A well-known phenomenon in human medicine known as “white coat hypertension”—when anxiety related to a doctor’s visit leads to unusually high blood pressure readings—may also occur in horses, according to new research from Switzerland.

The study, conducted at the University of Bern, was based on 40 horses who regularly received preventive care at the equine clinic there. While the horses were at the clinic, a researcher measured their blood pressure using a cuff at the base of the tail. The next day, the same researcher traveled to each horse’s home stable and again measured blood pressure using the same method. This two-day testing sequence was repeated with each study horse three times over the course of a year, with tests done approximately three months apart.

The data showed all of the horses had higher blood pressure readings in the clinic than they did at home. The researchers note that the difference did not take the measurements out of the “normal” reference range, but this might not be the case in a horse with chronically elevated blood pressure. In mature horses, normal systolic pressure, taken when the heart contracts, is 110 to 160 mm Hg (millimeters of mercury) and normal diastolic pressure, taken between heartbeats, is 90 to 110 mm Hg.

Given that recent studies have linked white coat hypertension to cardiovascular and kidney damage in people, the equine researchers call for more investigation into its possible clinical relevance in horses.

Reference: “Correlation of blood pressure with splenic volume in horses, daily variation in blood pressure and ‘white coat hypertension,’” Journal of Equine Veterinary Science, April 2018.

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