本帖最後由 lsc0019 於 2009-6-22 23:45 編輯
作者：Fran Lowry
出處：WebMD醫學新聞
June 3, 2009 — 根據線上發表於5月26日循環期刊的研究結果，肥胖且有第2型糖尿病的青少年與青年，頸動脈內膜中層厚度與硬度明顯較大。
俄亥俄州辛辛那提大學的Elaine M. Urbina醫師等人寫道，肥胖或有第2型糖尿病(T2DM)的成年人，中風和心肌梗塞的風險較高。這些高風險病患有許多人在發生心血管事件之前，出現頸動脈損傷(頸動脈內膜中層厚度與硬度增加)。肥胖或T2DM之青年人的頸動脈是否有類似的改變則未知。
【無併發症的肥胖者也發現厚度增加】
研究目標是確認這些變化是否實際上發生在肥胖且有第2型糖尿病的青少年與青年，對照組是體型瘦的人。研究對象屬於一項肥胖與第2型糖尿病對心臟與血管影響之研究中的446名青年，他們的年紀從10至24歲；65%非白人、39%為男性。
研究者測量頸動脈內膜中層厚度、血壓、人體計測資料與檢驗數據，計算楊氏彈性係數與beta硬化指數。共有182名體型瘦者、136名肥胖者、128名第2型糖尿病患者。
他們發現，纖瘦組、肥胖組、第2型糖尿病組的心血管風險因素一組比一組惡化。第2型糖尿病患者的頸動脈內膜中層厚度最大。肥胖組、第2型糖尿病組的內頸動脈、頸動脈內膜中層厚度都比纖瘦組大(整體P≦.05)。楊氏彈性係數與beta硬化指數都顯示肥胖組、第2型糖尿病組有比較硬的頸動脈。
研究作者報告指出，與頸動脈內膜中層厚度無關的因素，包括組別、組別與年紀交互關係、性別、一般頸動脈收縮壓(r 2 = 0.17)；年紀、種族、頸動脈球收縮壓(r 2 = 0.16)；年紀、種族、性別、收縮壓、舒張壓是所有頸動脈硬度測量的決定因素，性別與楊氏彈性係數有關(r 2 = 0.23)，身體質量指數Z分數、組別、組別與年紀交互關係對beta硬化指數有影響(r 2 = 0.31; 所有之P < .0001)。
研究作者寫道，發現較年輕的第2型糖尿病患者有明顯較厚的頸動脈內膜中層厚度，這並不令人驚訝。更重要的發現是，在無併發症的肥胖者也出現這樣增加的厚度，顯示肥胖的年輕人在出現碳水化合物不耐症之前即已發生血管構造與功能的早期變化。
【研究限制】
作者寫道，研究限制包括橫斷面研究設計無法確認從無併發症的肥胖到出現第2型糖尿病代謝症狀之間發生血管變化的時間序列。研究世代的年紀範圍狹窄，可能會限制測量纖瘦者之一般頸動脈內膜中層厚度增加情形的能力。此外，糖尿病組年紀略大且血壓和膽固醇值都較纖瘦組及肥胖組高。
他們也指出，各組之間頸動脈內膜中層厚度差異的絕對強度很小。這令人質疑測量頸動脈內膜中層厚度對於此類年輕病患之風險分類的效益，可能因為方法上的不精準以及生物差異性而抵銷。
最後，一般用超音波來測量頸動脈內膜中層厚度，但缺乏年紀、性別與種族等基本資料而受限。他們寫道，需要更精進的超音波技術以及健康孩童的更多資料，以使此一領域研究進步。
因為全球的肥胖相關代謝症候群以及第2型糖尿病盛行率增加，小兒健康照護執業者應持續篩檢心血管風險因素，特別是肥胖且有糖尿病者。研究作者結論表示，如果我們要預防年輕人的壽命縮短，現在就應該運用廣泛的生活型態介入來減少肥胖情況。
國家健康研究中心(國家心臟、肺臟與血液研究中心)贊助本研究。研究作者宣告沒有相關財務關係。
Circulation. 線上發表於2009年5月26日。
Teens, Young Adults With Obesity and Type 2 Diabetes Have Carotid Artery Abnormalities
By Fran Lowry
Medscape Medical News
June 3, 2009 — Adolescents and young adults with obesity and type 2 diabetes mellitus have significantly greater carotid intima-media thickness and carotid artery stiffness than their lean counterparts, according to the results of a new study published online May 26 in Circulation.
"Adults with obesity or type 2 diabetes mellitus (T2DM) are at higher risk for stroke and myocardial infarction," write Elaine M. Urbina, MD, from the University of Cincinnati, Cincinnati, Ohio, and colleagues. "Many of these high-risk individuals demonstrate evidence of target organ damage in the carotid arteries (increased carotid intima-media thickness and carotid stiffness) well before the adverse cardiovascular outcomes occur. Whether similar changes in the carotid arteries occur in youth with obesity or T2DM is not known."
Increased Thickness Found in Uncomplicated Obesity
The aim of the study was to determine whether such changes did, in fact, occur in adolescents and young adults with obesity and type 2 diabetes mellitus vs lean control subjects. The study population consisted of 446 youths who were part of an ongoing study of the cardiac and vascular effects of obesity and type 2 diabetes. Their ages ranged from 10 to 24 years; 65% were nonwhite and 39% were male.
The investigators measured carotid intima-media thickness, blood pressure, and anthropometric and laboratory values, and calculated the Young elastic modulus and beta stiffness index in 182 lean subjects, 136 obese subjects, and 128 subjects with type 2 diabetes.
They found that cardiovascular risk factors worsened from the lean group to the obese group to the type 2 diabetes group. Subjects with type 2 diabetes had greater carotid intima-media thickness than lean and obese subjects for the common carotid artery and bulb. For the internal carotid artery, carotid intima-media thickness measurements in both obese subjects and subjects with type 2 diabetes were thicker vs the lean subjects (P ? .05 for all). Obese subjects and subjects with type 2 diabetes had stiffer carotid arteries with higher Young elastic modulus and beta stiffness index than lean subjects.
Independent determinants of carotid intima-media thickness were group, group x age interaction, sex, and systolic blood pressure for the common carotid artery (r 2 = 0.17); age, race, and systolic blood pressure for the bulb (r 2 = 0.16); and age, race, sex, systolic blood pressure, and total cholesterol levels for the internal carotid artery (r 2 = 0.21). Age, systolic blood pressure, and diastolic blood pressure were determinants of all measures of carotid stiffness, with sex adding to the Young elastic modulus (r 2 = 0.23), and body mass index Z score, group, and group x age interaction contributing to the beta stiffness index (r 2 = 0.31; all P < .0001), the study authors report.
The finding that youngsters with type 2 diabetes have significantly thicker carotid intima-media thickness than their lean counterparts is not surprising, the authors write. A more important finding is that this increased thickness can be found in uncomplicated obesity, demonstrating that "early changes in vascular structure and function can be demonstrated in youth with obesity before the development of carbohydrate intolerance."
Study Limitations
Citing the limitations to the study, the authors write that the cross-sectional design of their study did not permit them to determine a time sequence for the development of vascular changes, from uncomplicated obesity to metabolic syndrome to type 2 diabetes. The age range of the cohort was narrow, which may have limited the ability to detect increases in common carotid intima-media thickness in lean subjects. Also, the group with diabetes was slightly older and had higher blood pressure and cholesterol levels than lean and obese subjects.
They also point out that the absolute magnitude of the differences in carotid intima-media thickness between the groups was small. This calls into question the usefulness of measuring carotid intima-media thickness for risk stratification of pediatric patients, which may be diminished by "imprecision of the methodology and biological variability."
Finally, ultrasound screening, which was used to measure carotid intima-media thickness, was limited by a lack of normative data across age, sex, and race/ethnicity. Further refinements in ultrasound techniques and more data in healthy children are needed to advance the field, they write.
With the prevalence of obesity-related metabolic syndrome and type 2 diabetes increasing across the globe, pediatric healthcare practitioners should continue to screen for abnormalities in cardiovascular risk factors, especially in obese and diabetic children. "Comprehensive lifestyle interventions to reduce obesity must be applied now if we are to prevent a projected decline in life expectancy for our youth," the study authors conclude.
The National Institutes of Health (National Heart, Lung, and Blood Institute) sponsored this study. The study authors have disclosed no relevant financial relationships.
Circulation. Published online May 26, 2009. |
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