Factors associated with orthostatic hypotension presence and severity in multiple system atrophy: a cross-sectional study

Background The factors governing the presence and severity of orthostatic hypotension (OH) in multiple system atrophy (MSA) may differ. We investigated factors independently associated with OH and severe OH in MSA, and assessed the consistency of these associations across subtypes. Methods We examined the clinical data of 242 MSA patients who had blood pressure evaluations to assess OH. We analyzed the clinical data of MSA patients with and without OH, as well as those with mild and severe OH, focusing on clinical characteristics and brain MRI features to identify factors associated with OH presence and severe OH. Results OH was present in 136 patients (56.2%). MSA-C subtype (OR = 2.42, 95% CI = 1.33–4.43, p = 0.004), probable MSA (OR = 2.68, 95% CI = 1.49–4.80, p = 0.001), and higher UMSARS-I scores (OR = 1.10, 95% CI = 1.03–1.17, p = 0.005) were independently associated with the presence of OH. Among OH-positive patients, male (OR = 2.57, 95% CI = 1.21–5.44, p = 0.014) and higher NMSS scores (OR = 1.06, 95% CI = 1.02–1.11, p = 0.009) were independently associated with severe OH, whereas MSA subtype was not. Subgroup analyses showed directionally consistent associations for male sex and NMSS across MSA-C and MSA-P subgroups. The association between NMSS and severe OH was statistically significant in the MSA-C subgroup (OR = 1.09, 95% CI = 1.03–1.15, p = 0.004), whereas the remaining subgroup estimates did not reach statistical significance. No neuroimaging marker was associated with OH. Conclusion Factors associated with OH presence differed from those associated with severe OH in MSA. MSA-C subtype, diagnostic certainty, and UMSARS-I score were associated with OH presence, whereas male sex and NMSS burden were associated with severe OH.