Study highlights need for regular home and doctor's blood pressure measurements for white-coat syndrome

By Suchandrima BhowmikReviewed by Benedette Cuffari, M.Sc.Mar 30 2023

White-coat hypertension, also known as white-coat syndrome, is when patients exhibit elevated blood pressure readings in a clinical setting, such as a doctor's office or hospital, due to anxiety or stress. This condition often progresses to general hypertension. Patients with white-coat hypertension are at a higher risk of kidney or cardiovascular disease than those with normal blood pressure levels. Thus, it is crucial to identify and closely monitor patients with white-coat hypertension to reduce their risk of developing cardiovascular diseases in the future.

Study: The long‑term reproducibility of the white‑coat effect on blood pressure as a continuous variable from the Ohasama Study. Image Credit: Prostock-studio / Shutterstock.com

Is the white-coat effect reproducible?

Scientists who study white-coat hypertension often encounter issues surrounding reproducibility. In fact, previous studies have shown that hypertension phenotypes are moderately reproducible, particularly when they occur in short intervals and in individuals without antihypertensive treatment.

In addition to fluctuating phenotypes in this patient population, the reproducibility of the 'white-coat effect' has also been challenging. Nevertheless, some studies have investigated the reproducibility of the white-coat effect over a one-year period in untreated individuals, mainly when these patients measure their blood pressure levels at home under less stressful conditions.

In the current study published in the journal Scientific Reports, researchers analyze the long-term reproducibility of the white-coat effect as a continuous variable in untreated individuals.

About the study

The current study utilized data obtained from a long-term study conducted in Ohsama, Japan, beginning in 1986. Moreover, data for the current study were collected between 2005 and 2019 using two types of devices for home and office blood pressure measurements.

Over the four-year period, study participants were visited once at baseline and four years later for a follow-up examination. Study participants were instructed to obtain their blood pressure measurements within one hour of waking and every evening before going to bed for a total of four weeks. Comparatively, office blood pressure levels were measured twice by medical staff after patients were allowed to rest for at least two minutes in a sitting position.

The white-coat effect was defined as the difference between office and home blood pressure measurements. Notably, home hypertension was defined as systolic and diastolic blood pressure exceeding 135 and 85 mmHg, respectively, whereas office hypertension was defined as over 140 and 90 mmHg, respectively.

Study findings

Taken together, a total of 153 participants were included in the study. Notably, the proportion of alcohol drinkers and body mass index (BMI) of the study participants decreased at the four-year visit as compared to baseline.

A total of 113, 23, eight, and nine participants exhibited normotension, white-coat hypertension, masked hypertension, and sustained hypertension at baseline, respectively. Among the 23 participants with white-coat hypertension, four and eight were subsequently diagnosed with normotension and sustained hypertension at the four-year visit, respectively.

At the four-year visit, the white-coat effect for systolic and diastolic blood pressure decreased by 0.17 and 1.56 mmHg, respectively. Home blood pressure had an intraclass correlation coefficient (ICC) of over 0.7, thus indicating its appreciable reproducibility. No significant differences were observed in terms of the white-coat effect when home morning and evening measurements were used for the comparison.

The researchers observed significant variability in-office blood pressure measurement, which limited their ability to accurately determine the white-coat effect. This is comparable to home blood pressure measurements, which were considered to be much more reproducible, particularly when assessed over a one-year period.

Another important observation is that hypertensive individuals cannot easily become normotensive, as only 11.1-25% of the previously hypertensive study participants were subsequently considered normotensive four years later.

Conclusions

Taken together, the study findings indicate that the white-coat effect cannot be reproducible when assessed as a continuous variable. This may be due to the long-term nature of the current study, as compared to previous studies reporting the reproducibility of the white-coat effect when assessed within one year.

Despite the limited reproducibility of the white-coat effect in the general population, the researchers emphasize the importance of continuously monitoring blood pressure levels in both home and office settings to identify any potential early signs of hypertension.

Limitations

Participants receiving new antihypertensive medications based on each hypertension subtype were not included. Furthermore, adherence to antihypertensive treatment was not assessed.

Another limitation of the current study was the exclusion of patients who were lost to follow-up, as this may have led to the poor reproducibility of the white-coat effect. Additionally, only the first value of each measurement occasion for home BP was considered. Finally, no information was available on the physical activity levels of the study participants, which is known to impact BP levels.