Prolonged seated immobility at work is a common risk factor for venous thromboembolism leading to hospital admission

A Comprehensive Review of Risk Factors and Thrombophilia Evaluation in Venous Thromboembolism

Venous thromboembolism (VTE), which encompasses deep vein thrombosis (DVT) and pulmonary embolism (PE), is a significant cause of morbidity and mortality worldwide. There are many factors, both acquired and inherited, known to increase the risk of VTE. Most of these result in increased risk via several common mechanisms including circulatory stasis, endothelial damage, or increased hypercoagulability. Overall, a risk factor can be identified in the majority of patients with VTE; however, not all risk factors carry the same predictive value. It is important for clinicians to understand the potency of each individual risk factor when managing patients who have a VTE or are at risk of developing VTE. With this, many providers consider performing a thrombophilia evaluation to further define a patient's risk. However, guidance on who to test and when to test is controversial and not always clear. This comprehensive review attempts to address these aspects/concerns by providing an overview of the multifaceted risk factors associated with VTE as well as examining the role of performing a thrombophilia evaluation, including the indications and timing of performing such an evaluation.

The Use of Compression Stockings to Reduce Water Retention in the Legs During Gaming and Esports: Randomized Controlled Field Study

Background

With the increasing digitalization of daily life, internet-based entertainment such as gaming and streaming has advanced to one of the megatrends of the 21st century. Besides offering a multitude of controversially discussed opportunities for entertainment and social interaction, there is reasonable concern about health issues caused by the absence of physical activity among activities linked to gaming and streaming.

Objective

The aim of this study is to compare the water balance of recreational gamers with and those without compression stockings during a gaming event.

Methods

We measured body composition and water balance with 8-electrode bioelectrical impedance analysis among 46 recreational gamers with an average age of 27.1 (SD 6.5) years (5/46, 11% women and 41/46, 89% men) before and after 24 hours at a gaming event. Of the 46 gamers, 23 (50%) gamers wore compression stockings for the duration of the study.

Results

Our study shows that prolonged gaming and associated behaviors during a 24-hour time frame lead to an increase in total body water (+0.76 L; P<.001) and a decrease of phase angle in the lower extremities (−0.47°; P<.001) but not in the upper extremities (+0.09°; P=.80), when no compression is used. Gamers using compression socks did not show any significant negative effects on their body composition.

Conclusions

Prolonged gaming and streaming are serious risk factors for diseases associated with water retention in the legs, and these risks can be measured by bioelectrical impedance and reduced by wearing compression stockings. We conclude that these findings should be discussed and replicated in larger studies and that there is a considerably large market for compression stockings among gamers and live streamers.

"Lockdown-thrombosis"-an unexpected problem of the COVID-19 pandemic?

Seated immobility thromboembolism syndrome (SIT) is the association of prolonged seated immobility with increased risk of venous thromboembolism (VTE). The advent of COVID-19 resulted in implementation of lockdowns to curb its spread. This resulted in compulsory work from home and minimization of outdoor activities. Consequently, this would have likely led to increased prolonged sitting and reduced mobility. Few case reports and studies have observed an increase in VTE incidence during the lockdown period. We likewise performed a clinical audit of our weekly thrombosis clinic cases and revealed three cases of VTE associated with prolonged sitting during Singapore's COVID-19 lockdown. Notably, all had other minor VTE risk factors in addition to prolonged sitting. All cases had intermediate-high risk pulmonary embolism and were given extended anticoagulation. With the pandemic still ongoing, periodic lockdown and quarantine measures may continue to be imposed. While the overall VTE risk conferred by prolonged seated immobility associated with lockdown measures is likely to be small, this risk can be easily mitigated and possibly prevented by simply staying mobile.

Association between self-rated health and venous thromboembolism in Malmö Preventive Program: A cohort study

INTRODUCTION

Venous thromboembolism (VTE) and cardiovascular disease (CVD) share some risk factors such as smoking, obesity, and dietary habits. Poor self-rated health (SRH) has been shown to be a predictor of arterial CVD and mortality for both men and women. The association between SRH and VTE has only been investigated in one previous Swedish study with a cohort that just contained women. This Swedish study did not show any significant associations between poor SRH and VTE in women.

METHODS

A cohort of 22,444 men and 10,902 women in the Malmö Preventive Program was followed for a period of 44 years. All participants in the baseline screening with measurements including SRH were traced in national registers. Data on VTE events were collected from national hospital registries. Cox proportional regression analysis was used to calculate the association between SRH and time to VTE.

RESULTS

During a follow-up time of 44.31 years, a total of 2612 individuals were affected by VTE. Good SRH was associated with a lower risk for VTE in women both in the univariate model (HR = 0.75, CI = 0.65-0.85) and after adjustments for age, smoking, BMI and varicose veins (HR = 0.81, CI 0.70-0.93). SRH was not a predictor for VTE in men, neither in the unadjusted (HR = 1.05, CI 0.90-1.13) nor in the fully adjusted model (HR = 1.00, CI = 0.88-1.14).

CONCLUSION

In this cohort study, SRH was associated with VTE in women but not among men. The association was significant even when adjusting for well-known risk factors such as varicose veins, BMI and smoking.

Lower limb venous and arterial peripheral diseases and work conditions: systematic review

OBJECTIVES

The individual peripheral vascular disease risk factors are well documented, but the role of work conditions remains equivocal. This systematic review aims to assess relationships between lower limb peripheral venous diseases (lower limb varicose veins (LLVV), venous thromboembolism (VTE) comprising deep vein thrombosis and pulmonary embolism), peripheral arterial disease (intermittent claudication, aortic dissection, aortic aneurysm) and occupational constraints among working adults.

METHODS

Several databases were systematically searched until February 2019 for observational studies and clinical trials. Preferred Reporting Items for Systematic Reviews and Meta-Analyses method was used for article selection. Quality assessment and risk of bias were evaluated using Strengthening the Reporting of Observational Studies in Epidemiology and Newcastle-Ottawa scales.

RESULTS

Among the 720 screened articles, 37 remained after full-text evaluation. Among the 21 studies on LLVV, prolonged standing was significantly associated to a higher risk of varicose veins with a threshold probably around >3 to 4 hours/day but exposure duration in years was not sufficiently considered. Seated immobility was often observed in workers, with no sufficient evidence to prove that prolonged sitting at work is related to VTE. Carrying heavy loads, stress at work and exposure to high temperatures have emerged more recently notably in relation to varicose veins but need to be better explored. Only three studies discussed the potential role of work on peripheral arterial disease development.

CONCLUSIONS

Although some observational studies showed that prolonged standing can be related to varicose veins and that seated immobility at work could be linked to VTE, very little is known about peripheral arterial disease and occupational constraints. Clinical trials to determine preventive strategies at work are needed.

PROSPERO REGISTRATION NUMBER

CRD42019127652.

Cardiac adaptation in hibernating, free-ranging Scandinavian Brown Bears (Ursus arctos)

During six months of annual hibernation, the brown bear undergoes unique physiological changes to adapt to decreased metabolic rate. We compared cardiac structural and functional measures of hibernating and active bears using comprehensive echocardiography. We performed echocardiography on 13 subadult free-ranging, anaesthetised Scandinavian brown bears (Ursus arctos) during late hibernation and in early summer. Mean heart rate was 26 beats per minute (standard deviation (SD): 8) during hibernation vs 71 (SD: 14) during active state. All left ventricular (LV) systolic and diastolic measures were decreased during hibernation: mean ejection fraction: 44.2% (SD: 6.0) active state vs 34.0 (SD: 8.1) hibernation, P = 0.001; global longitudinal strain: −11.2% (SD: 2.0) vs −8.8 (SD: 3.3), P = 0.03; global longitudinal strain rate: −0.82 (SD: 0.15) vs −0.41 (SD: 0.18), P < 0.001; septal e’: 9.8 cm/s (SD: 1.8) vs 5.2 (SD: 2.7), P < 0.001. In general, measures of total myocardial motion (ejection fraction and global longitudinal strain) were decreased to a lesser extent than measures of myocardial velocities. In the hibernating brown bear, cardiac adaptation included decreased functional measures, primarily measures of myocardial velocities, but was not associated with cardiac atrophy. Understanding the mechanisms of these adaptations could provide pathophysiological insight of human pathological conditions such as heart failure.

Impact of Knee Scooter Flexion Position on Venous Flow Rate

BACKGROUND:

The knee scooter is a commonly used mobility device in the setting of unilateral below-knee immobilization. The bent-knee posture has been shown to decrease venous flow in a seated position, but the knee scooter differs as the patient is weightbearing through the affected extremity. Our goal was to investigate the effects of knee scooter positioning on popliteal venous flow.

METHODS:

Duplex ultrasonography was performed to obtain venous diameter and flow velocity of the popliteal vein on healthy subjects over the age of 18 without immobilization. Measurements were performed on the left knee of each subject while standing and with the same knee flexed on the knee scooter, by 2 physicians trained in ultrasound techniques. Mean velocity, peak velocity, vessel diameter, and volumetric flow rate were calculated and t tests were performed for each variable. A power analysis was performed, determining that 9 subjects would provide 80% power with an alpha of 0.05. A total of 13 subjects participated in the study. Mean age was 33 (range 20-56) years, with 6 females and 7 males.

RESULTS:

Measurements of subjects while standing and on the knee scooter demonstrated a significant decrease in mean velocity (6.5 vs 3.2 cm/s, P < .01) and volumetric flow rate (227.8 vs 106.2 mL/min, P < .01) while subjects were using the scooter. Vessel diameter (0.82 vs 0.78 cm, P = .15) and peak velocities (19.8 vs 14.7 cm/s, P = .19) were not significantly different between standing and kneeling positions.

CONCLUSION:

Our findings demonstrated a statistically significant decrease in volumetric flow rate in subjects using a knee scooter device with a flexed knee. Although venous stasis is a known risk factor for DVT, flow rate thresholds for increased thrombus formation are not well defined. The duration of scooter use, or flexed knee positioning, may have some effect on the degree of stasis. This finding should caution orthopedists to consider the risk attributed to the knee scooter as part of their overall patient assessment.

LEVEL OF EVIDENCE:

Level II, therapeutic, comparative study.

e-thrombosis: epidemiology, physiopathology and rationale for preventing computer-related thrombosis

The large availability of computers (personal, laptop and tablet) has revolutionized human life more than any other discovery or invention over the past century. Nevertheless, prolonged use of computers may both directly and indirectly promote the onset of some serious human pathologies, thus including venous thromboembolism (VTE). Convincing epidemiological and biological evidence has been published that computer-related thrombosis (also known as "e-thrombosis") should now be regarded as an independent clinical entity, deserving enhanced healthcare focus and interventions, due to the growing worldwide diffusion of computer devices, which may ultimately contribute to enhance the risk of computer-related thrombosis, and turn it from a relatively rare disease to a noticeably frequent pathology. A set of preventive measures can thus be suggested, such as designing and setting up ergonomically suitable computer workstations, using comfortable sitting positions, avoiding long and uninterrupted computer-seated immobility, and avoiding the wearing of restrictive clothing on the legs. Reinforced measures should then be advised in patients with acquired, or inherited prothrombotic conditions, in whom the risk of computer-related thrombosis may be substantially magnified.

Prevalence of lower limb deep venous thrombosis among adult HIV positive patients attending an outpatient clinic at Mulago Hospital

Background

Deep venous thrombosis (DVT) and its major complication pulmonary embolism (PE) are collectively known as venous thromboembolism. In Uganda, the prevalence of DVT among HIV patients has not been previously published. The aim of the study was to determine the prevalence and sonographic features of lower limb deep venous thrombosis among HIV positive patients on anti-retroviral treatment (ART).

Methods

This was a cross sectional study in which HIV positive patients on ART were recruited from an out-patient HIV clinic at Mulago National Referral Hospital. Patients were randomly selected and enrolled until a sample size of 384 was reached. Study participants underwent compression and Doppler ultrasound studies of both lower limb deep veins using Medison Sonoacer7 ultrasound machine.

Resuts

We found a prevalence of DVT of 9.1% (35 of 384 participants) among HIV patients on ART. The prevalence of latent (asymptomatic) DVT was 2.3%. Among 35 patients with DVT, 42.8% had chronic DVT; 31.1% had acute DVT and the rest had latent DVT. Among the risk factors, the odds of occurrence of DVT among patients with prolonged immobility were 4.81 times as high as in those with no prolonged immobility (p = 0.023; OR = 4.81; 95% CI 1.25–18.62). Treatment with second line anti-retroviral therapy (ART) including protease inhibitors (PIs) was associated with higher odds of DVT occurrence compared with first line ART (p = 0.020; OR = 2.38; 95% CI 1.14–4.97). The odds of DVT occurrence in patients with a lower CD4 count (< 200 cells/µl) were 5.36 times as high as in patients with CD4 counts above 500 cells/µl (p = 0.008). About 48.6% patients with DVT had a low risk according to Well’s score.

Conclusion

DVT was shown in nearly 10% of HIV patients attending an out-patient clinic in an urban setting in Uganda. Risk factors included protease inhibitors in their ART regimen, prolonged immobility, and low CD4 count (< 200 cells/µl). Clinicians should have a low threshold for performing lower limb Doppler ultrasound scan examination on infected HIV patients on ART who are symptomatic for DVT. Therefore, clinicians should consider anti-coagulant prophylaxis and lower deep venous ultrasound screening of patients who are on second line ART regimen with low CD4 cell counts and/or with prolonged immobility or hormonal contraception.

Risk and management of venous thromboembolisms in bevacizumab-treated metastatic colorectal cancer patients

PURPOSE

Bevacizumab may potentiate the risk of venous thromboembolisms (VTEs) in cancer patients, who are already predisposed to pro-thrombotic states. We aimed to characterize the incidence of VTEs in a population-based cohort of metastatic colorectal cancer (mCRC) patients treated with bevacizumab, describe patient and treatment factors associated with VTEs, and examine how VTEs are managed.

METHODS

Patients diagnosed with mCRC from 2006 to 2009 and offered bevacizumab were included. Descriptive statistics were used to describe VTE occurrences and management. Univariate and multivariate regression models were constructed to explore associations between clinical factors and VTEs.

RESULTS

We identified 541 mCRC patients: 27 never started bevacizumab and 15 were lost to follow-up. Of the 499 evaluable patients, median age was 61, 59.3% were men, 88.1% had ECOG 0/1, and 5.2% reported previous VTEs. Mean number of bevacizumab doses was 13.3 cycles. After receiving bevacizumab, 81 patients developed 93 cases of VTEs, with 9 patients experiencing >1 event. Individuals who experienced VTEs were more likely to have had pre-existing cardiovascular disease (OR 2.259, p = 0.0245), resection of primary cancer (OR 3.262, p = 0.0269), pre-chemotherapy platelet count ≥350,000/μL (OR 2.295, p = 0.0293), and received >12 bevacizumab cycles (OR 2.172, p = 0.0158). Use of bevacizumab varied after occurrence of VTE where it was discontinued in 34.4%, continued in 34.4%, and temporarily held in 1.1%.

CONCLUSIONS

VTE risk can be high, especially in patients with specific pre-treatment risk factors as well as in those who received more bevacizumab, suggesting a potential dose-related effect. Management of bevacizumab-related VTEs was variable.

Low cardiac output as physiological phenomenon in hibernating, free-ranging Scandinavian brown bears (Ursus arctos) - an observational study

BACKGROUND

Despite 5-7 months of physical inactivity during hibernation, brown bears (Ursus arctos) are able to cope with physiological conditions that would be detrimental to humans. During hibernation, the tissue metabolic demands fall to 25% of the active state. Our objective was to assess cardiac function associated with metabolic depression in the hibernating vs. active states in free-ranging Scandinavian brown bears.

METHODS

We performed echocardiography on seven free-ranging brown bears in Dalarna, Sweden, anesthetized with medetomidine-zolazepam-tiletamine-ketamine during winter hibernation in February 2013 and with medetomidine-zolazepam-tiletamine during active state in June 2013. We measured cardiac output noninvasively using estimates of hemodynamics obtained by pulsed wave Doppler echocardiography and 2D imaging. Comparisons were made using paired T-tests.

RESULTS

During hibernation, all hemodynamic indices were significantly decreased (hibernating vs. active state): mean heart rate was 26.0 (standard deviation (SD): 5.6) beats per min vs. 75.0 (SD: 17.1) per min (P=0.002), mean stroke volume 32.3 (SD: 5.2) ml vs. 47.1 (SD: 7.9) ml (P=0.008), mean cardiac output 0.86 (SD: 0.31) l/min vs. 3.54 (SD: 1.04) l/min (P=0.003), and mean cardiac index 0.63 (SD: 0.21) l/min/kg vs. 2.45 (SD: 0.52) l/min/ m2 (P<0.001). Spontaneous echo contrast was present in all cardiac chambers in all seven bears during hibernation, despite the absence of atrial arrhythmias and valvular disease.

CONCLUSION

Free-ranging brown bears demonstrate hemodynamics comparable to humans during active state, whereas during hibernation, we documented extremely low-flow hemodynamics. Understanding these physiological changes in bears may help to gain insight into the mechanisms of cardiogenic shock and heart failure in humans.

Risk marker associations with venous thrombotic events: a cross-sectional analysis

OBJECTIVE

To examine the interrelations among, and risk marker associations for, superficial and deep venous events-superficial venous thrombosis (SVT), deep venous thrombosis (DVT) and pulmonary embolism (PE).

DESIGN

Cross-sectional analysis.

SETTING

San Diego, California, USA.

PARTICIPANTS

2404 men and women aged 40-79 years from four ethnic groups: non-Hispanic White, Hispanic, African-American and Asian. The study sample was drawn from current and former staff and employees of the University of California, San Diego and their spouses/significant others.

OUTCOME MEASURES

Superficial and deep venous events, specifically SVT, DVT, PE and combined deep venous events (DVE) comprising DVT and PE.

RESULTS

Significant correlates on multivariable analysis were, for SVT: female sex, ethnicity (African-American=protective), lower educational attainment, immobility and family history of varicose veins. For DVT and DVE, significant correlates included: heavy smoking, immobility and family history of DVEs (borderline for DVE). For PE, significant predictors included immobility and, in contrast to DVT, blood pressure (BP, systolic or diastolic). In women, oestrogen use duration for hormone replacement therapy, in all and among oestrogen users, predicted PE and DVE, respectively.

CONCLUSIONS

These findings fortify evidence for known risk correlates/predictors for venous disease, such as family history, hormone use and immobility. New risk associations are shown. Striking among these is an association of PE, but not DVT, to elevated BP: we conjecture PE may serve as cause rather than consequence. Future studies should evaluate the temporal direction of this association. Oxidative stress and cell energy compromise are proposed to explain and predict many risk factors, operating through cell-death mediated triggering of coagulation activation.

Associations of overall sitting time and TV viewing time with fibrinogen and C reactive protein: the AusDiab study

BACKGROUND/AIM

Sedentary behaviour is associated with increased risk for all-cause and cardiovascular mortality. Plasma fibrinogen and C reactive protein (CRP)-key inflammatory and/or haemostatic markers-may contribute to this association; however, few studies have examined their relationships with sedentary behaviours. We examined associations of overall sitting and TV viewing time with fibrinogen and high-sensitivity CRP (hsCRP).

METHODS

Plasma fibrinogen and hsCRP were measured in 3086 Australian adults (mean age: 55±12 years) who participated in the 2004-2005 AusDiab (Australian Diabetes, Obesity and Lifestyle) study. Multiple linear regression analyses examined cross-sectional associations of self-reported overall sitting and TV viewing time (h/day) with plasma fibrinogen and hsCRP, adjusting for sociodemographic, behavioural and medical treatments and conditions as potential covariates.

RESULTS

Overall sitting time and TV viewing time were positively associated with plasma fibrinogen (sitting: β: 0.02 g/L, 95% CI (0.01 to 0.02); TV time: 0.03 g/L (0.02 to 0.05)) and hsCRP (sitting: 2.4% (1.2% to 3.6%); TV time: 4.5% (1.7% to 7.4%)). Associations were independent of leisure-time physical activity, but after adjusting for waist circumference, they remained for fibrinogen, but for hsCRP were attenuated to the null. Interactions were observed for gender×TV (p=0.011) with fibrinogen (associations in women only) and for waist circumference×TV (p=0.084) with hsCRP (associations in low-risk only).

CONCLUSIONS

Overall sitting time was positively associated with plasma fibrinogen and hsCRP in men and women; associations of TV viewing time with fibrinogen were observed in women only. Abdominal adiposity-mediated associations for hsCRP but not for fibrinogen. Prospective and intervention studies are needed to establish likely causality and elucidate potential mechanisms.

Efficacy of micromobile foot compression device in increasing lower limb venous blood flow

Background. A novel, micromobile foot compression device (MMC) has been developed to reduce the risk of venous thromboembolism associated with prolonged seated immobility. Objective. To compare the efficacy of the MMC with graduated compression stockings in augmenting lower limb venous blood flow. Patients/Methods. Twenty participants were randomised to wear the MMC or a graduated compression stocking (GCS) on either the left or right leg while seated. Doppler ultrasound measurements of popliteal vein blood flow and leg circumference measurements were made -30 and -10 minutes (baseline) and +30 and +60 minutes following application of the interventions. The primary outcome variable was peak systolic velocity. A mixed linear model was used, with covariates including baseline measurement, randomised side, time, and a time by interaction term. Results. The mean popliteal vein peak systolic velocity at 60 minutes with the MMC was 20.1 cm/s which was significantly higher than with the GCS (difference 14.1 cm/s 95% CI 12.1-16.2), representing a 3.8-fold increase from baseline. Conclusion. The MMC resulted in a marked increase in lower limb venous blood flow which suggests that it may have efficacy in reducing the risk of venous thromboembolism associated with prolonged seated immobility, such as long distance air travel.

Cerebral “eThrombosis”: Cerebral Venous Sinus Thrombosis Associated with Prolonged Sitting in Front of a Computer

Venous thromboembolism caused by prolonged sitting during air travel has been recognised as economy-class syndrome for more than 30 years. Since 2003, the term “eThrombosis” has been proposed to describe the 21st Century variant of venous thromboembolism associated with immobilisation. We reported a case of cerebral venous sinus thrombosis presenting with severe headache after a prolonged period of sitting for over 12 hours in front of a computer for recreational purpose. We described this case as cerebral “eThrombosis”. Considering the widespread use of computers for many purposes including working, recreation and communications in the present digital era, we would like to put forward that prolonged immobilisation associated with computer use is a possible provoking risk factor of cerebral venous sinus thrombosis.

Merino wool graduated compression stocking increases lower limb venous blood flow: a randomized controlled trial

INTRODUCTION

Graduated compression stockings represent a nonpharmacological approach to reduce the risk of deep vein thrombosis (DVT) and pulmonary embolism (PE) due to prolonged immobility through reducing lower limb venous stasis. A novel merino wool, double-layer, below-knee graduated compression stocking has been developed to reduce the risk of air travel-related DVT and PE.

METHODS

Twenty healthy adult participants were randomized to wear the novel graduated compression stocking on either the left or right leg. Doppler ultrasound measurements of popliteal venous blood flow were made on both legs over a 120-minute period. The primary outcome was peak systolic velocity in the popliteal vein at 120 minutes. Secondary outcomes included mean flow velocity, total volume flow, vein cross-sectional area, and change in ankle and calf measurements.

RESULTS

The popliteal vein peak systolic velocity was 0.35 cm/s (95% confidence intervals [CI], 0.22 to 0.49, P<0.001) higher with stocking use at 120 minutes, a difference of 24%. Mean flow velocity and total volume flow were also significantly higher with stocking use. Ankle and calf circumference were decreased with stocking use, with an overall difference of -6.3 mm (95% CI, -11.3 to -1.2, P=0.021) and -7.9 mm (95% CI, -13.3 to -2.4, P=0.011), respectively.

CONCLUSION

The novel merino wool double-layer, below-knee graduated compression stocking increases lower limb venous blood flow during prolonged seated immobility. Its use is likely to reduce the risk of DVT and PE in situations of prolonged seated immobility, such as long-distance air travel. The reduction in lower limb swelling associated with their use suggests that the stockings are likely to have utility in the treatment of chronic venous insufficiency and lymphedema.

Prolonged work- and computer-related seated immobility and risk of venous thromboembolism

OBJECTIVE

To determine the risk of venous thromboembolism (VTE) associated with prolonged work- and computer-related seated immobility.

DESIGN

Case-control study in which cases were patients aged 18-65 years attending outpatient VTE clinics, and controls were patients aged 18-65 years admitted to CCU with a condition other than VTE. Interviewer-administered questionnaires obtained detailed information on VTE risk factors and clinical details.

SETTING

VTE Clinics and Coronary Care Unit (CCU), Wellington and Kenepuru Hospitals, Wellington between February 2007 and February 2009.

MAIN OUTCOME MEASURE

The relative risk of VTE associated with prolonged work- and computer-related seated immobility, defined as being seated at work and on the computer at home, at least 10 hours in a 24-hour period and at least 2 hours at a time without getting up, during the four weeks prior to the onset of symptoms that led to VTE diagnosis or CCU admission.

RESULTS

There were 197 cases and 197 controls. Prolonged work- and computer-related seated immobility was present in 33/197 (16.8%) and 19/197 (9.6%) cases and controls, respectively. In multivariate analyses, prolonged work- and computer-related seated immobility was associated with an increased risk of VTE, odds ratio 2.8 (95% CI 1.2-6.1, P=0.013). The maximum and average number of hours seated in a 24-hour period were associated with an increased risk of VTE, with odds ratios of 1.1 (95% CI 1.0-1.2, P=0.008) and 1.1 (95% CI 1.0-1.2, P=0.014) per additional hour seated.

CONCLUSION

Prolonged work- and computer-related seated immobility increases the risk of VTE. We suggest that there needs to be both a greater awareness of the role of prolonged work-related seated immobility in the pathogenesis of VTE, and the development of occupational strategies to decrease the risk.

Platelet function in brown bear (Ursus arctos) compared to man

Background

Information on hemostasis and platelet function in brown bear (Ursus arctos) is of importance for understanding the physiological, protective changes during hibernation.

Objective

The study objective was to document platelet activity values in brown bears shortly after leaving the den and compare them to platelet function in healthy humans.

Methods

Blood was drawn from immobilized wild brown bears 7-10 days after leaving the den in mid April. Blood samples from healthy human adults before and after clopidogrel and acetylsalicylic acid administration served as control. We analyzed blood samples by standard blood testing and platelet aggregation was quantified after stimulation with various agonists using multiple electrode aggregometry within 3 hours of sampling.

Results

Blood samples were collected from 6 bears (3 females) between 1 and 16 years old and from 10 healthy humans. Results of adenosine diphosphate, aspirin, and thrombin receptor activating peptide tests in bears were all half or less of those in humans. Platelet and white blood cell counts did not differ between species but brown bears had more and smaller red blood cells compared with humans.

Conclusion

Using three different tests, we conclude that platelet function is lower in brown bears compared to humans. Our findings represent the first descriptive study on platelet function in brown bears and may contribute to explain how bears can endure denning without obvious thrombus building. However, the possibility that our findings reflect test-dependent and not true biological variations in platelet reactivity needs further studies.

Susceptibility-weighted imaging: clinical angiographic applications

By combining filtered phase and magnitude information to create a novel and intrinsic source of contrast, susceptibility-weighted imaging (SWI) has shown great promise in clinical angiography and venography. SWI has contributed to new insights into traumatic brain injury, the role of calcification in atherosclerosis, and the possible relationship between blood settling and deep venous thrombosis. A further contribution from SWI to deep venous thrombosis research (and also stroke) involves its application to the noninvasive measurement of oxygen saturation in the brain and in other tissues. Altogether, SWI offers manifold and diverse avenues for further research using angiographic and venographic techniques.

A case-control study of seated immobility at work as a risk factor for venous thromboembolism

OBJECTIVE

To determine the relative risk of prolonged seated immobility at work in patients with a deep vein thrombosis (DVT) or pulmonary embolism (PE).

DESIGN

A case-control study: cases and controls completed an interviewer-administered questionnaire to obtain information on risk factors for venous thromboembolism (VTE), including prolonged seated immobility at work. Univariate and multivariate logistic regression was used to determine the association between predicted variables and the probability of being a case or control.

PARTICIPANTS

Cases were patients<65 years old attending the Wellington Hospital Outpatient VTE Clinic following hospital discharge for DVT and/or PE. Controls were patients<65 years old admitted to the Coronary Care Unit at Wellington Hospital.

SETTING

The Wellington Hospital Outpatient VTE Clinic and Coronary Care Unit.

MAIN OUTCOME MEASURES

Odds ratio of VTE for prolonged seated immobility.

RESULTS

There were 97 cases (53 DVT, 29 PE, 15 DVT and PE), and 106 controls. In the multivariate analysis the odds ratio of VTE for prolonged seated immobility at work was 1.8 (95% CI 0.71-4.8). The maximum number of hours seated at work was associated with VTE, with the risk increasing by 10% per hour longer seated (odds ratio 1.1, 95% CI 1.0-1.2). The maximum number of hours seated at work without getting up was associated with VTE, with the risk increasing by 20% per hour longer seated (odds ratio 1.2, 95% CI 0.96-1.6).

CONCLUSIONS

This study provides preliminary evidence that prolonged seated immobility at work may represent a risk factor for VTE.