Tie-wearers are compressing their veins and creating an unhealthy build-up of pressure.

Researchers from University Hospital Schleswig-Holstein in Germany say it might cause problems for groups that are already at risk from blood pressure issues, like smokers or the elderly.

Cerebral blood flow, the blood supply to the brain, was found to drop by an average of 7.5 percent in the men wearing a necktie, with no drop reported in the control group. The difference is likely to be caused by the extra pressure from the tie crushing blood vessels, the researchers say.

Blood flow to the brain is vital to its proper functioning. It gives brain cells access to the oxygen, glucose, and nutrients needed to do its job, and if the supply dries up, that can cause temporary blips or, in severe cases, permanent damage.

An earlier study in the British Journal of Ophthalmology (August 2003) says wearing a tie that’s too tight can increase intraocular pressure (IOP) in the eyes, possibly leading to glaucoma.

A tight necktie can also lead to wrong medical diagnoses, the researchers warn. When a necktie exerts too much pressure on the jugular vein in the neck, pressure is increased in the entire venous system. This can cause your doctor to diagnose you with ocular hypertension or even glaucoma when you don’t actually have it if you wear a necktie during the examination, the researchers caution.