Brain Volumetry and Structural

There were significant differences in grey matter (GM) and white matter (WM) volumes observed between Singaporean (SG) and Caucasian males. SG males had smaller total brain volumes, with stable GM and WM volumes until age 45, followed by a rapid decline after 55. In contrast, Caucasian males showed a gradual, linear decline throughout adulthood (Figure 3a). When normalized for intracranial volume, both groups exhibited linear reductions, though SG males had steeper declines (Figure 3b).

SG females also had smaller brain volumes compared to Caucasians. While Caucasian females displayed a U-shaped pattern with slight volume increases after 55, SG females experienced a steady decline from age 30, accelerating post-55 (Figure 4a). Normalized volumes confirmed steeper reductions in SG females, indicating distinct aging trajectories across populations (Figure 4b).

Cerebral Grey and White Matter ChangesIn both SG males and females, cerebral GM peaked in early childhood, declining steadily after 55, particularly in regions like the prefrontal cortex and hippocampus, crucial for cognitive functions (Figures 5a, 6, 7). The volume loss of the hippocampus was more pronounced in SG males, correlating with greater memory challenges. WM volume increased through adolescence, stabilized in early adulthood, and declined after 50, accelerating post-70 due to demyelination. WM hyperintensities, more common after 70, were linked to cognitive decline and dementia (Figure 5b). Males consistently exhibited higher GM and WM volumes, with the sharpest GM reductions in cognitive regions (Figure 8a).

Cerebellar Grey and White Matter Changes

Cerebellar GM volume rose rapidly in childhood, stabilizing in adulthood, with the decline becoming more evident after 70 (Figure 9a). This decline was less severe than in the cerebrum, reflecting the cerebellum’s sustained role in motor control. WM volume peaked in early adulthood, remaining stable until 60 before declining and affecting motor coordination in older adults (Figure 9b).

Combined Grey and White Matter Changes in the Cerebellum

Both GM and WM in the cerebellum declined gradually after age 30 in SG males and females. SG individuals showed slower declines compared to Caucasians, although Caucasians exhibit earlier onset volume loss (Figure 8b).