Secondary Prevention in a Large Stroke Population
A Study of Patients’ Purchase of Recommended Drugs
Background and Purpose— In this study, linked, anonymous data from The National Hospital Discharge Register and the Swedish Prescribed Drug Register were used for studying to what extent recommended drugs for secondary prevention after stroke and TIA were purchased by patients in the region of Stockholm, Sweden (2 million inhabitants).
Methods— Data on purchased drugs for secondary stroke prevention during July 2005 to June 2006 by 17 902 patients >18 years discharged after stroke or TIA during the period 1997 to June 2005 were analyzed by age, gender, and year of discharge.
Results— Antiplatelets and warfarin were purchased by 87% of all stroke and 83% of all TIA patients, antihypertensives by 74% and 70%, and lipid lowering drugs by 41% and 39%, respectively.
Conclusion— Time after discharge had only a minor influence on the proportion of patients purchasing the medicines.
Well known risk factors for stroke, ie, hypertension, hyperlipidemia, atrial fibrillation (AF), carotid stenosis, and diabetes, can be effectively treated. This has been shown in numerous studies on which evidence-based guidelines have been developed.1–2 However, many studies show that these guidelines are poorly followed in healthcare.1,3–7 Most studies are based on small patient samples captured from medical records or patient surveys. By combining data from the recent Swedish Prescribed Drug Register8 with diagnoses from the national Hospital Discharge Register9 it is now feasible to perform large-scale studies on actually purchased prescription medicines for entire patient populations. Preliminary analyses have been performed by the National Board of Health and Welfare in Sweden.9
Materials and Methods
The population studied was captured from the national Hospital Discharge Register. Patients >18 years living in Stockholm County or the island of Gotland, Sweden (2 million inhabitants) discharged after stroke (ICD codes I63.0 to I63.9) or TIA (G45.9) during the period 1997 to June 2005 were included. These patients’ purchase of medicines used for secondary stroke prevention in July 2005 to June 2006 was analyzed through anonymized record-linkage with the National Prescribed Drug Register containing complete data on dispensed medicines to the entire Swedish population.8 Data were analyzed by age, gender, and year of discharge. The study was designed to evaluate the treatment for all stroke/TIA patients in the region but did not allow analyses of concomitant diseases or risk factors requiring drug treatment. The study was approved by the regional ethical committee.
Statistical analyses were performed using Chi square test with Yates correction with 1 degree of freedom. Significance testing was performed at the 95% level with 2-sided probability values.
Results and Discussion
In all, 12 362 and 5540 patients with stroke and TIA, respectively, were included. A majority purchased some medicines recommended for secondary prevention, and there was no major difference in treatment between patients with stroke or TIA (Table 1).
In this study, 87% of all stroke-patients and 83% of all TIA-patients purchased any oral anticoagulant (OAC)/platelet aggregation inhibitor (PAI). This is similar to the 86% of patients discharged with these drugs according to the National Health Care Quality Registry based on voluntary reporting from participating hospitals.10 It is also considerably higher than what has been shown in other studies.5,11–12
AF was recorded as a diagnosis in 12% of all patients. The proportion of patients with AF treated with warfarin was 100% in the youngest age group and decreased by age. In the whole population, 54% of all stroke/TIA patients with AF purchased warfarin. The prevalence of AF was lower than expected and may be attributable to incomplete diagnosis registration. However, there are inconsistent findings from other studies reporting 14% to 37% of AF in stroke/TIA populations.13 The high proportion of patients with AF on OAC in our study is somewhat surprising, and further studies are in progress. In the whole stroke/TIA population, a higher proportion of men was treated with warfarin compared to women (Table 2⇓). However, among the stroke/TIA patients with AF, women were treated to a larger extent in all age groups except among the elderly.
Antihypertensive drugs were used by 74% and 70% of Stroke/TIA patients, respectively. However, purchasing antihypertensive drugs is not synonymous with adequate blood pressure control.14 Women received thiazides to a greater extent, whereas men used more ACEi. This is in accordance to what has been shown previously for hypertension in the general population14 and may be attributable to the fact that women suffer from side effects of ACEi more frequently and a potentially antiosteoporotic effect of thiazides.14 Men were also treated with statins to a greater extent: 46% compared to 34% for women. Overall the use of LLA was lower for patients discharged in the late 90s. This indicates that statins are increasingly prescribed today. An alternative explanation is that patient compliance decreases more over time for these drugs than for others.15
ASA was used by a greater proportion of patients discharged in recent years (Table 3). The total utilization of dipyridamol and especially the fixed combination with ASA has decreased over the years. Betablockers, the mostly used antihypertensive drugs, were used slightly more for patients discharged in recent years. Treatment with ACEi increased markedly in 2005. Whereas purchase of diuretic agents remained stable during the period, the proportion of patients using thiazides increased and the proportion of patients using loop-diuretics decreased over the years.
This study shows the feasibility to perform large scale population-based studies on actually purchased medicines in patients with specific diseases. However, the quality of such studies depends on the quality of record keeping. Hospital reimbursement in Sweden is based on diagnosis-related groups, and primary diagnoses are validated. The quality of the Hospital Discharge Register is high, and the coverage is complete since 1987. The Swedish Prescribed Drug Register is complete with regard to dispensed pre-scribed drugs for the entire Swedish population, regardless of reimbursement status.8 Purchase of medicine provides a more accurate picture of actual medications used than data captured from medical records. Still, it is important to emphasize that purchase is not synonymous with actual consumption.
In conclusion, this study shows that stroke/TIA patients in the region of Stockholm, Sweden discharged in the last 10 years purchased many of the recommended medications for secondary prevention of stroke. Furthermore, it seems as if the patients continue to take the secondary preventive drugs even many years after the original stroke. However, there is still a need for improvement in pharmacological secondary prevention after stroke and TIA to reduce the stroke burden of society and limit the suffering for the individual.
We gratefully acknowledge Andrejs Leimanis at the National Board of Health and Welfare for valuable assistance.
Sources of Funding
This work was supported by a grant from the Research Foundation of Capio.
- Received January 4, 2008.
- Accepted February 12, 2008.
Sacco RL, Adams R, Albers G, Alberts MJ, Benavente O, Furie K, Goldstein LB, Gorelick P, Halperin J, Harbaugh R, Johnston SC, Katzan I, Kelly-Hayes M, Kenton EJ, Marks M, Schwamm LH, Tomsick T; American Heart Association/American Stroke Association Council on Stroke; Council on Cardiovascular Radiology and Intervention; American Academy of Neurology. Guidelines for prevention of stroke in patients with ischemic stroke or TIA. Stroke. 2006; 37: 577–617.
Micieli G, Cavallini A, Quaglini S. Guideline compliance improves stroke outcome. Stroke. 2002; 33: 1341–1347.
Gibbs RG, Newson R, Lawrenson R, Greenhalgh RM, Davies AH. Diagnosis and initial management of stroke and TIA across UK health regions from 1992–96. Stroke. 2001; 32: 1085–1090.
Sappok T, Faulstich A, Stuckert E, Kruck H, Marx P, Koennecke HC. Compliance with secondary prevention of ischemic stroke: A prospective Evaluation. Stroke. 2001; 32: 1884–1889.
National Board of Health and Welfare. Stroke care in Sweden. Stockholm 2007.
Filippi A, Bignamini AA, Sessa E, Samani F, Mazzaglia G. Secondary prevention of stroke in Italy. Stroke. 2003; 34: 1010–1014.
Volpato S, Maraldi C, Blè A, Ranzini M, Rita Atti A, Dominguez LJ, Barbagallo M, Fellin R, Zuliani G; Gruppo Italiano di Farmacoepidemiologia nell’Anziano (GIFA). Prescription of antithrombotic therapy in older patients hospitalised for TIA and ischemic stroke: the GIFA study. Stroke. 2004; 35: 913.
Andersen KK, Olsen TS. Reduced poststroke mortality in patients with stroke and atrial fibrillation treated with anticoagulants. Stroke. 2007; 38: 259–263.
Swedish Council on Technology Assessment in Health Care (SBU). Moderately Elevated Blood Pressure. SBU report 170, 2004. Stockholm, 2004.
Ovbiagele B, Saver JL, Bang H, Chambless LE, Nassief A, Minuk J, Toole JF, Crouse JR; VISP Study Investigators. Statin treatment and adherence to national cholesterol guidelines after ischemic stroke. Neurology. 2006; 66: 1164–1170.