Effect of tight control of HbA1c and blood pressure on cardiovascular diseases in type 2 diabetes: An observational study from the Swedish National Diabetes Register (NDR)
Introduction
Hypertension is a well-established risk factor for micro- and macrovascular complications in type 2 diabetic patients. An observational analysis in the UKPDS [1] has demonstrated a linear relationship between mean in-study systolic blood pressure (BP) and the risk of cardiovascular disease (CVD). Tight BP control in hypertensive type 2 diabetic patients, and several antihypertensive drug classes versus placebo, have been documented to reduce the risk of both micro- and macrovascular disease, in the UKPDS [2], [3] as well as in several other intervention studies [4], [5], [6], [7]. A positive association between HbA1c and risk of micro- and macrovascular complications in type 2 diabetic patients has also been shown in previous epidemiological studies [2], [8], [9], [10] and a meta-analysis [11]. It is well established that improved glycaemic control reduces the risk of microvascular complications in both type 1 and type 2 diabetes [12], [13], while the role of glycaemic control in reducing the risk of macrovascular disease is less clear.
UKPDS has shown that tight control of HbA1c is beneficial with regard to CVD risk during 10 years of post-trial follow-up [14], while the ACCORD [15], ADVANCE [16] and VADT [17] trials have not been able to confirm the beneficial effect of tight HbA1c control on CVD risk. Further studies analysing the effect of tight control of both HbA1c and BP, and analysis of predictors for a tight control, should be of value. The convincing results of the long-term follow-up in the Steno-2 study of type 2 diabetic patients with microalbuminuria have also underlined the importance of concomitant treatment of multiple cardiovascular risk factors [18].
At this background, this observational study in type 2 diabetic patients was carried out with the aim to analyse the effect of baseline tight control of HbA1c and BP, compared to adverse control, on the risk of cardiovascular diseases, and also with the aim to analyse the association between baseline clinical characteristics and tight control.
Section snippets
Material and methods
The NDR was launched in 1996 as part of the Swedish implementation of the principles of the St. Vincent declaration on quality in diabetes care, with reports of patient data nationwide, and offers a unique possibility to survey the treatment and risk factor control in diabetic patients in everyday clinical practice. Reporting to the NDR is based on information collected at least once a year during patient visits at hospital outpatient clinics and primary health care clinics all over Sweden, and
Baseline data
Baseline clinical characteristics and risk factors are shown in Table 1, in 2593 patients with tight control of HbA1c <7.5% and BP ≤140/90 mmHg, and in 2160 patients with adverse control of HbA1c 7.5–9.0% and BP 141–190/91–100 mmHg. Median HbA1c and BP were 6.5% and 130/80 mmHg with tight control and 8.1% and 155/85 mmHg with adverse control, a difference of 1.6% and 25/5 mmHg. The frequency of hypertension (treated with antihypertensive drugs or untreated with BP >130/80 mmHg) was around 80% and
Discussion
This observational study has shown that female and male type 2 diabetic patients followed for 6 years, with baseline more tight control of HbA1c <7.5% and BP ≤140/90 mmHg (median HbA1c and BP 6.5% and 130/80 mmHg, around 80% hypertensive patients), compared to those with adverse HbA1c and BP control (median HbA1c and BP 8.1% and 155/85 mmHg, all hypertensive patients), had a 33% lower risk of fatal/non-fatal CVD, 31% lower risk of fatal/non-fatal CHD, and 38% lower risk of fatal/non-fatal stroke,
Conflict of interest
There were no conflicts of interest.
Acknowledgements
The NDR Working Group consists of Soffia Gudbjörnsdottir (national coordinator), Jan Cederholm, Björn Eliasson, Peter M. Nilsson, Björn Zethelius and Katarina Eeg-Olofsson. We thank the regional NDR coordinators, all participating nurses, physicians, and other staff members who have contributed to the study. We also thank the patients with diabetes who, both individually and collectively, through their patient organization, the Swedish Diabetes Federation, support the NDR. The Swedish Board of
References (38)
- et al.
Effects of intensive blood-pressure lowering and low-dose aspirin in patients with hypertension: principal results of the Hypertension Optimal Treatment (HOT) randomised trial
Lancet
(1998) - et al.
Effects of a fixed combination of perindopril and indapamide on macrovascular and microvascular outcomes in patients with type 2 diabetes mellitus (the ADVANCE trial): a randomised controlled trial
Lancet
(2007) - et al.
Microalbuminuria and risk factors in type 1 and type 2 diabetic patients
Diabetes Res. Clin. Pract.
(2005) - et al.
Insulin resistance is a characteristic feature of primary hypertension independent of obesity
Metabolism
(1990) - et al.
Association of systolic blood pressure with macrovascular and microvascular complications of type 2 diabetes (UKPDS 36): prospective observational study
BMJ
(2000) - et al.
Risk factors for coronary artery disease in non-insulin dependent diabetes mellitus: United Kingdom Prospective Diabetes Study (UKPDS: 23)
BMJ
(1998) Tight blood pressure control and risk of macrovascular complications in type-2 diabetes: UKPDS 38
BMJ
(1998)Effects of ramipril on cardiovascular and microvascular outcomes in people with diabetes mellitus: results of the HOPE study and MICRO HOPE substudy
Lancet
(2000)Effects of different blood pressure-lowering regimens on major cardiovascular events in individuals with and without diabetes mellitus
Arch. Intern. Med.
(2005)- et al.
Incidence of coronary heart disease in type 2 diabetic men and women: impact of microvascular complications, treatment, and geographic location
Diabetes Care
(2007)