| 作者：Allison Gandey | | 出處：WebMD醫學新聞 |
August 29, 2008 — 一項新研究結果顯示，隨著人們變老，他們會體驗到認知功能下降的速度變快，即使他們並沒有癡呆的問題。
主要作者、來自瑞典哥丁堡大學精神研究部門的Valgeir Thorvaldsson碩士向Medscape神經與精神學表示，根據過去的研究結果，我們預期看到過世前認知能力的下降速度加快，然而，該速度加快的時間比我們預期的早。
Thorvaldsson先生指出，特別是直覺印象，開始最終下降的平均值為過世前15年；他表示，這項發現代表，老年病患影響認知能力的腦部變化發生在很長的一段時間之前。
他們的研究線上發表於8月27日的神經學期刊。
【改變的速度】
在這項研究中，研究團隊希望找出認知功能開始下降的時間，以及老年認知能力與死亡率有關的變化；他們針對288位於1901年到1902年出生於歌丁堡的居民進行研究，這些居民中，沒有罹患癡呆症的個體們從70歲後一直接受後續追蹤，直到死亡。
研究者針對三種不同的認知功能，口語能力、空間判斷能力與直覺印象能力進行測試，他們透過一種全自動分段線性混合模式方法來進行改變點的分析；該團隊使用這來找出代表與死亡率相關個體變化加速的轉折點。
【最終下降的開始】 認知功能的改變
| 過世前年份 | 口語能力
| 6.6 | 空間判斷能力
| 7.8 | 直覺認知功能
| 14.8 |
研究者指出，在他們的研究中，最終下降期的開始，比來自其他類研究估計的長；他們表示，一項研究發現，過世前3.33年的語意記憶力下降、過世前6年有視覺空間能力下降、以及僅於過世前2.75年有直覺認知功能下降速度加快的證據（Neurology. 2003; 60:1782-1787）。
另外一項他們引用的研究結果發現，片段記憶的下降期約在過世前8.4年附近（Eur Psychol. 2006;11: 172-81）；研究者表示，我們的研究發現，口語能力及空間能力的改變與估計的差不多，但是我們對於直覺感受能力下降速度的估計則是較長的。
處理速度的測量典型地是與年齡相關改變、與個體間年齡差異最敏感的指標之一；我們的發現是，速度是與死亡率相關線性下降最早期的一個指標。
【神經生物學指標作為最終下降仍是未知的】
研究者表示，有許多因素可能可以解釋這些發現，心臟血管疾病與未偵測到的臨床前癡呆就是兩個例子。
醫療負擔的上升與老年病患的孱弱，經常使得他們活動力下降，以及缺乏運動及認知功能的刺激，這都可能加速認知功能下降的速度；他們寫到，需要後續的研究來釐清這些問題，並且確認最終下降的神經生物標記。
Thorvaldsson先生解釋，這項縱向研究的一個限制是，這項研究遠在35年之前開始，當時我們並沒有太多有關於腦部病理學的資訊，這些資訊可以透過腦部斷層掃描或是腦脊髓液的生物標記獲得。
他附帶表示，另一個限制是，相關的批評可能會把重點放在我們的檢測並未針對所有的面向；舉例來說，片段記憶已知在老化的過程中與許多疾病中是非常敏感的。
Thorvaldsson先生建議，需要更多的研究來確認問題原因，並尋找預防與治療認知功能下降的問題；他指出，因為我們現在知道完整認知功能對於老年病患維持健康與日常生活功能的重要性。
研究者們表示無相關資金上的往來。 | |
Decline in Mental Skills Begins Years Before Death
By Allison Gandey
Medscape Medical News
August 29, 2008 — As people grow older, they experience a substantial acceleration in cognitive decline — even if they don't have dementia, a new study suggests.
"Based on previous studies, we expected to see an acceleration in the decline in cognitive abilities before death," lead author Valgeir Thorvaldsson, from the department of psychology at Goteborg University, in Sweden, told Medscape Neurology & Neurosurgery. "However, the onset of this acceleration was much earlier than we expected."
Mr. Thorvaldsson said this was especially the case for perceptual speed, where the average onset of terminal decline was almost 15 years before death.
"The findings imply that the brain changes that influence cognitive abilities in old age occur over a relatively long period of time," he noted.
Their findings were published online August 27 in Neurology.
Rate of Change
In this investigation, the researchers wanted to identify the time of onset and rate of mortality-related change in cognitive abilities in later life. They studied 288 people in Goteborg who were born in 1901 and 1902. The individuals, who did not have dementia, were followed from age 70 until death.
Investigators tested participants on 3 cognitive abilities — verbal skills, spatial ability, and perceptual speed. They performed change-point analyses using an automated piecewise linear mixed-modeling approach. The group used this to identify the inflection point indicating accelerated within-person change related to mortality.
Onset of Terminal Decline | Cognitive Ability | Years Before Death | | Verbal skills | 6.6 | | Spatial ability | 7.8 | | Perceptual speed | 14.8 |
The researchers point out that the terminal-decline phases in their work were considerably longer than estimates from similar studies. "One study found evidence for terminal decline 3.33 years before death in semantic memory, 6 years in visuospatial ability, and only 2.75 years in perceptual speed," they note (Neurology. 2003; 60:1782-1787).
Another study they cite found a terminal-decline phase on episodic memory ranging over 8.4 years before death (Eur Psychol. 2006;11:172-181). "Our findings for both verbal ability and spatial ability are similar to this estimate, but our estimate for perceptual speed is much longer," note the researchers.
Measures of processing speed are typically 1 of the most sensitive markers of age-related change and between-person age differences, they point out. "Our finding that speed was the earliest marker of mortality-related decline is in line with these findings."
Neurobiological Markers for Terminal Decline Unknown
There are a number of factors that might explain these findings, note the researchers. Cardiovascular conditions and undetected preclinical dementia are 2 examples.
Increased medical burden and frailty in old age often lead to inactivity and a lack of physical exercise and cognitive stimulation, which can accelerate decline. "Subsequent studies need to illuminate these issues and identify the neurobiological markers for terminal decline," they note.
"One of the limitations to this longitudinal study that started more than 35 years ago is that we do not have detailed information about brain pathology from brain scans or indexes of biomarker from cerebrospinal fluids," Mr. Thorvaldsson explained.
"Another limitation that critics might address is that our tests didn't cover all cognitive domains; for example, episodic memory known to be highly sensitive for change in aging and in various diseases," he added.
Mr. Thorvaldsson recommends additional study to identify the causes of the problem and to find methods to prevent or treat decline. Because, he noted, "we know how important intact cognitive capabilities are for well-being and everyday-life functioning in old age."
The researchers have disclosed no relevant financial relationships.
Neurology. Published online August 27, 2008. Abstract
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[ 本帖最後由 goodcat1111 於 2008-9-9 22:34 編輯 ] |
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