主動脈鈣化與骨質流失、骨折的速度增加有關


  Sept. 13, 2004 - 根據一項發表於9月號臨床內分泌學與代謝期刊上的回溯性、縱向研究結果顯示,主動脈鈣化是停經後婦女骨質密度降低與髖關節與脊椎骨折強力的預測因子。
  
  美國加州Loma Linda大學醫學中心放射部門Eloy Schulz醫師指出,冠狀動脈鈣化與骨質疏鬆症是多發性、退化性疾病,好發於老年人,而且發生率持續增加,因為它們是常見的,因此在同一個體這兩種疾病都是經常發生的。
  
  研究人員指出,雖然許多報導暗示冠狀動脈鈣化與骨質疏鬆症之間是有關聯的,但要在這兩種情況之間找到明確的關連是不容易的;在這項試驗中,研究人員使用電腦斷層攝影(CT)來定量動脈與骨骼肌組織的礦物質,這樣的方式是精準且正確的,可以避免傳統放射學、光子或是X光吸收量表的限制。
  
  試驗中,研究人員以2,348位50歲以上健康停經後婦女的CT與病歷用來檢驗主動脈鈣化、骨密度(BMD),容易骨折的數目;一群健康的次團體(平均年齡為65.2±9.8歲),而且在構成試驗中縱向團體起始檢查後的2.1±1.9年,進行反覆CT測試。
  
  起始的團體中,70%患有骨骼疏鬆症、30%至少有一個以上的脊椎骨折,9%至少有一個以上的髖骨骨折;在調整年齡的影響後,主動脈鈣化可以預測BMD流失26.1%的變異性(P<.001)。
  
  主動脈鈣化被發現直接地與骨折數目有關,相較於沒有鈣化的婦女,主動脈鈣化的婦女,承擔4.8倍更容易發生脊椎骨折風險(95%信賴區間為3.6-6.5)。
  
  而相較於沒有鈣化的婦女,主動脈鈣化的婦女承擔2.9倍更容易發生近端股骨骨折風險(95%信賴區間為1.8-4.8),且相較於沒有鈣化的婦女,更容易發生雙側骨折(19.8相較於14.3%;P=.04)。
  
  至於縱向世代內的結果則是相似的,每年增加的鈣化解釋了骨質流失47%的變異性(P<.001);根據每年鈣化改變百分比的四分位數中,鈣化的進展與骨質流失之間有強烈的關係,處於鈣化最高四分位數婦女的骨質流失,明顯比年齡相近但四分位數較低的婦女高(每年5.3%相較於1.3%;P<.001)。
  
  研究人員指出,這項試驗結果顯示,除了老化過程外,在冠狀動脈鈣化與骨質疏鬆症之間仍然有顯著的關係,這應該激勵研究調控礦物質在結締組織沈積的機轉,以及可能同時修飾這兩種常見狀況風險的有效預防及治療策略;研究人員進一步指出,停經後婦女的鈣化斑塊與骨質流失,應可幫助早期確認那些骨質疏鬆症與骨折的高危險群。
  
  這項試驗由國家健康組織及陸軍部門部份贊助。
  
  在伴隨研究的一篇評論中,紐約市哥倫比亞大學Mishaela R. Rubin醫師與Shonni J. Silverberg醫師指出,在這項試驗中,使用CT技術來評估主動脈與脊椎使得這成為現存文獻中一個很重要的結果。
  
  不過,這也暗示仍需進一步的研究,找出高BMD的男性與女性,而且使用大型的、前瞻性試驗,配合標準化的電腦斷層掃描間距,以確定目前的縱向試驗結果;Rubin醫師與Silverberg醫師的結論是,這樣的臨床觀察將會與來自血管鈣化與骨骼生物學實驗交集所產生的數據互補。

Aortic Calcifications Linked W

By Yael Waknine
Medscape Medical News

Sept. 13, 2004 — Aortic calcifications are a strong predictor for low bone density and fragility fractures of the hip and spine in postmenopausal women, according to the results of a retrospective, longitudinal study published in the September issue of the Journal of Clinical Endocrinology and Metabolism.

"Atherosclerosis and osteoporosis are polygenic, degenerative diseases common in the elderly population, and their prevalence is increasing," write Eloy Schulz, MD, from the Department of Radiology at Loma Linda University Medical Center in California, and colleagues. "Because they are common, both diseases are frequently observed in the same individual."

Although multiple reports have suggested a link between atherosclerosis and osteoporosis, making an unequivocal connection between the two conditions has been difficult, the authors point out. In this study, investigators used computed tomography (CT) to quantify the mineral in arterial and skeletal tissues with precision and accuracy, avoiding the limitations of conventional radiography and photon or x-ray absorptiometry that were used in the past.

The CTs and medical records of 2,348 healthy postmenopausal women aged 50 years and older were examined for measures of aortic calcification, values for bone mineral density (BMD), and number of fragility fractures. A subgroup of women remaining healthy (mean age, 65.2 ± 9.8 years) and having repeat CT studies at 2.1 ± 1.9 years after the initial examination constituted the longitudinal group in the study.

Of the initial cohort, 70% had osteoporosis, 30% had at least one vertebral fracture, and 9% had at least one hip fracture. After adjusting for age, increases in aortic calcification predicted 26.1% of the variance in BMD loss (P < .001).

Aortic calcification was found to be directly related to the number of fractures. Women with aortic calcification were an estimated 4.8 times more likely to sustain a vertebral fracture compared with women having no calcification (95% confidence interval [CI], 3.6 - 6.5).

Women with aortic calcification were 2.9 times more likely to sustain a fracture of the proximal femur (95% CI, 1.8 - 4.8), and they experienced a higher rate of bilateral fractures (19.8% vs. 14.3%; P = .04) compared with women who did not have calcification.

Results within the longitudinal cohort were similar: the annual increase in calcification accounted for 47% of the variance in the rate of bone loss (P < .001). Within quartiles based on the percentage annual change for calcification, calcification progression and bone loss were strongly associated. Women in the highest calcification rate quartile had significantly higher bone loss than did those of similar age in the lowest quartile (5.3% vs. 1.3% annually; P < .001).

"The findings of this study, showing that beyond the aging process there is a significant relation between atherosclerosis and osteoporosis, should encourage research on the mechanisms regulating mineral deposition in connective tissues...[and] effective prevention and treatment strategies that may simultaneously modify the risk for these two common conditions," the authors note, adding that the connection between calcified plaques and bone loss in young postmenopausal women should aid in early identification of those at risk for osteoporosis and fractures.

The study was supported in part by grants from the National Institutes of Health and the Department of the Army.

In an accompanying editorial, Mishaela R. Rubin, MD, and Shonni J. Silverberg, MD, from Columbia University in New York City, write, "The use of CT technology for both aortic and spine measurements in this study makes it an important addition to the existing literature."

Suggesting further investigation of the association in men and women with a larger BMD spectrum, and the use of larger, prospective studies with a standardized interscan time to confirm the current longitudinal results, Drs. Rubin and Silverberg conclude, "Such clinical observations will complement the growing body of data emerging from the laboratory on the intersection of vascular calcification and bone biology."

J Clin Endocrinol Metab. 2004;89:4243-4245, 4246-4253

Reviewed by Gary D. Vogin, MD

    
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