# Variable shift work in family medicine residents is associated with a non-dipper pattern and reduced phase angle: possible adaptive blood pressure mechanisms and body composition imbalance

## TL;DR

This study finds that shift work in medical residents is linked to altered blood pressure patterns and body composition changes, which may increase heart disease risk.

## Contribution

The study identifies a non-dipper blood pressure pattern and reduced phase angle in shift workers, suggesting a link to cardiovascular risk.

## Key findings

- Non-dipper blood pressure patterns were more common in residents after shift work.
- Phase angle was significantly lower in non-dipper individuals, indicating potential body composition imbalance.
- Diastolic blood pressure decreased during night shifts compared to after rest.

## Abstract

Shift work is associated with alterations in blood pressure (BP), metabolic changes, and unhealthy lifestyle patterns. However, the relationship between BP and variability in work hours remains poorly understood. Moreover, ambulatory blood pressure monitoring (ABPM) is a reliable approach to assess BP variability.

The aim of this study was to evaluate whether shift work in family medicine residents (FMRs) modifies BP circadian patterns and whether these changes are related to body composition parameters.

Thirty-eight FMRs were studied during 1 continuous 24-h day (D1) followed by 3 days of 6-h shifts (D2, D3, and D4). ABPM and body composition were assessed on D1 (postguard) and D4 (preguard). Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were analyzed using nightly recordings from 10:00 p.m. to 3:00 a.m. Body composition was evaluated by electrical bioimpedance.

Of the 38 participants, 72.3% were women (30.2 ± 3.1 years old). Skeletal muscle mass (SMM) (24.0 ± 4.4 vs. 34.3 ± 6.2), p < 0.001, and total protein mass (TPM) (9.1 ± 2.0 vs. 11.8 ± 2), p < 0.001, were lower in women than in men. SBP showed significant positive correlations with SMM, fat mass (FM), fat mass at constant hydration, total body water, and TPM, while DBP was positively correlated only with TPM. On D1, the frequency of the non-dipper pattern was higher than the dipper p = 0.037. Furthermore, the phase angle (PhA) was significantly lower in the non-dipper group (6.8° ± 0.7°; p = 0.04) than the dipper group (7.4° ± 0.9°). DBP between 10 p.m. and 3 a.m. was lower (p = 0.010) on D4 (64.9 ± 6.3 mmHg) than on D1 (68.8 ± 5.2 mmHg).

The non-dipper pattern was the most frequent in FMRs, and the reduction in PhA indicates that this type of nocturnal BP alteration could be related to CVD risk.