By Paul Clerc,

Knowing your correct blood pressure (BP) is important as increased resting BP is correlated with increased stroke risk, cardiac disease and kidney disease 1,2. High BP, typically considered to be >140/90, is often referred to as ‘silent’ since despite the severe outcomes that are associated with it, there are often few signs or symptoms 1. Hypertension is quite common in Canadians as the prevalence has been estimated at 22.6% 3. Diabetics have an even greater prevalence at 67.1% 3. Regular monitoring (at least once a year) is therefore recommended 1.

Two common phenomena exist that may lead to incorrect BP readings. The first is ‘white coat hypertension’ and presents when BP is higher in the doctor’s office than if measured at home (BP Doctor > BP Home) 1,2. Approximately 13% of individuals in 4 European prevalence studies showed a ‘white coat hypertension’ effect 2. If BP readings are only performed at the doctor’s office, this effect may lead to over-diagnosis and over-treatment of the individual. Additionally, many procedural errors lead into similar overestimation of BP and potential over-treatment. Some key procedure points are highlighted as well as their effect on BP (change in SBP/change in DBP) 1. Even healthcare professionals may measure systolic blood pressure (SBP) up to +9 mmHg and diastolic blood pressure (DBP) up to +6 mmHG higher when not following the standardized procedure 1.

Arm not positioned at level of heart:                                                            7-10/8-11 mmHg higher
Legs crossed during measurement:                                                              8-10/4-5 mmHg higher
Talking during the procedure:                                                                            17/13 mmHg higher
Acute exposure to cold:                                                                                         11/8 mmHg higher
Unsupported arm:                                                                                                     2/2 mmHg higher
Cuff size too small:                                                                                                     8/8 mmHg higher
Terminal digit preference (rounding to 0 or 5):                                      3/3 mmHg higher or lower

These risks of overestimating blood pressure and therefore over-treating are highlighted in several studies. A study amongst American veteran diabetics looked into the associated risks of blood pressure over-treatment. They found that up to 8% of hypertensive diabetics may be over-treated and suggested that impaired coronary perfusion could result 5. Correspondence to the article also implied that acute renal failure, cerebral ischemia, dementia and orthostatic hypotension were also risks of increased management 6. A Dutch study focused on prevalence of hypertensive individuals found that many patients with low risk were being treated despite guidelines not indicating treatment 4. Main concerns from this study’s authors included side effects of medications and reduced cost effectiveness at the healthcare level 4. This effect is not recent as letters to the editor from as far back as 1988 suggest that over-diagnosis and overtreatment may be occurring due to the ‘white coat effect’ 7.

‘Masked hypertension’ conversely represents having normal BP readings at the doctor’s office but elevated readings at home or in daily activity (BP Doctor < BP Home) 1,2. Random BP fluctuations as well as lifestyle factors such as smoking, coffee intake, physical activity and stress can lead to BP being identified as higher outside the doctor’s office 8. In the doctor’s office, patients wait several minutes sitting in a quiet room. This quiet waiting lowers blood pressure but is unlikely to be replicated in daily life. Family history of hypertension, chronic kidney disease, obesity and diabetes increase the likelihood of experiencing masked hypertension 2. The prevalence is around 13% in 4 European studies 2. The significant difficulty with masked hypertension is that it remains undetected leading to the harsh consequences of regular sustained hypertension 2,8. It seems suitable that treatment of masked hypertension should be in the same manner as regular sustained hypertension due to the similar risks and target organ effects; however, there is limited experimental data supporting this theory 8. Identification remains a challenge and it has been suggested that due to the masking effect, home monitoring of blood pressure may a better predictor of cardiovascular risk 8. Importantly, up to 15 out of office measurements are required for proper diagnosis and accurate participant training and use is needed 8. Masked hypertension thus presents many difficulties in identification, diagnosis and treatment.

In summary, increases in BP and over-diagnosis of hypertension are tied to higher health risks in the cardiovascular and kidney systems. Masked Hypertension and White Coat Hypertension are two phenomena that make determining BP difficult and out of office monitoring can help confirm/deny these effects. Standardized procedures for measuring BP are necessary and should be followed to determine the proper BP and therefore cardiovascular risk profile. Following the recommendations of both the Canadian and European Guidelines on Hypertension, it is encouraged that individuals check blood pressures outside the doctor’s office, especially if masked or white coat hypertension is suspected 1,2,8. Local pharmacies often have a BP machine for shoppers to use or home BP machines can be purchased. A list of devices endorsed by Hypertension Canada is available online (https://www.hypertension.ca/en/devices-endorsed-by-hypertension-canada). Maintaining a healthy lifestyle with respect to diet, physical activity and stress management can also limit the effects of hypertension. More information on BP and Hypertension can be found at the Canadian Hypertension Education Program (CHEP) at http://guidelines.hypertension.ca/.

 

References:

  1. Leung, A. L., Nerenberg, K., Daskalopoulou, S. S., McBrien, K., Zarnke, K. B., Dasgupta, K., … Rabi, D. M. (2016). Hypertension Canada’s 2016 Canadian Hypertension Education Program Guidelines for Blood Pressure Measurement, Diagnosis, Assessment of Risk, Prevention, and Treatment of Hypertension. Canadian Journal of Cardiology, 32, 569-588.
  2. Mancia, G., Fagard, R., Narkiewicz, K., Redon, J., Zanchetti, A., Böhm, M., … Zannad, F. (2013). 2013 ESH/ESC Guidelines for the management of arterial hypertension. European Heart Journal, 34, 2159-2219.
  3. Padwal, R. S., Bienek, A., McAlister, F. A., Campbell N. R. C. (2016) Epidemiology of Hypertension in Canada: An Update. Canadian Journal of Cardiology, 32 (5), 687-694.
  4. Scheltens, T., Bots, M.L., Numans, M.E., Grobbee, D.E., Hoes, A.W. (2007) Awareness, treatment and control of hypertension: the ‘rule of halves’ in an era of risk-based treatment of hypertension. Nature, 21, 99-106.
  5. Kerr, E. A., Lucatorto, M. A., Holleman, R., Hogan, M. M., Klamerus, M. L., Hofer, T. P. (2012) Monitoring Performance for Blood Pressure Management Among Patients With Diabetes Mellitus. Archives of Internal Medicine, 172 (12), 938-945.
  6. Rosansky, S. (2012, December) Is Hypertension Overtreatment a Silent Epidemic? [Letter to the Editor]. Archives of Internal Medicine, 172 (22),
  7. O’Brien, E., O’Malley, K. (1988) Overdiagnosing Hypertension. British Medical Journal (297),
  8. McKay, D. W., Myers, M. G., Bolli, P., Chockalingam, A. (2006) Masked Hypertension: A Common but Insidious Presentation of Hypertension. Canadian Journal of Cardiology, 22 (7), 617-620.