作者：Lisa Nainggolan
出處：WebMD醫學新聞
December 24, 2008 — 根據年輕成人發生冠狀動脈風險(Coronary Artery Risk Development in Young Adults，CARDIA)研究(註[1])的新資料，每晚多睡1小時可以減少33%發生冠狀動脈鈣化(coronary artery calcification，CAC)的風險。Christopher Ryan King(伊利諾州芝加哥大學)等人在12月24日的美國醫學會期刊中報告他們的研究發現。
資深作者Diane S Lauderdale醫師(芝加哥大學)向heartwire表示，這是第一篇客觀連結測量睡眠期間與心臟疾病標記的研究；她表示，額外一小時睡眠的好處相當於降低16.5 mm Hg的收縮壓，這的確是相當驚人的效果。
她們有許多關於睡眠期間和CAC之關聯的理論，但她表示，這是一個觀察研究，需要以其他族群研究來確認此結果；再者，除非我們瞭解背後的機轉，我們不曉得它是否有因果關係，所以無法提出哪些介入方法有效。
【較長的睡眠時間顯著降低CAC風險】
King等人使用CARDIA研究的資料，這個持續進行的健康志願者研究始於1985年。目前的研究著眼於495位研究對象，指定評估發生冠狀動脈疾病之各種因素的長期影響。
參與者接受兩次「電子束電腦斷層掃描(electron-beam computed-tomography，EBCT) 」，用來評估有無發生CAC，兩次掃描間隔五年。他們也填寫睡眠問卷，睡眠時間則以儀器測量，且在這五年期間參與六個晚上的睡眠研究，運用的技術稱為「腕動計(Wrist. actigraphy ) 」 ，上有動作感測器— 配戴方式如同一只手錶— 可評估實際睡眠期間。Lauderdale醫師表示，此方法比自我報告提供更準確的測量規律睡眠行為。
她解釋，幾乎每個研究對象都使用腕動計測量兩次，每次間隔至少一年，每次測量三個晚上，包括兩晚於週間以及一晚於週末，以對正常睡眠模式獲得良好的瞭解。她指出，每晚之間有許多變化，但是大多數人的平均值相似。
在五年的追蹤期間，約有12%的研究對象首次發生CAC。每晚睡眠不到五小時者有27%發現有鈣化的動脈，睡眠五至七小時者有11%發生，睡眠超過七小時者有6%發生。
測得的睡眠時間越長，與減少鈣化顯著相關(校正勝算比0.67; p=0.01)。女性的睡眠好處較大，與種族無關。
【與此關聯有關的三個理論】
Lauderdale醫師向 heartwire 表示，她們嘗試進行解釋。開始時有關各種生理測量的資料很少。我們以統計方式嘗試是否可以從中獲得有關機轉的暗示，但我們徒勞無功，這相當令我們驚訝，因此我們提出三個看似合理的理論來討論，但還需要進一步確認。
她表示，首先，可能只是因為未測得的因素導致。她解釋，我們對於影響人類睡眠的因素仍所知有限—健康、生理因素、生活型態等等—所以可能有些因素會一起影響人類睡眠以及CAC風險；那樣的話，它就不是直接關聯，單單改變睡眠習慣將不會改變你發生CAC的風險。
她表示，其次，介入因素可能是可體松值。我們從它處得知，短睡眠時間會增加可體松值，其他研究認為，高可體松值是CAD的風險因素。不過，在此研究中，他們並沒有可以探究此一可能性的相關資料。
最後，她表示，可能是因為血壓。睡眠時血壓下降，所以睡眠少者的夜間血壓下降時間可能較短，導致他們的24小時平均血壓相對高於日間測量值。我們偏好這個假設，但我們沒有可以研究的資料，如同其他研究，我們只有對有藥物史的人測量血壓。
【每晚至少睡六小時】
如果後續研究確認此發現，Lauderdale 醫師表示，重點將在研究睡眠是否可以調節鈣化累積率、且觀察睡眠是否實際與長期冠狀疾病事件有關。
研究者指出，如果證明此關聯，需進行介入研究，以指引臨床建議。
Lauderdale 醫師結論表示，這是一個有新發現的小型研究，我們樂見以其他研究族群再現；不過此研究已足以提出此論點。
雖然總是有一些誘惑讓人睡眠減少，但有越來越多證據顯示，睡眠時間少可能會有一些健康上的後果。雖然單就此一研究無法證明睡眠少導致冠狀動脈疾病，但每晚睡眠至少六小時是安全的建議。
資料來源
1. King CR, Knutson KL, Rathouz PJ等人。短睡眠時間與偶發冠狀動脈鈣化(Short sleep duration and incident coronary artery calcification)。 JAMA. 2008;300:2859-2866.
Another Reason to Get 40 Winks? Reduced CAC
By Lisa Nainggolan
Medscape Medical News
December 24, 2008 — One extra hour of sleep per night is associated with a 33% reduction in the development of coronary artery calcification (CAC), according to a new look at data from the Coronary Artery Risk Development in Young Adults (CARDIA) study [1]. Christopher Ryan King (University of Chicago, IL) and colleagues report their findings in the December 24, 2008, issue of the Journal of the American Medical Association.
Senior author Dr Diane S Lauderdale (University of Chicago) told heartwire that this is the first study to objectively link measured sleep duration to a marker for heart disease. The benefit of one hour of additional sleep was comparable to the gains from lowering systolic blood pressure by 16.5 mm Hg, she said. "It really was a surprisingly strong effect," she commented.
She and her colleagues have a number of theories as to how sleep duration may be linked to CAC, but she cautioned that this was an observational study and that the results need to be confirmed in other populations. "And, until we understand the mechanism behind this, we don't know whether it's a causal association and so can't say whether intervening will have any effect," she added.
Longer Sleep Duration Significantly Associated With Lower CAC
King and colleagues used data from the CARDIA study, an ongoing project using healthy volunteers begun in 1985. The current research focused on 495 participants and was designed to assess the long-term impact of various factors on the development of coronary artery disease.
Participants underwent two electron-beam computed-tomography (EBCT) scans, designed to assess the buildup of CAC, five years apart. They also filled out sleep questionnaires, kept a log of their hours in bed, and participated in six nights of sleep studies during the course of the five years, using a technique called wrist actigraphy that uses a motion sensor — worn like a watch — to estimate actual sleep duration. This approach provides a more accurate measure of routine sleep behavior than self-reported sleep, said Lauderdale.
She explained that almost everyone in the study had their sleep assessed by actigraphy twice, at least a year apart, and for three nights at a time, including two weeknights and one weekend night, to give a good snapshot of normal sleep patterns. "There was a great deal of night-to-night variation," she noted, "but the underlying average in each wave was similar for most people."
About 12% of those in the study first developed CAC over five years of follow-up. Calcified arteries were found in 27% of those who slept less than five hours a night, dropping to 11% in those who slept five to seven hours, and just 6% for those who slept more than seven hours a night.
Longer measured sleep duration was thus significantly associated with reduced calcification (adjusted odds ratio 0.67; p=0.01). The benefits of sleep appeared greater for women but did not vary according to race.
Three Theories as to the Link
Lauderdale told heartwire that she and her colleagues had tried to look for explanations. "There was a fair amount of data at baseline about different physiologic measurements. We tried, statistically, to see whether we could get a hint of what the mechanism was, but nothing that we looked at had any effect at all, which surprised us.
"So we've come up with three theories that seem plausible to us but would require confirmation," she noted.
First, she said, it's possible that the association is simply due to unmeasured confounding. "We still have a poor idea of what factors influence how much people sleep — health, psychological factors, lifestyle, etc — so it's possible that some combination of factors that influences how much people sleep also influences their risk of CAC. In that case, it's not a direct association, and just changing your sleep habits isn't going to change your risk of developing CAC," she explained.
Second, the intervening factor could be cortisol levels, she said. "We know from elsewhere that short sleep duration raises cortisol levels, and other studies suggest that high cortisol levels are a risk factor for CAD." However, in this study, they did not have the data to explore this possibility, she noted.
Finally, "It could be blood pressure," she said. "BP [blood pressure] dips when people sleep, so it's possible that people who sleep less don't have as prolonged or as steep a dip in their BP at night, so that their average 24-hour BP is relatively higher than the daytime measure makes it look. We like this hypothesis, but we don't have the data to investigate it because, like most studies, we just measured BP when people had their medical exams."
Get at Least Six Hours of Sleep a Night
If future studies do confirm their findings, Lauderdale said it will be important to look at whether sleep moderates the rate at which calcification accumulates and whether objective sleep actually ties to coronary disease event outcomes over the long term.
"If this association is borne out, interventional studies will be needed to guide clinical advice," the researchers add.
In conclusion, Lauderdale said: "This was a small study and a new finding, so we would love to see it duplicated in another study population. But there is enough here to make a point.
"Although there are constant temptations to sleep less, there is a growing body of evidence that short sleep may have subtle health consequences. Although this single study does not prove that short sleep leads to coronary artery disease, it is safe to recommend at least six hours of sleep a night."
Source
King CR, Knutson KL, Rathouz PJ, et al. Short sleep duration and incident coronary artery calcification. JAMA. 2008;300:2859-2866.
The complete contents of Heartwire, a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.
[ 本帖最後由 goodcat1111 於 2009-1-8 22:25 編輯 ] |
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