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Regular Napping Linked to Greater Brain Volume
Daily napping may help preserve brain health, new research suggests.
Investigators at University College London, United Kingdom, and the University of the Republic of Uruguay, Montevideo, found individuals genetically predisposed to regular napping had larger total brain volume, a surrogate of better cognitive health.
"Our results suggest that napping may improve brain health," first author Valentina Paz, MSc, a PhD candidate at the University of the Republic of Uruguay in Montevideo told Medscape Medical News. "Specifically, our work revealed a 15.8 cubic cm increase in total brain volume with more frequent daytime napping," she said.
The findings were published online June 19 in Sleep Health.
Higher Brain Volume
Previous studies examining the potential link between napping and cognition in older adults have yielded conflicting results.
To clarify this association Paz and colleagues used Mendelian randomization to study DNA samples, cognitive outcomes, and functional magnetic resonance imaging (fMRI) data in participants from the ongoing UK Biobank Study.
Starting with data from 378,932 study participants (mean age 57), investigators compared measures of brain health and cognition of those who are more genetically programmed to nap with people who did not have these genetic variations.
More specifically, the investigators examined 97 sections of genetic code previously linked to the likelihood of regular napping and correlated these results with fMRI and cognitive outcomes between those genetically predisposed to take regular naps and those who weren't.
Study outcomes included total brain volume, hippocampal volume, reaction time, and visual memory.
The final study sample included 35,080 with neuroimaging, cognitive assessment, and genotype data.
The researchers estimated that the average difference in brain volume between individuals genetically programmed to be habitual nappers and those who were not was equivalent to 15.8 cubic cm, or 2.6-6.5 years of aging.
However, there was no difference in the other three outcomes — hippocampal volume, reaction time, and visual processing — between the two study groups.
注释：
predispose: v
表示" (使)易罹患；(使)预先偏向于"，means "make susceptible"，如：The inhabitants are predisposed to rheumatism by the damp climate. 因气候潮湿，居民易患风湿症。
surrogate: n
表示"代理人；代用品"，means "someone who takes the place of another person"，如：I do not know if your company has surrogate in our country. 我不知道贵公司在我国是否有代理。
resonance: n
表示" 共鸣；共振；反响"，means " quality of being resonant"，如：His voice can produce a great resonance. 他的声音能发出深沉的共鸣声。
hippocampal: adj
表示"海马趾的"，如：Hippocampal Damage in Mouse and Human Forms of Systemic Autoimmune Disease. 系统性自身免疫性疾病的海马损伤。
neuroimaging: n
表示"神经影像"，如：Tumors were diagnosed by neuroimaging and pathological examinatons. 所有病人都经神经影像学和病理学检查确诊。
genotype: n
表示" 基因型；遗传型"，means "a group of organisms sharing a specific genetic constitution"，如：The genotype of the individual is permanently set. 个体的基因型就永久地被固定下来。
中文简要说明：
现代人每天需要消化大量信息，负担是过去农业时代的好几倍，如何增进脑力便成了重要课题。国外一项医学研究指出，有午睡习惯的人「脑容量」比起一般人多出15.8立方公分，意味着认知能力更强大。这项研究于今年6月发表在《睡眠健康》（Sleep Health）期刊。
根据美国知名医学网站Medscape报导，英国和乌拉圭的研究团队以英国人类基因数据库中约38万人为样本，分为「有午睡基因」和「没有午睡基因」两组，检视这些人的大脑体积、海马回（负责保管短期记忆和空间定位）体积、反应时间和视觉记忆。
研究发现，比起「没有午睡基因」的人，「有午睡基因」者大脑体积平均多了15.8立方公分，这个差异相当于逆龄2.6至6.5年。
不过，在海马回体积、反应时间和视觉记忆方面，是否午睡则没有任何影响。
研究的第一作者、乌拉圭共和大学（University of the Republic of Uruguay in Montevideo）博士生帕兹（Valentina Paz）表示，这项研究显示中午小睡一下，「有可能增进大脑的认知健康」。
未参与研究的英国神经科学会（British Neuroscience Association）主席史派尔斯-琼斯（Tara Spires-Jones）则认为，研究结果说明睡眠与大脑健康的关联，也就是说，充足的睡眠对维持认知健康是非常重要的，但她也不忘提醒，这项研究还有一些不足之处，像是参与者通报的午睡习惯未必正确，以及午睡与认知的基因印记大幅重迭、导致因果关系薄弱等，未来仍有进一步发展的必要。
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