White coat hypertension is when a person’s blood pressure is higher than normal when it’s measured in a clinical environment (doctor’s office, clinic, hospital, etc). However, when they measure their blood pressure outside of a clinic, it returns to a normal reading.
Although white coat hypertension has been recognized for many years, there are some things about it that still remain unclear. But first of all, let’s look at some key concepts that will help us to better understand the white coat hypertension phenomenon.
What is blood pressure?
Blood pressure is the force that the blood exerts against artery walls. This pressure is an indispensable part of blood to circulating through blood vessels and giving oxygen and nutrients to all the organs of the body. It allows the body to function properly.
Blood pressure has two components:
- Systolic blood pressure: the maximum value of blood pressure during systole (when the heart contracts). It refers to the effect of pressure exerted on the wall of the vessels by the blood pumped from the heart.
- Diastolic blood pressure: the minimum value of blood pressure when the heart is in diastole or between heartbeats. It depends mainly on peripheral vascular resistance (the flow of blood in peripheral arterial vessels).
Blood pressure abnormalities
People may have the following abnormalities or dysfunctions related to blood pressure:
- Hypertension: an increase in blood pressure, whether systolic or diastolic. Hypertension, together with high cholesterol and smoking, are the main (and most preventable) causes of cardiovascular problems.
- Hypotension: a decrease in blood pressure to below normal limits. The person tends to become fatigued and dizzy more easily.
White coat hypertension
As we said, white coat hypertension happens to certain people when they go to hospitals or any other medical setting, such as clinics. We can define white coat hypertension as a reaction to perceived danger when the patient finds themselves in front of a doctor. The reaction is a complex and stereotyped response to an emotional stimulus. It feels like a threat.
The reaction consists of an increase in blood pressure and heart beat when the doctor starts to take a patient’s blood pressure. The doctor’s presence during the reading triggers it.
Interestingly, if the person measuring the blood pressure is a friend, family member, or the patient themselves, they don’t react like that. Nurses may also trigger it, but less frequently. The setting where blood pressure is taken also plays a role, like we mentioned.
What are the criteria for diagnosing white coat hypertension?
The European Society of Cardiology (ESC) suggests the following diagnostic criteria for white coat hypertension:
- Blood pressure readings over 140/90 mmHg in the clinic for three different visits.
- At least two blood pressure readings outside the clinic under 140/90 mmHg.
- Absence of damage in specific organs.
- An average ABPM less than 135/85 mmHg. ABPM stands for Ambulatory Blood Pressure Monitoring.
What characteristics do people with white coat hypertension have?
Patience prone to suffering from white coat hypertension tend to have the following characteristics:
- Blood pressure reading in the clinic of 140/90 mmHg to 159/99 mmHg.
- Recently diagnosed hypertension.
- Absence of left ventricular hypertrophy. Left ventricular hypertrophy is when the heart is enlarged and its walls are thick. It’s generally a consequence of hypertension.
What causes white coat hypertension and the white coat effect?
Until now, no one has clearly identified any mechanisms that could explain this phenomenon. However, we do know of some clues that we’ll explain next.
Increased blood pressure in the clinical setting due to an alert reaction
All of our hearts beat faster and our blood pressure rises when we perceive something as a threat (stress). For people with white coat hypertension, this threatening or stressful stimulus is a clinical environment.
It makes them experience the same physical changes as a stress response. In this case, it’s neither cholesterol nor any other physical cause that’s causing the hypertension. The cause is the stress itself.
So, this effect is the result of a conditioned response to a clinical or hospital environment, and not to the “white coat” itself. We understand a conditioned response as a reflexive reaction or response learned before a stimulus. It has the name “conditioned” because it happens after being conditioned to something: associating a stimulus with something else.
What are conditioned responses?
A famous example of conditioned responses is Pavlov’s dog. The dog learned to salivate when provided an unnatural stimulus not normally associated with food: the sound of a bell. He responded so because he had linked the bell sound with food in his mouth.
The body shows conditioned responses after “conditioned stimulus”. In reference to the matter at hand, the conditioned stimulus is the clinical or hospital environment, and not the white coat. The response is increased activity in the sympathetic nervous system and reduced activity in the parasympathetic nervous system.
The sympathetic nervous system causes nervousness, unrest, stress, etc. The parasympathetic nervous system is in charge of the opposite. It is responsible for feelings of calm and relaxation.
With white coat hypertension there is greater activity in the sympathetic nervous system. This causes an increase in heartbeat and blood pressure. But evidence indicates that the main cause of increases in cardiac frequency is the parasympathetic nervous system’s reduced activation.
The white coat effect vs. white coat hypertension
The terms “white coat effect” and “white coat hypertension” are not the same thing. The white coat effect refers to a temporary blood pressure increase that happens as a reaction of alert. The clinical environment is what mainly triggers the alert reaction.
As for white coat hypertension, we are talking about a clinical diagnosis of hypertension in a medical environment while the patient has normal blood pressure readings during their daily activities. The white coat effect is not related to the basal blood pressure level, and it can happen to patients with or without hypertension.
As we’ve seen, white coat hypertension is essentially generated and controlled by psychological factors. Basically, a person’s blood pressure and heartbeat increase when faced with a conditioned stimulus like a hospital or clinical environment. Given that, the treatment should also be psychological.
Hernández, Edelsys; Grau, Jorge (2005). Psicología de la Salud. Fundamentos y aplicaciones (Primera edición). Guadalajara, México: Universidad de Guadalajara.
Morrales Rueda, A., Ortega García A., Sierra Santos L. Prevalencia de hipertensión de bata blanca durante la perimenopausia. Medifam, 2001.