{"id":8003,"date":"2018-09-04T05:00:46","date_gmt":"2018-09-04T04:00:46","guid":{"rendered":"https:\/\/blogs.bmj.com\/bjsm\/?p=8003"},"modified":"2018-09-04T05:08:41","modified_gmt":"2018-09-04T04:08:41","slug":"do-the-associations-of-sedentary-behaviour-with-cardiovascular-disease-and-cancer-mortality-differ-by-physical-activity-level-a-systematic-review-and-harmonised-meta-analysis-of-data-from-85","status":"publish","type":"post","link":"https:\/\/blogs.bmj.com\/bjsm\/2018\/09\/04\/do-the-associations-of-sedentary-behaviour-with-cardiovascular-disease-and-cancer-mortality-differ-by-physical-activity-level-a-systematic-review-and-harmonised-meta-analysis-of-data-from-85\/","title":{"rendered":"\u201cDo the associations of sedentary behaviour with cardiovascular disease and cancer mortality differ by physical activity level? A systematic review and harmonised meta-analysis of data from 850,060 participants\u201d \u2013 What it all means"},"content":{"rendered":"

The Physical Activity and Population Health BJSM Blog Series\u00a0<\/strong><\/span><\/p>\n

By Sonia Cheng @soniawmcheng<\/a><\/strong><\/em><\/p>\n

Standing desks! Walking meetings!<\/p>\n

With phrases like \u201cSitting is the new smoking\u201d making headlines in the media and almost 40% of Australian newspaper stories about sedentary behaviour suggesting that the benefits of physical activity (PA) are negated by too much sitting1<\/sup>, I must admit \u2013 there is extra incentive to be on my best behaviour and minimise the amount of time spent in prolonged sitting.<\/p>\n

The idea that the negative health effects of too much sitting cannot be countered by sufficient levels of moderate-vigorous intensity physical activity (MVPA) is hotly debated, and researchers continue to investigate the joint effects of PA and sitting time on mortality risk.<\/p>\n

We bring you the latest update on this highly contentious topic, following the publication of a systematic review and harmonised meta-analysis of data from over 850,000 participants\u00a0<\/a>in this month\u2019s issue of BJSM.<\/p>\n

How compelling is the current evidence?<\/strong><\/p>\n

The harmonised\u00a0<\/a>pooled analysisto directly compare the joint effects of different combinations of PA and sitting time on all-cause mortality risk was also conducted by Ekelund and colleagues in 2016.<\/p>\n

Using a harmonised meta-analysis of data from more than one million men and women, the authors reported that at least 60 minutes\/day of moderate-intensity PA appeared to eliminate the detrimental association between sitting time and all-cause mortality, even in those who sat for more than 8 hours\/day2<\/sup>.<\/p>\n

In their recent publication, Ekelund and colleagues again used a harmonised meta-analytical approach to examine whether PA also has a modifying effect on associations between sitting time and cardiovascular disease (CVD) and cancer mortality risk3<\/sup>.<\/p>\n

Does physical activity attenuate the relationship between sitting time and CVD mortality risk?<\/strong><\/p>\n

The authors\u2019 answer is a clear \u2018yes\u2019.<\/p>\n

In those who were least active and reported <2.5 MET-hours\/week of PA (approximately equivalent to <5 minutes\/day of moderate-intensity activity), there was a strong dose-response association between sitting time and CVD mortality risk. Participants who were inactive and reported sitting for >8 hours\/day had a 32% higher risk of CVD mortality compared to those who sat for <4 hours\/day.<\/p>\n

Associations between sitting time and CVD mortality were less consistent with increasing levels of PA. For those who reported anywhere between \u22655 to 65 minutes\/day of moderate-intensity PA, a higher CVD mortality risk was only observed in those who reported sitting for >8 hours\/day. And in participants who were most active (reporting >35.5 MET-hours\/week of PA, or >65 minutes\/day of moderate-intensity activity) there was no increased CVD mortality risk with increasing sitting time.<\/p>\n

Do keep in mind the limitations of the study:<\/p>\n