This study investigated the prevalence and predictors of stroke among adults who reported having either prediabetes or diabetes in Florida. The percentages of stroke among adults with prediabetes (7.8%) and diabetes (11.2%) were higher than among the general population of Florida (3.6%) in 2019 . No previous studies have investigated predictors of stroke among adults with prediabetes and diabetes and yet this information is critical for guiding health programs aimed at reducing stroke burden in Florida.
The identification of hypertension as a common predictor of stroke among adults with prediabetes and diabetes in this study is consistent with the findings from previous studies [22,23,24]. According to a report by the AHA, hypertension increases risk of stroke by weakening arteries and weakened arteries are more likely to burst or clog resulting in hemorrhagic or ischemic stroke, respectively . Evidence suggests that persons with prediabetes and diabetes have damaged blood vessels and compromised functionalities of heart and kidney due to higher than normal blood glucose levels [25, 26]. Compromised kidney functions increase blood volume and again decrease the stretching capacity of blood vessels [25, 26]. As a result, adults with prediabetes and diabetes are more likely to experience stroke if they also have hypertension.
Previous studies reported age as a non-modifiable risk factor of stroke among both males and females [27,28,29]. Similar to these findings, this study identified higher odds of stroke among individuals ≥45 years old who had prediabetes [27,28,29]. A study by Bushnell et al. reported that the risk of stroke doubles every 10 years after age 55 . The possible mechanism underlying the effect of age is that arteries naturally became narrower and harder with increasing age due to the change mediated by endothelial dysfunction and impaired cerebral autoregulation . Moreover, certain stroke risk factors such as diabetes, hypertension, atrial fibrillation, and coronary and peripheral artery diseases steadily increase with age . However, evidence also suggests that adolescents and younger people aged 15–49 years also have a high risk of stroke due to obesity and high blood pressure . In contrast to the previous findings, age was not significantly associated with stroke risks among persons with diabetes in this study [27,28,29]. The reason for this remains unclear. However, two or more comorbidities are quite common among older individuals with diabetes, which could potentially interact with conventional cardiovascular risk factors (i.e., age) to increase the risk of stroke .
Similar to the findings of this study, several studies suggested that high blood cholesterol levels increased risk of stroke [32, 33]. Higher odds of stroke among individuals with both prediabetes and hypercholesterolemia could be explained by the changes of lipid metabolism among these populations. Adults with prediabetes have distinctive form of dyslipidemia characterized by low levels of High Density Lipoprotein (HDL)-cholesterol and moderately elevated levels of Triglyceride (TG)-rich lipoprotein . Dysmetabolism of TG-rich lipoprotein increases the level of smaller and denser Low-Density Lipoprotein (LDL) particles. Overall, non-HDL cholesterol levels, including TG and LDL, almost always increase among adults with prediabetes. Moreover, increased non-HDL cholesterol levels due to lipid dysmetabolism and weakened blood vessels due to hyperglycemia among adults with prediabetes increase the risk of atherosclerosis and ischemic stroke . Surprisingly, hypercholesterolemia was not a significant predictor of stroke among adults with diabetes in this study. This is possibly due to the fact that anti-diabetic medications such as sulfonylurea and insulin can control hypercholesterolemia and, to some extent, reduce the risk of developing stroke [36, 37].
Risks of stroke among populations with diabetes vary by race. The higher odds of stroke among non-Hispanic Black compared to non-Hispanic White, identified in this study, is consistent with reports from previous studies [38,39,40,41]. There is evidence that non-Hispanic Black populations have high risks of stroke because they are more likely to have hypertension and diabetes [39,40,41]. However, another study by Heyman et al. suggested that even after adjusting for hypertension and diabetes, non-Hispanic Black individuals had consistently higher risk of stroke than non-Hispanic White [38, 42]. Studies have reported that only half of the excess risk of stroke among non-Hispanic Black could be attributed to traditional risk factors (such as poor diet, obesity, and high salt diet), implying that genetic and biological factors might have potential roles in stroke disparities among non-Hispanic Black population [43,44,45]. Additionally, non-Hispanic Black adults with diabetes often do not have access to healthcare due to low socioeconomic conditions and tend to have uncontrolled diabetes . The presence of inherent excess risk of stroke and uncontrolled diabetes may be responsible for higher odds of stroke among non-Hispanic Black individuals with diabetes compared to non-Hispanic White individuals with diabetes. Although Hispanic individuals had seemingly higher odds of stroke than non-Hispanic White individuals, this association was not statistically significant. A study by Rodriguez et al. also reported that age-adjusted prevalence of stroke among Hispanic individuals ≥18 years were similar to stroke prevalence among their non-Hispanic White counterparts . However, this relationship may vary by geographic region as several studies, conducted in other US states, reported a significantly higher risk of stroke among Hispanic individuals compared to their non-Hispanic White counterparts. Similarly, the risk of stroke among non-Hispanic other races, including Asian and American Indian/Alaskan Native, also vary by geographic location . This study identified significantly lower risk of stroke among non-Hispanic other races than non-Hispanic White individuals in Florida, while studies in other US states reported the opposite [49,50,51]. However, it is worth pointing out that non-Hispanic other races represent a small portion of the Florida population. Overall, reasons for identified disparities in stroke risks among minority populations could be genetic and higher prevalence of traditional risk factors such as diabetes, hypertension, low socioeconomic status, and healthcare system challenges . Surprisingly, race was not a significant predictor of stroke among adults with prediabetes. The reason for this is not apparent but may be due to the fact that other factors such as age, hypertension, hypercholesterolemia are more important predictors of stroke among these populations.
Based on the findings from this study, adults that had both diabetes and depression had two times higher odds of stroke compared to those that had diabetes but no depression and this finding is consistent with those from a meta-analysis of 17 epidemiological prospective studies showing significant positive associations between depression and stroke even after adjusting for diabetes, hypertension, and other risk factors . Individuals experiencing depression tend to have unhealthy lifestyles, get less exercise, often times do smoke, and are more likely to miss prescribed medication . Other possible mechanisms linking depression to stroke could be inflammation, atherosclerosis, lesions in cerebral white matter, cardiac arrhythmia, and increased platelet activity [53, 54].
Since estimates obtained from the BRFSS data are representative of the adult population of Florida, they are generalizable to Florida adults. Thus, the findings from this study are useful for guiding health planning for the state of Florida. However, Florida population could also be representative of similar populations in other high- and middle-income countries with similar socioeconomic structure and quality of life. Moreover, identified predictors of stroke in this study such as hypertension and hypercholesterolemia are common comorbidities among populations all over the world. Therefore, the findings of this study could provide guidance to conduct similar studies among populations of other high- or middle-income countries. However, it is worth noting that differences in healthcare systems, environment, and inherent biological factors among populations of different races and ethnicities in different countries could result in the identification of different sets of predictors of stroke.
Strengths and limitations
To our knowledge, this is the first study that estimated the prevalence and investigated predictors of stroke among populations with prediabetes. The findings are critical for reducing stroke burden considering the fact that populations with prediabetes represent 1/3 of the US adult population. This is also the first study investigating predictors of stroke among populations with diabetes in Florida. Identifying populations that have prediabetes or diabetes with a high risk of stroke will help enhance evidence-based programs targeting those populations in Florida. These findings are important as the Florida Department of Health seeks to implement the new Paul Coverdell National Acute Stroke Program which aims to improve the quality of care for stroke patients. A strength of the BRFSS data is that it is based on statistical survey sampling methodology and therefore provide representative estimates that are generalizable to the population. However, this study is not without limitations. First, since the BRFSS was based on self-reported responses, prevalence estimates calculated from this survey could be affected by reporting or recall biases. For instance, it is possible that people who had not suffered a severely disabling stroke might forget to mention having a stroke (recall bias). However, these will bias the estimates of associations towards the null, implying that the true associations are even stronger than the results shown in this study. Additionally, since the study used secondary data, there was no way to cross-check medical records with self-reported responses in the BRFSS survey. However, studies have shown that BRFSS data are accurate even after considering reporting bias [55, 56]. Secondly, rates of detection of prediabetes or diabetes might be higher among individuals of higher socioeconomic status than those in low status. Therefore, more affluent individuals might be overrepresented among those reporting prediabetes and diabetes . In addition, the BRFSS did not collect data on: (a) the duration of prediabetes and diabetes, (b) medications for management of stroke risk factors (i.e., hypertension and hypercholesterolemia), and (c) effectiveness of control of blood sugar, blood pressure, and cholesterol among populations with prediabetes and diabetes. Therefore, the impacts of these on the risk of stroke could not be assessed. Finally, the BRFSS survey did not gather information on types of stroke and hence stroke risks could not be investigated based on types of stroke. These limitations notwithstanding, the findings of this study provide useful information to guide health planning and programs aimed at reducing stroke burden in Florida.