TNF and multiple system atrophy: Our study also found a positive correlation between serum TNF-α levels and age at onset in MSA patients, which is also consistent with previous findings that serum TNF-α levels were related to aging and significantly higher in older adults than in younger adults (Nozu et al., 2018; Chen et al., 2023; Wyczalkowska-Tomasik et al., 2016).