Objectively Measured Sitting and Standing in Workers: Cross-Sectional Relationship with Autonomic Cardiac Modulation

Abstract

Excessive sitting and standing are proposed risk factors for cardiovascular diseases (CVDs), possibly due to autonomic imbalance. This study examines the association of objectively measured sitting and standing with nocturnal autonomic cardiac modulation. The cross-sectional study examined 490 blue-collar workers in three Danish occupational sectors. Sitting and standing during work and leisure were assessed during 1–5 days using accelerometers. Heart rate (HR) and heart rate variability (HRV) were obtained during nocturnal sleep as markers of resting autonomic modulation. The associations of sitting and standing still (h/day) with HR and HRV were assessed with linear regression models, adjusted for age, gender, body mass index, smoking, and physical activity. More sitting time during leisure was associated with elevated HR (p = 0.02), and showed a trend towards reduced HRV. More standing time at work was associated with lower HR (p = 0.02), and with increased parasympathetic indices of HRV (root mean squared successive differences of R-R intervals p = 0.05; high-frequency power p = 0.07). These findings, while cross-sectional and restricted to blue-collar workers, suggest that sitting at leisure is detrimental to autonomic cardiac modulation, but standing at work is beneficial. However, the small effect size is likely insufficient to mitigate the previously shown detrimental effects of prolonged standing on CVD.

Prolonged bouts of sedentary time and cardiac autonomic function in midlife

“…Hallman et al reported higher sitting time at work being associated with lower nocturnal rMSSD but no relationship was found between rMSSD and leisure‐related sitting time among blue‐collar workers (n = 126). However, in their recent study with larger study population (n = 490, blue‐collar workers) they reported a small negative association between nocturnal rMSSD and leisure time sitting in crude model (no association between rMSSD and occupational sitting) but after controlling for age, body mass index, smoking, and leisure MVPA time, no significant association was found between rMSSD (or other HRV indexes) and leisure or occupational or sitting times . These findings are in line with the present study reporting no association between total SED and HRV indexes after adjusting for confounders, although the study designs were slightly different.…”

“…These findings are in line with the present study reporting no association between total SED and HRV indexes after adjusting for confounders, although the study designs were slightly different. Hallman et al used HRV measured during sleep, and their study sample consisted solely of individuals with physically active work …”

“…Previously, no differences in LF and HF frequencies were reported between SED tertiles in hypertensive patients regardless of sex . A recent study reported a small negative association with LF and leisure time sitting but after adjustments the association became non‐significant . The LF/HF ratio has been considered as a rather controversial measure, with the argument being that LF power would reflect sympathetic outflow only poorly .…”

“…High occupational sitting time has been found to be associated with reduced HRV, but the same association was not found for sitting during leisure time . A more recent study found no association between HRV and occupational or leisure time sitting after adjusting for potential confounders …”

“…The previous evidence on the association between SED, independently of PA, and HRV is limited. Only few studies have examined the association between objectively measured SED and HRV with inconsistent results, and no previous study has included accumulation patterns of SED . High occupational sitting time has been found to be associated with reduced HRV, but the same association was not found for sitting during leisure time .…”