Masked Hypertension

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Masked Hypertension is a situation where blood pressure (BP) measurement in the hospital / doctor’s office is normal but when measured outside the hospital setting, it is elevated. This is a direct opposite of white coat hypertension. Though this has been attributed to the techniques of blood pressure measurement, this condition has serious consequences to the diagnosis and management of hypertension. 

Why is blood pressure higher outside doctor’s office? 

  1. Blood pressure measurement after a large meal may be lower than it normally is, especially in the elderly. If an elderly just finished eating before clinic visit, it may give a falsely low reading BP than what is obtainable outside the clinic setting. 
  2. Mental stress at work and at home may raise blood pressure to hypertensive levels while you are within this environment. While at the clinic, because of being outside the stress environment, your blood pressure may read normal.
  3. Smoking and excess alcohol predispose to masked hypertension. These agents may raise blood pressure while their contents are active in the body, with temporary decline when not active on the substances, which may correspond to the period of office measurement.
  4. Obese individuals with poor exercise tolerance may have relatively normal or slightly elevated blood pressure when measured at rest in doctor’s office but markedly elevated BP when they move around or exercise.
  5. Those with obstructive sleep apnoea or shortened sleep time from adolescent period may have elevated night time or early morning BP but normal BP in the doctor’s office.
  6. In the elderly, with poor functioning of blood pressure regulating system, there may be increased variation of blood pressure, with the period of low measurement corresponding to the time of hospital measurement.
  7. Patients on antihypertensive drugs may have normal blood pressure measurement at the doctor’s office if the time of consultation coincides with the peak of the action of their medication. The BP may then go high before the next dose of the drug. These patients are said to exhibit masked uncontrolled hypertension, suggesting that the drugs being taken might not be enough and may need to be reviewed. 

Risk factors for having masked hypertension – The following categories of people are at higher risk of masked hypertension than the general population:

  1. Male gender.
  2. Obesity.
  3. Advanced age.
  4. Smoking.
  5. Diabetes.
  6. Long duration of hypertension

Diagnosis of masked hypertension – The diagnosis is made by home monitoring of BP or ambulatory BP monitoring (BP monitoring while carrying out the normal activities of the day such as going to work and coming back, cooking, sitting down, sleeping etc), which records BP at every 20 to 30 minutes intervals for 24 hours. With this, round-the-clock BP fluctuations can be recorded instead of one-off office monitoring.

Treatment for masked hypertension – If you discover that your blood pressure usually reads higher at home than it is when measured in the hospital, please, report to your doctor so that it can be investigated and treatment commenced as soon as it is deemed necessary.

It should be noted that persons with masked hypertension run similar risks as those with sustained hypertension (i.e. those with high BP both in and out of the doctor’s office). These risks include: heart failure, kidney failure, stroke etc. Hence the need for investigation and treatment.

Prevention of risks associated with masked hypertension – To prevent the associated risks with masked hypertension, the following categories of persons should have ambulatory BP monitoring device or home BP monitoring device if ambulatory BP monitoring device is not available.

  1. Persons with family history of hypertension.
  2. Patients on antihypertensive treatment.
  3. Smokers.
  4. Patients with diabetes.
  5. The elderly (65 years and above).
  6. Men after 40 years.
  7. Women after menopause.
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