睡眠模式的明顯改變可以影響死亡率風險


  November 27, 2007 — 根據登載於12月1日的睡眠(Sleep)期刊中的一篇研究,明顯地改變正常睡眠模式—不論是睡太多或睡太少—都會增加死亡風險。
  
  研究發現夜間睡眠時數從6、7或8小時減少會增加兩倍的心血管死亡風險,若從7或8小時增加則會增加兩倍的非心血管死亡風險。
  
  本研究者主要作者,英國倫敦學院大學流行病學與公共衛生系資深研究員Jane E. Ferrie博士表示,如果你有規律的睡眠模式 —6、7或8小時— 且一直如此維持,可以保護免於太早死亡;如果你變得睡超過9小時,會增加各種原因導致的死亡,非心血管之死亡類型會增加;如果你變得睡眠減少,會增加心血管死亡風險。
  
  【改變睡眠模式】
  Ferrie醫師向Medscape精神病學表示,相較於其他有關睡眠與死亡率的研究,這是第一個研究睡眠模式改變對健康之影響的研究。
  
  以35-55歲的倫敦公務員為基礎的Whitehall II研究,在1985年開始招募病患進行第一期篩選,直到1988年初;在1992至1993進行第3期的資料蒐集;兩期均包括臨床評估,測量心血管風險因素(身體質量指數、收縮壓和舒張壓、總膽固醇),以及自我評答問卷,問題包括睡眠時間;第一期的參與者的選項有:小於等於5 小時;6小時;7小時; 8小時;以及大於等於9小時。第三期中,睡眠時數之填答類別從1 到12小時,以與第一期區別。
  
  研究者在第一期蒐集9781位參與者,第三期蒐集7729位參與者的資料;死亡率資料來自國家健康服務中心迄2004年9月為止的資料,第一期的是17.1年,第三期的是11.8年。
  
  【兩倍的死亡風險】
  研究發現兩期的睡眠與後續的各種原因死亡有 U型關聯,也顯示睡眠時間從6、7或8小時減少,會增加兩倍的心血管死亡風險(心血管死亡的完整校正風險比是2.04) ,從7或8小時增加,則會提高兩倍的非心血管死亡風險 (非心血管死亡的完整校正風險比是2.06)。
  
  (他們指出,因為研究者沒有足夠的資料將6、7或8小時的睡眠分類,所以視為同屬於“正常”睡眠組。)
  
  作者指出,減少睡眠時數與升高的心血管死亡率之間的關聯看似有點道理:短睡眠時數是體重增加、胰島素阻抗、第二型糖尿病的風險因素;睡眠時短也伴隨可體松(cortisol) 增加,以及異常生長激素分泌,也伴有高血壓和一些心血管疾病;Ferrie 醫師指出,這顯然有那麼一回事。
  
  【死亡與睡眠時間長之間的關係不清楚】
  不過,死亡與長時間睡眠之間的關係並沒那麼清楚,Ferrie 醫師表示,在另一方面,除非我們在非心血管死亡組有足夠的死亡案例,這需要進一步探索;我們真的不清楚是何原因,不過,長時間睡眠與憂鬱有關,研究者需探究病患睡眠時間變長後,癌症死亡或創傷死亡風險有無增加。
  
  她指出,這篇新的研究即將引起睡眠研究者的興趣,我認為有許多人對此有興趣,希望他們能闡明那些非心血管死亡的原因。
  
  她表示,明顯的改變睡眠模式會是許多潛在疾病的警戒訊號,如果有人就醫並表示從原本正常的睡眠模式變成睡太短或睡太多的話,這可能會有一些問題值得注意。
  
  她表示,睡眠專家經常討論的是每晚規律睡眠9個小時以上對人們的好處。
  
  共同作者Francesco P. Cappuccio醫師,掌理Warwick Medical School醫學院所資助的Cephalon Chai,這來自某公司的贊助;主席的運作完全不受公司干涉,可以自由的決定研究計畫;Cephalon 與作者並無任何關係,主席完全學術獨立;其他作者宣稱無利益衝突。

Significant Changes in Sleep P

By Pauline Anderson
Medscape Medical News

November 27, 2007 — Significantly changing normal sleep patterns — either getting much more or much less sleep — increases the risk for mortality, according to a new study appearing in the December 1 issue of Sleep.

The study found that decreasing nightly sleep from 6, 7, or 8 hours doubles the risk for cardiovascular death, while increasing sleep from 7 or 8 hours doubles the risk for noncardiovascular death.

“If you have a regular pattern — 6, 7, or 8 hours — and you maintain that over time, that’s protective against premature mortality,” said Jane E. Ferrie, PhD, a senior research fellow in department of epidemiology and public health at University College, London, in the United Kingdom, and lead author of the study. “If you move out of that to the 9-hours-or-more category, that seems to increase all-cause mortality and the group of deaths that increases is the noncardiovascular deaths. If you go to the short end of the spectrum, you increase your risk for cardiovascular mortality.”

Changing Sleep Patterns

While other studies have looked at associations of sleep and mortality, this is the first to look at the health effects of significant changes in sleep patterns over time, Dr. Ferrie told Medscape Psychiatry.

The Whitehall II study of London-based civil servants aged 35 to 55 years began enrolling participants in 1985 with baseline (phase 1) screening continuing until early 1988. Data collection for phase 3 took place in 1992–1993. Both phases involved a clinical evaluation, including measurement of cardiovascular risk factors (body-mass index, systolic and diastolic blood pressure, total cholesterol), and self-administered questionnaires that included questions about duration of sleep. Participants in phase 1 selected from these sleep categories; 5 hours or less; 6 hours; 7 hours; 8 hours; and 9 hours or more. For phase 3, the response categories of 1 to 12 hours of sleep were collapsed to form categories identical to the initial phase.

Researchers collected data on 9781 participants at phase 1 and on 7729 in phase 3. Mortality data were available from the National Health Services central registry until September 2004, a mean of 17.1 years from phase 1 and 11.8 years from phase 3.

Double Mortality Risk

The study found a U-shaped association in both phases between sleep and subsequent all-cause mortality. It also showed that decreasing sleep from 6, 7, or 8 hours doubled the cardiovascular mortality risk (fully adjusted hazard ratio for cardiovascular disease of 2.04) and that increasing sleep from 7 or 8 hours also doubled the risk for death, but for noncardiovascular mortality (fully adjusted hazard ratio for noncardiovascular deaths of 2.06).

(“Normal” sleep categories of 6, 7, and 8 hours had to be pooled because researchers did not have enough data to look at the categories separately, they note.)

The link between decreased hours of sleep and higher cardiovascular mortality risk seems to make some sense: Short sleep duration is a risk factor for weight gain, insulin resistance, and type 2 diabetes, the authors write. Short sleep is also accompanied by increased cortisol levels and abnormal growth hormone secretion and has been associated with hypertension and some cardiovascular diseases, they said. “It’s fairly obvious what’s going on there,” Dr. Ferrie added.

Link Between Deaths and Long Sleep Unclear

However, the link between deaths and longer sleep patterns is not as clear. “At the other end of the spectrum, until we have sufficient deaths where we can see what is making up that noncardiovascular group of deaths, we can’t explore that any further,” said Dr. Ferrie. “We really don’t know what’s driving that.” She did say, though, that long sleep is associated with depression and that researchers may want to take a look at the role of increased cancer deaths or trauma deaths among patients changing to a long sleep pattern.

This new research is bound to generate a lot of interest among sleep researchers, she added. “I think lot of people will look at this . . . and hopefully they will be able to elucidate what’s making up those noncardiovascular deaths,” said Dr. Ferrie.

A significant change in sleep patterns may be a red flag for some underlying disease, she said. “If somebody comes to you and they’re now reporting having moved from a normal sleep pattern either to the very short end of the sleep spectrum or the long end of the sleep spectrum and that appears to be a pattern that’s continuing over time and is not their regular pattern, then that is probably a marker of something.”

Sleep experts are even discussing the merits of restricting sleep of people who regularly sleep 9 or more hours per night, she said.

Coauthor Francesco P. Cappuccio, MD, holds the Cephalon Chair, an endowed post at Warwick Medical School, in Coventry, United Kingdom, the result of a donation from the company. The appointment to the chair was made entirely independently of the company and the postholder is free to devise his own program of research. Cephalon does not have any stake in IP associated with the postholder, and the chair has complete academic independence from the company. Other authors declare no conflicts of interest.

Sleep. 2007;30:1659-1666.

    
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