Cost-effective treatment of hyperlipidemia in patients with diabetes mellitus
Diabetes mellitus (DM) is an important risk factor for cardiovascular disease. The results of clinical studies indicate that lipid-lowering therapy is especially effective for their prevention in patients with diabetes. A 4S study (Scandinavian Simvastatin Survival Study) showed that patients suffering from cardiovascular disease and diabetes received much more benefit from treatment with simvastatin than patients without diabetes. SA Grover et al. compared the effectiveness and cost-effectiveness of lipid-lowering therapy (as primary and secondary prevention of cardiovascular disease) in patients with and without diabetes.
Methods The efficacy and cost-effectiveness of treating hyperlipidemia were calculated using the Model Life Expectancy for Cardiovascular Diseases. This model estimates a decrease in cardiovascular morbidity and mortality after exposure to risk factors; it is applicable both to persons who do not have cardiovascular diseases (primary prevention), and to patients who already have coronary pathology or have suffered a cerebrovascular accident (secondary prevention). The risk factors for cardiovascular disease, taken into account in this model, include age, gender, mean blood pressure, the natural logarithm of the ratio of LDL / HDL cholesterol, smoking, diabetes and the presence of proven cardiovascular diseases in the outcome.
The benefit of simvastatin therapy was calculated as the difference between the life expectancy of subjects treated and untreated with simvastatin and was expressed in “extra years of life”. The cost of medical care consisted of the cost of hospitalization, outpatient care, emergency care, doctors’ salaries. The cost of outpatient care included the cost of outpatient medical visits, diagnostic tests and medications. The average dose of simvastatin was calculated based on the results of the 4S study. The annual cost of outpatient treatment for patients with diabetes was estimated based on a rough estimate of the frequency of their visits to doctors and the number of studies conducted during the year, the annual cost of drugs, etc. Finally, the ratios of the cost-effectiveness of simvastatin treatment among patients with and without diabetes were calculated by dividing the difference between the cost of treatment over the life of treated and untreated people by the difference in their expected life expectancy.
Results. According to the model used, the frequency of cardiovascular accidents was comparable with the results of the 4S study.
The predicted positive effect of simvastatin therapy among patients with diagnosed coronary artery disease was significant. Among men with diabetes, the increase in life expectancy ranged from 0.78 to 5.3 extra years of life (DL) depending on age. The benefit in male patients without diabetes was less pronounced and ranged from 0.62 to 4.58 DL. Among women suffering from coronary heart disease, the difference was much more pronounced.
Among people without verified coronary heart disease and high LDL cholesterol, the positive effect of therapy was also significantly higher among patients with diabetes. The amount of DLV in this group ranged from 0.79 to 5.4. Among people with high LDL but without diabetes, the increase in life expectancy was negligible – from 0.44 to 2.5 DL. Even among people with coronary heart disease and with moderate to mild lipid metabolism disorders, the effect of statins on life expectancy was more pronounced in the group of people suffering from diabetes. Among women without coronary heart disease, the benefit of lowering lipids was less than that of men, which reflects a lower absolute risk of developing cardiovascular disease in women.
The ratios of the cost-effectiveness of simvastatin treatment among men suffering from cardiovascular diseases and not having diabetes ranged from $ 5,000 for 1 additional year of life (BPH) to $ 14,000 for BPH, depending on the age and baseline LDL cholesterol. Among men with diabetes, the same ratios were only $ 4,000 – $ 8,000 for BPH. Similar results were observed in the group of women, which indicates that patients with diabetes make up the group of patients in whom secondary prophylaxis with simvastatin is especially cost-effective.
Cost-effectiveness ratios associated with primary prevention among men without diabetes and high baseline LDL cholesterol ranged from $ 12,000 to $ 24,000 for BPH, depending on age. In the group of men with diabetes, these ratios were significantly less and ranged from $ 4,000 to $ 10,000 for BPH. Noticeable differences were also found between groups of male patients with lower baseline LDL cholesterol levels. Among women without cardiovascular disease, the ratios of profitability were higher than in men. Even among patients with diabetes without cardiovascular disease and having very moderate changes in blood lipids, lipid-lowering therapy is still economically viable.
Discussion. Patients with diabetes and lipid metabolic disorders have a very high risk of cardiovascular disease, even in the absence of other risk factors. It was previously shown that lipid-lowering therapy in patients with diabetes is especially important and economically justified in relation to secondary prevention – that is, with existing cardiovascular diseases. The analysis carried out in this work showed, however, that lipid-lowering therapy in relation to their primary prophylaxis in patients with diabetes is also very effective and cost-effective. The goal of their treatment should be to achieve a cholesterol level of less than 100 mg / dl. Consideration should also be given to the need for clinical trials whose goal would be to study the efficacy and cost-effectiveness of treating “normal” lipid levels among diabetics.