Global life expectancy has increased tremendously over the past decades, and so has the number of older adults. Preferably, these later years are spent in good health living independently at home, rather than suffering from physical and mental declines. However, a common consequence of ageing is the decrease in muscle mass, muscle strength and physical functioning. Diet and exercise interventions have been proven to be effective in counteracting this deterioration in health status in (pre-)frail older adults. However, the ageing population can be referred to as a heterogeneous population. Not only in terms of personal characteristics, ethnicity, and health status, but also in its responsiveness to treatments or interventions. To be able to serve a wide population, it is important to assess heterogeneity in older adults’ health status and subsequently study the heterogeneity in responsiveness to diet and exercise interventions. Besides, factors on the organisational and contextual level are expected to influence responsiveness to lifestyle interventions. Therefore, the aim of this thesis was threefold: 1) To study the sarcopenia prevalence, dietary protein intake, and underlying behavioural and environmental factors affecting protein intake in ethnic minorities in the Netherlands, 2) To study the personal, organisational, and other contextual factors affecting responsiveness to a diet and exercise intervention, and 3) To study the cost-effectiveness of ProMuscle in Practice.
Chapter 2 and 3 focused on the Healthy Life in an Urban Setting (HELIUS) study: a large cohort which includes participants from Dutch, South Asian Surinamese, African Surinamese, Turkish, Moroccan, and Ghanaian ethnic origin living in Amsterdam. Chapter 2 includes the results of a cross-sectional study of the HELIUS data, presenting the sarcopenia prevalences and its relation to protein intake in ethnic minorities in the Netherlands. The results show that sarcopenia prevalence varies across sexes and ethnic groups, being lowest in Turkish women and men and highest in South-Asian Surinamese women and men. Besides, higher protein intake was associated with a 4% lower odds of sarcopenia in the population and across ethnic groups, being only significant in the South-Asian Surinamese group.
In chapter 3 we investigated the dietary protein intake and underlying behavioural and environmental factors affecting protein intake in ethnic minority populations. The dietary protein recommendation (1.0 g/kg bw/day) was not met by 40-60% of the Dutch, South Asian Surinamese, African Surinamese, and Moroccan older adults. Major sources of protein intake were found to be ethnic-specific. In addition, focus group discussions revealed that participants appeared to have little knowledge of and awareness on protein and its role in ageing.
Chapter 4, 5 and 6 focused on the ProMuscle intervention, a diet and exercise intervention targeted at older adults. In chapter 4 we investigated which subgroup benefited most from the ProMuscle in Practice intervention. Results of in-depth analyses show that participants aged 75 years and younger and women benefited to a great extent from the intervention, as they improved significantly on nearly every outcome. Effects in participants with and without a mobility-impairing disorder (frailty, sarcopenia, or osteoarthritis) were comparable, indicating that the intervention is suitable for older adults regardless of having a mobility-impairing disorder.
In chapter 5, the effects and contextual factors of the three successive ProMuscle interventions are pooled and compared in a mixed-methods study. The intervention was conducted in the controlled setting (ProMuscle), real-life setting (ProMuscle in Practice) and real-life setting of the implementation pilots (ProMuscle Implementation Pilots). Quantitative results show that the intervention led to improvements on chair-rise performance and leg strength in each setting, with the largest improvements in the ProMuscle Implementation Pilots. Qualitative results show that room for adapting and tailoring the intervention, the availability of and access to facilities, the involvement of experienced professionals, and participant characteristics might contribute to explaining the variation in effects across settings.
In chapter 6, we investigated the cost-effectiveness of ProMuscle in Practice and its perceived benefits regarding quality of life. Results show an Incremental Cost-Effectiveness Ratio of €2988 per point increase in the Short Physical Performance Battery (SPPB). The intervention has an 82.4% probability of being cost-effective at a willingness to pay of €12.000 per point increase in SPPB. No change in quality of life was found using the EQ-5D-5L questionnaire, however, interviews revealed a wide range of function-related perceived benefits. Evaluating preventive interventions using QALY measures could underestimate the benefits of such interventions. For this reason, other methods, such as topic-specific questionnaires, might be more suitable when conducting an economic evaluation in the field of public health.
Overall, we can conclude that one size does not fit all. This thesis emphasizes the importance of considering heterogeneity in the older population. Personal characteristics, organizational aspects, and the general setting influence the effects of lifestyle interventions. Adapting ProMuscle in Practice to the needs and possibilities of older adults, to the working procedures and facilities of professionals, while considering economic aspects is of major importance for a successful intervention and implementation. Successfully implementing an effective intervention such as ProMuscle in Practice will lead to an increased physical functioning status in older adults. As a results, older adults are more likely to maintain their independence and live longer at home in a healthy and vital way.