral. A systematic review was done to establish present current
evidence of all-cause and cause-specific mortality amongst T1D patients.
Methods: A retrospective cohort study design, 1786 patients diagnosed with T1D extracted
from the Wirral Diabetes Register (WDR). The follow-up period was between 1st of January,
2000 to 31st December, 2012. The primary outcome measured was all-cause mortality.
Results: 1458 participants with T1D meet the inclusion criteria, after a follow-up period of 12
years, 113(7.75%) deaths were recorded. While the incidence rate was steady over the study
period, the prevalence rate continued to increase over the study period.
Significant predictors of mortality in this cohort were age of diagnosis, duration of diabetes,
HbA1c,systolic blood pressure (SBP), diastolic blood pressure (DBP), and triglyceride levels.
The predicting risk gender, age at diagnosis, duration of T1D, BMI, serum creatinine levels,
SBP, total cholesterol, LDL, HDL, TC\HDL, and LDL\HDL showed a linear increase in
mortality risk. IMD and DBP followed a U-shaped relationship with relative and absolute
mortality, while HbA1c levels reveal a sinusoidal pattern with the highest risk of mortality at
the levels ≤ 5.9% (41 mmol/mol). The risk of mortality for the predicting risk factors for this
study ranged between 5% and 9%. Maximal risk of mortality of 9% was recorded in the
predicting risks of smoking, BMI, SBP, and DBP. The risk of mortality of 8% was recorded
for IMD, serum creatinine, total cholesterol, TG, LDL\HDL ratio, and TSH. The risk of
mortality of 7% was recorded for the predicting variables of HbA1c, HDL, LDL, and TC\HDL
ratio. The minimum risk of mortality of 5% was recorded for the predictor variable of the
duration of diabetes. The significant predictors of mortality were the age at diagnosis, duration
of diagnosis, systolic and diastolic blood pressure, HbA1c. The burden of mortality rest
disproportionately with females who had higher relative risk of mortality of 4 times that of
their male counterparts, however, the burden of premature mortality as recorded by the years
of potential life lost was slightly higher in males (1797[53.6%]) as compare to females
(1553[46.4%]). Of the 113 deaths recorded for the cohort that indicated a proportion of 7.75%
of the total T1D patients, records for only 37 participants were retrieved. The principal cause
of death in this cohort was malignancy-related 8 deaths (21.6%), this was followed by
cardiovascular disease and sepsis, each having 6 deaths (16.2%) respectively. Cerebrovascular
disease accounted for 5 deaths (13.5%). Death from diabetes complications (hypoglycaemia)
was recorded in 1 patient (2.7%). There were marked reductions in life expectancy for this
cohort. Life expectancy at 40 years for females was to an average age mortality of 66.2 years
as compared to males 78.3 years. There has been improved survival for T1D in this cohort,
77.185 years [95% CI: 75.191 – 79.179] in males and 76.011 years [95% CI: 73.169 – 78.000]
in females.
The systematic review highlighted increased mortality in those with T1D as compared to the
general population, females showed greater risk of vascular complications as compared to the
males with T1D. 35 studies were included. Results showed all-cause mortality RR 3.73 (95%
CI 3.19, 4.36) compared to general population, with gender specific mortality RR 1.17 (95%
CI 1.06, 1.29). For cause specific mortality risk (overall and gender specific): cardiovascular
v
disease RR 3.48 (95% CI 3.14, 3.86) and RR 1.41 (95% CI 0.92, 2.17); renal disease RR 1.06
(95% CI 0.89, 1.26) and RR 0.63 (95% CI 0.38, 1.04); neoplasms RR 1.03 (95% CI 0.92, 1.16)
and RR 1.18 (95% CI 0.75, 1.86); cerebrovascular disease according to gender RR 0.99 (95%
CI 0.66, 1.48), and accidents and suicides according to gender RR 2.30 (95% CI 1.31, 4.06).
Conclusion
In conclusion, the study highlighted significant mortality risk in females as compared to their
male counterparts; there has been progress in the survival of patients with T1D. However, life
expectancy remains reduced as compared to those without the condition. Prevalence of T1D
continues to increase, and the complex interplay of the predictor variables support the need for
an individualised approach to care.
Citation
Akata, E. (2019). Predictors of mortality and survival in type 1 diabetes: a retrospective cohort study of type 1 diabetes mellitus (T1D) in the Wirral Peninsula (Doctoral dissertation). University of Chester, UK.
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University of Chester
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Thesis or dissertation
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en