Musculoskeletal health in ambulatory physically active men with Cerebral Palsy : seasonal variations and the role of vitamin D

Langley, Christina Kate (2021) Musculoskeletal health in ambulatory physically active men with Cerebral Palsy : seasonal variations and the role of vitamin D. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Background: Individuals with Cerebral Palsy (CP) show impairments in muscle strength and power. Impairments in strength, in typically developed controls (TDC) low levels of force production and poor bone health are associated with low levels of vitamin D, and a high falls prevalence. It is possible that the severity of musculoskeletal impairments in individuals with CP is exacerbated by living in northern latitudes such as the UK and may contribute to high falls prevalence. Methods: Forty-eight participants were split into two groups of 24 active, ambulant men with CP (Gross Motor Function Classification Score I-II) and 24 healthy TDC completed one in vivo assessment of musculoskeletal health during the winter1, including: Vastus Lateralis anatomical cross-sectional area (VL ACSA), isometric knee extension maximal voluntary contraction (KE iMVC), 10 m sprint, vertical jumps, radius and tibia bones Tus and Zus scores. Plus falls frequency questionnaires to measure fear of falling and risk-taking behaviour were completed by 19 men with CP and 19 TDC. Assessments of vitamin D status through venous samples of serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone, dietary vitamin D intake from food diary and total sun exposure via questionnaire were also taken. 16 of the ambulant men with CP and 16 healthy TDC repeated these measures to assess seasonal variations on two separate occasions (the winter and in the summer). Results: Men with CP had 40.5% weaker KE iMVC, 23.7% smaller VL ACSA, 22.2% lower vertical jump, 14.6% lower KE iMVC/VL ACSA ratio, 22.4% lower KE iMVC/body mass (BM) ratio and 25.1% lower KE iMVC/lean body mass (LBM) ratio (all p<0.05). Radius Tus and Zus scores were 1.75 and 1.57 standard deviations lower than TDC, respectively (p<0.05). 25(OH)D was not different between groups, and 90.9% of men with CP and 91.7% of TDC had low 25(OH)D levels when compared to current UK recommendations. 25(OH)D was positively associated with KE iMVC/LBM ratio in men with CP (r = 0.500, p=0.020). Men with CP and TDC showed a 70.5% and 85.7% increase in serum 25(OH)D from winter to summer months (p<0.05) respectively, yet the mean of men with CP was below the adequate threshold of 30 ng∙mL-1 in the summer. PTH decreased with increased levels of 25(OH)D during the summer months in both groups (p<0.05). Men with CP showed an increase in radius Tus and Zus scores in the summer (p<0.05). 47% of men with CP were classified as fallers, fear of falling was 26.2% greater and risk-taking behaviours was 14.5% lower compared to TDC (p<0.05). Lower levels of KE iMVC in men with CP were associated with higher falls prevalence. Conclusion: A higher falls prevalence in men with CP, was associated with muscle weakness (chapter 3), where men with CP also showed large decrements in both bone and muscle outcomes compared to TDC (chapter 4). There was a high prevalence of vitamin D insufficiency presented in men with CP and TDC, and as a result was associated with muscle weakness in men with CP but did not contribute to other musculoskeletal decrements shown in men with CP compared to TDC (Chapter 4). Similarly, these vitamin D insufficiencies were inadequately overcome with an increase in TSE from winter to summer months, showing almost no benefit of large seasonal increases in vitamin D with no musculoskeletal improvement in either men with CP (Chapter 5). The findings of this thesis suggest a greater sensitivity to low vitamin D in men with CP with regards to bone and muscle content and functional outcomes and emphasise the importance for future research into vitamin D supplementation in populations with musculoskeletal impairments.