The Association des Infirmières et Infirmiers du Canada (AIIC) (2008), defines Advanced Practice Nursing (APN), as �an advanced level of nursing practice that maximizes the use of specialized skills and nursing knowledge in order to respond to the customers� needs in health�s sphere". APNs� programs, were initially introduced in the 1960s to fulfil gaps both in services traditionally carried by physicians, in order to improve access to care particularly in under-served services and contexts by doctors (Delamaire & Lafortune 2010), and also as a consequence to the reduction of physicians� and resident doctors hours internationally (Dowling et al. 2013; Olson & Chioffi 2005; Por 2008). Despite that, advanced practice is still being unclear due to the differences related to health settings and policies (Gardner et al. 2007). In the recent years, it has been introduced the concept of �complex chronic disease�, which is linked to the concept of aging and frailty, and determined by the presence of multiple and complex chronic conditions. The most differential characteristics of this group of people are the presence of several chronic diseases concurrently, multiple admissions in hospital emergency services in the same year, the presence of certain diseases such as heart failure or Chronic Obstructive Pulmonary Disease (COPD), polypharmacy and reduced personal autonomy. In addition, there are additional factors such as older age, living alone or not having enough family support and being in risk of falling, among others (Contel et al. 2012). In this sense, the APN is in an ideal position to cover the necessities of this population group. Case management and telemonitoring could be essential to the success in the developing of individualized care plans to improve chronic patients� health status (Contel et al. 2012; Carroll et al. 2007; Clark et al. 2010). Moreover, several models of APN attention have been developed in a wide variety of heath contexts in the elderly population (Oeseburg et al. 2009; Low et al. 2011), with remarkable outcomes in terms of effectiveness. Examples of those models could be those in transitional care (Brand et al. 2004), case management (Leung et al. 2004) or heart diseases (Blaha et al. 2000; Duffy et al. 2010) to improve quality of life or reduce rehospitalizations. Also, APN carried out interventions in patients that suffered dementia (Callahan et al. 2006), with older people with low incomes and acute health problems (Counsell et al. 2007), or in the community, giving support to families and patients to manage resources (Thompson et al. 2008). However, there is a deficit of conceptual frameworks to characterize and describe the range of interventions and services by APNs in the older population (Morales Asencio 2010). In this sense, the availability of a standardized language to describe nursing interventions (Nursing Intervention Classification, NIC) (Bulecheck GM et al. 2008; Thoroddsen 2005) can provide an additional resource to classify the components of different APN models and could facilitate the description of APN in a universal language, available in a vast majority of health care record systems around the world. Aims: The aims of this thesis are: 1. To identify, assess and summarise available scientific evidence about the effect of interventions deployed by APNs when providing care to older people in different settings (hospital, home, outpatient, residential). 2. To describe the roles and components of the interventions developed by APNs in the contexts mentioned before. 3. To identify the interventions provided by APNs to older people in different contexts (acute and long-term care) with a Standardized Nursing Language, in the studies included in the Systematic Review. Design: The present study was divided in two parts: firstly, a systematic review, and secondly, a qualitative with mixed methods study. Methods: Systematic review: Data Sources: Sixteen electronic databases were consulted (1990-2010). The research also included reviews, papers, reports and evaluations from research health services centres and Health Technology Agencies. Review Methods: Studies that met inclusion criteria were reviewed for quality, using RevMan 5 application�s checklist of bias, together with the methodological quality criteria of the Cochrane COPD group. Qualitative study Quotes of the interventions carried out by advanced practice nurses were codified by experts into the Nursing Intervention Classification. A content analysis was carried out, followed by a Delphi technique Results: Systematic review: Eleven studies were included. They were classified depending on the follow-up period, and also on the scope of the advanced practice nursing services. In both cases, integrative, multi-component and continuous advanced practice nursing care, reduced readmissions, improved patients� self-care and quality of life, as well as increased patients� and caregivers� satisfaction. Qualitative study: In total 73 different interventions codified in the Nursing Intervention Classification were extracted from the studies in different care contexts, with a clear predominance of interventions related to the Behavioural and Health care system domains, which could be explained due to the need of improving the psychosocial functioning and self-care of these patients to lead them to preserve their quality of life. Conclusion: Advanced practice nurses seems to be crucial to improve the health status of elderly people, which main characteristic is to bear with chronic diseases, in almost every care context. Moreover, Advanced Practice Nurses� interventions could be considered as complex but with the use of standardized nursing languages as the Nursing Intervention Classification, they can be better described, reported and analysed along different contexts. Moreover, core elements of the APNs� roles can be identified and they could be used for delineating or remodelling services. Further investigation will be needed to confirm that advanced practice nursing programs decreases health costs, to compare their effectiveness in both, the generalist and the specific model, and to analyse the pertinence of a mixed model. Bibliografía Morilla-Herrera, J.C. et al., 2012. Effectiveness of advanced practice nursing interventions in older people: protocol for a systematic review and qualitative study. 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