Department of Neuromedicine and Movement Science, NTNU, Faculty of Medicine and Health Sciences, Trondheim N-7491, Norway; Department of Radiology and Nuclear Medicine, St Olav's Hospital, Trondheim University Hospital, Postboks 3250 Torgarden, Trondheim 7006, Norway.
Department of Electrical, Electronic, and Information Engineering 'Guglielmo Marconi', University of Bologna, Via dell'Università 50, Cesena 47521, Italy.
Neuroimage. 2022 Aug 1;256:119226. doi: 10.1016/j.neuroimage.2022.119226. Epub 2022 Apr 18.
Physical inactivity has been identified as an important risk factor for dementia. High levels of cardiorespiratory fitness (CRF) have been shown to reduce the risk of dementia. However, the mechanism by which exercise affects brain health is still debated. Fractal dimension (FD) is an index that quantifies the structural complexity of the brain. The purpose of this study was to investigate the effects of a 5-year exercise intervention on the structural complexity of the brain, measured through the FD, in a subset of 105 healthy older adults participating in the randomized controlled trial Generation 100 Study. The subjects were randomized into control, moderate intensity continuous training, and high intensity interval training groups. Both brain MRI and CRF were acquired at baseline and at 1-, 3- and 5-years follow-ups. Cortical thickness and volume data were extracted with FreeSurfer, and FD of the cortical lobes, cerebral and cerebellar gray and white matter were computed. CRF was measured as peak oxygen uptake (VO) using ergospirometry during graded maximal exercise testing. Linear mixed models were used to investigate exercise group differences and possible CRF effects on the brain's structural complexity. Associations between change over time in CRF and FD were performed if there was a significant association between CRF and FD. There were no effects of group membership on the structural complexity. However, we found a positive association between CRF and the cerebral gray matter FD (p < 0.001) and the temporal lobe gray matter FD (p < 0.001). This effect was not present for cortical thickness, suggesting that FD is a more sensitive index of structural changes. The change over time in CRF was associated with the change in temporal lobe gray matter FD from baseline to 5-year follow-up (p < 0.05). No association of the change was found between CRF and cerebral gray matter FD. These results demonstrated that entering old age with high and preserved CRF levels protected against loss of structural complexity in areas sensitive to aging and age-related pathology.
身体活动不足已被确定为痴呆的一个重要危险因素。较高水平的心肺适能（CRF）已被证明可降低痴呆风险。然而，运动影响大脑健康的机制仍存在争议。分形维数（FD）是量化大脑结构复杂性的指标。本研究旨在调查一项为期 5 年的运动干预对 105 名参加随机对照试验 Generation 100 研究的健康老年人亚组的大脑结构复杂性的影响，该研究通过 FD 进行测量。受试者被随机分为对照组、中等强度持续训练组和高强度间歇训练组。在基线和 1、3 和 5 年随访时采集脑 MRI 和 CRF。使用 FreeSurfer 提取皮质厚度和体积数据，并计算皮质叶、大脑和小脑灰质和白质的 FD。CRF 通过在递增最大运动测试期间使用测功计测量峰值摄氧量（VO）来测量。线性混合模型用于研究运动组差异以及 CRF 对大脑结构复杂性的可能影响。如果 CRF 与 FD 之间存在显著关联，则对 CRF 随时间的变化与 FD 之间的关联进行了分析。组间差异对结构复杂性没有影响。但是，我们发现 CRF 与大脑灰质 FD（p < 0.001）和颞叶灰质 FD（p < 0.001）呈正相关。皮质厚度没有这种效果，表明 FD 是结构变化的更敏感指标。CRF 随时间的变化与从基线到 5 年随访时颞叶灰质 FD 的变化相关（p < 0.05）。在 CRF 和大脑灰质 FD 之间没有发现变化的关联。这些结果表明，进入老年时保持较高的 CRF 水平可防止对衰老和与年龄相关的病理学敏感的区域的结构复杂性丧失。
