A group of Finnish scientists found that those working more than 55 hours a week had poorer cognitive performance than those who worked 40 hours a week (standard working hour). It's not clear why working long hours might have a negative effect on the brain. But researchers say that it could be due to increased sleeping problems, depression, an unhealthy lifestyle and a raised risk of cardiovascular disease, probably linked to stress. The research work was publish on the January issue of American Journal of Epidemiology.
芬兰一组科学家通过跟踪调查发现，相对于标准工作时长（每周40小时），每周工作超过55小时的人在认知能力上会出现障碍。目前还不清楚长时间工作对大脑造成不良影响的原因，但是有可能和睡眠不足，精神压抑，不健康生活习惯以及因精神紧张而引发的心血管疾病有关。
原始研究论文见：
http://aje.oxfordjournals.org/cgi/content/full/169/5/596
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