Hypertension (HTN) is a major preventable cause of cardiovascular diseases and all-cause mortality worldwide, with an overall prevalence of 30–45%.1 There is growing evidence suggesting that shift work is a risk factor for many negative health outcomes, including cardiovascular disease and HTN.2–4 Also, there is evidence noting an association between shift work and sleep deprivation, and between sleep deprivation and HTN.5–7

So far, most studies about shift work classified HTN based on office blood pressure (BP) measurement.4 However, ambulatory blood pressure monitoring (ABPM) techniques have expanded the knowledge regarding the circadian rhythm of BP and now, ABPM is considered as the gold standard method for evaluating BP, providing a more accurate estimation of BP related risks.8,9 People with a reduced nighttime dip in BP (<10% of the daytime average BP or a night/day ratio>0.9) have an increased cardiovascular risk.10,11

The main objective of the study was to describe the different patterns in BP among pediatricians who work in long on-duty shifts in relation with sex, medical rank (resident physicians vs consultants) and sleeping time.

Fifty-one physicians were included in the study (mean age 31±7.5 years old). Forty (78.4%) were female, 34 were resident physicians (66.7%). Mean of BMI was 22.3±2.2. All ABPM records were valid. Description of the population according to sex appears in Table 1.

Resident physicians had a higher night/day ratio (0.91±0.05 vs 0.85±0.05; p<0.001) and a shorter nighttime period (3.87±1.36h vs 5.41±1.23h, p<0.001) than Consultants. Description of the population according to medical rank appears in Table 2, while Table 3 describes the population according to hours of sleep. Physicians who sleep less than 5h had a higher night/day ratio (0.91±0.04 vs 0.87±0.07, p=0.014).

Univariate and multivariate logistic regression models were built to determine the dipper profile (Table 4). We found a significant relationship between medical rank and dipping BP pattern, which remains after adjusting for sleeping time. Being a Resident seems to increase the probability of non-dipping BP pattern more than 4.5 times compared to being a Consultant (p=0.033).

The present study describes a potential link between being a Resident and the non-dipping BP pattern in physicians during prolonged shifts.

So far, recognized reasons for an absence of nocturnal BP dipping are sleep disturbance, obstructive sleep, apnea, obesity, high salt intake in salt-sensitive subjects, orthostatic hypotension, autonomic dysfunction, chronic kidney disease, diabetic neuropathy and old age.12 However, none of the participants of our study met these characteristics, except sleep disturbance during the shift.

Furthermore, non-dipping pattern was more frequent in Resident physicians (who were under 30 years of age), in contrast to previous studies showing an increased risk of a non-dipping BP related to an increasing age.12 This could be related to the fact that the study was carried out in university hospitals, where Resident physicians have increased workload because they are responsible for providing initial care to the patients.

It has been reported a significantly higher prevalence of HTN in people with sleep disturbances, such as airline pilots.13 Sleep disturbance has been described as the main cause of nocturnal hypertension.14 Anxiety disorder15 and insomnia16 have also been associated to nocturnal hypertension, probably resulted from excessive tension due to sleep disturbance during the night. However, we have not found a significant relationship between non-dipping BP pattern in Resident physicians, based on sleeping time, after adjusting in the multivariate analysis. Future studies with larger number of subjects are needed to determine if sleeping time influences the BP pattern in Resident physicians.

It has also been reported an association between history of shift work and rates of hypertension in both men and women.7 We have found that females were classified as a non-dipping pattern more frequently than males, but they were no differences by sex in night/day ratio SBP. Also, in our study, males and females had normal BP values, based on classification of hypertension grade1 and differences by sex are similar to those of the general population.

Some studies17,18 reported that circumstances which cause frequent awakenings during sleep increased heart rate (HR). Although we found that heart rate values are higher in individuals who sleep fewer hours, resting values do not exceed 80 beats/min, so we cannot consider it an added cardiovascular risk factor.1

Our study has several limitations. First, it is a cross-sectional study and results are limited to a low number of subjects of Caucasian population in a single Health area in the Autonomous Region of Asturias, in Northern Spain. Second, results are limited to a single time on each participant. Dipping status has a low reproducibility, with up to 40% of individuals from Europe19 changing status between repeated recordings.

In contrast, this is one of the few times that continuous BP measurement and non-dipping pattern are reported during shift work and the first time that BP is reported during a medical shift in a pediatric department, which could have implications for future studies on the impact of medical shifts on the health of the physicians. Moreover, the main strength of this study is that it was performed in a well-delimitated area, which allows a detailed study of each participant.

We found a potential link between both being a Resident and, probably, having shorter sleeping time, and the non-dipping blood pressure pattern in physicians during prolonged shifts. Future studies with larger numbers of subjects are needed to corroborate the association between non-dipping pattern and shift work in medical shifts and obtain stronger conclusions.

The authors have no conflicts of interest to disclose.

This research has not received specific aid from public sector agencies, the commercial sector or non-profit entities.

The authors have no financial relationships relevant to this article to disclose.

We obtained approval from the Clinical Research Ethics Committee of the Autonomous Region of Asturias. All persons gave their written informed consent prior to their inclusion in the study.

All authors have read and approved the final revised version. They are willing to take responsibility for the entire manuscript. All authors substantially contributed to the writing (i.e. drafting and/or critical revision) of the manuscript.