Workplace Standing Desks and Arterial Stiffness

Many jobs in today’s society require sitting at a desk with little physical activity. Individuals who engage in ten hours of sedentary behavior per day double their CVD risk. Standing desks are thought to decrease sedentary time and improve cardiovascular health. Acute use of standing desks is shown to lower PWV. However, chronic effects remain unknown. Forty eight participants qualified as seated (19 females, 5 males: age 41 ± 2 years, BMI 25 ± 1 kg/m2) or standing (21 females, 3 males: age 45 ± 2 years, BMI 25 ± 1 kg/m2) groups based on habitual workplace use. Arterial stiffness was assessed as pulse wave velocity (PWV) by using applanation tonometry in conjunction with electrocardiography. No differences were detected in carotid-femoral PWV (cfPWV) between seated and standing groups (p = 0.47). However, age (p \u3c 0.01), aerobic fitness (p \u3c 0.01), and fat percentage (p = 0.02) classifications revealed significant differences between groups. Standing for 50% of a workday does not affect cfPWV. Although, cardiorespiratory fitness and healthy body composition are associated with less arterial stiffness

Socio-economic determinants of anthropometric measures of abdominal adiposity among older people in England

Objective: to look into the socio-economic determinants of levels of three anthropometric measures of abdominal adiposity among older people in England -body mass index, waist circumference (WC), and waist-hip ratio (WHR)- and of changes along two health risk classifications: the World Health Organisation classification based on BMI levels and the WHO combined classification based on BMI and waist circumference measurements.
Design: quantile regression and multinomial analysis using data from the English Longitudinal Study of Ageing (ELSA), wave 2 (2004-05) and wave 4 (2008-09)
Results: The quantile analysis on levels led to disparate results depending on the wave, which would question results previously published based on only one wave. However, we found that age tends to present an inverse U-shaped relationship with BMI and WC, smoking is negatively associated with BMI and positively with WC and WHR, alcohol consumption is negatively associated with BMI and WC levels, net total wealth is negatively related with the three anthropometric measures, educational attainment is negatively associated with each measure, and depression is positively associated with each measure. The multinomial analysis found that living in a larger household size increases the likelihood of becoming or remaining unhealthy irrespective of which classification we used. Furthermore, using the BMI-based categorisation, the initial category is highly relevant as a predictor of the category four years later and alcohol consumption would be positively associated with being or becoming obese. From the combined BMI-WC categorisation, we found that net total wealth would be negatively associated with becoming or remaining unhealthy whereas depression is a significant predictor of becoming or remaining unhealthy.
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Impact of Prolonged Sitting on Cognitive Function: Implications for Cardio-metabolic Risk

Purpose: To determine if prolonged sitting negatively impacts cognitive function, cerebral perfusion, and central cardiovascular hemodynamics; and secondly, to test whether weight or physical activity status alters this response. Methods: Participants (N=20, age=26±7; BMI=30±7 kg/m2; 7 female) were taken through 3 hrs of sitting followed by a 10-min walk (treadmill). Cognitive function was assessed during sitting (10, 60, 120, and 180 mins) and following the walk using a color/word Stroop test. Cerebral perfusion was measured via near infrared spectroscopy (total hemoglobin—tHb). Central cardiovascular hemodynamics and aortic stiffness (pulse wave velocity—PWV) were measured using the SphygmoCor XCEL device before, during and after sitting. Body mass index, %-bodyfat, and accelerometry data were used to characterize weight and physical activity status. Results: Following sitting, there was no change in Stroop completion time; however, both Color and Text times significantly decreased following the walk (e.g., Color Time: 10 mins sitting, 19±3 sec vs. Post walk, 16.7±3.6 sec, pConclusion: These findings suggest that prolonged sitting does not alter cognitive function or cerebral perfusion, but sitting does increase aortic stiffness in normal weight individuals. Walking can improve cognitive function, an effect possibly related to increases in cerebral perfusion

Impact of body tilt on the central aortic pressure pulse.

The present work was undertaken to investigate, in young healthy volunteers, the relationships between the forward propagation times of arterial pressure waves and the timing of reflected waves observable on the aortic pulse, in the course of rapid changes in body position. 20 young healthy subjects, 10 men, and 10 women, were examined on a tilt table at two different tilt angles, -10° (Head-down) and + 45° (Head-up). In each position, carotid-femoral (Tcf) and carotid-tibial forward propagation times (Tct) were measured with the Complior device. In each position also, the central aortic pressure pulse was recorded with radial tonometry, using the SphygmoCor device and a generalized transfer function, so as to evaluate the timing of reflected waves reaching the aorta in systole (onset of systolic reflected wave, sT1r) and diastole (mean transit time of diastolic reflected wave, dMTT). The position shift from Head-up to Head-down caused a massive increase in both Tct (women from 130 ± 10 to 185 ± 18 msec P < 0.001, men from 136 ± 9 to 204 ± 18 msec P < 0.001) and dMTT (women from 364 ± 35 to 499 ± 33 msec P < 0.001, men from 406 ± 22 to 553 ± 21 msec P < 0.001). Mixed model regression showed that the changes in Tct and dMTT observed between Head-up and Head-down were tightly coupled (regression coefficient 2.1, 95% confidence interval 1.9-2.3, P < 0.001). These results strongly suggest that the diastolic waves observed on central aortic pulses reconstructed from radial tonometric correspond at least in part to reflections generated in the lower limbs

Validity and reliability of lower-limb pulse-wave velocity assessments using an oscillometric technique

There is a growing interest in the deleterious effects of sedentary behaviour on lower-limb arterial health. To permit further investigation, including in larger epidemiological studies, there is a need to identify lower-limb arterial health assessment tools that are valid and reliable, yet simple to administer. Purpose: This study sought to determine the validity and between-day reliability of femoral-ankle pulse-wave velocity (faPWV) measures obtained using an oscillometric-based device (SphygmocCor XCEL) in supine and seated positions. Doppler ultrasound (US) was used as the criterion. Methods: A total of 47 healthy adults were recruited for validity (n=32) and reliability (n=15) analyses. Validity was determined by measuring faPWV in seated and supine positions using the XCEL and US devices, in a randomised order. Between-day reliability was determined by measuring seated and supine faPWV using the XCEL on 3 different mornings, separated by a maximum of 7 days. Results: The validity criteria (absolute standard error of estimate [aSEE] <1.0 m/s) was met in the supine (aSEE = 0.8 m/s, 95% CI: 0.4-1.0), but not the seated (aSEE = 1.2 m/s, 95 % CI: 1.1, 1.2) position. Intras-class correlation coefficient estimates revealed the XCEL demonstrated good reliability in the supine position (ICC=0.83, 95% CI: 0.65, 0.93), but poor reliability in the seated position (ICC = 0.29, 95% CI: 0.23, 0.63). Conclusions: The oscillometric XCEL device can be used to determine lower-limb PWV with acceptable validity and reliability in the conventionally recommended supine position, but not the seated position

Evaluation of 24-Hour Arterial Stiffness Indices and Central Hemodynamics in Healthy Normotensive Subjects versus Treated or Untreated Hypertensive Patients: A Feasibility Study

Objective. Central blood pressure (BP) and vascular indices estimated noninvasively over the 24 hours were compared between normotensive volunteers and hypertensive patients by a pulse wave analysis of ambulatory blood pressure recordings. Methods. Digitalized waveforms obtained during each brachial oscillometric BP measurement were stored in the device memory and analyzed by the validated Vasotens technology. Averages for the 24 hours and for the awake and asleep subperiods were computed. Results. 142 normotensives and 661 hypertensives were evaluated. 24-hour central BP, pulse wave velocity (PWV), and augmentation index (AI) were significantly higher in the hypertensive group than in the normotensive group (119.3 versus 105.6 mmHg for systolic BP, 75.6 versus 72.3 mmHg for diastolic BP, 10.3 versus 10.0 m/sec for aortic PWV, −9.7 versus −40.7% for peripheral AI, and 24.7 versus 11.0% for aortic AI), whereas reflected wave transit time (RWTT) was significantly lower in hypertensive patients (126.6 versus 139.0 ms). After adjusting for confounding factors a statistically significant between-group difference was still observed for central BP, RWTT, and peripheral AI. All estimates displayed a typical circadian rhythm. Conclusions. Noninvasive assessment of 24-hour arterial stiffness and central hemodynamics in daily life dynamic conditions may help in assessing the arterial function impairment in hypertensive patients

Investigating the relationship between habitual physical activity and cardiovascular health in healthy and clinical populations

Physical activity (PA) is beneficial for arterial and autonomic health and, subsequently, cardiovascular disease risk. However, fundamental questions remain regarding the relationship between PA and health, the relative importance of the volume, intensity or composition of PA, and whether this differs in chronic conditions. Therefore, the aim of this thesis was to explore the influence of movement behaviours on key cardiovascular risk factors in healthy populations and those with T1D using novel methods and analysis techniques. Chapter 4 revealed that, contrary to expectation, the composition of daily movement and sleep behaviours was not associated with arterial stiffness in healthy children, with the reallocation of time between any behaviours not predicting significant change in arterial stiffness. It was hypothesised that this may be related to the measurement duration being insufficient to reflect habitual PA and its health-associated fluctuations. Therefore, a 28-day measurement period was used in Chapter 5, which revealed that, whilst there was minimal fluctuation in movement behaviours, PA metrics derived from 28 days were more strongly associated with cardiovascular health markers. Using a similar measurement protocol, children with type I diabetes (T1D) were found to engage in more light and less moderate-to-vigorous physical activity (MVPA) than healthy peers and were characterised by poorer arterial stiffness and autonomic function (Chapter 6). Importantly, Chapter 6 suggested that the intensity of PA was more influential than the volume. Subsequently, Chapter 7 supported this contention, revealing that the reallocation of time from any behaviour to MVPA was the most potent stimulus to cardiovascular health in T1D. Overall, this thesis demonstrates that the composition and the relative importance of the volume and intensity of PA must be considered when investigating the relationship with health. The findings highlight key targets for future interventions seeking to enhance the cardiovascular function of youth, especially in T1D

The effect of obesity on venous impedance and outflow measured by ultrasound

Obesity has been identified epidemiologically as a risk factor for development of chronic venous disease. To examine whether abdominal adiposity obstructs venous outflow from the legs, 26 females aged 34-49 years with no clinical venous disease and body mass index (BMI) between 20.9 – 46.7 kg/m$^2$ were studied. A novel measurement of the extent of abdominal fat along the legs when seated correlated well with BMI and other measures of central fat (sagittal-abdominal diameter, ultrasound fat thickness, % truncal fat by DEXA scan). On sitting, inguinal tissue pressure recorded by needle manometry increased more in obese (BMI > 30) than normal weight (BMI 20-25) subjects (8.2 vs 1.5 mmHg, p<0.01) as did the femoral vein cross-sectional area (129 vs 60%, p<0.05). Both measures correlated with increasing abdominal fat but were not associated with each other. In the lower leg, saphenous vein distensibility and compliance correlated positively with abdominal fat and BMI, but there was no such association for the popliteal vein. Female sex hormones, physical activity levels and insulin status did not affect venous haemodynamics. Thus, increased abdominal fat can potentially hinder venous return when sitting, leading to distension and changes in vein biomechanics, which could over time contribute to venous disease

Exploring Sedentary Behavior as a Secondary Prevention Target for Heart Disease

The purpose of this dissertation series was to describe sedentary behavior and its associations with cardiovascular disease (CVD) biomarkers and outcomes, and to explore the potential that reducing sedentary behavior may be a secondary prevention target for Acute Coronary Syndrome (ACS) survivors. As such, the following series of research studies evaluate the mechanisms, patterns, and correlates of sedentary behavior in relation to CVD risk and examine whether sedentary behavior might be a risk factor for CVD outcomes among ACS survivors. In Chapter II, a cross-sectional study of young, healthy adults examined a set of biomarkers representing several aspects of endothelial cell health to elucidate the relationship between free-living, habitual sedentary time and endothelial dysfunction. Results showed that there were no differences in measures of endothelial cell injury, endothelial cell reparative capacity, or upper extremity endothelium-dependent vasodilatation in participants with high compared with low volumes of device-measured sedentary behavior in a sample of young, healthy adults. These findings suggest that physiological mechanisms other than endothelial dysfunction may need to be explored as a potential link between habitual prolonged sedentary time and CVD in young adults. Chapter III employed group-based trajectory modeling to identify distinct patterns of sedentary behavior, as measured by accelerometry, in ACS survivors over the 28 consecutive days following hospital discharge, and, secondly, to explore potential correlates of these patterns. Results demonstrated that ACS patients as a group engaged in high volumes of accelerometer-measured sedentary time. Three patterns of sedentary behavior over the first month post-discharge were identified; these involved either gradual or rapid reductions in sedentary behavior. Several measures of disease severity and physical health (e.g., GRACE CVD risk score, physical health-related quality of life), and partner status (i.e., married or partnered or without partner), were associated with the worst patterns of sedentary behavior (i.e., high volume of sedentary time with only a slight decline over time). These findings provide insight on the different patterns of sedentary behavior that emerge as patients resume their daily life over the first month post hospital discharge. Chapter IV, building upon the study presented in Chapter III, examined whether accelerometer-measured sedentary behavior of ACS survivors over the first month post hospital discharge was associated with 1-year health outcomes. The purpose of this study was to understand whether sedentary behavior in the early post hospital discharge period may be an important risk factor in ACS survivors, that might be targeted in secondary prevention strategies. Results demonstrated that the average sedentary behavior over the first month post hospital discharge was not significantly associated with increased risk of 1-year recurrent major adverse cardiovascular events or hospitalizations. These findings do not support sedentary behavior in the early post hospital discharge period as a prognostic risk factor that should be modified in ACS survivors as part of secondary heart disease prevention strategy. However, studies with larger sample sizes, and that evaluate sedentary behavior patterns beyond the first month are needed. Collectively, these studies show that high volumes of sedentary behavior are prevalent in ACS survivors over the first month immediately following hospital discharge. Future work is needed to further study the underlying mechanisms through which sedentary behavior may confer CVD risk and to determine whether sedentary behavior is an important modifiable risk factor in ACS survivors