In this study, we estimated the proportion of post-stroke patients whose secondary prevention was optimal over one year post-stroke and described the characteristics of these post-stroke patients. Optimal secondary prevention was recorded in 28.1% of post-stroke patients with diabetes and 49.2% of those without diabetes. In post-stroke patients with diabetes, we found that sex, ethnicity, BMI, smoking, AF, and CKD were significantly associated with the achievement of overall control. While in post-stroke patients without diabetes, we found sex, ethnicity, BMI and AF were significantly associated with the achievement of overall control. Irrespective of the diabetes status, being female, having high BMI, and of Malay ethnicity were associated with poor overall control.
Comparisons with other studies
Published studies mainly explored the control of individual risk factors rather than the overall control achieved. Comparing our results with single risk factor studies, we found examples of some study populations doing better and others worse. For example, comparing the proportion of post-stroke patients having an optimal level of blood pressure, two studies reported a higher level of control at 89.9% [15], and 86% [21], as compared to our estimate of 71.4%. Those studies reporting a lower level of blood pressure control as compared to our estimate reported values ranging from 23.8% to 62.4%. [10, 17, 22-24] Comparing the level of lipid control across different studies, all the reviewed studies reported a lower level of lipid control as compared to our estimate of 66.6%, with reported estimates ranging from 13.9% to 49.0%. [15, 17, 21, 23, 24]. We found 52.9% of post-stroke patients with diabetes achieving the target level of glycemic control. Compared to existing literature, two studies reported a higher proportion of glycaemic control [10,15], and another two reported a lower proportion of glycaemic control. [17, 21]
Our study filled an important gap in current literature as a limited number of current studies address the level of secondary prevention attained. Among the studies reviewed, only two attempted to report a composite or combined estimate of control of risk factors achieved, with one reporting 3.3% of ischemic stroke patients achieving control of all risk factors.[17] Another study reported the proportion of post-stroke patients achieving control of both blood pressure and lipids to be about 19.4%.[24] While our study reported more encouraging levels of secondary prevention achieved, as compared to the above two studies, there remains considerable room for improvement. The reasons for not achieving the optimal level of control of risk factors could be multiple. These could be at the patient level, the physician level, the health system level, or a combination of these. A study reported that in spite of 90% of post-stroke patients being on specific drug regimens, only about one-fourth of them achieved the recommended risk factor control. [17] This highlights the complexity of addressing secondary control post-stroke. For example, the patient’s adherence to medication, compliance to lifestyle factors or healthcare system factors such as difficulty in accessing services or financial barriers, can all play a part. Another study based in Canada reported poor control of risk factors after either a coronary artery disease (CAD) or cerebrovascular disease (CVD).[24] Those with CVD had worse control of risk factors as compared to those with CAD, with the former group having 46.0%, 40.5% and 19.4% of post-CVD patients meeting target levels of blood pressure, LDL and both respectively. In spite of good adherence to secondary prevention guidelines (medication rates ranging from 76.5% to 91.3%), it did not translate to the achievement of risk factor control suggesting the importance of other elements like patient factors.
We reported lower overall control in post-stroke patients with diabetes as compared to post-stroke patients without diabetes. There are literature that support poorer control of other risk factors in post-stroke patients who have diabetes. Patients with diabetes were associated with lower odds (OR=0.16; 95% CI: 0.14, 0.19) of achieving the target blood pressure level compared to patients with a previous cerebrovascular event.[24] Another study reported lower levels of control of lipids in post-stroke patients with diabetes.[15] Another possible explanation could be the difficulty managing co-occurrence of multiple chronic conditions experienced by both healthcare providers and patients.
Our finding was in agreement with other studies that showed, a significant association between sex and achievement of target levels of risk factors.[15, 24] One such study reported the largest difference across males and females in the achievement of the target level of serum LDL levels, with 46.1% of men and 38.3% of women achieving the target.[15] It is important to further study these sub-groups of post-stroke patients to intervene in an evidence-based manner and promote optimal secondary prevention since diabetes itself is an independent predictor of recurrent stroke with about 9.1% of stroke cases being attributable to it.[25-27]
Strengths and Limitations of this study
Our study has several strengths including the large sample size from 10 polyclinics over a period of five years. We captured major risk factors associated with recurrent stroke with a large database. Compared to observational study design which includes self-reported data, our study has the advantage of including a relatively objective source of data from electronic health records. This was one of the few studies to provide estimates of the overall control of risk factors post-stroke in an Asian setting, and we have added new knowledge to the existing literature on the prevalence of control of individual risk factors.
The study also has several limitations. The database could not provide the causation of stroke (ischemic versus haemorrhagic) experienced by each patient, which may influence treatment recommendations by clinicians. Moreover, the database did not have information on other relevant variables such as the functional status of the stroke patients, education level, employment status and available psychosocial support. Another limitation was related to missing data, for which we opted to conduct complete case analysis. Another shortcoming was that we could only assess the proportion of patients meeting or not meeting the treatment goals but could not elicit the reasons why. Qualitative research exploring the experiences of post-stroke patients and their caregivers engaging in secondary prevention related behaviours will be needed.