To our knowledge this is the first study to report white matter hyperintensity and predictors in PD patients in Ethiopia. The mean age of study participants was comparable to previous reports from Ethiopia (13, 14). Majorities of the participants were males; were on levodopa; and tremor dominant. Hypovitaminosis D was observed in close to half of the study participants. Anemia was observed in nearly one third of participants. Furthermore, negative correlation was observed increasing age and anemia. Age and dyslipidemia were found to be independent predictor of white matter hyperintensity.
In the present study, young age was associated with lower risk of WMH on brain MRI. This finding is in congruent with previous reported studied (8, 9). Likewise, age was independent predictor of WMH. This is likely because of the fact that, white matter hyperintensity is common among elderly individuals compared to younger age group. Furthermore, cardiometabolic risk factors that often associated with WMH such as hypertension, diabetes, and dyslipidemia were less prevalent in young age PD patients compared to the older age patients (Table 2). Thus, it’s important to screen older patients with PD for WMH. In current observation, no association was found between disease stage and types of PD. These findings were contrary to previously reported studies; which reported WMH among PD patients with advanced disease stage and tremor dominant PD variants (5, 15, 16). These discrepancies could be explained by the fact that majorities of our PD patients had mild to moderate disease stage.
In the present study, even though non-significant, the prevalence of modifiable vascular risk factors such as hypertension and diabetes mellitus was higher in PD with MRI evidences of WMH compared to those individuals with normal MRI. However, significant proportions of PD patients with dyslipidemia have WMH compared to individuals with no-dyslipidemia; and dyslipidemia was independent predictor of WMH. These findings were in line with similar report by Chahine et al. 2019 (17), which indicates, modifiable vascular risk factors are associated with white matter hyper intensities on brain MRI; and concluded that, WMH may serve as a surrogate marker for the effect of vascular risk factors on cognitive abilities in PD. These findings will support the need to adopt routine vascular risk factors screening for our PD patients, in order to identify the modifiable vascular risk factors early.
In this survey, even though non-significant, the proportion of patients with subjective complaint of forgetfulness and hallucination were higher in WMH group compared to those with normal MRI. These findings were consistent with plethora of scientific evidences which indicates high prevalence of cognitive impairment/ or dementia and neuropsychiatric symptoms in PD patients with high burden of WMH (5, 15–21). These results support the need to routinely screen PD patients for cognitive impairment and comorbid psychiatric disorders; as early identification and treatment of PD dementia is associated with better quality of life in PD patients (21).
In present study, the overall prevalence of hypovitaminosis was high; however, no association was observed with WMH compared to those with normal brain MRI. In the recent decades, increasing scientific evidences have suggested possible association between hypovitaminosis D and PD; low vitamin D level has been associated with endothelial dysfunction which may play a role in the pathogenesis and progression of PD (12, 22). Moreover, studies have reported reduced plasma vitamin D levels were associated with low mini mental state examination (MMSE) scores in patients with Alzheimer’s disease (AD) associated dementia and non-AD dementias (23, 24). These results further support the need of conducting future well designed controlled studies to investigate these observational results; as hypovitaminosis D is one of the easily reversible metabolic disorders. The limitation of this study includes: small sample size; lack of healthy control group for comparison of the findings; lack of using cognitive assessment batteries.
In summary, the present study indicates advanced age and dyslipidemia were associated with increased risk of having white matter hyperintensity on brain MRI of Ethiopian PD patients compared to those patients with normal MRI. Even though non-significant, the trend of vascular risk factors was in line with WMH. We recommend conducting future controlled study to consolidate our findings.