The act of tightening a tie can be seen as a sign of getting down to business, or inferring superiority, or putting your best foot forward – but it might also be restricting the blood flow to the brain, according to a new study.

By compressing the veins in the neck, tie-wearers could be pushing blood into the skull and creating an unhealthy build-up of pressure.

The difference isn't enough to be a serious health risk to most people, the researchers from University Hospital Schleswig-Holstein in Germany say – but it might cause problems for groups that are already at risk from blood pressure issues, like smokers or the elderly.

Previous studies have already linked tight ties with an increase in pressure on the eyes, and a possible association with glaucoma risk as a result.

"Based on these [previous] results, the aim of this study was to further investigate the effect of how wearing a necktie can negatively affect cerebral blood flow (CBF) and jugular venous flow," write the researchers.

Using MRI scans, the team analysed 15 male volunteers who were wearing neckties tightened to a "point of slight discomfort", and 15 male volunteers who weren't wearing neckties at all.

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.

Meanwhile venous blood flow around the rest of the body wasn't affected in either of the two groups.

Blood flow to the brain is vital to its proper functioning, as you can imagine. 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.

However, Steve Kassem from Neuroscience Research Australia, who wasn't involved in the study, told Alice Klein at New Scientist that a 7.5 percent drop is unlikely to cause noticeable symptoms.

That said, people who already problems with blood flow – smokers, the elderly, those with high blood pressure, for example – might be more at risk, Kassem says. Headaches, dizziness, and nausea might be brought on.

Even though the drop noticed in this small sample isn't too damaging, it's one excuse to get your boss to go along with dress-down Fridays – or to maybe loosen your tie at little at the next wedding you go to.

As always though, it's important to get context. Take for example the 2015 study that found that wearing a suit could make the wearer feel more powerful and see the bigger picture. Maybe that's worth a little reduction in blood flow.

Based on the results of the study, the team wants to expand the research to cover those at-risk groups, to see whether wearing a necktie or not could have significant impacts on health. For those in an office job, a tie might be expected for eight hours of each day.

For now though, the majority of us can carry on tightening or loosening our ties as we prefer. The researchers conclude by pointing out that most patients don't expect their doctors to wear a tie – so that's one profession that's off the hook.

The research has been published in Neuroradiology.