Socially active people who were not easily stressed had a 50 percent lower risk of developing dementia compared with men and women who were isolated¹ and prone² to distress³, they reported in the journal Neurology.

"In the past, studies have shown that chronic⁴ distress can affect parts of the brain, such as the hippocampus, possibly leading to dementia," Hui-Xin Wang of the Karolinska Institute in Sweden, who led the study, said in a statement.

"But our findings suggest that having a calm and outgoing personality in combination with a socially active lifestyle may decrease the risk of developing dementia even further."

An estimated 24 million people worldwide have the memory loss, problems with orientation⁵ and other symptoms that signal Alzheimer's disease and other forms of dementia.

Researchers believe the number of people with dementia may quadruple by 2040, underlining the importance of better understanding the condition.

The Swedish study involved 506 elderly people who did not have dementia when first examined. The volunteers were given questionnaires about their personality traits and lifestyles and then tracked for six years.

Over that time, 144 people developed dementia with more socially active and less stressed men and women 50 percent less likely to be diagnosed with the condition.

"The good news is, lifestyle factors can be modified as opposed to genetic⁶ factors which cannot be controlled," Wang said. "But these are early results, so how exactly mental attitude influences risk for dementia is not clear."

研究人员在《神经学》期刊上称，常参加社交活动的人不易感到压力，他们患痴呆症的风险比那些孤僻、易抑郁的人低50%。

负责该项研究的瑞典卡罗林斯卡学院的王慧欣（音译）在研究报告中称：“此前的研究证实，长期抑郁会损害大脑的海马体等部位，从而可能会导致痴呆。”

“但我们的研究表明，平和外向的性格再加上爱社交的生活方式可能会降低患痴呆症的风险。”

据估计，目前全球约有2400万人有失忆、不辨方向等阿尔兹海默症等各种形式痴呆症的症状。

研究人员认为，到2040年全球的痴呆症患者数量可能将翻两番，因此必须引起重视。

该研究共对506位初诊时未患痴呆症的老年人进行了调查。研究人员让他们填写了一份有关性格特点和生活方式的调查问卷，并对他们进行了为期六年的跟踪调查。

在此期间，共有144人患上痴呆症，而常参加社交活动且压力较小的人患此病的几率要低50%。

王慧欣说：“值得庆幸的是，生活方式可以改变，不像基因那样无法控制。但这仅仅是初期研究成果，所以精神状态究竟在多大程度上影响患痴呆症的风险目前还不清楚。”