In August 2018 researchers from Germany published the results of their study to assess the effect of wearing a necktie on cerebral blood flow and jugular venous flow. A total of 30 individuals were involved in the study, and were divided into two groups. One group underwent MRI whilst wearing a necktie, and the other group an MRI without a necktie. Results showed that there was a significant decrease in cerebral blood flow after tightening of the necktie whereas there were no significant changes in the jugular venous flow.
Lüddecke R et al. Should you stop wearing neckties?-wearing a tight necktie reduces cerebral blood flow. Neuroradiology. 2018 Aug;60(8):861-864.