Mini-mental state examination as a predictor of mortality among older people referred to secondary mental healthcare.

Yu-Ping Su,Robert Stewart,David To,Richard D Hayes,Matthew Broadbent,Chin-Kuo Chang,Gayan Perera,Matthew Hotopf,Mohammad Arfan Ikram

doi:10.1371/journal.pone.0105312

Abstract

BackgroundLower 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 FindingsData 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.ConclusionCurrent 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.

Highlights

Current study identified an association between cognitive impairment and increased mortality in older people using secondary mental health services regardless of a dementia diagnosis
Lower cognitive function in dementia is a predictor of mortality [1,2,3], this has primarily been described in severe impairment, and effects of milder dysfunction remain controversial [4,5,6,7,8,9,10]
The difference between Mini-Mental State Examination (MMSE) groups was statistically significant on log-rank tests (p-value,0.001) with similar patterns

Summary

Introduction

Lower cognitive function in dementia is a predictor of mortality [1,2,3], this has primarily been described in severe impairment, and effects of milder dysfunction remain controversial [4,5,6,7,8,9,10]. Some research has suggested that depression is an independent risk factor for mortality in people without dementia [10,22], others have not found this [16], and the diagnosis of depressive disorder itself is recognised to be associated with elevated mortality risk in older people [23]. 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. Lower levels of cognitive function have been found to be associated with higher mortality in older people, in dementia, but the association in people with other mental disorders is still inconclusive

Methods

Results

Conclusion