Conclusions
Here we analyzed baseline data of 604 SwissDiab participants with DM1 and DM2 with respect to compliance with a subset of SSED national guidelines for good disease management in diabetes focused mainly on clinical and biochemical targets.13 The results show that the majority of the criteria under study were achieved in a tertiary care setting. Exceptions were annual nutrition counseling in ≥80% of patients with a BMI ≥25 kg/m2 which was not achieved in either the DM1 or DM2 group, and an HbA1c<7% in ≥40% of patients which was not reached among participants with DM1. However, taking into consideration duration of diabetes, the SSED target of an HbA1c<7% in ≥40% of patients was achieved among participants diagnosed ≤5 years ago, regardless of diabetes type. Considering participants diagnosed with DM2 >5 years ago, the SSED target was no longer met, illustrating that compliance with treatment targets is partly dependent on the composition of the patient group. Overall, the results reflect a comparably high standard of diabetes care among SwissDiab participants at the two tertiary care centers in the German-speaking part of Switzerland.
The sex distribution in SwissDiab was similar to that observed among the 392 participants (68% men and 32% women) with DM2 in the CoLaus study, a population-based cross-sectional study of >6000 adults living in Lausanne, in the French-speaking part of Switzerland.16 Both results are in line with national data on the prevalence of diabetes based on the 2012 Swiss Health Survey (6% among men and 4% among women) and earlier studies.17 18 A relatively high proportion of DM1 compared with DM2 in SwissDiab is expected. Given the complexity of maintaining glycemic control in DM1, these patients are often referred to tertiary care which has more experience and expertise in treatment options (eg, implementation of new technologies, flexible insulin therapy, and diabetes education).
Epidemiological data regarding clinical characteristics as well as quality of care of patients with diabetes in Switzerland are scarce. In the 1970s, the WHO Multinational Study of Vascular Disease in Diabetes was established with the aim to compare prevalence of vascular disease in diabetes.19 20 In 2009, Allemann et al conducted a 30-year follow-up in the 533 Swiss participants recruited by local practitioners.5 All-cause and cardiovascular mortality was higher in participants with DM1 and DM2 compared with the general population, but decreased during the last two decades, indicating improved treatment strategies.
In 2011, Gerber et al published data on 1121 patients with DM2 treated by general practitioners in the four linguistic regions (German, French, Italian, and Romansh) of Switzerland.21 The mean HbA1c level was 6.9%±1.0% in the German-speaking region compared with 7.3%±1.1% (median 7.1% (6.6–7.9)) in SwissDiab. Furthermore, mean BMI (29.5±5.4 kg/m2) as well as BP (SBP, 138.2±16.4 mm Hg; DBP, 81.1±10.4 mm Hg) tended to be lower in the study by Gerber et al compared with the SwissDiab study (BMI, mean=32.8±6.2 kg/m2, median=32.1 kg/m2 (28.4–36.5); SBP, mean=138.7±16.6 mm Hg, median=138.0 mm Hg (127.0–149.5); DBP, mean=77.4±10.0 mm Hg, median=77.5 mm Hg (72.0–83.5)), suggesting that the metabolic profile of participants in the former study was better, which is not surprising given the different clinical settings in which the participants of the two studies were recruited. Mean age at diagnosis of DM2 in SwissDiab was 48.3±10.4 years (median 48.0 years (42.0–56.0)), and the mean age at start of therapy in the study by Gerber et al was 60.9±11.2 years. Given that antidiabetic treatment is generally initiated within 1 year of diagnosis,14 this might indicate an earlier onset and a more advanced and progressive course of disease in the SwissDiab participants, which would be in line with the tertiary care setting in which participants were recruited. It is also possible that variations in diabetes therapy contribute to the differences; however, data on medication are not yet available in SwissDiab.
In 2013, Burgmann et al published a retrospective study comparing data of all patients with DM2 admitted to the general clinic of medicine at the Hospital Centre Biel in 2009 to the treatment recommendations published by the SSED the same year.12 22 Mean age was higher compared with the SwissDiab participants (74.2±10.8 years vs 61.3±10.4 years, median=62.1 years (54.7–68.8)) as was the mean HbA1c (7.7%±1.7% vs 7.3±1.1%; median=7.1% (6.6–7.9)).22 The authors concluded that metabolic control was suboptimal in the majority of patients with DM2 and implementations of treatment guidelines by general practitioners as well as hospitals need to be improved. However, the results may rather reflect a greater disease burden of hospitalized patients with DM2, and as such, may not reflect a general failure to adhere to treatment guidelines. Burgmann et al do not provide detailed information on disease burden or the reason behind hospitalization but 44% of patients with DM2 presented with an HbA1c level ≤7%, which is similar to the proportion seen in the tertiary setting of SwissDiab. Furthermore, 20% had an HbA1c>8.5% (11% in SwissDiab), supporting the assumption that glycemic control in individuals with DM2 and need of hospitalization tends to be worse compared with patients in outpatient clinics.
In 2014, Zuercher et al published baseline data from the CoDiab-VD Study, a population-based cohort of participants with diabetes recruited in the French speaking canton of Vaud.23 Of the 519 participants, 67% were diagnosed with DM2. Mean age and diabetes duration were similar to that observed in SwissDiab. Self-reported HbA1c was available in 177 participants (34%) with unspecified diabetes type and was similar to baseline HbA1c in the SwissDiab DM1 and DM2 groups (7.3% (95% CI 7.1 to 7.5) vs 7.5% (95% CI 7.3 to 7.6) and 7.3% (95% CI 7.2 to 7.4), respectively).23 The recruitment strategy via community pharmacies (participation rate <50%) has the potential to capture a more health-conscious fraction of the target population. Further assuming that HbA1c-aware participants are more health-conscious and therefore better controlled, the HbA1c level is likely to be an underestimation of the population average. General practitioners might measure HbA1c less frequently in patients with milder forms of diabetes, for example, those treated only with oral antidiabetic medication (51% in CoDiab-VD), or might communicate good HbA1c levels less actively as they may not have an immediate therapeutic consequence. With the limited information provided, it is difficult to draw any conclusions regarding differences in disease severity between the two studies.
The SSED targets for LDL-cholesterol were met in both SwissDiab and the inpatients with DM2 in Burgmann et al.22 Lack of information in the study by Gerber et al and in CoDiab-VD precludes comparisons with these study populations.21 23 That LDL-cholesterol was better controlled in the DM2 compared with the DM1 group is to be expected as cardiovascular risk is higher in DM2 compared with DM1 in the absence of secondary complications. Therefore, one can assume that the proportion of participants on statins was higher in the DM2 group. Higher mean total and LDL-cholesterol levels in participants diagnosed with DM2 ≤5 years ago were unexpected. Given the better glycemic control in this group, one possible explanation is that healthcare professionals in charge are less stringently targeting lipids. Suboptimal adherence to prescribed lipid-lowering medications might also be an explanation. However, information on medication is not yet available for analysis in SwissDiab.
Out of 511 participants in CoDiab-VD, 58% attended an ophthalmic examination during the previous year,23 whereas the SSED target of ≥80% was achieved in SwissDiab. How representative these results are to the primary care setting is unclear. It is possible that patients with more severe diabetes, as often is the case in tertiary settings, are more carefully screened.
The SSED criterion regarding weight maintenance addresses the importance of raising patient awareness of the central role of weight and diet for good diabetes management through annual discussions with the healthcare provider. In CoDiab-VD, written or verbal diet recommendations were received by 49% of the participants.23 Distinction between DM1 and DM2, or based on BMI category was not provided, preventing direct comparisons with SwissDiab, where 47% and 56% of overweight/obese participants with DM1 and DM2, respectively, received nutrition counseling. Irrespectively, this area of diabetes care and management can clearly be improved. The primary focus of the SSED criteria is the primary care setting, where fostering of healthy lifestyle choices likely has the potential to substantially reduce the risk of future need of tertiary care, improve quality of life and reduce the burden on healthcare systems. Future studies assessing compliance in the primary care setting are therefore warranted.
Applying diabetes care targets primarily aimed at the primary care setting to tertiary care could be considered too stringent as the patient group of the latter likely includes patients with a more advanced and progressive course of disease where, for example, glycemic control is likely harder to achieve. On the other hand, benefits of intensive multifactorial therapy in reducing microvascular and/or macrovascular complications have been shown,2 24–26 and might thus be beneficial to the high-risk patient group with diabetes treated in tertiary care. As this study illustrates, it is possible to adhere to the majority of the SSED targets in this high-risk patient group. However, although shown to be beneficial, intensive therapy including tight glycemic control has also been associated with increased mortality in high-risk individuals with DM2,27 emphasizing that on the individual level, treatment goals should always be based on patient-specific characteristics, including risk of hypoglycemia, diabetes duration, life expectancy, comorbidities, and other relevant factors.12 Longitudinal studies of the SwissDiab participants will be able to assess whether adherence to the SSED targets influences incidence of diabetes-related complications and comorbidities in this patient group.
The main limitation is that the study is based on two out of the six largest tertiary diabetes care centers in the German-speaking part of Switzerland. Although similar hospital standards and access to care are expected, the generalizability of the results to tertiary care in the German-speaking part and Switzerland as a whole is unclear. To what extent the enrolled patients are representative of the patient group at large at the two centers is also not known, but currently under investigation. A further limitation is that not all of the SSED criteria could be assessed due to lack of information on physical activity and smoking cessation counseling, and the inability to provide meaningful data on the performance of nephropathy screenings and foot exams that would be representative of the general clinical practice at the tertiary care centers involved, as these two exams are an integral parts of the annual SwissDiab examination.
As patients treated at tertiary care centers are more likely to present with advanced disease stages and diabetes-related complications, the study population represents a patient group that generally requires a large proportion of healthcare resources. It is thus important to obtain information on the status of quality of care and treatment in this patient group. Next to CoDiab-VD, SwissDiab is the largest observational study in Switzerland including patients with DM1 and DM2. The longitudinal setting and standardized annual examinations gain advantage over the CoDiab-VD Study, which is based largely on self-report. SwissDiab is thus a resource that has the potential to provide comprehensive and significant information on diabetes care in Switzerland. This will be of vital importance for decision makers in politics and the health sector in view of rising patient numbers and limited financial resources. As additional study centers are recruited, including the other language regions, SwissDiab will continue to give an even more complete picture on the quality of diabetes care and patient outcomes in Switzerland in the future.