© 2003 by the American Diabetes Association, Inc.
The National Diabetes Register in SwedenAn implementation of the St. Vincent Declaration for Quality Improvement in Diabetes Care
1 Diabetes Centre, Sahlgrenska University Hospital, Göteborg, Sweden
OBJECTIVETo monitor glycemic control, treatable risk factors, and treatment profile for quality assessment of diabetes care on a national scale. RESEARCH DESIGN AND METHODSFour samples of 23,546, 32,903, 30,311, and 29,769 patients with diabetes (19961999) were studied based on a repeated national screening and quality assessment of diabetes care by the National Diabetes Register, Sweden, with participation of both hospitals and primary health care. Clinical characteristics included were age, sex, diabetes duration and treatment, glycemic control (HbA1c), office blood pressure (BP), BMI, smoking habits, and use of lipid-lowering drugs in patients with type 1 or type 2 diabetes.
RESULTSFavorable decreases of mean HbA1c and BP values were registered during the 4-year study period for both type 1 (HbA1c 7.57.3% and BP 130/75130/74 mmHg) and type 2 diabetic patients (HbA1c 7.06.7% and BP 151/82147/80 mmHg). Treatment aims of HbA1c and BP levels were also achieved in increasing proportions for type 1 (HbA1c <7.5%: 5058% and BP CONCLUSIONSDecreasing mean HbA1c and BP levels and the wider use of lipid-lowering drugs during the late 1990s in patients with diabetes in a national sample from Sweden should translate into clinical benefits regarding micro- and macrovascular complications as well as diabetes-related mortality.
Abbreviations: ADA, American Diabetes Association BP, blood pressure DCCT, Diabetes Control and Complications Trial HCM, hospital outpatient clinic for departments of medicine LDC, Lunds Data Central NDR, National Diabetes Registry NHANES, National Health and Nutrition Examination Study PHC, primary health care UKPDS, U.K. Prospective Diabetes Study
The Swedish National Diabetes Register (NDR) was initiated in 1996 by the Swedish Society for Diabetology as a response to the demands of the St. Vincent Declaration for Quality Assurance in Diabetes Care (1). National guidelines for diabetes care were established at the same time (2), and indicators of quality were introduced. These guidelines have recently been revised (3). Thus, the NDR was started as a tool for local quality control and benchmarking against the national treatment aims, based on several large randomized intervention trials in both type 1 and type 2 diabetic patients. These important trials included the Diabetes Control and Complications Trial (DCCT) (4) and the U.K. Prospective Diabetes Study (UKPDS) (5). One aim of the NDR is that all diabetic patients in Sweden should ideally be reported yearly, based on registered annual data from actual patient visits in primary health care (PHC) or at hospital outpatient clinics for departments of medicine (HCMs). Demographic data, diabetes duration, treatment modalities, as well as various risk factors and diabetes complications are reported. After statistical analysis, all participating centers have received a yearly report with local results as well as comparisons with national data. NDR is probably among the largest national diabetes registers in the world, and the unique size of NDR, with repeated annual surveys and with the geographical distribution all over Sweden, should reasonably well mirror the treatment traditions and results at large in Sweden. It is therefore of interest to compare these repeated population-based data of NDR in order to investigate whether clinical practice in the management and care of diabetes has changed during recent years, as measured by changes in mean/median levels of the variables, e.g., HbA1c and blood pressure (BP) levels. In this first general report from NDR, the aim has been to present data from type 1 and type 2 diabetic patients irrespective of health care level, regarding age, sex, diabetes duration and treatment, HbA1c, BP, BMI, smoking, and use of lipid-lowering drugs from 1996 to 1999. During this period, several major clinical trials in the area of diabetes care were published (4,5). A second report from NDR will shortly be published regarding BP control in diabetic patients on antihypertensive treatment or with nephropathy (6).
Our data represent diabetic patients from 75% of 80 HCMs and 15% of nearly 900 PHCs, collected from all parts of Sweden. A total of 46 HCMs in 1996, 60 in 1997, 55 in 1998, and 57 in 1999 participated. A total of 162, 174, 139, and 141 PHCs participated in the respective years. Only adult patients (>18 years of age) were registered. All patients gave written informed consent to participate. However, the participation in NDR was nonmandatory for patients and treatment units. The mean number of subjects with diabetes was 314439 patients per HCM unit and 78127 patients per PHC unit, implying that the main part of all diabetic patients per unit of HCM and PHC were included in NDR by most of the participating centers. Registrations at local centers were generally performed by experienced physicians and nurses. All participating diabetic patients were registered on a paper form or via a specially designed database software supplied on diskette or CD-ROM, developed by Lunds Data Central (LDC), Lund, Sweden. All registrations were sent to a central database and analyzed by use of SAS (SAS, Cary, NJ). The registrations have so far been performed during the year after the clinical data were collected, i.e., data from 1999 were registered in the year of 2000. Yearly reports of all registered diabetic patients separated into HCMs and PHCs have been presented by NDR to Swedish authorities (also available online at www.ldc.lu.SE/ndr).
The Swedish Health Care system for diabetic patients
Definitions of study participants The definition of type 1 diabetes was based on onset of diabetes before the age of 30 years in combination with treatment with insulin only. The corresponding definition of type 2 diabetes was onset of diabetes at the age of 40 years or above, irrespective of type of treatment. This means that all patients with diabetes onset between 30 and 39 years, as well as all patients with diabetes onset before the age of 30 years on oral treatment or on combined oral and insulin treatment were excluded from further analyses. Furthermore, some patients also had to be excluded due to missing data regarding various measured variables, e.g., diabetes duration.
Clinical investigations
Statistical methods
Number of patients included in NDR All diabetic patients included in the NDR from HCMs and PHCs during the years 19961999 are shown in Table 1. The larger proportion of patients that were excluded from this study in 1999 was due to missing data regarding onset of diabetes, mainly in PHCs.
Clinical characteristics of type 1 and type 2 diabetic patients Patient characteristics concerning age, sex, duration of diabetes, BMI, and smoking habits are shown in Table 2. Mean age was lower in type 1 (39 years) than in type 2 (67 years) diabetic patients, but mean duration of diabetes was longer in type 1 (23 years) than in type 2 (9 years) diabetic patients. The proportions of men/women were similar in the type 1 and type 2 diabetic patients, 55/45%. Mean BMI levels increased significantly from 1996 to 1999 in both type 1 diabetic men (24.8 to 25.1 kg/m2) and women (24.8 to 25.1 kg/m2). This was also seen in type 2 diabetic men (28.0 to 28.2 kg/m2) and women (28.6 to 28.9 kg/m2). Smoking frequency was unchanged in type 1 diabetic patients from 1996 to 1999 (14.5 to 13.5%) but was higher in younger type 2 diabetic patients <60 years of age (21.5 to 20.4%) than in older type 2 diabetic patients 60 years of age (7.8 to 7.6%). The proportion of patients prescribed lipid-lowering drugs increased significantly from 1997 to 1999, both in type 1 (4 to 11%) and type 2 diabetic patients (10 to 22%).
Trends in glycemic and BP control Mean HbA1c levels decreased significantly from 1996 to 1999, both in type 1 (7.5 to 7.3%) and type 2 (7.0 to 6.7%) diabetic patients (Table 3). The proportion of patients with diabetes that reached the national treatment target level of HbA1c <7.5% increased significantly from 1996 to 1999 in type 1 (50 to 58%) as well as in type 2 (66 to 73%) diabetic patients. Similar tendencies were seen regarding limits of excellent treatment levels (HbA1c <6.5%) and poor treatment levels (HbA1c 9.0%).
Mean BP levels also decreased significantly from 1996 to 1999, concerning diastolic BP (130/75130/74 mmHg) in type 1 diabetic patients and combined systolic and diastolic BP (151/82147/80 mmHg) in type 2 diabetic patients (Table 3). The proportion of diabetic patients who reached BP target levels 140/85 mmHg increased significantly from 1996 to 1999 in type 1 (77 to 79%) as well as type 2 (32 to 42%) diabetic patients.
Trends in glycemic control based on individual data
Type 2 diabetes in HCMs and PHCs For type 2 diabetic patients in 1999, we found that those treated in PHCs constituted 61% (not shown). Compared with those in HCMs, patients treated in PHCs were older (mean age 69 vs. 64 years; P < 0.001), had a shorter mean diabetes duration (7 vs. 11 years; P < 0.001), had a higher mean BMI (men 28.5 vs. 27.8 kg/m2; women 29.2 vs. 28.2 kg/m2; both P < 0.001), and were less often smokers (11 vs. 13%; P < 0.001). They also had a lower mean HbA1c (6.5 vs. 7.1%), a higher rate of HbA1c <7.5% (80 vs. 63%; P < 0.001), a higher mean BP (149/80 vs. 144/79 mmHg; P < 0.001), a lower proportion of BP 140/85 mmHg (37 vs. 50%), and less use of lipid-lowering drugs (18 vs. 28%).
Trends in the treatment profile for diabetes
Predictors of HbA1c and BP in type 2 diabetes A prospective multivariate analysis was performed in type 2 diabetic patients (n = 5,426), with HbA1c (1999) and BP (1999) as dependent variables, and with baseline (1996) age, sex, diabetes duration, smoking, and BMI, plus increase of BMI from 1996 to 1999, as independent predictors (Table 6). It was found that both a high HbA1c value and high systolic and diastolic BP values at follow-up (1999) were independently and significantly related to a high BMI value in 1996 and also to a high increase of BMI from 1996 to 1999. Diabetes duration but not age was positively related to HbA1c at follow-up (1999). Age, but not diabetes duration, was positively related to systolic BP (1999), while age and diabetes duration were both negatively related to diastolic BP at follow-up.
The main findings of this study, based on a repeated cross-sectional, large-scale screening of various risk factors in patients with diabetes at four independent surveys during 19961999 in Swedish healthcare, are the tendencies of decreasing mean HbA1c and BP values in both type 1 and type 2 diabetic patients. Furthermore, for both type 1 and type 2 diabetic patients a tendency was also demonstrated for improving achievement of treatment target levels of HbA1c (<6.5% or <7.5%) and BP ( 140/85 mmHg or <130/85 mmHg). The mean decrease of HbA1c (0.3%) from 1996 to 1999 in type 2 diabetic patients of this study (Table 3) can be approximately calculated to correspond to a reduction of 4% in any diabetes complications and of 8% in microvascular complications, as a conservative estimation based on UKPDS predictions in all diabetic patients (5). Similarly, the mean decrease of systolic BP 3.5 mmHg in type 2 diabetic patients of this study should approximately correspond to a reduction of 3.5% in any diabetes complications, 5% in diabetes-related deaths, 3.5% in myocardial infarctions, and 4% in microvascular complications (9). The trend was further strengthened by the prospective analysis of those patients (cohort substudy) with available repeated measurements from 1996 to 1999 (Table 4), showing a significant decrease in mean HbA1c levels. The benefit of lowering HbA1c levels in order to prevent diabetes complications has been clearly demonstrated in recent intervention studies, e.g., DCCT (4), the Stockholm study (10), the Kumamoto study (11), and UKPDS (5). A troubling finding was the relatively high frequency of smokers in middle-aged patients with type 2 diabetes (<60 years of age), similar to figures for the nondiabetic Swedish population in the same age-group. These findings underline the need for further tobacco preventive measures in middle-aged subjects (12,13), being a highly cost-effective intervention regarding prevention of cardiovascular complications (14,15). We also documented an increasing use of lipid-lowering drugs from 1996 to 1999 in type 1 as well as in type 2 diabetic patients. Several recent large-scale studies, e.g., 4S (16) and the Heart Protection Study (17), have shown the importance of treating diabetic patients with lipid-lowering drugs in order to decrease the risk for macrovascular complications and cardiovascular mortality. These important findings seem to have influenced clinical practice.
Limitations of the study
The increasing participation by HCMs all over Sweden from 1996 to 1999, currently 71%, should make the sample of 6,00010,000 type 1 diabetic patients in this study sufficiently representative for the whole population of Our findings were somewhat limited, as they were based on a comparison of data from four cross-sectional surveys. We have, however, shown that the favorable trend in glycemic control was still present in a substudy of subjects (cohort study) with repeated measurements (Table 4). In absolute terms, the reduction of HbA1c was small, but this is in our view a marker for more general trends in the diabetes population and therefore of interest.
Obesity trends and treatment changes in NDR Type 2 diabetic patients treated with oral agents constituted 44% in PHCs but only 11% in HCMs (1999), with a tendency toward a decreasing use of oral agents in monotherapy from 1996 to 1999 in both PHCs and HCMs. Concomitantly, we found an increasing use of the combination therapy of oral agents and insulin from 1996 to 1999, with a higher rate in HCMs (24%) than in PHCs (14%) in 1999. The tendency seen in NDRs from 1996 to 1999 of a decreasing use of oral agents and of a concomitant increasing use of insulin combined with oral agents in both PHCs and HCMs should reflect ongoing discussions in Swedish health care regarding the best treatment choice for diabetes with progressive secondary failure.
The role of NDR and standardization procedures NDR has therefore been initiated as a national tool for a continuous quality assessment of diabetes care in Sweden. One aim is to provide population data regarding clinical practice, complementary to data from previous and ongoing clinical trials. Another aim is to provide local centers with data regarding the quality indicators of diabetes care, also making a comparison possible with the national or regional NDR data. Further quality validation of sampled data should be of value. Local reports are used by the physicians and nurses for a continuous evaluation and quality assessment of diabetes care, with the aim to increase the degree of fulfillment of treatment goals regarding glucose, BP, and other variables and with the assistance by regional NDR coordinators. NDR also intends to introduce the use of an Internet-based data registration, which will further simplify the process and allow individual patients to follow their own diabetes data by use of the Internet. Validation has been carried out continuously by communication between participating centers and the central database at LDC. Regarding HbA1c, Swedish HCM and PHC centers nowadays take part in a quality validation assessed by a collaboration between all laboratories measuring HbA1c (a project called Equalis that started in 1995). This means that HbA1c measurement has been quality-assured since the beginning of NDR by calibration to the standard Swedish high-performance liquid chromatography Mono-S method (22,23).
NDR in comparison with U.S. data In conclusion, the NDR is a tool for continuous quality assessment of Swedish diabetes care. Improving trends based on results from 1996 to 1999 were seen in both type 1 and type 2 diabetes according to decreasing mean HbA1c and BP values and increasing use of lipid-lowering drugs. These trends could translate into clinical benefits regarding micro- and macrovascular complications and diabetes mortality. Obesity and smoking are still major health problems that need to be addressed in the diabetic population.
NDR is financially supported by the Swedish Board of Health and Welfare, Stockholm. The NDR Working Group consists of Soffia Gudbjörnsdottir (National Coordinator), Björn Eliasson, Jan Cederholm, Peter Nilsson, Thomas Fritz (representative of primary health care centers), and Christian Berne (President of the Swedish Society for Diabetology). Anders Nilsson and Göran Blohmé were in charge of the registry from 1996 to 2000. Carl-David Agardh implemented the idea of a national diabetes registry in 1995. We thank all of the participating physicians, nurses, and other staff members who contributed data to NDR. Most of all we thank the diabetic patients who both individually and collectively, via the organization of the Swedish Diabetes Federation, have supported NDR. Data management and its compilation into the computerized register has been handled on a daily basis by staff at LDC, Lund, Sweden.
Address correspondence and reprint requests to Soffia Gudbjörnsdottir, MD, PhD, Diabetes Centre, Sahlgrenska University Hospital, S-413 45 Göteborg, Sweden. E-mail: soffia.gudbjornsdottir{at}medic.gu.se. Received for publication 21 May 2002 and accepted in revised form 10 January 2003. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
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