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作者：Fran Lowry  
出處：WebMD醫學新聞

　　December 17, 2009 — 活動血壓監測須在晚上醒來檢測，也會影響白天的活動，因而會影響血壓下降—血壓值降低一般發生在睡眠時。根據線上發表於12月17日美國腎臟學會臨床期刊(Clinical Journal of the American Society of Nephrology)的研究結果，這使得此項檢查在評估心血管疾病風險的信賴度降低。
　　
　　印第安那大學退伍軍人事務醫學中心的Rajiv Agarwal醫師與Robert Light寫道，活動血壓監測一般被用來評估血壓的晝夜變化模式，生理活動和睡眠週期會影響血壓的晝夜變化模式，監測血壓本身對於生理活動和睡眠的影響依舊未知，如果監測血壓會影響這些參數，那麼，監測方法本身也會影響血壓的晝夜變化模式。
　　
　　本研究的目標是，評估活動血壓監測對於睡眠期間、睡眠效率、日間活動等的影響。
　　
　　該研究包括103名有慢性腎臟病的退伍軍人，多數(97%)為男性，83%是白人，他們的平均身體質量指數為30 ± 4.7 kg/m2。
　　
　　研究者使用腕動計測量他們的生理活動。連續監測6-7天的活動之後，除了腕動計之外，研究對象接受活動血壓監測。
　　
　　1個月之後重複此步驟。
　　
　　研究者發現，當配戴活動血壓監測器時，病患夜間臥床時間減少(-92分鐘；P < .0001)，睡眠時間也減少(-98分鐘；P < .0001)。開始時最酣睡的病患，配戴監測器時醒來最多次。最酣睡者的入睡後清醒時間在開始時為41分鐘，配戴監測器時之後增加了24分鐘(P < .0001)，睡眠效益降低5% (開始時為82% ，配戴監測器時為77%；P = .02)。
　　
　　配戴監測器之後，病患的活動力也降低，日間久坐時間增加了27分鐘(P = .002)。
　　
　　作者們指出，配戴監測器引起的睡眠干擾也增加了血壓非下降時間(勝算比為10.5；P = .008)。
　　
　　他們寫道，我們的研究結果與解釋活動血壓監測下降模式有關，因為活動血壓監測會干擾睡眠，如果有較不會干擾的活動血壓監測方式，會比較有助於活動血壓監測的預測價值。
　　
　　作者們指出，該研究僅限於多數為年長與退休的退伍軍人，因此，活動力低於年輕人。因為活動血壓監測比較會影響睡眠特徵，他們認為，根據這個研究結果，活動血壓監測比較適合活動力較佳且睡眠較好的人。
　　
　　此外，作者們寫道，本研究排除病態肥胖病患，未進行多層次睡眠檢查，因此，我們無法就睡眠呼吸中止對於血壓未下降有無影響提出看法。
　　
　　作者們在結論中表示，血壓未下降有許多原因，慢性腎臟病患者的血壓未下降率最高，這有諸多原因，包括夜尿、夜間活動增加、增加產生症狀的活動、鈉敏感性。
　　
　　作者們結論表示，現在應將活動血壓監測引起的睡眠干擾列入血壓未下降的原因之一。
　　
　　VA Merit Review提供研究資金。Agarwal醫師與 Light先生皆宣告沒有相關財務關係。
　　
　　J Am Soc Nephrol. 線上發表於2009年12月17日。


Ambulatory Blood Pressure Monitoring Disrupts Sleep and Prevents Dipping

By Fran Lowry
Medscape Medical News

December 17, 2009 — Ambulatory blood pressure (BP) monitoring wakes people up at night and reduces their physical activity during the day, thus preventing dipping — the lowering of BP that usually occurs during sleep. This makes the test less reliable in assessing cardiovascular disease (CVD) risk, according to the results of a study published online December 17 in the Clinical Journal of the American Society of Nephrology.

"Ambulatory [BP] monitoring is commonly used to assess the circadian pattern of BP," write Rajiv Agarwal, MD, and Robert Light, BS, from Indiana University and Veterans Affairs Medical Center, Indianapolis. "Circadian BP pattern is influenced by physical activity and sleep cycle. The effect of BP monitoring itself on the level of physical activity and sleep remains unknown. If BP monitoring affects these parameters, then monitoring itself may influence the circadian BP pattern."

The goal of this study was to assess the effect of ambulatory BP monitoring on sleep duration, sleep efficiency, and daytime activity.

The study included 103 veterans with chronic kidney disease (CKD). Most (97%) were men, 83% were white, and their mean body mass index (BMI) was 30 ± 4.7 kg/m2.

The investigators used wrist actigraphy to measure physical activity. After 6 to 7 days of continuous activity monitoring, participants underwent ambulatory BP monitoring in addition to actigraphy.

This procedure was repeated after 1 month.

The researchers found that, when wearing the ambulatory BP monitor, patients spent less time in bed at night (?92 minutes; P < .0001) and slept less (?98 minutes; P < .0001). Patients who were the soundest sleepers at baseline were awakened the most when wearing the monitor. The wake-after-sleep-onset time of the soundest sleepers was 41 minutes at baseline, which increased by 24 minutes (P < .0001) when they were wearing the monitor. In addition, sleep efficiency was reduced by 5% (82% at baseline vs 77% with the monitor; P = .02).

Patients were also less active after they had been wearing the BP monitor. Sedentary time during the day increased by 27 minutes (P = .002).

The sleep disturbance caused by wearing the monitor also increased nondipping (odds ratio, 10.5; P = .008), the authors report.

"The results of our study are relevant for interpretation of ambulatory BP dipping patterns," they write. "Given that [ambulatory BP monitoring] is a cause of sleep disturbance, it is possible that a less intrusive method of [ambulatory BP monitoring] may better assess the prognostic value of [ambulatory BP monitoring]."

The study was limited to mostly older veterans who are generally retired, and therefore less physically active than younger individuals, the authors point out. Because ambulatory BP monitoring was most disruptive in subjects with better sleep characteristics, the results of this study might be more applicable to individuals who are more active and who sleep better, they suggest.

In addition, although morbidly obese patients were excluded from this study, polysomnography was not performed, "therefore we cannot comment on the role of sleep apnea on dipping or lack thereof," the authors write.

Nondipping BP has numerous causes, the authors write in their conclusion. Patients with CKD have the highest prevalence of nondipping, and this has numerous causes, including nocturia, increased physical activity at night, increased sympathetic activation, and sodium sensitivity.

"[Ambulatory BP monitoring]-induced sleep disturbance should now be added to the list of causes of nondipping," the authors conclude.

The study was supported by a grant from the VA Merit Review. Dr. Agarwal and Mr. Light have disclosed no relevant financial relationships.

J Am Soc Nephrol. Published online December 17, 2009.