慢性脱水与老年认知损伤及饮水干预

Chronic Dehydration and Regularly Drinking Water to Mitigate Age-Related Cognitive Impairment

老年认知损伤被认为是一个连续发展的病理生理学过程,包括轻度认知损伤前期(pre-mild cognitive impairment,pre-MCI)、轻度认知损伤(mild cognitive impairment,MCI)、阿尔茨海默病(Alzheimer’s disease,AD)三个阶段,慢性脱水是老年性痴呆患者共同具有的一种特征。红外线摄像监控C57 BL/6小鼠饮水频率和饮水量的结果显示,老龄鼠的饮水频率和饮水量均较年轻对照组显著减少(P<0.05,P<0.01)。一方面,认知损伤患者"口渴"的感受降低、记忆能力减退,被认为是造成老年慢性脱水的原因;脱水引起脑内细胞毒性代谢物如内源性甲醛等增加、积累,加重认知损伤,形成"脱水-认知损伤-脱水"的恶性循环。另一方面,体内甲醛浓度随老龄化(>65岁)而逐渐升高,且AD病人脑内甲醛含量也显著升高。研究表明,甲醛代谢失调所造成的中枢神经系统慢性损伤被认为是老年认知损伤的原因之一,合理饮水不但可以改善老龄化人群的慢性脱水状态,同时能够明显降低体内的甲醛浓度,防止甲醛过量对中枢神经系统的危害,因此,合理饮水习惯的建立,被认为是减缓中老年人慢性脱水和体内细胞毒性代谢产物累积的方法之一,也可能在某种程度上,起到干预老年认知损伤早期发生发展的效果。

Age-related cognitive impairment undergoes a continuous progression:pre-mild cognitive impairment(preMCI),mild cognitive impairment(MCI)and Alzheimer’s disease(AD). So far,chronic dehydration is regarded as a common symptom for the patients with age-related cognitive impairment,in particular of those with AD. Monitored with an infrared-CCD camera,a marked decrease in the drinking frequency(P<0.05)and water consumption quantity(P<0.01)of 10-month old C57 BL/6 mice was observed in comparison with that of 1-month old counterparts. On the one hand,chronic dehydration for the patients may be resulted from their declined of the perception of“thirsty”and loss of memory. On the other hand,dehydration causes accumulation of cytotoxic metabolic compounds such as endogenous formaldehyde,worsening cognitive impairment worse. The interaction between dehydration and cognitive impairment leads to a vicious circle. Furthermore,chronic impairment of central nervous system due to the disorder of formaldehyde metabolism is believed as one risk factor for age-related impairment because of the increase in endogenous formaldehyde with aging(>65 years old)and in the hippocampus of Alzheimer’s patients. Regularly drinking water relieves not only chronic dehydration for aging people,but also significantly decreases the concentration of endogenous formaldehyde, which may offer protection of central nervous system. Therefore,building the habit to regularly drink water should be emphasized at the early stage to relieve chronic dehydration and scavenge cytotoxic metabolic products including formaldehyde for aging people,which might be beneficial to mitigate age-related cognitive impairment at its early stage.