Assessing the impact of type 2 diabetes on mortality and life expectancy according to the number of risk factor targets achieved: an observational study

Abstract

Background: Type 2 diabetes (T2D) is associated with an increased risk of premature death. Whether multifactorial risk factor modification could attenuate T2D-related excess risk of death is unclear. We aimed to examine the association of risk factor target achievement with mortality and life expectancy among patients with T2D, compared with individuals without diabetes.

Methods: In this longitudinal cohort study, we included 316 995 participants (14 162 with T2D and 302 833 without T2D) free from cardiovascular disease (CVD) or cancer at baseline between 2006 and 2010 from the UK Biobank. Participants with T2D were categorised according to the number of risk factors within target range (non-smoking, being physically active, healthy diet, guideline-recommended levels of glycated haemoglobin, body mass index, blood pressure, and total cholesterol). Survival models were applied to calculate hazard ratios (HRs) for mortality and predict life expectancy differences.

Results: Over a median follow-up of 13.8 (IQR 13.1-14.4) years, deaths occurred among 2105 (14.9%) participants with T2D and 18 505 (6.1%) participants without T2D. Compared with participants without T2D (death rate per 1000 person-years 4.51 [95% CI 4.44 to 4.57]), the risk of all-cause mortality among those with T2D decreased stepwise with an increasing number of risk factors within target range (0-1 risk factor target achieved: absolute rate difference per 1000 person-years 7.34 [4.91 to 9.78], HR 2.70 [2.25 to 3.25]; 6-7 risk factors target achieved: absolute rate difference per 1000 person-years 0.68 [-0.62 to 1.99], HR 1.16 [0.93 to 1.43]). A similar pattern was observed for CVD and cancer mortality. The association between risk factors target achievement and all-cause mortality was more prominent among participants younger than 60 years than those 60 years or older (P for interaction = 0.012). At age 50 years, participants with T2D who had 0-1 and 6-7 risk factors within target range had an average 7.67 (95% CI 6.15 to 9.19) and 0.99 (-0.59 to 2.56) reduced years of life expectancy, respectively, compared with those without T2D.

Conclusions: Individuals with T2D who achieved multiple risk factor targets had no significant excess mortality risk or reduction in life expectancy than those without diabetes. Early interventions aiming to promote risk factor modification could translate into improved long-term survival for patients with T2D.

Keywords: Cohort study; Life expectancy; Mortality; Risk factor; Type 2 diabetes.

Fig. 1

Risk of mortality according to the number of risk factors within target range among participants with type 2 diabetes compared with those without diabetes. Hazard ratio was estimated using Cox proportional hazards regression with age as time scale and adjusted for sex, ethnicity, education, and Townsend deprivation index. CVD, cardiovascular disease; HR, hazard ratio

Fig. 2

Risk of all-cause mortality according to the number of risk factors within target range among participants with type 2 diabetes compared with those without diabetes by age (A) and sex (B) categories. Hazard ratio was estimated using Cox proportional hazards regression with age as time scale and adjusted for sex (for analyses by age categories only), ethnicity, education, and Townsend deprivation index. Interactions with age and sex for the association of all-cause mortality according to the number of risk factors within target range among participants with diabetes compared to those without diabetes: P for interaction with age = 0.012; P for interaction with sex = 0.74. HR, hazard ratio

Fig. 3

The estimates of years of life lost by the number of risk factors within target range among participants with type 2 diabetes compared with those without diabetes (A) Age-specific life-year lost by the number of risk factors on target among participants with type 2 diabetes versus those without diabetes. (B) Years of life lost at age 50 years by the number of risk factors on target among participants with type 2 diabetes versus those without diabetes. Models with age as time scale were adjusted for sex, ethnicity, education, and Townsend deprivation index