Risk of cardiovascular and all-cause mortality: impact of impaired health-related functioning and diabetes: AusDiab study

Williams ED, Rawal L, Oldenburg BF, Renwick C, Shaw JE, Tapp RJ. Risk of cardiovascular and all-cause mortality: impact of impaired health-related functioning and diabetes: the Australian Diabetes, Obesity and Lifestyle (AusDiab) study. Diabetes Care. 2012;35:1067-1073.  

In this substudy of the Australian Diabetes, Obesity and Lifestyle (AusDiab) study, Williams and colleagues demonstrated for the first time that combined exposure to type 2 diabetes and health-related functioning is associated with an increased risk of both cardiovascular (CV) and all-cause mortality.  

This AusDiab substudy assessed the effects of health-related functioning and type 2 diabetes, alone and in combination, on CV and all-cause mortality. Subjects (N=9,979) were aged ≥25 years, of whom 802 had diabetes at baseline. Diabetes status was classified using the 1999 World Health Organization diabetes classification and was diagnosed on the basis of FPG ≥7.0 mmol/L, 2-h plasma glucose ≥11.1 mmol/L, or current treatment with insulin or oral hypoglycemic medication.

Health-related functioning was assessed using version 1 of the SF-36 Health Survey, a self-administered measure of perceived health status over the preceding week, comprising eight elements: physical functioning, role-physical, bodily pain, general health vitality, social functioning, role-emotional, and mental health. The survey also included scores for physical health component summary (PCS) and mental health component summary (MCS). Mortality status and causes contributing to death were determined by linking the study cohort to the Australian National Death Index.  

Results:  

Among the study cohort, mean age was 51 years among those without diabetes, and 62 years among those with diabetes; CVD history was present among 7% without diabetes and 22% with diabetes. Subjects with diabetes had lower scores for each element of the SF-36 compared with subjects without diabetes.  

Over 7.4 years of follow-up, 57 subjects with diabetes and 105 subjects without diabetes had died of CVD.  

After adjustment for age and sex, the following parameters were associated with higher CVD and all-cause mortality:  

  • CVD mortality: low levels of physical functioning, general health perception, vitality  
  • All-cause mortality: low levels of physical functioning, physical role limitation, bodily pain, general health perception, vitality, social functioning, and emotional role limitation  

The association for CVD mortality was only partly attenuated after adjustment for covariates including BMI, smoking, CVD history, systolic BP, lipid therapy, total cholesterol, and triglycerides. Adjustments for covariates had little impact on all-cause mortality.  

When models examining all-cause and CVD mortality by type 2 diabetes and health-related functioning measures (PCS and MCS) were assessed:  

  • Type 2 diabetes and poor PCS were each associated with increased hazard ratios (HRs) for CVD mortality and all-cause mortality. However, when both type 2 diabetes and impaired PCS were present, much higher rates of CVD and all-cause mortality were seen compared to those without diabetes and normal PCS (see below).*  
  • When adjusted for MCS, no appreciable effect on the impact of PCS was seen, either alone or combined with type 2 diabetes, on all-cause or CVD mortality.  

 

HR (95% CI)  

for CVD mortality* 

HR (95% CI)  

for all-cause mortality* 

Type 2 diabetes only 

1.4 (0.7–2.7) 

1.2 (0.8–1.8) 

Impaired PCS only 

1.5 (1.0–2.4) 

1.6 (1.3–2.0) 

Type 2 diabetes + impaired PCS 

2.8 (1.6–4.7) 

2.8 (2.1–3.7) 

  • HR for CVD mortality among those with both type 2 diabetes and impaired MCS was higher than either parameter alone compared to those without diabetes or with poor MCS; the HR for all-cause mortality among those with both type 2 diabetes and impaired MCS was slightly higher than for type 2 diabetes only compared to those without diabetes or with poor MCS (see below).*  
  • When adjusted for PCS, there was no substantial effect on these results.  

 

 

HR (95% CI)  

for CVD mortality* 

HR (95% CI)  

for all-cause mortality* 

Type 2 diabetes only 

1.4 (0.9–2.1) 

1.5 (1.1–1.9) 

Impaired MCS only 

0.7 (0.4–1.3) 

1.0 (0.8–1.3) 

Type 2 diabetes + impaired MCS 

2.3 (1.2–4.1) 

1.8 (1.3–2.6) 

 

The authors also tested the nature of the relationship between diabetes and health-related functioning on mortality by assessing interactions between domains of the SF-36 and A1C.   

  • CVD mortality: significant interaction was seen between bodily pain and A1C (P=0.015)  
  • All-cause mortality: significant interactions between physical functioning and A1C (P=0.035), and bodily pain and A1C (P=0.033)  
  • No significant interaction between A1C and mental health-related functioning  

*After adjustment for age, sex, BMI, smoking, CVD history, systolic BP, lipid therapy, total cholesterol, and triglycerides  

 

September 2012  

This overview was created by KnowledgePoint360 Group, LLC, and was not associated with funding via an educational grant or a promotional/commercial interest.  

Related content 

Read more about this study and additional cutting-edge diabetes data in the September 2012 issue of Clinical Insights® in Diabetes. Click here. 

AusDiab Substudy: Design 

AusDiab Substudy: Results 

AusDiab Substudy: Physical Health Component Summary (PCS) Results 

AusDiab Substudy: Mental Health Component Summary (MCS) Results 

Last Modified: 11/18/2013