Cardiovascular risk factor profiles in the development and progression of physical limitation in old age : a population-based study

Abstract

Preservation of independence has been reported to be highly desired by older adults, even more than longevity. However, subclinical cardiovascular pathology can threaten a healthy older adult’s maintenance of physical function. Therefore, the aim of this thesis was to investigate the role and potential neuropathological mechanisms of cardiovascular disease-related risk factors in the development of physical limitation and disability in older adults. Data were taken from the Swedish National study on Aging and Care in Kungsholmen (SNAC-K) for the initial three studies and from the embedded SNAC-K MRI sub-study for the final study.

Study I. Over six years of follow-up, of the 1971 persons free of disability in activities of daily living (ADL) at baseline, 119 (6.0%) persons developed ADL-disability. Limitation in both the one-leg balance stand (<5 sec.) and walking speed (<0.8 m/s) tests at baseline were associated with increased risk of future ADL-disability, but having both simultaneously showed a 10-fold higher likelihood of future ADL-disability. Study II. In a sample free of cardiovascular diseases (CVDs) and physical limitation at baseline (n=1441), a greater cardiovascular risk burden, defined by the Framingham general cardiovascular risk score (FRS), was associated with increased risk of walking speed limitation over nine years of follow-up, but only in the younger-old adults (60-72 years old), not in the older-old (≥78 years old) (Hazard Ratio [HR] 1.09, 95% confidence interval [CI] 1.02–1.17; HR 0.98, 95% CI 0.92–1.03, respectively). Moreover, the FRS was not associated with future balance performance or muscle strength. Study III. In the sample free of CVD and ADL-disability at baseline (n=1756), among the younger-old adults, physical inactivity (HR 4.10, 95% CI 1.22-13.76), diabetes (HR 5.61, 95% CI 1.17-26.82), and high C-reactive protein (HR 95% 2.78, 95% CI 1.07-7.22) were associated with disability over nine years of follow-up. Among the older-old (≥78 years old), only physical inactivity was associated with greater risk of ADL-disability (HR 1.99, 95% CI 1.36-2.93), and walking speed modified this association, such that being physically inactive and having walking speed limitation, concomitantly, showed an even higher risk of ADL-disability. Study IV. A faster average annual decline in walking speed over nine years of follow-up, in older adults free of walking speed limitation at baseline (n=331), was observed for those with greater volumes of white matter hyperintensities (WMH) at baseline, or having a higher burden of brain abnormalities (WMH+lacunes+ perivascular spaces).

Conclusion. Cardiovascular risk factors increase the risk of future physical limitation and disability, and brain abnormalities explain part of the underlying pathology driving the decline in physical function. However, risk profiles may differ between age groups of older adults, which suggests that interventions targeting decreasing cardiovascular risk may be more beneficial among younger-old adults, while older-old may benefit more from the maintenance of physical function.