The major limitations of this study include mostly the limitations in register database. Because of the cross-sectional nature of these studies it was not possible to establish the chronological order of any associations.
5.3.1 Limitations of the MDS
The MDS is a multidimensional assessment tool originally created for both clinical work and for research. This duality leads to compression of all data collection to the minimum necessary to reveal the main problem areas, not to assess these areas fully.
The limitations of the ability of the MDS to reveal the lack of individual indications for the use, doses (except Study IV), duration and discontinuation of antipsychotics are not available. Moreover, generic names of antipsychotics were not available in long-term institutional care studies (I-III), thus, distinguishing between atypical and typical antipsychotics was not possible. Lack of documentation of indications makes it impossible to know whether these drugs were being used for the appropriate reasons. Even though adherence to
medications was checked in home care as a routine part of the MDS questionnaire and home care nurses delivered the medications, some uncertainty about the actual consumption cannot be totally excluded (Study IV-V).
Although the MDS is a standardized, comprehensive assessment instrument, the recording of psychiatric symptoms was not its main focus. Psychiatric symptoms were assessed by nursing staff (including the attending physician), and the potential for over- and underestimation remains. In addition the data collected do not include any severity or frequency assessment of psychiatric or behavioural symptoms.
Although the MDS items have demonstrated good to excellent general reliability, it is uncertain how appropriate the MDS is in the nursing home assessment of the oldest old or people with chronic mental illness. In addition, the MDS, however, has not been validated specifically for nursing home residents with schizophrenia. Little is known about the ability of nursing home personnel to accurately recognize the symptoms of schizophrenia. Bowie et al.
suggest that symptoms such as thought disorder and hallucinations go almost completely unnoticed by nursing staff when they were asked to give a present-absent rating (Bowie et al. 2001).
Other limitations include uncertainty that not all psychiatric and dementia diagnoses have been adequately recorded in the files. The concern in Study III was the reliability of the database diagnosis of schizophrenia. Earlier studies indicate that Finnish psychiatrists tend to apply a narrow definition of schizophrenia in their clinical practice and that the diagnosis of schizophrenia can be considered reasonably reliable (Salokangas 1993, Isohanni et al. 1997, Kampman et al. 2004).
5.3.2 Reliability
The characteristics, diagnoses and symptoms of residents, residential care systems and clinical practices vary widely between countries making international comparisons and reliability in other populations complex. Despite
the common use of the term “nursing home”, there are no generally accepted definitions for the different types of long-term care services. There will be differences in the types of patients who are admitted to these facilities and the ways in which they are diagnosed and treated. Additionally, the more standardized way of assessing residents in long-term institutional and home care might also influence care practice with antipsychotics. Furthermore, the samples in Studies IV and V consisted solely of users of home care services, especially home care patients and the results cannot be generalized to all community-dwelling elderly people. No direct comparison of antipsychotic use between home care patients and community-dwelling individuals is available.
5.3.3 Unstudied factors
These studies did not include antipsychotic medications prescribed “as required”.
However, some “as required” medications may actually be used quite regularly.
Thus, the actual prevalences of antipsychotic medication use may have been higher than is reported here.
There may be an association between facility characteristics and the use of antipsychotics (Hughes et al. 2000) suggesting that the high prevalence of antipsychotic use may be related to low staffing rates in Finnish nursing homes.
The mean actual staffing level during the past 5 years in nursing homes in Finland has been 0.43 nurses per resident on weekdays (Noro A et al. 2005). The National Framework for High-Quality Care and Services for Older People suggest an appropriate staffing level of 0.8 nurses per resident. However, there are no comparisons of staffing rates between different countries. In the present study it was impossible to evaluate the influence of staffing rate on the use of antipsychotics. It may be possible that low staffing rates and pressure of work life have affected assessments of patients. Other possible predictors of antipsychotic use such as costs and prescription procedures are beyond of the present thesis.
5.3.4 Strengths of the study
The only exclusion criteria were aged <65 years and assisted living. Every resident in every participating institution and every patient in only home nursing, and common patients for home nursing and home care units were included. In addition, total population sizes were relatively large in all levels studied. The total units comprised approximately 17% of long-term institutional care for the elderly in 2001 in Finland. All types of institutional settings in Finland took part:
small and large, from cities and from rural areas, nursing homes and hospital-based beds. These study populations can be considered to be representative of older populations in long-term care in Finland. Thus, the spectrum of cognitive and physical impairment together with essential psychiatric disorders and symptoms prevalent was likely to be captured.