Cardiovascular

In a small group of desk-based office workers who changed to a standing work position using an ergonomically adjustable desk, postprandial glycaemic excursions were attenuated. There was a corresponding small but significant increase in daily energy expenditure. These results provide an initial insight into a possible key physiological mechanism (improved glycaemic regulation), of why avoiding sedentary behaviour at work could benefit cardio-metabolic health. It provides a strong rationale for us and others to now seek more substantive funding to further elucidate the cardio-metabolic effects of standing-based office work. - British Medical Journal: Standing-based office work shows encouraging signs of attenuating post-prandial glycaemic excursion

 

In adults, we found strong evidence of a relationship between sedentary behavior and all-cause mortality, fatal and non-fatal cardiovascular disease (based on TV viewing, screen-time and sitting time), type 2 diabetes (TV viewing and screen-time) and metabolic syndrome (based on TV viewing, screen-time, sitting time and objectively measured sedentary time). In addition, there is moderate evidence for incidence rates of ovarian (sitting time), colon (TV viewing) and endometrial cancers (sitting outside of work and overall sitting) and type 2 diabetes (sitting time).

 

PLOS ONE: Sedentary Behaviour and Health Outcomes.

Back & Neck Pain

There was a significant positive association between total sitting time and high LBP intensity (OR = 1.43). Adjustment for various confounders such as individual factors (age, gender, BMI, and smoking) and occupational factors (seniority, influence at work, and occupational lifting/ carrying time) did not markedly influence the estimates or level of significance. We observed similar results for leisure-time sitting and high LBP intensity (OR = 1.38), which remained consistent after additional adjustment for occupational sitting time. We also found positive associations between occupational sitting time and high LBP intensity (OR = 1.36), but although the estimates remained similar, they became marginally insignificant (P = 0.06) with further adjustment for individual and occupational factors.

 

Sitting time is positively associated with Lower back pain intensity among blue-collar workers. Future studies using a prospective design with objective measures of sitting time are recommended.

 

PLOS One: Is Objectively Measured Sitting Time Associated with Low Back Pain?

Mental Health

There is mounting evidence to suggest detrimental effects of excess sedentary time on mental health, although plausible biological mechanisms are currently lacking. There are numerous data showing associations between sedentary time and cardiometabolic risk factors2 19 20; thus, the links with mental health might act partly through these mechanisms. In particular, the role of low-grade inflammation in depression has gained substantial attention,although in a recent study C reactive protein did not explain the link between TV viewing and depressive symptoms in older adults. Psychosocial mechanisms might also be important. For example, passive sedentary activities such as TV viewing might encourage social isolation and limit the development of social networks. We are not aware of any other studies that have compared associations of objective and self-reported sedentary/MVPA in relation to mental health outcomes. There was a consistent association between sedentary time and adverse mental health whether using objective or self-reported measures, albeit stronger with the objective measure. In contrast, we observed a discrepancy in results between self-reported and objectively assessed MVPA in relation to psychological distress, showing associations only for self-reported measures. In our recent studies, where we also compared accelerometry and self-reported exposures but in relation to cardiometabolic outcomes, we found associations between MVPA and most outcomes for self-reported and objective measures. Thus, one interpretation of the present results is that self-reported mental health and MVPA might have conceptual overlap causing participants with poor mental health to misreport their activity levels. For example, symptoms such as lethargy may cause individuals to under-report their activity. In addition, cognitive impairment that is sometimes associated with depression could impair recall, introducing bias into the results. Nevertheless, one might view objective and selfreported activity as different measures since objective assessment cannot take context into account and, by definition, measure slightly different aspects of MVPA. In this regard, context might be extremely important as some of the effects of physical activity on mental health are most likely driven by factors such as social interaction, whereas accelerometry is simply a measure of body movement and cannot capture contextual information such as ‘where’ and ‘who with’. We did not, however, take contextual information into account in our analysis of self-reported MVPA.

British Medical Journal: Associations between objectively assessed and self-reported sedentary time with mental health in adults: an analysis of data from the Health Survey for England

Diabetes (Type 2)

Ten participants agreed to participate; eight women (22–59 years; 45–82 kg) and two men (21 and 62 years; 80 and 110 kg). All had a Body Mass Index <30. Prerandial (Lunch) blood glucose levels on sitting and standing days ranged between 3.3 and 6.0mmo/L/min, and 4.3 and 7.1mmo/L/min, respectively. The intraindividual differences in these daily baseline pre-prandial levels were all less the CGM’s 15%error of sensitivity. The postprandial (lunch +185 min) area-under-the-curve analysis (figure 1) showed a 43% lower excursion (p=0.022) of blood glucose for standing (143, 95% CI 5.09 to 281.46 mmol/L/min) compared to seated desk-work (326, 95% CI 228 to 425 mmol/L/min). From lunch, mean blood glucose continued to rise during seated work for 85 min by 3.1 mmol/L, whereas for standing work, it peaked at 50 min to 1.8 mmol/L. At the end of the working day, mean blood glucose from seated work had decreased to its lowest level at 1.7 mmol/L above baseline, whereas for standing work at the same time point, it was 0.5 mmol/L above base line. Mean overnight (19:00–07:00 h) blood glucose values after seated and standing work were not different at 6.3 (±1.0) mmol/L and 6.2 (±0.8) mmol/L, respectively. The variability of the overnight blood glucose measures (SDs), demonstrated a trend of being lower by 0.2 mmol/L after the standing versus the sitting work day, but this did not reach statistical significance (n=9; p=0.052). The posthoc power calculation for these 10 participants was 75%, with an estimate of 15 participants required for future studies to achieve >90% power. Total mean energy expenditure for the afternoon (area under the curve for 210 min) was 174±66 kcals greater (p=0.028) in standing (487±174 kcals) versus seated work (313±139 kcals).

British Medical Journal: Standing-based office work shows encouraging signs of attenuating post-prandial glycaemic excursion

Obesity

Following adjustment for several potential confounding variables, we observed significant independent associations of sedentary time, light-intensity time, and mean activity intensity with waist circumference and clustered metabolic risk score and of moderate-to-vigorous–intensity activity with triglycerides. Importantly, all levels of activity were measured objectively, using the same measurement tool. This al lows for the direct comparison of the different intensities of activity with the outcome measures. When associations with waist circumference were examined, sedentary time was independent of moderate-to-vigorous–intensity physical activity; however, moderate-to-vigorous– intensity activity was not independent of sedentary time. This suggests that sedentary time may have a stronger influence on waist circumference than moderate to-vigorous physical activity. On average, the majority of waking hours (90%) were spent either in sedentary or in light-intensity activity. These two variables were highly negatively correlated. This has important clinical and public health implications, as it suggests that metabolic benefits may be obtained by substituting light-intensity activity for sedentary time. Activities of daily living have been shown to result in substantial increases in total daily energy expenditure and resistance to fat gain (16). Regular participation in moderate-to-vigorous– intensity activity should still be promoted as the predominant physical activity message. However, promoting a reduction in sedentary time through increasing light intensity day-to-day activity may be another important public health message for reducing central obesity and overall metabolic risk. Our findings are consistent with those of larger-scale population-based studies with more representative samples, in which self-reported measures of sedentary time have been shown to be significantly associated with metabolic risk (2,6). However, as these are cross sectional associations, prospective studies, or, ideally, intervention trials using objective measures are required to determine the physiological and behavioral mechanisms that underlie these associations. Nevertheless, there is important public health implications for reducing time spent in sedentary behavior and increasing time spent in both light and moderate-to- vigorous–intensity physical activity (17).

The Australian Diabetes, Obesity and Lifestyle Study: Objectively Measured Sedentary Time, Physical Activity, and Metabolic Risk

Cancer

When the highest levels of sedentary behavior were compared to the lowest, the researchers found a statistically significantly higher risk for three types of cancer—colon, endometrial, and lung. Moreover, the risk increased with each 2-hour increase in sitting time, 8% for colon cancer, 10% for endometrial cancer, and 6% for lung cancer, although the last was borderline statistically significant. The effect also seemed to be independent of physical activity, suggesting that large amounts of time spent sitting can still be detrimental to those who are otherwise physically active. TV viewing time showed the strongest relationship with colon and endometrial cancer, possibly, the authors write, because TV watching is often associated with drinking sweetened beverages, and eating junk foods.

The researchers write “That sedentariness has a detrimental impact on cancer even among physically active persons implies that limiting the time spent sedentary may play an important role in preventing cancer….”

Journal of the National cancer Institute: Sedentary behavior increases the risk of certain cancers

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