Physical activity is a protective factor against brain atrophy, while loss of brain volume could also be a determinant of physical activity. Therefore, we aimed to explore the bidirectional association of physical activity with brain structures in middle-aged and older adults from the UK Biobank. Overall, 3027 participants (62.45 ± 7.27 years old, 51.3% females) had data at two time points. Hippocampal volume was associated with total (β=0.048, p=0.016) and household (β=0.075, p<0.001) physical activity. Global fractional anisotropy (β=0.042, p=0.028) was also associated with household physical activity. In the opposite direction, walking was negatively associated with white matter volume (β=-0.026, p=0.008). All these associations were confirmed by the linear mixed models. Interestingly, sports at baseline were linked to hippocampal and frontal cortex volumes at follow-up but these associations disappeared after adjusting for multiple comparisons (p>0.104). In conclusion, we found more consistent evidence that a healthier brain structure predicted higher physical activity levels than for the inverse, more established relationship.

中文翻译：

---

大脑结构与身体活动之间的双向关系：英国生物银行的纵向分析

体力活动是防止脑萎缩的保护因素，而脑容量的减少也可能是体力活动的决定因素。因此，我们旨在探索英国生物银行中老年人体力活动与大脑结构的双向关联。总体而言，3027 名参与者（62.45 ± 7.27 岁，51.3% 女性）在两个时间点都有数据。海马体积与总体力活动（β=0.048，p=0.016）和家庭体力活动（β=0.075，p<0.001）相关。整体分数各向异性（β=0.042，p=0.028）也与家庭身体活动相关。相反，步行与白质体积呈负相关（β=-0.026，p=0.008）。所有这些关联均由线性混合模型证实。有趣的是，基线时的运动与随访时的海马和额叶皮层体积有关，但在调整多重比较后这些关联消失了（p>0.104）。总之，我们发现了更一致的证据表明，与相反的、更确定的关系相比，更健康的大脑结构预示着更高的身体活动水平。