Changes to volumetric bone mineral density and bone strength after stroke: a prospective study

Stroke Prevents Exercise-induced Gains in Bone Microstructure But Not Composition in Mice

Ischemic stroke induces rapid loss in bone mineral density up to 13 times greater than during normal aging, leading to markedly increased risk of fracture. Little is known about skeletal changes following stroke beyond density loss. In this study we use a mild-moderate middle cerebral artery occlusion model to determine the effects of ischemic stroke without bedrest on bone microstructure, dynamic bone formation, and tissue composition. Twenty-seven 12-week-old male C57Bl/6J mice received either a stroke or sham surgery and then either received daily treadmill exercise or remained sedentary for four weeks. All mice were ambulatory immediately following stroke, and limb coordination during treadmill exercise was unaffected by stroke, indicating similar mechanical loading across limbs for surgery groups. Stroke did not directly detriment microstructure, but exercise only stimulated adaptation in sham group, not stroke group, with increased bone volume fraction and trabecular thickness in the sham distal femoral metaphysis. Stroke differentially decreased cortical area in the affected limb relative to the unaffected limb of the distal femoral metaphysis, and endosteal bone formation rate in the affected tibial diaphysis. Although exercise failed to improve bone microstructure following stroke, exercise increased mineral-to-matrix content in stroke but not sham. Together, these results show that stroke inhibits exercise-induced changes to femoral microstructure but not tibial composition, even without changes to gait. Similarly, affected-unaffected limb differences in cortical bone structure and bone formation rate in ambulatory mice show that stroke affects bone health even without bedrest.

Upright activity and higher motor function may preserve bone mineral density within 6 months of stroke: a longitudinal study

PURPOSE

Bone fragility contributes to increased fracture risk, but little is known about the emergence of post-stroke bone loss. We investigated skeletal changes and relationships with physical activity, stroke severity, motor control and lean mass within 6 months of stroke.

METHODS

This is a prospective observational study. Participants were non-diabetic but unable to walk within 2 weeks of first stroke. Distal tibial volumetric bone mineral density (vBMD, primary outcome), bone geometry and microstructure (high-resolution peripheral quantitative computed tomography) were assessed at baseline and 6 months, as were secondary outcomes total body bone mineral content and lean mass (dual energy X-ray absorptiometry), bone metabolism (serum osteocalcin, N-terminal propeptide of type 1 procollagen (P1NP), C-terminal telopeptide of type 1 collagen (CTX)), physical activity (PAL2 accelerometer) and motor control (Chedoke McMaster) which were also measured at 1 and 3 months.

RESULTS

Thirty-seven participants (69.7 years (SD 11.6), 37.8% females, NIHSS 12.6 (SD 4.7)) were included. The magnitude of difference in vBMD between paretic and non-paretic legs increased within 6 months, with a greater reduction observed in paretic legs (mean difference = 1.5% (95% CI 0.5, 2.6), p = 0.007). At 6 months, better motor control was associated with less bone loss since stroke (r = 0.46, p = 0.02). A trend towards less bone loss was observed in people who regained independent walking compared to those who did not (p = 0.053). Higher baseline daily count of standing up was associated with less change in bone turnover over 6 months: osteocalcin (r = -0.51, p = 0.01), P1NP (r = -0.47, p = 0.01), CTX (r = -0.53, p = 0.01).

CONCLUSION

Better motor control and walking recovery were associated with reduced bone loss. Interventions targeting these impairments from early post-stroke are warranted.

CLINICAL TRIAL REGISTRATION

URL: http://www.anzctr.org.au . Unique identifier: ACTRN12612000123842.

Reducing sedentary time and fat mass may improve glucose tolerance and insulin sensitivity in adults surviving 6 months after stroke: A phase I pilot study

INTRODUCTION

Deranged glycaemic control is common post-stroke, increasing risks of recurrent stroke and development of diabetes. The aim of the study is to examine glucose metabolism in relation to body composition, physical activity and sedentary time post-stroke.

PATIENTS AND METHODS

Observational study: Non-diabetic adults, unable to walk independently, were recruited within 2 weeks of first stroke. Primary outcome: 2-h glucose level (mmol/l, oral glucose tolerance test), assessed at baseline and 6 months. Homeostasis Model Assessment of Insulin Sensitivity, total body fat and lean mass (dual energy X-ray absorptiometry), sedentary time (lying or sitting), standing and walking (PAL2 accelerometer) were assessed at baseline, 1, 3 and 6 months. Generalised estimating equations were used to examine change over time and associations between outcome measures.

RESULTS

Thirty-six participants (69.5 years (standard deviation 11.7), 13 (36.1%) female, moderate stroke severity (National Institute of Health Stroke Scale 11.5 (interquartile range 9.75, 16)). Within 6 months, adjusting for age and National Institute of Health Stroke Scale, every month 2-h glucose reduced by 4.5% (p < 0.001), Homeostasis Model Assessment of Insulin Sensitivity improved 3% (p = 0.04) and fat mass decreased 490 g (95% confidence interval 325, 655; p = 0.01). For every extra kilogram of body fat, 2-h glucose increased by 1.02 mmol/L (95% confidence interval 1.01, 1.02; p = 0.001); Homeostasis Model Assessment of Insulin Sensitivity reduced by 0.98% (95% confidence interval 0.97, 0.99; p = 0.001). Time spent sedentary reduced from 98.5% of measurement period (interquartile range 94.3, 99.8) to 74.3% (interquartile range 65.5, 88.6), by 2.8% monthly (95% confidence interval 1.8, 3.9, p < 0.001). For every additional 5% sedentary time, 2-h glucose increased by 1.05 mmol/L (95% confidence interval 1.04, 1.07; p < 0.001).

CONCLUSION

Reducing sedentary time and fat mass within 6 months of stroke may improve glucose tolerance and insulin resistance.

Impact and risk factors of post-stroke bone fracture

Bone fracture occurs in stroke patients at different times during the recovery phase, prolonging recovery time and increasing medical costs. In this review, we discuss the potential risk factors for post-stroke bone fracture and preventive methods. Most post-stroke bone fractures occur in the lower extremities, indicating fragile bones are a risk factor. Motor changes, including posture, mobility, and balance post-stroke contribute to bone loss and thus increase risk of bone fracture. Bone mineral density is a useful indicator for bone resorption, useful to identify patients at risk of post-stroke bone fracture. Calcium supplementation was previously regarded as a useful treatment during physical rehabilitation. However, recent data suggests calcium supplementation has a negative impact on atherosclerotic conditions. Vitamin D intake may prevent osteoporosis and fractures in patients with stroke. Although drugs such as teriparatide show some benefits in preventing osteoporosis, additional clinical trials are needed to determine the most effective conditions for post-stroke applications.