Long-term Follow-up after Stroke - Adherence to Physical Activity and Exercise, Its Association with Functional Recovery, and Prediction of Cardiorespiratory Fitness
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Stroke affects approximately 11,000 individuals in Norway annually, and it is considered one of the leading causes of disability among elderly persons. Due to an aging population, milder strokes, and decreased mortality rates following stroke, the actual numbers of people living with the consequences of stroke are expected to rise in coming years. Physical activity and exercise should be started early after stroke and sustained throughout the continuum of care. In the chronic phase, both are highly recommended to maintain functions regained in rehabilitation and as part of long-term secondary prevention to reduce the risk of recurrent stroke and other vascular events. Still, few individuals with stroke exercise regularly. Emerging evidence indicates that individualized counseling may improve adherence to physical activity after stroke. However, interventions are sparsely described, with few details of the degree to which an intervention was implemented as prescribed in the original protocol. This limits the replication and interpretation of the results, thereby further limiting information to guide clinical practice. The overall aim of the present thesis was, therefore, to obtain a more comprehensive understanding of the effectiveness of a long-term physical activity and exercise program after stroke by addressing aspects of treatment fidelity and, in addition, to investigate a more feasible outcome measure in predicting future cardiorespiratory fitness after stroke. Three substudies were conducted, all based on the randomized controlled trial Life After Stroke (LAST), which was designed to investigate whether a long-term, individualized, regular coaching program increased activity levels to maintain optimal functional recovery after stroke. In this thesis, we aimed to assess participants’ adherence to the long-term physical activity and exercise program of LAST, to explore determinants of long-term adherence, and to investigate how adherence was associated with functional recovery at 18-month follow-up. An additional aim was to explore whether simple functional walk tests performed in the subacute phase after stroke can provide information about future cardiorespiratory fitness levels in the chronic phase following stroke. First, a prospective longitudinal observational study was conducted to investigate participants’ adherence to a long term physical activity and exercise program, and how specific factors were influencing adherence over time (Paper I). Participants who were allocated to the intervention group of LAST (n=186) were included and followed continuously for 18 months. Results showed that the participants established and maintained moderate-to-good adherence to daily physical activity and weekly exercise over time. Adherence to physical activity increased over time, and adherence to exercise remained stable during the long-term follow-up. However, significant discrepancies between individuals were observed, and those with higher degrees of functional dependency were less likely to adhere to physical activity. Both increasing age and being female were associated with reduced adherence to exercise over time. The study also showed that the majority of physical activity and exercise was performed with moderate intensity. Only one-fourth of the amount of exercise was performed with vigorous intensity as recommended per protocol. Furthermore, the average achievement of individual goals related to physical activity and exercise was poor. Subsequently, an observational study including the same participants from the intervention group of LAST was conducted (Paper II). The aim was to examine the associations between adherence to the long-term physical activity and exercise program and functional outcomes 18 months after inclusion. Results showed a significant positive association between increasing levels of adherence to physical activity and exercise and improvements in motor function, walking capacity, balance, and self-perceived physical function. Compared with adherence to exercise and functional recovery, associations between adherence to physical activity and functional recovery were stronger. Lastly, a prospective cohort study was conducted in which we investigated whether simple functional walk tests performed three months after stroke added value to the prediction of peak oxygen consumption (VO2peak) in the chronic phase following stroke, in combination with previously established predictors of VO2peak (Paper III). A secondary aim was to investigate the associations between daily physical activity and walking capacity and between daily physical activity and VO2peak in chronic stroke. Participants included exclusively from St. Olav’s University Hospital in LAST were eligible for inclusion in this substudy. A total of 92 participants were assessed with a cardiopulmonary exercise test, approximately 20 months after inclusion in LAST. Results showed that the six-minute walk test (6MWT) added significant value to the prediction of mean cardiorespiratory fitness levels in the chronic phase following mild strokes in combination with age, sex, and degree of functional dependency. Although the model was not sufficiently accurate to predict cardiorespiratory fitness at an individual level, it provides valuable information about predicting VO2peak k at an aggregated level. Secondary results showed statistically significant but clinically insignificant associations between daily physical activity and walking capacity, and between daily physical activity and VO2peak. In conclusion, the results of this thesis contribute to increased knowledge of the current evidence of treatment fidelity of a long-term physical activity and exercise program after stroke. Developing interventions to enhance adherence should be given priority within this patient population, and our results provide information to guide clinical practice regarding the factors that influence adherence in a long-term perspective in people mildly and moderately affected by stroke. The prediction model may facilitate clinical decisions and strategies for mildly affected individuals with stroke at risk for low levels of VO2peak. More research is needed to explore the relationship between walking capacity and cardiorespiratory fitness, and future research should validate the model in various stages after stroke and in individuals moderately and severely affected by stroke.