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Quality of life in autism across the lifespan: A meta-analysis
van Heijst, B.F.C.; Geurts, H.M.
DOI
10.1177/1362361313517053
Publication date
2015
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Autism
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Citation for published version (APA):
van Heijst, B. F. C., & Geurts, H. M. (2015). Quality of life in autism across the lifespan: A
meta-analysis.
Autism
,
19
(2), 158-167. https://doi.org/10.1177/1362361313517053
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DOI: 10.1177/1362361313517053
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Introduction
Autism
1
is a lifelong neurodevelopmental disorder, yet the
developmental trajectory of people with autism is not well
understood. A minority of adults with autism, although
continuing to be affected by their autism, can find work,
live independently and develop meaningful relationships
with others. However, the majority have an overall poor
outcome (Billstedt et al., 2005). They remain dependent
on their parents or others, are either unemployed or under-
employed and lead fairly isolated lives (Howlin et al.,
2004, 2013). Moreover, a large number of adults with
autism remain without appropriate services and effective
interventions (Barnard et al., 2001; Gerhardt and Lainer,
2011). Consequently, many parents of children with autism
do not know what to expect for the future of their children.
They worry about what will happen to their children when
they are not around to care for them anymore, and they
fear that the adult services are not as good as those for
children (Eaves and Ho, 2008). These factors combined
highlight a growing need to describe the developmental
trajectory of people with autism, so that the appropriate
steps in provision of care can be taken.
The majority of research on outcomes in autism has
focused on one or a few domains (e.g. work, friendships) or
only on objective measures (e.g. employment status, but
not employment satisfaction). Quality of life (QoL) is a
more comprehensive, multidimensional concept that
includes subjective well-being, and is well suited to assess
people with autism (Burgess and Gutstein, 2007). The
World Health Organization (WHO, 1995) defines QoL as
the individual’s perception of his or her position in life in
the context of the culture and value system, and in relation
to one’s goals, expectations, standards and concerns. It
incorporates the individual’s physical health, psychological
state, level of independence, social relationships, personal
beliefs and his or her relationship to salient features of the
environment in a complex way. Therefore, the first goal of
this study is to investigate the QoL of people with autism.
Quality of life in autism across the
lifespan: A meta-analysis
Barbara FC van Heijst
1
and Hilde M Geurts
1,2,3
Abstract
Autism is a lifelong neurodevelopmental disorder, with a known impact on quality of life. Yet the developmental trajectory
of quality of life is not well understood. First, the effect of age on quality of life was studied with a meta-analysis. Our
meta-analysis included 10 studies (published between 2004 and 2012) with a combined sample size of 486 people with
autism and 17,776 controls. Second, as there were no studies on quality of life of the elderly with autism, we conducted
an empirical study on quality of life of the elderly (age range 53–83) with autism (N = 24) and without autism (N = 24).
The meta-analysis showed that quality of life is lower for people with autism compared to people without autism, and
that the mean effect is large (Cohen’s d = −0.96). Age did not have an effect on quality of life. The study concerning the
elderly with autism showed that the difference in quality of life is similar in the elderly. Age, IQ and symptom severity did
not predict quality of life in this sample. Across the lifespan, people with autism experience a much lower quality of life
compared to people without autism. Hence, the quality of life seemed to be independent of someone’s age.
Keywords
age, autism, meta-analysis, quality of life, review
1
d’Arc, Brain & Cognition, Department of Psychology, University of
Amsterdam, The Netherlands
2
Dr Leo Kannerhuis, The Netherlands
3
Cognitive Science Center Amsterdam, University of Amsterdam, The
Netherlands
Corresponding author:
Hilde M Geurts, d’Arc, Brain & Cognition, Department of Psychology,
University of Amsterdam, Weesperplein 4, 1018 XA Amsterdam, The
Netherlands.
Email: H.M.Geurts@uva.nl
517053
AUT0010.1177/1362361313517053Autismvan Heijst and Geurts
research-article2014
Original Article
at Universiteit van Amsterdam on April 1, 2015aut.sagepub.comDownloaded from
van Heijst and Geurts 159
Previous research on unidimensional outcome meas-
ures suggests that one of the predictors contributing to bet-
ter adult outcomes are less severe autism symptoms (Eaves
and Ho, 2008; Kuhlthau et al., 2010). Autism symptoms
seem to show modest improvement with age (Esbensen
et al., 2009; Happé and Charlton, 2012). Age also has an
effect on other aspects of autism, as older people have
shown fewer sensory abnormalities (Kern et al., 2006) and
less maladaptive behaviour (Shattuck et al., 2007) than
younger people with autism. However, not all individuals
improve. Some people reach a plateau in their develop-
ment, and others decline (McGovern and Sigman, 2005).
In addition, while some symptoms show modest improve-
ments, this seldom leads to functioning in the normal
range, which reinforces the notion that autism is a lifelong
condition (Seltzer et al., 2004). Therefore, the second goal
of this study is to assess the effect of age on QoL.
To our knowledge, there is currently no quantitative
review of QoL in autism, but there are two qualitative
reviews of QoL in autism by the same authors: Kamp-Becker
et al. (2010) – 7 studies, and Kamp-Becker et al. (2011) – 9
studies, of which 5 studies overlap with those of the 2010
paper. The authors did not draw a general conclusion across
studies, as between studies there was a wide variety in patient
population, design, treatments and outcome measures.
However, most studies show that QoL is relatively low in
people with autism. Moreover, the effect of age was not stud-
ied, despite reports that in the general population QoL
decreases with age (StatLine, 2010). Therefore, a direct com-
parison between the QoL of people with autism and people
without autism is needed in order to control for the effects of
aging on QoL found in the general population.
In this study, we investigate how the QoL of people with
autism can be described over the entire lifespan. In Study 1,
we will examine QoL quantitatively by performing a meta-
analysis on QoL studies. We will describe the magnitude of
the difference between QoL of people (i.e. children, adoles-
cents and adults) with and without autism. As elderly peo-
ple with autism are likely to be underrepresented in the
existing studies (Mukaetova-Ladinska et al., 2012), we
conducted Study 2, which will focus on QoL among the
elderly with autism. In both studies, we explore the effect
of age as well as other factors that influence QoL.
We hypothesize that independent of age, QoL will be
lower for people with autism than for people without
autism. Although there will be individual differences in
people’s life trajectory (Seltzer et al., 2004), we hypothe-
size that age plays a role in QoL, because autism symptoms
often reduce with age. As people might learn to compen-
sate, accept impairments and follow successful treatment
(García-Villamisar et al., 2002), QoL could improve with
age. However, a contrasting hypothesis would be that QoL
will decrease with age. Age brings about increased respon-
sibilities and decreased parental support, which may cause
impairments to be perceived more intensively in adulthood
than in childhood. There may even be an accumulative
impact of autism impairments on finances, health and
social life, as was found for attention deficit hyperactivity
disorder (ADHD) impairments (Bernardi et al., 2012; Brod
et al., 2012). For these reasons, we will explore the direc-
tion of the hypothesized age effect.
Methods study 1: quantitative review
Literature search
The databases PubMed, PsycINFO and Web of Knowledge
were searched for studies (including theses and disserta-
tions) that focus on QoL in autism (up to January 2013).
Search terms relating to autism (e.g. autism, autism spec-
trum disorder (ASD), Asperger, pervasive developmental
disorder–not otherwise specified (PDD-NOS) were com-
bined with QoL and measures of QoL (e.g. quality of life,
health-related QoL (HRQOL), World Health Organization
Quality of Life-Brief (WHOQOL), PedsQL). We did not
search unpublished work by authors, but cross-references
of the obtained studies were checked for studies that might
have been missed in the electronic search.
Inclusion criteria
The inclusion criteria were that a study: (a) concerned par-
ticipants that were diagnosed with autism by clinical con-
sensus (usually verified with standardized instruments);
(b) included a self-report or proxy-report measure of QoL;
(c) used a standardized, valid and reliable measure of QoL;
and (d) addressed a comparison between groups with and
without autism. Studies concerning people with autism
and a co-morbid disorder were included, as this would
increase generalizability.
Obtained studies
The literature search generated 3231 hits; based on titles
and abstracts, 42 studies were selected. After full text
screening, 28 out of the 42 studies did not meet inclusion
criteria. Reasons for excluding studies were that the autism
diagnosis was not validated (N = 3), the studies used a non-
standardized QoL measure (N = 5), no control group was
included (N = 17) or a different type of QoL (family QoL,
communication QoL) was assessed (N = 3). Of the 14 stud-
ies that met inclusion criteria, 9 studies did not include all
of the necessary information; authors were contacted and 5
provided the requested information. This resulted in 10
studies available for the meta-analysis, with 486 partici-
pants with autism and 17,776 participants without autism
(Table 1). The large number of control participants is
mainly due to the use of normative comparison groups. All
the information in Table 1 was recorded by the first author
and verified by the second author.
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160 Autism 19(2)
Table 1. Main characteristics of the studies included in the meta-analysis.
Author Cohen’s d Variance Autism N Control N Age
a
Control
b
Informant Questionnaire Diagnosis
c
Co-morbidity
d
Bastiaansen et al. (2004) −0.43 0.04 28 215 9.7 (2.4) Clinical
e
Self PedsQL CC, SI NM
Bastiaansen et al. (2004) −0.38 0.04 28 215 9.7 (2.4) Clinical
e
Proxy PedsQL CC, SI NM
Bennet et al. (2005) −0.24 0.17 9 22 40.7 (9.3) Learning Disability
f
Proxy LEC CC, Q NM
Jennes-Coussens et al. (2006) −0.62 0.18 12 13 20.3 (1.3) TD Self WHOQOL-BREF CC, Q NM
Limbers et al. (2009) −2.26 0.05 22 427 9.3 (2.2) TD Proxy PedsQL CC, Q NM
Kamp-Becker et al. (2010) −0.81 0.05 26 124 21.6 (3.4) TD Self WHOQOL-BREF CC, SI M
Kamp-Becker et al. (2011)
g
−0.20 0.03 40 9947 12.7 (2.6) TD Self ILK CC, SI M
Kamp-Becker et al. (2011)
g
−1.14 0.02 42 1721 12.7 (2.6) TD Proxy ILK CC, SI M
Shipman et al. (2011)
g
−0.65 0.03 39 1170 14.8 (1.9) TD Self PedsQL CC NM
Shipman et al. (2011)
g
−1.69 0.03 39 1384 14.8 (1.9) TD Proxy PedsQL CC NM
Tavernor et al. (2012)
g
−1.81 0.10 10 1033 10.9 (1.4) TD Self PedsQL CC NM
Tavernor et al. (2012)
g
−2.58 0.10 11 427 10.9 (1.4) TD Proxy PedsQL CC NM
Kamio et al. (2012)
g
−0.97 0.01 154 828 27.6 (6.5) TD Self WHOQOL-BREF
h
CC M
Cottenceau et al. (2012)
g
0.34 0.04 26 250 15.0 (2.5) TD Self VSP-A
i
CC M
ADHD: attention deficit hyperactivity disorder; CC: diagnosis via clinical consensus; ILK: Inventory for the Assessment of Quality of Life in Children and Adolescents; LEC: Life Experiences Checklist; M:
mentioned; NM: not mentioned (no full assessment); PedsQL
™
: Pediatric Quality of Life Inventory; Q: questionnaires and rating scales; SI: structured instrument such as structured interviews and obser-
vation schedules; TD: typically developing; VSP-A: Experience and Perceived Health for Adolescents; WHOQOL-BREF: World Health Organization Quality of Life abbreviated version.
a
The age of the autism group.
b
When possible a TD control group was chosen as a comparison group.
c
The autism assessment procedure as described by the authors.
d
How co-morbidity was addressed.
e
Bastiaansen et al. (2004) compared to multiple clinical groups (people with ADHD, anxiety disorders, mood disorders and other disorders). Scores were combined into one clinical group by using the
formula for combining groups from the Cochrane handbook (Higgins and Deeks, 2011). The group ‘No diagnosis’ was neither included as a clinical control group (because no Diagnostic Manual of Statis-
tic Disorders–Fourth Edition (DSM-IV) diagnosis could be made) nor TD control group (because there were problems for which they were referred to mental health services).
f
Bennet et al. (2005) had two comparison groups: (1) high scorers on an autism questionnaire, but no autism diagnosis and (2) low scorers on an autism questionnaire and no autism diagnosis. Group 2 was
chosen as a comparison group since that group did not have any autism symptomatology.
g
Information to calculate effect size obtained through personal communication with the author.
h
Kamio et al. (2012) measured two subscales from the WHOQOL-BREF: psychological health and social relationships. To calculate the effect size psychological health was chosen, because this subscale
consists of more items, and has a high test reliability, internal consistency, construct validity and a strong correlation with, and high factor loading on, overall QoL (Skevington et al., 2004; Wang et al.,
2006).
i
Cottenceau et al. (2012) calculated two global scores from the VSP-A; Index 2 without ‘relationships with medical staff’ and ‘affective and sexual life’ dimensions and Index 4 without ‘relationships with
medical staff’ but with the ‘affective and sexual life’ dimension. To calculate an effect size, Index 4 was chosen since this included more dimensions.
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van Heijst and Geurts 161
Independent variables
For each study, the age of the autism participants was coded
as a continuous variable. The following categorical variables
were also coded: the respondent to the QoL questionnaire
(self-report or proxy-report), the comparison group (typi-
cally developing (TD) or clinical control group) and the QoL
questionnaire utilized (WHOQOL-BREF, Pediatric Quality
of Life Inventory (PedsQL) or other). The study characteris-
tics served as the independent variables in order to determine
whether these characteristics moderated the effect size.
Dependent variable
The QoL questionnaires generated continuous outcomes,
for which a standardized mean difference (Cohen’s d) was
calculated. This effect size is widely used, is easily inter-
pretable and can be calculated from t-test statistics
(Thalheimer and Cook, 2002; Turner and Bernard, 2006).
Data analyses
The data were analysed using the Metafor package for R
(Viechtbauer, 2010). A random effects meta-analysis was
performed to provide an average effect for the population
of studies, as the included studies were assumed to be a
random selection of the entire study population. We con-
ducted a mixed effects meta-analysis to determine the
moderating effects of the study characteristics. Effect sizes
were regressed on the study characteristics in a restricted
maximum likelihood meta-regression (Viechtbauer, 2010).
We tested the heterogeneity with conventional Q tests
and with the I
2
statistic. The I
2
statistic estimates how
much of the total variability in the effect size estimates
(composed of heterogeneity and sampling variability) can
be attributed to heterogeneity among the true effects. We
checked for publication bias with funnel plots and the fail-
safe analysis (Rosenthal, 1979).
Results study 1
Overall result
Based on our qualitative analysis, there were many differ-
ences in QoL between people with and without autism.
The most affected domain of QoL seemed to be social
functioning (Bastiaansen et al., 2004; Jennes-Coussens
et al., 2006; Kamio et al., 2012; Kamp-Becker et al.,
2010). Other relevant reported findings were that the
autism group had fewer friends and more special educa-
tion (Bastiaansen et al., 2004); lower physical health
(Jennes-Coussens et al., 2006); lower QoL relating to
relationships with friends, leisure, affective and sexual
relationships; and placed less importance on activities
with peers and more importance on activities with parents
(Cottenceau et al., 2012).
Our quantitative analysis showed that the mean effect
size is large, d = −0.96; 95% confidence interval = −1.39,
−0.52; range = −2.58 to 0.34 (Figure 1). People with
autism had a lower QoL than people without autism, z =
−4.29, p < 0.001. There was significant heterogeneity
between the effect sizes, τ
2
= 0.63, Q(13) = 168.80, p <
Figure 1. Forest plot of the standardized mean difference (Cohen’s d) and 95% confidence interval of QoL. Negative effect sizes
imply that the QoL is lower in people with autism as compared to controls while positive effect sizes suggest the opposite pattern.
*Effect sizes were calculated separately for self-report and proxy-report. Thus, 14 effect sizes were calculated from 10 studies.
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