Mini-Mental State Examination as a Predictor of Mortality among Older People Referred to Secondary Mental Healthcare

et al. (2014) Mini-Mental State Examination as a Predictor of Mortality among Older People Referred to Secondary Mental Healthcare. PLoS ONE 9(9): e105312. doi:10.1371/journal.pone.0105312 Mini-Mental State Examination as a Predictor of Mortality among Older People Referred to Secondary Mental Healthcare Yu-Ping Su 0 Chin-Kuo Chang 0 Richard D. Hayes 0 Gayan Perera 0 Matthew Broadbent 0 David To 0 Matthew Hotopf 0 Robert Stewart 0 Mohammad Arfan Ikram, University Medical Center Rotterdam, Netherlands 0 1 King's College London (Institute of Psychiatry) , London , United Kingdom , 2 Dept of Psychiatry, Cathay General Hospital , Taipei, Taiwan , 3 School of Medicine, Fu-Jen Catholic University , Taipei, Taiwan , 4 South London and Maudsley NHS Foundation Trust , London , United Kingdom Background: Lower levels of cognitive function have been found to be associated with higher mortality in older people, particularly in dementia, but the association in people with other mental disorders is still inconclusive. Methods and Findings: Data were analysed from a large mental health case register serving a geographic catchment of 1.23 million residents, and associations were investigated between cognitive function measured by the Mini-Mental State Examination (MMSE) and survival in patients aged 65 years old and over. Cox regressions were carried out, adjusting for age, gender, psychiatric diagnosis, ethnicity, marital status, and area-level socioeconomic index. A total of 6,704 subjects were involved, including 3,368 of them having a dementia diagnosis and 3,336 of them with depression or other diagnoses. Descriptive outcomes by Kaplan-Meier curves showed significant differences between those with normal and impaired cognitive function (MMSE score,25), regardless of a dementia diagnosis. As a whole, the group with lower cognitive function had an adjusted hazard ratio (HR) of 1.42 (95% CI: 1.28, 1.58) regardless of diagnosis. An HR of 1.23 (95% CI: 1.18, 1.28) per quintile increment of MMSE was also estimated after confounding control. A linear trend of MMSE in quintiles was observed for the subgroups of dementia and other non-dementia diagnoses (both p-values,0.001). However, a threshold effect of MMSE score under 20 was found for the specific diagnosis subgroups of depression. Conclusion: Current study identified an association between cognitive impairment and increased mortality in older people using secondary mental health services regardless of a dementia diagnosis. Causal pathways between this exposure and outcome (for example, suboptimal healthcare) need further investigation. - Funding: This research was supported by the Biomedical Research Nucleus data management and informatics facility at South London and Maudsley NHS Foundation Trust, which is funded by the National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and Kings College London and a joint infrastructure grant from Guys and St Thomas Charity and the Maudsley Charity. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. " These authors share first authorship in this research. Lower cognitive function in dementia is a predictor of mortality [13], although this has primarily been described in severe impairment, and effects of milder dysfunction remain controversial [410]. Lower cognitive function in older people without dementia has also been found to be associated with higher mortality, although this again remains inconclusive [8,1117] and evidence on interventions to prevent mortality remains limited [18]. A better understanding is therefore needed of factors influencing prognosis in older people with and without dementia to aid care planning and clinical decision making [8,18,19]. Depression is commonly comorbid with dementia, and associated itself with worse outcome [10,16,20], although the relationship between the two may be complex, with depression potentially a cause of dementia, a consequence, a prodromal symptom, and/ or a condition with shared risk factors [20,21]. Some research has suggested that depression is an independent risk factor for mortality in people without dementia [10,22], although others have not found this [16], and the diagnosis of depressive disorder itself is recognised to be associated with elevated mortality risk particularly in older people [23]. In the study described here, we analysed data from a retrospective cohort aged 65 years and above, using information from a large secondary mental healthcare provider in southeast London. We hypothesised that lower cognitive function assessed by Mini-Mental State Examination (MMSE) would be an independent risk factor for mortality in those with dementia, depression and those with a psychiatric diagnosis other than the former ones. Study setting The South London and Maudsley NHS Foundation Trust (SLAM) Case Register has been described in detail previously [24]. In brief, the Clinical Record Interactive Search (CRIS) program allows researchers to access full but anonymised data from a large electronic mental health records dataset [25]. Within the UK National Health Service, secondary mental health care is provided according to defined geographic catchment areas. SLAM is one of the largest mental health providers in Europe, delivering comprehensive secondary mental health services to a population of approximately 1.23 million residents in four London boroughs (Lewisham, Lambeth, Southwark, and Croydon), including outpatient/community, inpatient, and general hospital liaison services. Currently, there are records on over 220,000 cases accessed by CRIS and this database has been extensively utilised [2628]. The SLAM Case Register has been approved as an anonymised data resource for secondary analyses by Oxfordshire Research Ethics Committee C (08/H0606/71+5) and governance is provided for all projects by a patient-led oversight committee. Analysed sample All cases with at least one MMSE score recorded during the period between 1st Jan 2007 and 31st Dec 2010 were first identified. This sample was restricted to cases aged at least 65 years Number (%)/mean SD All (N = 6,704) Table 1. Distribution of baseline covariates among clients of a secondary mental health service provider aged 65 years old or more and by psychiatric diagnoses. Dementia (n = 3,368) Depression (n = 1,129) Others (n = 2,207) Hazard Ratio (95% Confidence Interval) Age at MMSE assessment Married/Civil partner/Cohabiting Area-level deprivation score 1st tertile (1.6322.16, the lest deprived group) 2nd tertile (22.1735.25) 3rd tertile (35.2665.53, the most deprived group) Diagnosis of dementia Diagnosis of depression Normal (MMSE: 30-25) Impaired (MMSE: 24-0) MMSE score in quintiles 1st quintile (30-28) 2nd quintile (27-25) 3rd (...truncated)