Dyslipidemia in primary care – prevalence, recognition, treatment and control: data from the German Metabolic and Cardiovascular Risk Project (GEMCAS)

We analysed the dataset of a nationwide cross-sectional prevalence study in primary care. General practitioners and internists with focus on primary health care (GPs) were selected by a stratified, randomized sampling method to receive a random distribution across all German regions. The methods of this study have been described in detail earlier [10].

The study population comprised all male and female patients ≥ 18 years of age who visited their GP at the participating sites on the day of the survey regardless of the reason for visiting and who gave their written informed consent to participate. The only reasons for exclusion were conditions that made it impossible for the patient to participate (serious disabilities or diseases, acute emergencies, or pregnancies and breast-feeding within the previous 3 months). The study protocol did not allow for further selection of patients. All patients who were eligible on the given day were included consecutively. In total, 1,511 general practices from 397 out of 438 German cities and administrative districts enrolled 35,869 patients (age range: 18 – 99, women 61.1%).

An initial screening blood glucose quick test from a capillary (finger stick) was performed in every patient and the results were documented in the reporting form. Additionally, for each patient, venous blood samples were collected and shipped within 24 hours to the central laboratory (Labor 28, Berlin, Germany) by an assigned courier service. The blood samples were analyzed for levels of glucose, LDL-cholesterol, HDL-cholesterol, total cholesterol and triglycerides. GPs were equipped from the central laboratory with pre-labelled serum- and natriumfluoride-(NaF) tubes for taking the samples.

Dyslipidemia was defined on the basis of the European guidelines on cardiovascular disease prevention in clinical practice [4] using TC and LDL-C to guide treatment. In general TC < 190 mg/dl and LDL-C < 115 mg/dl were regarded as normal (non dyslipidemic). In patients with established cardiovascular disease (items: myocardial infarction/acute coronary syndrome, stroke/TIA, PAD if questionnaire indicated to be present) or type-2-diabetes mellitus thresholds of < 175 for TC and < 100 mg/dl for LDL-C were applied. So if patients exceeded either one of their thresholds, dyslipidemia was assumed. HDL-C and triglycerides were not used to define dyslipidemia. Ongoing treatment or doctors' diagnosis (lipid disorder indicated to be present) was likewise defined as dyslipidemia. Lipid lowering agents were assumed to be necessary in dyslipidemic patients if the absolute risk based on the SCORE Scoring system exceeded 5% [11] or 20% on the PROCAM Score [12].

For the main variables of the study, basic descriptive statistics (number of observations, mean, median, proportions) and corresponding measures of variability (standard deviation, standard error of the mean, 95% confidence intervals) were calculated. Crude and adjusted prevalence rate ratios PRRs and 95% confidence intervals were computed with the SAS procedure GENMOD. All statistical analyses were conducted using the statistical software package SAS 9.1 (SAS Institute, Cary, NC, USA) [13].

Basis of the present analysis was a sample of 35,869 patients from the GEMCAS study. Patients had a mean age of 51.7 ± 16.1 years and a mean BMI of 26.9 ± 5.2 kg/m². Patients with dyslipidemia were more frequently male, past smokers, had a higher BMI and waist circumference, and had more frequently cardiovascular disease (Table 2). Overall 76.4% of patients in GEMCAS met the criteria of the ESC for the diagnosis of dyslipidemia [4].

Dyslipidemia, based on the current ESC guideline definition, was a frequent condition in all age groups from 18 up to 100 years (Figure 1). While the proportion of dyslipidemic patients was low in the young age group (20.9% in male and 39.8% in female patients up to an age of 20 years) it peaked in the age group of 61 – 70 years in both genders with a gradual decline thereafter, more so in male than in female patients.

The proportion of patients whose dyslipidemia was known to the treating physician was between 9.5 and 64.3% in men, and 5.7 and 63.6% in women. Highest rates were seen in men between 61 and 70 years, the lowest in female patients between 18 and 20 years (Figure 2). Table 3 displays that the proportion of diagnosed patients was generally higher in women than in men (PRR 1.15 [95%CI 1.12–1.17]), likewise this was true for higher age (PRR 1.68 [95%CI 1.64–1.72]), risk factors like type-2-diabetes (PRR 1.51 [95%CI 1.41–1.58]), hypertension (PRR 1.70 [95%CI 1.65–1.76]), and a high BMI (PRR 1.48 [95%CI 1.42–1.53]) and WC (PRR 1.50 [95%CI 1.44–1.56]). Patients with cardiovascular end organ damage (cardiovascular disease, PAD, stroke, myocardial infarction, and heart failure) had more often a diagnosis of dyslipidemia. The same was true for patients with liver disease (PRR 1.57 [95%CI 1.47–1.68]).

Patients' knowledge about cardiovascular risk factors and disease was also associated with a higher proportion of a diagnosis of dyslipidemia (Hypertension, MI, Diabetes, and many dietary attempts).

The overall percentage that dyslipidemia in patients with no pharmacotherapy but life style intervention or no therapy at all is controlled was low (about 10%). The percentage of controlled dyslipidemia increased when patients were male (PRR 2.00; [95%CI 1.60–2.50]), had type-2-diabetes (PRR 1.37 [95%CI 1.10–1.72]), prior MI (PRR 1.48; [95%CI 1.09–2.01]), CVD (PRR 1.34 [95%CI 1.06–1.70]), or heart failure (PRR 1.78 [95%CI 1.32–2.40]). If patients knew about their MI (PRR 2.13 [95%CI 1.53–2.96]), had diabetes (PRR 1.38 [95%CI 1.10–1.74]), or reported dyspnoea on exertion (PRR 1.82 [95%CI 1.05–3.17]) control of dyslipidemia was increased (Table 3).

Up to 62.4% of male and 48.7% of female patients with known dyslipidemia were treated with pharmacotherapy (Figure 2). There was an age-related increase in both genders until the age group 81 – 90 in men and until the age group 71 – 80 in women. Control rates on pharmacotherapy varied between 28.4 and 100.0% in men and 24.4 – 100.0% in women.

Patients with higher age (> 65 years, PRR 1.14 [95%CI 1.03–1.26]), with hypertension (PRR 1.20 [95%CI 1.05–1.37]), cardiovascular disease like CVD (PRR 1.46 [95%CI 1.29–1.64]), and MI (PRR 1.32 [95%CI 1.19–1.47]) were more likely to be controlled using pharmacotherapy. Patients with a high BMI (PRR 0.84 [95%CI 0.73–0.97]) or WC (PRR 0.77 [95%CI 0.68–0.87]) were less likely well controlled (Table 3). Additionally, patients reporting a low level of education (< 10 years of schooling, PRR 0.89) and apprenticeship only (PRR 0.80) as well as patients reporting to have arthritis (PRR 0.87) or having ever smoked (PRR 0.87) had lowest rates of control.

It is recommended by international guidelines that patients without existing cardiovascular disease (primary prevention) should receive lipid lowering therapy if their SCORE score exceeds 5% or their PROCAM score 20% or when Diabetes mellitus is present [14]. These patients are the basis of Figure 3. Amongst these about 2/3 were known to have dyslipidemia, 1/3 was treated with pharmacotherapy (with an age-dependent increase from 22.2 to 47.7%) and little more than 10% were finally controlled (low 8.1% in the age group 41 – 50, high 18.0 to 29.7% in the elderly).

Pharmacotherapy is necessary in dyslipidemic patients with pre-existing cardiovascular disease like myocardial infarction, stroke, peripheral arterial disease, or heart failure. These patients are displayed in Figure 4. In these patients, dyslipidemia was usually known (between 50 and 78% per age group), treated up to 50% of cases, and finally controlled in up to about 20%.

In total, we documented a prevalence of dyslipidemia using the ESC criteria of 76.4%. This figure is nominally higher as compared to prevalence rates reported from population-based cohort studies like MONICA [15], PROCAM [16], or GRIPS [17]. Similarly studies from primary care have reported high rates of uncontrolled dyslipidemia [8, 9, 18, 19]. A meaningful comparison with results of other studies is however difficult because of different study populations (patient-based versus population-based), different age-distributions, different and less tight definitions used for dyslipidemia (i.e. TC/HDL-C ratio). Furthermore, there are even differences between the current guidelines in the extent of recommended LDL-C lowering thus giving rise to different prevalence estimates. An example for this is a comparable recent study conducted in primary care (DETECT) which reported prevalence rates for dyslipidemia of approximately 50% based on the NCEP criteria [5, 7]. For example, for patients with lower NCEP risk classifications, the European guidelines recommend an optimal LDL-C level of below 115 mg/dl, while the NCEP guidelines recommend an LDL-C below 160 mg/dl. These differences may well account for the different prevalence rates reported.

A number of secondary prevention trials have shown the benefit of lipid lowering in patients with pre-existing cardiovascular disease [20‐24]. Furthermore, because of a high baseline risk in these patients the benefit of pharmacotherapy translates into a high absolute risk reduction and in these patients statins are highly cost-effective drugs. This is also the apparent focus in primary care in Germany as patients with cardiovascular risk factors like type-2 diabetes or pre-existing cardiovascular end organ damage are diagnosed, treated and controlled to a higher extent than patients without. Control rates however are not sufficient in patients in which physicians decided to use pharmacotherapy. Only about 55% of male and 40% of female patients are controlled to the extent the ESC guidelines ask for. However, this rate is substantially higher compared to rates in hypertension, where control rates of about 20% have been reported for primary care [25, 26].

Primary prevention is warranted only in patients not meeting the currently accepted thresholds of the ESC or NCEP guidelines respectively, unless their risk for cardiovascular death exceeds 5% or the risk of cardiovascular events 20% including patients with diabetes [11, 12, 14]. This is reasonable given the risk benefit ratio of currently available pharmacotherapy favouring the use of drugs in high risk patients. It is also reasonable because of the price of pharmacotherapy. Considering a substantial proportion of the German population to be dyslipidemic (irrespective whether the ESC or the less tight NCEP guidelines are used as a reference) it would be a substantial cost burden for the health care system with an uncertain outcome. The prices for statins have dropped over the last years, but still the general distribution of statins to every patient appears neither feasible nor wanted.

It is however unclear whether the currently available pharmacotherapeutic options, despite being highly effective in clinical trials, are sufficient or even suitable in clinical practice to control dyslipidemia in a large proportion of patients. This study clearly shows that reaching prevention targets on a larger scale is very difficult to achieve. Several steps may improve the situation: 1) Physicians could be more aggressive to meet their patients' treatment goals; 2) Patients should be more compliant with therapy; 3) guidelines could be tailored more to the need of physicians in primary care. It may however be questioned whether reaching these lower goals has benefit for the individual or the collective at all. All this points to the fact that dyslipidemia is a multifactorial disease which has to be addressed at multiple levels to achieve long-term control. Prevention aiming at reducing the metabolic syndrome by increasing physical activity and controlling waist circumference has been shown to be highly effective if these steps are installed early enough in the course of a person's life.