A new review in the journal Mental Health and Physical Activity looks at the potential impact of sedentary behaviour on mental health:
It is generally understood that regular moderate to vigorous physical activity (MVPA) promotes good health from head to toe. Evidence also supports the notion that too much sitting can increase all-cause mortality and risk of chronic diseases such as diabetes. Moreover, there is evidence that daily MVPA may not offset negative effects of sedentary behavior on systemic risk factors. We extend the discussion to brain structure and function and argue that while MVPA is recognized as a protective behavior against age-related dementia, sedentary behavior may also be an important contributor to brain health and even counteract the benefits of MVPA due to overlapping or interacting mechanistic pathways. Thus, the goals of this review are (1) to outline evidence linking both PA and sedentary behavior to neurobiological systems that are known to influence behavioral outcomes such as cognitive aging and (2) to propose productive areas of future research.
The full article is now available via the journal Mental Health and Physical Activity.
Dr Meredith Peddie of the University of Otago (New Zealand) is currently looking for a PhD/MSc student to investigate the energy expenditure and possible dietary compensation associated with prolonged sitting, continuous physical activity, and regular activity breaks.
The full posting can be found below:
University of Otago Scholarships to undertake a PhD are available to those candidates with an excellent academic record.
The Heart Foundation of Australia has created a series of excellent workplace wellness posters targeting sedentary behaviour that can be printed off from their website.
Sit-Less PostersA range of four posters that act as a visual cue to prompt workers to stand or move more frequently in a workplace setting. These posters also provide imagery on ways that people can reduce extended sitting throughout the day.
Download your copies :
More workplace wellness resources are available via the Heart Foundation website.
Earlier this week we posted the abstract of a study concluding that sedentary behaviour may not have health effects independent of physical activity. David Dunstan and colleagues have responded with a comment on the article, available via PLOS ONE.
From the comment:
Maher and colleagues report findings from a secondary analysis of accelerometer data collected as part of the US National Health and Nutrition Examination Survey (NHANES). They found no associations of sedentary time with cardiometabolic risk biomarkers, when controlling for a measure of “total physical activity” that was composed of time spent in both moderate- to vigorous-intensity and light-intensity physical activity (that is, all non-sedentary time), weighted by intensity (accelerometer counts). On this basis, they concluded that sedentary time may not have health effects independent of physical activity. Leaving aside legitimate concerns with interpreting null results in this fashion, a broader conclusion that might be drawn is that there is limited (or no) merit in searching for “independent” effects of behaviours that are unavoidably “interdependent”.
Both the full article and the full comment are available via PLOS ONE.
New study suggests that prolonged sitting is linked to excess mortality. From Stone Hearth Newsletter:
Led by Cornell University nutritional scientist Rebecca Seguin, a new study of 93,000 postmenopausal American women found those with the highest amounts of sedentary time – defined as sitting and resting, excluding sleeping – died earlier than their most active peers. The association remained even when controlling for physical mobility and function, chronic disease status, demographic factors and overall fitness – meaning that even habitual exercisers are at risk if they have high amounts of idle time.
The full article is available via Stone Hearth Newsletter.
SBRN members have recently compiled a list of 12 different validated sedentary behaviour questionnaires, which are now available on the SBRN website. The questionnaires have been validated in age groups ranging from adolescence to the elderly, and in both population-based and clinical studies. If you have a questionnaire to add to the list (or a comment/correction) please email saunders (dot) travis (at) gmail (dot) com.
The full list is available here.
On October 28 the American Academy of Pediatrics updated their media/screentime recommendations for children and youth, published in the journal Pediatrics. The paper includes recommendations for healthcare providers, schools, and parents.
Recommendations for parents:
- Limit the amount of total entertainment screen time to < 1 to 2 hours per day.
- Discourage screen media exposure for children < 2 years of age.
- Keep the TV set and Internet-connected electronic devices out of the child ’ s bedroom.
- Monitor what media their children are using and accessing, including any Web sites they are visiting and social media sites they may be using.
- Co-view TV, movies, and videos with children and teenagers, and use this as a way of discussing important family values.
- Model active parenting by establishing a family home use plan for all media. As part of the plan, enforce
a mealtime and bedtime “ curfew ” for media devices, including cell phones. Establish reasonable but
ﬁrm rules about cell phones, texting, Internet, and social media use.
The full set of recommendations are available in the journal Pediatrics.
From the American Journal of Preventive Medicine:
Associations of sitting-time and physical activity with depression are unclear.
To examine concurrent and prospective associations between both sitting-time and physical activity with prevalent depressive symptoms in mid-aged Australian women.
Data were from 8950 women, aged 50-55 years in 2001, who completed mail surveys in 2001, 2004, 2007, and 2010. Depressive symptoms were assessed using the Center for Epidemiological Studies Depression questionnaire. Associations between sitting-time (≤4 hours/day, >4-7 hours/day, >7 hours/day) and physical activity (none, some, meeting guidelines) with depressive symptoms (symptoms/no symptoms) were examined in 2011 in concurrent and lagged mixed-effect logistic modeling. Both main effects and interaction models were developed.
In main effects modeling, women who sat >7 hours/day (OR=1.47, 95% CI=1.29, 1.67) and women who did no physical activity (OR=1.99, 95% CI=1.75, 2.27) were more likely to have depressive symptoms than women who sat ≤4 hours/day and who met physical activity guidelines, respectively. In interaction modeling, the likelihood of depressive symptoms in women who sat >7 hours/day and did no physical activity was triple that of women who sat ≤4 hours/day and met physical activity guidelines (OR 2.96, 95% CI=2.37, 3.69). In prospective main effects and interaction modeling, sitting-time was not associated with depressive symptoms, but women who did no physical activity were more likely than those who met physical activity guidelines to have future depressive symptoms (OR=1.26, 95% CI=1.08, 1.47).
Increasing physical activity to a level commensurate with guidelines can alleviate current depression symptoms and prevent future symptoms in mid-aged women. Reducing sitting-time may ameliorate current symptoms.
For links to other sedentary behaviour studies, please visit the SBRN Research Database.
Today’s guest post comes from PhD student Bethany Howard. You can find out more about Bethany at the bottom of this post. The study that she is discussing was recently published in MSSE, and can be found here.
I am sure by now you have all heard the messages to avoid your chair and the increased risk of premature death it may be kindly bestowing on you. Indeed there are slogans out there such as “your chair is sending you to an early grave”, “make a stand”, “sitting is the new smoking” and big corporations that promote this important rapidly evolving area of research – that is the study of the health consequences of “too much sitting”.
What do we know?
It’s important to appreciate that these messages about the hazards of sitting are not entirely new – as early as the 1950’s physicians were advocating breaks from sitting. Homans (1954) suggested that the “Such matters are important enough to suggest the advisability of making movement of the toes, feet and lower legs when one is sitting for long periods and of getting up and exercising when opportunity offers.” Such recommendations were drawn from cases of thrombosis – the formation of a blood clot that obstructs blood flow – with prolonged sitting at the theatre, whist watching TV and during travel.
Today the research initiated from such early work is now evident in the recommendations when we fly. For those of you who are avid jetsetters you will be familiar with the announcement to “get up and move around to reduce the risk of deep vein thrombosis (VT)”. There is now evidence to suggest that this increased risk extends to prolonged bus travel and prolonged workplace sitting. But the question we wanted to ask with our experimental study published recently in Medicine & Science and Sports & Exercise was:
What are the potential reasons for this increased risk?
Virchow describes three components that contribute to the risk of VT, known commonly as Virchows Triad: Impaired blood flow, Hyper-coagulation and Disturbed Endothelium. Of these, there is substantial evidence linking sitting to impaired blood flow, limited evidence on hypercoagulation and little or no evidence for possible effects on the endothelium. The majority of studies that have been conducted in this area have focused on air travel. Although high amounts of sitting are present, air travel does not provide the typical environment in which sitting accumulates in our daily lives.
What did we do?
In order to address these knowledge gaps, we used an experimental study design to examine the effects of sitting (uninterrupted) on markers of thrombosis, specifically markers that relate to clot formation (through haemostasis) and blood viscosity. We then compared these effects to interrupted sitting, to assess whether breaks involving walking were indeed effective at reducing thrombotic risk. To do this we undertook an acute randomized cross-over trial design with subjects being their own controls. The trial consisted of 3 conditions all of which lasted for 7 hours:
1) Uninterrupted sitting
2) Sitting interrupted by light-intensity walking breaks
3) Sitting interrupted by moderate-intensity walking breaks
The two different intensity activity break conditions were incorporated into the study design to determine if there is an intensity effect of the breaks. That is, for a benefit to be seen, do the breaks need to be of a higher intensity? Earlier observational work from our group using objective activity monitoring suggested that the intensity wasn’t as important – having breaks, and frequently seemed most important.
What did we find?
For the common blood viscosity markers (plasma volume, hematocrit, hemoglobin, red blood cells) breaks were beneficial irrespective of the intensity. That is, with the introduction of breaks in sitting time blood viscosity appeared to be reduced. This is likely to have improved blood flow, one of three elements of Virchows triad. Continue Reading
The American College of Sports Medicine will be hosting their annual scientific meeting in Indianapolis, USA, this week, and there is a wealth of sedentary behaviour research on the program. You can find a full list of the presentations related to sedentary behaviour here.
The below presentations will be led by members of SBRN. If you are giving a presentation related to sedentary behaviour at ACSM or another conference, send the presentation time and location to Travis Saunders at tsaunders (at) cheo (dot) on (dot) ca.
Sedentary/active Behaviors And Cardiometabolic Risk: Protective Effects Of Sleep Duration, Nhanes 2005-2006. Matthew P. Buman, Elisabeth A. H. Winkler, Jonathan M. Kurka, Eric B. Hekler, Neville Owen, Barbara E. Ainsworth, Genevieve N. Healy, Paul A. Gardiner. Session: Thematic Poster B-18. Sedentary Behavior: Effects on Health Wednesday, May 29, 2013 1:00 – 3:00 PM
Sedentary Behaviour, Visceral Fat And Cardiometabolic Risk: 6-year Longitudinal Study From The Quebec Family Study. Travis J. Saunders, Mark S. Tremblay, Jean-Pierre Després, Claude Bouchard, Angelo Tremblay, Jean-Philippe Chaput. Session: Thematic Poster B-18. Sedentary Behavior: Effects on Health Wednesday, May 29, 2013 1:00 – 3:00 PM.
Sedentary Behavior and Cardiometabolic Risk: Emerging Experimental Evidence. SBRN members presenting during this session include Neville Owen (Chair), Sarah Kozey-Keadle (Does Reducing Sedentary Behavior Enhance the Benefits of Exercise?), Travis Saunders (The Metabolic and Behavioral Impact of One Day of Prolonged Sitting in Children and Youth) and David Dunstan (Understanding the Acute and Cumulative Metabolic Effects of Prolonged Sitting in Adults).