182
European Journal of Public Health
.........................................................................................................
European Journal of Public Health, Vol. 26, No. 1, 182–187
ß The Author 2015. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.
doi:10.1093/eurpub/ckv052 Advance Access published on 28 March 2015
.........................................................................................................
Clément Pimouguet1,2,3, Debora Rizzuto1, Pär Schön1,4, Behnaz Shakersain1, Sara Angleman1,
Marten Lagergren1,4, Laura Fratiglioni1,4, Weili Xu1
1 Aging Research Center, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet and Stockholm
University, Stockholm, Sweden
2 INSERM, ISPED, Centre INSERM U897-Epidemiologie-Biostatistique, Bordeaux, France
3 University of Bordeaux, Centre INSERM U897-Epidemiologie-Biostatistique, Bordeaux, France
4 Stockholm Gerontology Research Center, Stockholm, Sweden
Correspondence: Clément Pimouguet, Institut de Santé Publique, d’Epidémiologie et de Développement, Université
Victor Segalen Bordeaux 2, 146 rue Leo Saignat, 33076 Bordeaux Cedex, France. Tel: +33 05 57 57 56 44,
Fax: +33 05 56 24 00 81, e-mail: clement.pimouguet@isped.u-bordeaux2.fr
Background: Living alone is common among elderly people in Western countries, and studies on its relationship
with institutionalization and all-cause mortality have shown inconsistent results. We investigated that the impact
of living alone on institutionalization and mortality in a population-based cohort of elderly people. Methods: Data
originate from the Swedish National study on Aging and Care-Kungsholmen. Participants aged 66 years and
living at home (n = 2404) at baseline underwent interviews and clinical examination. Data on living arrangements
were collected in interviews. All participants were followed for 6 years; survival status and admission into institutions were tracked continuously through administrative registers from 2001 to 2007. Data were analysed using
Cox proportional hazard models, competing risk regressions and Laplace regressions with adjustment for potential
confounders. Results: Of the 2404 participants, 1464 (60.9%) lived alone at baseline. During the follow-up, 711
(29.6%) participants died, and 185 (15.0%) were institutionalized. In the multi-adjusted Cox model, the hazard
ratio (HR) of mortality in those living alone was 1.35 (95% confidence interval [CI] 1.18 to 1.54), especially among
men (HR = 1.44, 95% CI 1.18 to 1.76). Living alone shortened survival by 0.6 years and was associated with the risk
of institutionalization (HR = 1.74, 95% CI 1.10 to 2.77) after taking death into account as a competing risk.
Conclusions: Living alone is associated with elevated mortality, especially among men and an increased risk of
institutionalization. Over a 6-year period, living alone was related to a half year reduction in survival among
elderly people in Sweden.
.........................................................................................................
Introduction
emographic projections predict a sharp increase in the
of elderly people in the near future in most
developed countries.1 The living arrangements of older people
have been substantially affected by reduced intergenerational
living, greater social and geographical mobility and widowhood.2
As a consequence, an increased proportion of elderly people now
live alone in Western countries.2–3 Among elderly people, the
prevalence of living alone varies widely by country and by sex. In
Sweden, half of women aged 65 and over live alone; this proportion
is about twice high as among men.1 Elderly people who live alone
may be particularly vulnerable to poorer medical follow-up, social
isolation and loneliness, all of which have been described as
predictors of mortality4–7 and institutionalization.8 However,
several recent studies addressing these issues have shown inconsistent results. Some studies reported that living alone was associated
with increased mortality, particularly among the young-old.9–10 In
contrast, other studies reported no association between living alone
and increased mortality11–12 or even increased survival among frail
elderly people who live alone.13
Most elderly people prefer to remain in their homes because this
enables them to maintain the integrity of their social network.2
Furthermore, admission to nursing homes is expensive both in
terms of public and private finances. Institutionalization is,
therefore, a relevant prognostic outcome for individuals, families
and policy makers. The association between living arrangements
and institutionalization has been addressed in several studies with
Dpopulation
inconsistent findings mostly due of methodological limitations.14
Importantly, previous studies have not addressed death as a
competing risk which could have led underestimation of the role
of living arrangements.15
To date, no population-based longitudinal study has examined
the association between living alone and both mortality and institutionalization taking into account death as a competing risk. In this
study, we aimed to use 6-year follow-up data from a populationbased cohort study to investigate the impact of living alone on
morality and on institutionalization.
Methods
Study population
Data were derived from the Swedish National study on Aging and
Care in Kungsholmen (SNAC-K).16 This study includes two parts:
the SNAC-K care system study and the SNAC-K population study.
Study participants were randomly selected from adults aged 60
years living at home or in institutions in Kungsholmen, a central
district of Stockholm, Sweden. Eleven age cohorts were chosen with
different follow-up examination intervals, 6 years between groups in
the younger cohorts (aged 60 to 78), and 3 years in the older cohorts
(aged 81 or over). The baseline examination was carried out between
March 2001 and June 2004. A total of 5111 persons were initially
selected for participation. Of the latter, 4590 were eligible persons
(those who were alive, contactable, speaking Swedish and living in
Kungsholmen) and 3363 (73.3%) participated at the baseline exam.
Downloaded from https://academic.oup.com/eurpub/article-abstract/26/1/182/2467054 by University of Maryland College Park user on 08 March 2019
Impact of living alone on institutionalization and
mortality: a population-based longitudinal study
A population-based longitudinal study
Data collection
The baseline survey collected information about present status and
past events through interviews, clinical examinations and psychological testing by trained staff, including nurses, psychologists and
physicians, following structured protocols (available at http://www.
snac.org). Assessments comprised a social interview to collect sociodemographic data, evaluation of physical function performed by a
nurse, clinical examination performed by a physician and a psychological test battery administered by a psychologist.
Information on living arrangements, age, sex and education were
recorded during the nurse interview. Participants were asked at
baseline if they lived alone in their household or not. Education
was measured as the highest level of formal schooling and was
categorized as elementary school (grades 1–9), high school (grades
10–12), or university or above. Financial status was ascertained with
a question about the presence of any trouble keeping up with regular
expenses in the last 12 months. Smoking status was assessed, and
participants were classified as current smokers, former smokers and
persons who had never smoked. Alcohol consumption was assessed
on the basis of self-reported frequency of alcohol intake on a typical
day and was classified as no or occasional drinking, light to
moderate drinking (1–14 drinks per week for men or 1–7 drinks
per week for women) and heavy drinking (>14 drinks per week for
men or >7 drinks per week for women).17 Loneliness was assessed by
asking the participants if they ever felt lonely, and, if so, how strong
(mild, moderate or strong) the feeling was. Medical conditions
(diabetes, hypertension, stroke, heart failure, coronary heart
disease, depression, dementia, cancer) were diagnosed by the
examining physicians based on the clinical examination, selfreported medical history and laboratory data (see Supplementary
file for more information). Information on medical history was
also taken from the computerized inpatient register system that encompassed all hospitals in Stockholm since 1967 in which the
criteria of International Classification of Diseases, ninth and 10th
revision (ICD-9 and ICD-10) were followed (full description in
Supplementary file).
Nurses measured weight and height using a standard scale with the
participant in light clothing and no shoes. Body mass index (BMI) was
calculated as weight in kilograms divided by squared height in metres.
BMI was divided into four categories: underweight (BMI < 20),
normal weight (BMI between 20 and 24.9), overweight (BMI
between 25 and 29.9) and obese (BMI 30).18 As BMI was missing
for 7.6 % of the sample, a specific missing category was created and
used for survival analyses. The Mini-Mental State Examination score
(MMSE) was used to control for global cognitive abilities.19 Basic
activities of daily living (ADL) and instrumental activities of daily
living (IADL) were assessed. Disability in ADL was defined as any
restriction in bathing, dressing, toileting, mobility, continence or
feeding. Disability in IADL was defined as the inability to carry out
at least one of the following four activities: using the telephone, using
public transportation, handling finances and shopping.
Ascertainment of death and institutionalization
Death certificates from the Swedish Cause of Death Register at the
National Board of Health and Welfare were used to ascertain deaths
and dates of deaths from baseline to 15 October 2012. Data on
institutionalization and the dates of institutionalization were ascertained through linkage to the care system part of SNAC-K (from
baseline to 25 February 2013) that recorded the amount of public
eldercare services granted in accordance with the Social Services Act.
Statistical analyses
Baseline characteristics were compared by living arrangement status
(living alone or not living alone) with 2 test for categorical
variables and t-test for continuous variables. Outcomes studied
included time to death and time to institutionalization. We
investigated survival and institutionalization over 6 years because
this timeframe was close to the median delay for the two
outcomes. Incidence rates of death and institutionalization by
living arrangements and 95% CIs were estimated using a Poisson
regression model. Cox proportional hazards regression models were
used to estimate the hazard ratio (HR) of all-cause mortality and
95% CIs associated with living alone. Survival time was calculated as
the number of years from the baseline interview to the date of death
or the censored date for those who were still alive at the end of the
follow-up time. Laplace regression was used to model percentiles of
survival.20 In our study population, 29.6% of the participants died
during the follow-up period. We therefore used the first quartile (the
25th percentile) of the survival time, expressed in years; that is the
time by which 25% of the participants in the current study had died.
As risk for death competes with risk for institutionalization,
competing risk models were used to estimate the association
between living alone and institutionalization, treating death as an
explicit competing risk.21 Time to institutionalization was measured
in years from the baseline survey to either the date of admission to
an institution, date of death (without prior institution admission),
or 6 years after baseline for those still living at home. In all Cox and
competing risk regression analyses, age, sex, educational level,
presence of a recent financial difficulty, vascular risk factors (BMI,
smoking habits and alcohol consumption), chronic diseases,
cognitive function, functional disability and feelings of loneliness
were considered as confounders. We also adjusted the survival
analyses by using institutionalization as a time dependant variable
because moving into an institution can be considered a proxy of
functional and/or cognitive decline and could modify the relationship between living arrangements and survival. We tested for
possible interactions between living arrangements, age (
Purchase answer to see full
attachment