即便BMI低 久坐仍與脂肪肝疾病有關


  【24drs.com】一篇大型的橫斷面研究指出,久坐和少運動與非酒精性脂肪肝疾病(nonalcoholic fatty liver disease,NAFLD)有關,體重正常且有運動者也是如此。這些結果線上發表於9月15日肝病學期刊,強調有越來越多的證據指出減少久坐時間與增加運動的重要性,以預防慢性疾病和早逝。
  
  南韓首爾成均館大學醫學院江北三星醫院職業暨環境醫學系的Seungho Ryu醫師等人寫道,這篇研究的結果認為,增加運動時間和減少久坐時間對於NAFLD風險都相當重要。
  
  Ryu醫師等人分析了「180,000-strong Samsung Health Study」世代近140,000名韓國人的資料,這些研究對象在2011年3月至2013年12月間,在江北三星醫院的全面健康照護中心進行一年一度或兩年一度的綜合檢查,使用確效過的韓文版「短版國際體能活動問卷」評估體能活動程度與久坐時間;已知有肝臟疾病或前一年內曾服用與NAFLD有關之藥物者,則不被納入分析。
  
  根據久坐時間將研究對象分成三類:每天不到5小時、每天5-9小時、每天10小時以上;他們的活動程度分為不運動、很少運動、可促進健康的運動。另外,依據超音波確認有無脂肪肝。
  
  139,056名研究對象中,46.7%是女性、52.4%是男性,研究對象平均年齡為39.9歲(標準差[SD]為8.8歲),平均身體質量指數(BMI)為23.0 kg/m2 (SD, 3.2 kg/m2;範圍為13.3 - 47.7 kg/m2),平均坐姿時間為7.6小時(SD, 3.8小時),坐姿時間與體能活動程度的關聯性為- 0.15 (P < .001)。
  
  每天坐姿時間10小以上者,比較可能是較年輕、男性、有較高的BMI與總熱量攝取,且他們比較沒有心血管疾病、糖尿病或高血壓病史。
  
  研究者發現,39,257名(28%)研究對象有NAFLD。多變項校正模式發現,長時間坐姿和少運動都與NAFLD盛行率增加有關。每天坐姿時間5-9小時、每天坐姿時間10小時以上者的NAFLD盛行率比率,分別是每天坐姿時間不到5小時者的1.04倍(95%信賴區間[CI], 1.02 - 1.07)和1.09倍(95% CI, 1.06 - 1.11),趨勢P值 < .001。
  
  有趣的是,即便是體重正常者,包括那些BMI低於23 kg/m2者,這些關聯依舊為真。很少運動者和可促進健康之運動者的NAFLD盛行率比率,分別是不運動者的0.94倍(95% CI, 0.92 - 0.95)和0.81倍(0.79 - 0.83)(趨勢P值< .001)。
  
  坐姿時間對於NAFLD的不良影響,受到脂肪量增加或骨骼肌肉量減少影響。值得一提的是,即使是有運動者,坐姿時間增加(每天10小時以上)對於NAFLD也會有不良影響。
  
  Ryo醫師表示,一般人的工作日有半數以上是久坐型,NAFLD相當普遍。就公衛觀點來看,減少坐姿時間對於一般人的肝臟代謝健康會有明顯影響。所以,醫師必須教育病患,不只要增加運動,還要減少坐姿時間。
  
  在一篇相關評論中,英國泰恩河畔新堡大學代謝暨生活型態醫學教授Michael I. Trenell博士指出,Ryu醫師等人的資料增添了有力的警示證據,坐太久與動太少對於心臟代謝健康有明顯的負面影響。他提醒,這個訊息相當清楚,椅子正緩慢而堅定地在殺死我們。
  
  雖然提到運動和久坐型態對於心臟代謝健康有獨立的影響,Trenell博士指出,問題在於缺乏有關NAFLD之久坐與運動的實證指引。依舊缺乏大型研究探討NAFLD的體能活動和運動、合併或者未合併飲食改變/藥物治療,因而限制了NAFLD之特定指引的發展。
  
  一般指引是每週中等強度運動150分鐘或者每天1萬步,這在經驗上是有助於初步預防心血管疾病的不錯指引;不過,Trenell博士寫道,目前的文獻還無法告知我們坐多久才是過久,我們只知道少坐比久坐好。
  
  他指出,人體的構造是設計來活動的,因此,久坐與少活動對於生理有負面影響並不令人意外,因為NAFLD沒有獲得核准的藥物療法,生活型態改變仍然是臨床治療的基石。
  
  他寫道,對於NAFLD,不論是生理上或譬喻上,我們當今的挑戰是「站起來」並且運動。對於哪些久坐行為會如何影響肝臟健康與其原因,需要後續研究,以揭櫫真正的機轉。
  
  資料來源:http://www.24drs.com/
  
  Native link:Even With Low BMI, Sitting Linked to Fatty Liver Disease

Even With Low BMI, Sitting Linked to Fatty Liver Disease

By Diana Swift
Medscape Medical News

A large, cross-sectional Korean study has linked prolonged sitting and decreased physical activity with nonalcoholic fatty liver disease (NAFLD), even in physically active people of normal weight. The results, published online September 15 in the Journal of Hepatology, underscore mounting evidence of the importance of reducing sedentary time and increasing physical activity to prevent chronic illnesses and premature death.

"The findings of this study suggest that both increasing participation in physical activity and reducing sitting time are independently important for NAFLD risk," Seungho Ryu, MD, PhD, from the Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea, and colleagues write.

Dr Ryu and fellow researchers analyzed almost 140,000 Koreans from the 180,000-strong Samsung Health Study cohort. Participants underwent a comprehensive annual or biennial examination at Kangbuk Samsung Hospital Total Healthcare Centers in Seoul and Suwon, South Korea, from March 2011 to December 2013. Physical activity levels and sitting times were assessed using the validated Korean version of the international Physical Activity Questionnaire Short Form. Cohort subjects with known liver disease or who had taken medications associated with NAFLD in the past year were excluded from the analysis.

Participants fell into three categories of sitting time: less than 5 hours a day, 5 to 9 hours a day, and 10 or more hours a day. Their activity levels were categorized as inactive, minimally active, and health-enhancing physically active. Fatty liver was determined by ultrasound.

Of the 139,056 participants, 46.7% were women and 52.4% were men. Participants had a mean age of 39.9 years (standard deviation [SD], 8.8 years), a mean body mass index (BMI) of 23.0 kg/m2 (SD, 3.2 kg/m2; range, 13.3 - 47.7 kg/m2), and a mean sitting time of 7.6 hours (SD, 3.8 hours). The correlation between sitting time and physical activity level was ?0.15 (P < .001).

Subjects who reported the longest sitting time of 10 or more hours a day were more likely to be younger and male and to have a higher BMI and total calorie intake, and they were less likely to have a history of cardiovascular disease, diabetes, or hypertension.

The researchers found 39,257 participants (28%) had NAFLD. A multivariable-adjusted model found both prolonged sitting time and decreased physical activity were independently associated with increasing NAFLD prevalence. The prevalence ratios for NAFLD comparing 5 to 9 hours a day and 10 or more hours a day sitting time with less than 5 hours a day were, respectively, 1.04 (95% confidence interval [CI], 1.02 - 1.07) and 1.09 (95% CI, 1.06 - 1.11), P for trend < .001.

Interestingly, these associations held even in normal-weight individuals, including those with BMIs lower than 23 kg/m2. The prevalence ratios for NAFLD comparing the minimally active and the health-enhancing physically active groups with the inactive group were 0.94 (95% CI, 0.92 - 0.95) and 0.81 (0.79 - 0.83), respectively (P for trend < .001).

The adverse effect of sitting time on NAFLD was mediated by increased fat mass or decreased skeletal muscle mass. Notably, an adverse effect of prolonged sitting (10 or more hours a day) on NAFLD emerged even among the physically active group.

"More than half of the average person's waking day involves sedentary activities, and NAFLD is very common," Dr Ryo told Medscape Medical News. "From the viewpoint of public health, reducing sitting time could have a substantial impact on liver metabolic health in the general population. So doctors need to educate patients not only about increasing physical activity but also about reducing time spent sitting."

In an accompanying editorial, commentator Michael I. Trenell, PhD, a professor of metabolism and lifestyle medicine at Newcastle University, Newcastle upon Tyne, United Kingdom, adds, "The data from Ryu and colleagues add to the strong and alarming evidence that sitting too much and moving too little has significant negative consequences for cardio-metabolic health."

He warns: "The message is clear, our chairs are slowly but surely killing us."

Although noting that physical activity and sedentary behavior clearly have independent effects on cardiometabolic health, Dr Trenell noted a problematic absence of evidence-based guidelines for sedentary behavior and physical activity in NAFLD. "There remains a significant lack of large scale studies exploring physical activity and exercise in NAFLD, with and without dietary change/pharmacotherapy, limiting the generation of guidelines specific for NAFLD," he writes.

General guidelines of 150 minutes of moderate exercise per week or 10,000 steps per day are good rules of thumb based on guidelines for the primary prevention of cardiovascular disease; however, "the current literature cannot inform us how much sitting is too much, we just know that it is better to sit less than to sit more," writes Dr Trenell.

The human body is designed to move, and hence it comes as no surprise that sedentary behavior and low muscle activity negatively affect physiology, he adds. With a dearth of approved drug therapies for NAFLD, lifestyle changes remain the cornerstone of clinical care.

"The challenge for us now is to 'stand up' and move for NAFLD, both physically and metaphorically," he writes, adding that unraveling the mechanisms at the core of the "what, why and how of sedentary behaviour and liver health is a promising area for future research."

The study authors have disclosed no relevant financial relationships. Dr Trenell is supported by a senior fellowship from the UK National Institute for Health Research and the National Institute for Health Research Biomedical Research Centre for Ageing and Age Related Disease.

J Hepatol. Published online September 14, 2015.

    
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