Abstract
Abstract Objectives Tests of physical function are often thought to measure functioning that is (1) musculoskeletal, and (2) newly declining in adult life. In contrast, this study aimed to: (1) add to evidence that physical-function tests also measure brain function, and (2) test the novel hypothesis that adult physical function is associated with brain function beginning in early childhood. We investigated early childhood brain function and midlife physical function in the Dunedin Study, a 5-decade longitudinal birth cohort (n = 1,037). Methods Brain function was measured at age 3 using 5 measures which formed a reliable composite (neurological examination, cognitive and motor tests, and temperament ratings). Physical function was measured at age 45 using 5 measures which formed a reliable composite (gait speed, step-in-place, chair stands, balance, and grip strength). Results Children with worse age-3 brain function had worse midlife physical function as measured by the age-45 composite, even after controlling for childhood socioeconomic status (β: 0.23; 95% CI: 0.16 to 0.30; p < .001). Worse age-3 brain function significantly predicted slower gait speed, fewer steps-in-place and chair-stands, worse balance, and weaker grip strength. Discussion Children with poorer brain function were more likely to have poorer physical-function scores as adults. In addition to indicating recent musculoskeletal decline, physical-function tests may also provide indications of lifelong, integrated brain–body health. By reconceptualizing the meaning of physical-function scores, clinicians can orient the use of physical-function tests in a more holistic approach to health care.