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Development of the FOSQ-10 A Short Version of the Functional Outcomes of Sleep Questionnaire

Development of the FOSQ-10 A Short Version of the Functional Outcomes of Sleep Questionnaire - Clinical Hub, UW Health Clinical Tool Search, UW Health Clinical Tool Search, Questionnaires, Related

SLEEP, Vol. 32, No. 7, 2009
TIVITIES affecting quality of life. The Functional Outcomes
of Sleep Questionnaire (FOSQ)
is the gold-standard, disease-
specific instrument designed to assess the impact of sleepiness
on the ability to conduct daily activities, conceptually defined
as functional status, a component of quality of life. The 30-item
FOSQ has proven validity and reliability, performing well as
an outcome measure in clinical trials.
However, it may be
too long to easily employ in large-scale studies and monitoring
as well as clinical practice. A shortened version may
facilitate the assessment of functional impairments consequen-
tial to excessive daytime sleepiness as well as the evaluation
of treatment-associated outcomes. The purpose of this study
was to develop a short version of the FOSQ (FOSQ-10) that (1)
could explain at least 90% of the variance in the long version;
(2) have psychometric properties and generate scores that were
comparable to the original FOSQ (FOSQ-30); (3) be able to
show comparable change with treatment, demonstrated by ef-
fect sizes, with the FOSQ-30.
Instrument development
Participants in all 3 of the samples used to develop and test
the FOSQ-10 were predominantly male, reflecting the repre-
sentation of this gender in the OSA population. The FOSQ-10
version of the instrument was developed using data (n = 155)
(Sample 1) from a multisite study of the effectiveness of 3
months of objectively monitored continuous positive airway
pressure (CPAP) treatment in participants with moderate to se-
vere obstructive sleep apnea (OSA) (apnea + hypopnea index
(AHI) = 63 ± 31).
Inclusion criteria for participation in this
study were men and women ages 20 to 60 years; qualitative
clinical evaluation of daytime sleepiness by a sleep physician;
AHI ≥ 15 events per hour; and a candidate for treatment with
CPAP. Persons were excluded if they had a diagnosis of any
coexisting sleep disorder by history or polysomnogram; use of
sedative or hypnotic medications; shift work; and any physi-
cal, cognitive, or psychological condition that might affect the
results. As shown in Table 1, the mean age of the participants
was 46.3 ± 9.18 years, 89% were male, and mean body mass in-
dex was 37.7 ± 8.49 kg/m
. Participants completed the original
FOSQ at baseline and again after 3 months of CPAP treatment.
Mean CPAP use was 4.91 ± 2.05 h/night.
The length of the FOSQ-10 was based on several consider-
ations. First, the overall goal was to develop a brief questionnaire
easily applied in clinical practice. Second, we wanted the shorter
questionnaire to reflect the 5 domains currently in the FOSQ
30: General Productivity, Activity Level, Vigilance, Social Out-
short versIon of the fosQ
Development of the FOSQ-10: A Short Version of the Functional Outcomes of
Sleep Questionnaire
Eileen R. Chasens, DSN, RN
; Sarah J. Ratcliffe
; Terri E. Weaver, PhD, RN
Assistant Professor, School of Nursing, University of Pittsburgh, Pittsburgh, PA;
Assistant Professor of Biostatistics, Center for Clinical
Epidemiology and Biostatistics, University of Pennsylvania School of Medicine, University of Pennsylvania, Philadelphia, PA;
Professor of
Nursing, Chair, Biobehavioral and Health Sciences Division, School of Nursing, Center for Sleep and Respiratory Neurobiology, Division of Sleep
Medicine, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA
Introduction: The Functional Outcomes of Sleep Questionnaire
(FOSQ), has been used in research and clinical practice to measure the
impact of daytime sleepiness on activities of daily living. The purpose of
this study was to develop a shorter version of the instrument (FOSQ-10)
that may be more easily implemented in clinical practice.
Methods: Data from a study of CPAP-treated obstructive sleep apnea
(OSA) patients (Sample 1) (n = 155, AHI = 63 ± 31) were used to de-
velop the FOSQ-10. Of the 30 original FOSQ items, 10 questions rep-
resenting each of the 5 subscales were selected if they had a normal
distribution of responses and the largest pre- to post-treatment effect
size. The psychometric properties of the instrument were then evalu-
ated with data from a second, independent sample of CPAP-treated
OSA patients (n = 51 AH I = 51 ± 28).
results: Internal consistency of the FOSQ-10 was α = 0.87. Pre-treat-
ment correlations of the 2 scales was r = 0.96. After 3 months of treat-
ment the correlation was r = 0.97 (P < 0.0001). Subscales were also
highly correlated at baseline and following treatment. Effect sizes for
both instruments were highly correlated and indicated ability to mea-
sure meaningful change. Differences were observed between scores
on the FOSQ-10 for normal controls and OSA patients.
Conclusions: The FOSQ-10 is a psychometrically strong instrument
that performs similarly to the long version. The rapidly completed and
easily scored FOSQ-10 shows promise for application in the clinical
Keywords: Functional status, sleepiness, outcome measure, sleep
disorders, CPAP, nasal continuous positive airway pressure, sleep ap-
nea, quality of life
Citation: Chasens ER; Ratcliffe SJ; Weaver TE. Development of the
FOSQ-10: a short version of the functional outcomes of sleep question-
naire. SLEEP 2009;32(7):915-919.
submitted for publication June, 2008
Submitted in final revised form March, 2009
Accepted for publication April, 2009
Address correspondence to: Terri E. Weaver, PhD, RN, FAAN, Professor
of Nursing, Chair, Biobehavioral and Health Sciences Division, University
of Pennsylvania School of Nursing, Claire M. Fagin Hall, 418 Curie Blvd.,
Philadelphia, PA 19104-6096; Tel:(215) 898-2992; Fax: (215) 573-7492;
E-mail: tew@nursing.upenn.edu
FOSQ-10—Chasens et al

SLEEP, Vol. 32, No. 7, 2009
comes, and Intimate and Sexual Relationships, and maintain the
high level of internal consistency found in the FOSQ 30. A length
of 10 questions was determined to meet these goals.
The FOSQ-10 was constructed by first examining the distribu-
tion of responses among the 4 possible choices for each item on
the long version to determine the frequency of endorsement.

Those items with evenly distributed pre- and post-treatment re-
sponses that also had the highest treatment effect sizes within
each subscale, reflecting the greatest magnitude of change, were
identified for inclusion in the shorter instrument. The number of
items selected from each subscale was dependent upon the length
of the subscale (i.e., the longer the subscale, the more items were
selected) as well as the strength of the effect size. Consideration
was also given to the cultural applicability or commonality of
the task assessed. Although the questionnaire contains a response
indicating that the patient does not engage in a particular activ-
ity, a decrease in the number of items answered would affect the
scoring of a shorter form more than a longer version (with several
items in each subscale). For example, as shown in Table 2, falling
asleep while taking public transportation had a higher effect size
than having difficulty remembering. However, not all patients
regularly take public transportation and would have to indicate
that they do not participate in that activity. Although difficulties
with arousal had a larger effect size (0.44) than difficulty with
intimacy (0.39), in some cultures asking such explicit questions
about sexual functioning is considered inappropriate. Therefore,
we chose the question on intimacy, which had the next highest
effect size and would be more culturally acceptable, while pro-
viding valuable information regarding the impact of sleepiness
on sexual activity. We also selected questions that represented the
range of activities within a subscale. For example, although dif-
ficulty being active in the afternoon had a higher effect size (1.0)
than relationships being affected (0.69), we chose to include the
latter because we had already included questions about activity
level in the morning and in the evening and believed it was more
pertinent to include a question regarding relationships, providing
a comprehensive assessment, than to include another question re-
garding activity level. It was also felt that the question regarding
activity in the evening would be sufficient to reflect activity level
in the latter half of the day. Thus, of the FOSQ-30 questions, 2
questions were selected from General Productivity, 3 from Activ-
ity Level, 3 from Vigilance, and one each from the Social Out-
come and the Intimacy and Sexual Relationships subscales. As
shown in Table 3, the effect sizes of the selected questions ranged
from 0.50 to 1.07, indicating a moderate to large treatment ef-
fect and clinically meaningful change
; except for the question
from the Intimacy and Sexual Relationships subscale, which had
a smaller effect size (0.39). Further eliminating items from the
FOSQ-10 did not produce a Cronbach α greater than that ob-
tained with the 10-item instrument (see below) and may be too
short to comprehensively assess daily functioning. A length of
11 or 12 items also did not appreciably improve the internal reli-
ability of the instrument (Cronbach α; data not shown) and would
likely impose on the goal of brevity and clinical utility. Effect
sizes for the FOSQ-10 and FOSQ-30 for Sample 1 were similar
for the 2 instruments as well as the baseline and post-treatment
range of scores (see Table 2). Thus, the 10-item scale was suffi-
cient to provide a global assessment of daily functioning yet short
enough to be completed rapidly.
Instrument evaluation
sample and Procedure
As an outcome measure, according to Kirshner and Guyatt,

psychometric evaluation would include analysis of the internal
reliability of the instrument and sensitivity to change. We used a
second independent sample to evaluate these psychometric prop-
erties in the FOSQ-10. The second sample (n = 51, 72% male)
consisted of patients (see Table 1) with obstructive sleep apnea
(AHI = 51 ± 28) who participated in a randomized study evaluat-
ing continuous flexible airway pressure (CFLEX
, Philips Re-
spironics) (n = 26) compared to CPAP (n = 25). The mean age of
the participants was 48 ± 10 years with a mean body mass index
of 33.98 ± 6.18 kg/m
. Mean adherence to treatment was 5.74 ±
1.38 h/night; statistically higher in the CFLEX group than CPAP
(CFLEX mean hours of use = 6.13 ± 1.35; CPAP mean hours
of use = 5.17 ± 1.28, P = 0.02). Participants in the study com-
pleted the original FOSQ at baseline and again after 90 days of
treatment. Study criteria included adherence to CPAP treatment
≥ 4 h per night; stable medical and psychiatric condition; no evi-
dence of significant upper respiratory symptoms or anatomical
abnormality; baseline Epworth Sleepiness Scale (ESS) score ≥
10; confirmed diagnosis of OSA with AHI ≥ 10/h; and success-
ful titration of CPAP with an AHI of < 5 with positive pressure.
Sample 3 (Table 1), who served as normal controls, were indi-
viduals (n = 57) recruited from the community who did not have
any sleep disorders as determined by polysomnography.
The scoring scheme for the original version of the FOSQ
was applied to the shorter instrument. As FOSQ-10 subscales
contained only 1 to 3 questions, for measurement precision, it is
anticipated that only the Total score would be employed as the
metric for the evaluation of the FOSQ-10. To obtain the Total
score, a mean-weighted item score was first computed for those
FOSQ-10—Chasens et al
Table 1—Demographic Characteristics of Sample 1, Sample 2, and Normal Controls
Characteristic Sample 1 (n = 155) Sample 2 (n = 51) Normal Controls (n = 57)
Mean ± SD or % Mean ± SD or % Mean ± SD or %
Age 46.3 ± 9.18 48 ± 10 43.17 ± 7.54
Sex 89% male 72% male 66% male
BMI 37.7 ± 8.49 33.98 ± 6.18 26.70 ± 6.6
AHI 63 ± 31 51 ± 28 < 5
ESS (baseline) 14.46 ± 4.93 ≥ 10 NA
Mean Hours Adherent to CPAP 4.91 ± 2.05 h/night 5.74 ± 1.38 h/night NA

SLEEP, Vol. 32, No. 7, 2009
subscales with more than one item. This approach prevented the
distortion of the score resulting from missing responses. The
Total score was derived by calculating the mean of the subscale
scores and multiplying that mean by 5. As shown in Table 3,
scores on the FOSQ-10 were quite comparable to scores ob-
tained using the long version and a distribution that included
the potential range of scores.
Psychometric Properties
The internal consistency of the 10-item instrument was simi-
lar to the long form with a Cronbach α of 0.87 (compared to
0.95 for the long version). Prior to treatment, the Total score of
FOSQ-10—Chasens et al
Table 2—FOSQ-30 Baseline and Post-Treatment Range of Scores and Effect Sizes for Treatment Response from Sample 1 for the FOSQ-30
and FOSQ-10 Subscales
FOSQ Subscale Question Domains FOSQ-30
Range of
Post Tx
Range of
Effect Size
Effect Size
Effect Size
General Productivity Concentration 2.5–2.9 3.3–3.5 0.83 1.22 0.99
Getting things done
because too sleepy to
0.6–1.2 0.90–2.5 0.81
Remembering 2.6–3.0 3.09–3.5 0.50
Working on hobby 2.6–3.1 3.3–3.7 0.57
Taking care of financial
affairs & paperwork
2.8–3.3 3.2–3.5 0.33
Employed or volunteer
2.8–3.2 3.1–3.6 0.33
Maintain telephone
3.0–3.5 3.4–3.8 0.34
Finishing a meal 3.3–3.7 3.5–3.8 0.16
Activity Level Activity in evening 2.2–2.6 3.2–3.5 1.1 1.34 1.4
Activity in morning 2.4–2.8 3.4–3.8 1.0
Activity in afternoon 2.4–2.8 3.4–3.8 1.0
Relationships affected 2.7–3.1 3.4–3.7 0.69
Keeping pace with others 2.7–3.1 3.3–3.7 0.63
General level of activity 2.1–2.4 2.6–2.9 0.63
Doing things for family 2.9–3.3 3.4–3.8 0.49
Doing housework 2.7–3.1 3.2–3.4 0.45
Exercising 2.6–3.1 2.8–3.4 0.21
Vigilance Watching movies 2.3–3.7 3.2–3.6 0.90 1.25 1.16
Watch TV 2.3–2.7 3.05–3.5 0.77
Enjoy a lecture 2.1–2.5 3.0–3.5 0.76
Driving long distance 2.3–2.8 3.1–3.6 0.69
Driving short distance 2.7–3.2 3.4–3.8 0.59
Participate in meeting 2.4–2.9 3.1–3.5 0.53
Enjoy a concert 2.2–2.7 2.6–3.3 0.34
Social Outcomes Visit in your home 2.8–3.3 3.4–3.8 0.57 0.91 1.0
Visit in their home 2.9–3.3 3.4–3.8 0.55
Intimacy and Sexual
Arousal 2.9–3.4 3.4–3.8 0.44 0.61 0.72
Desire intimacy 2.7–3.2 3.2–3.6 0.39
Sexual relationships 2.5–3.0 3.0–3.5 0.38
Orgasm 3.0–3.5 3.4–3.8 0.30

SLEEP, Vol. 32, No. 7, 2009
ment and post-treatment scores. The change scores of the two
instruments trend together, and although the short form has
fewer questions obtaining less information, the strong correla-
tion indicates that similar conclusions can be drawn when us-
ing the short form as would be the case if the longer form were
employed. Applying the criteria suggested by Nunnally and
Bernstein, the internal consistency of the short form surpasses
the threshold of 0.70 for application of the measure in both re-
search and clinical practice.
The range of pre-treatment and
post-treatment scores obtained for the Total score of the short
form indicates that, like the original instrument, it has the abil-
ity to detect a wide range of functional limitations. The two
versions of the FOSQ were able to reach the same statistical
conclusion regarding differences between normal controls and
patients with OSA.
With similar psychometric performance, the FOSQ-10
provides a simple means to assess functional status both in
the clinical arena and in large-scale health assessments with
minimizing information loss.
The importance of measuring
clinically salient outcomes such as functional status has been
highlighted by Ellwood who considers functional status, an
aspect of quality of life, a key component of outcomes man-
Indeed, the American Academy of Sleep Medicine
has identified improving quality of life as an indication for
The fact that the short version of the FOSQ is brief, can be
easily administered, and rapidly completed makes it an ideal
measure to assess functional status in clinical practice. In this
circumstance, only the Total score would be used in interpret-
ing the degree of impairment associated with daytime sleepi-
ness. If a more comprehensive evaluation of daily functioning
is desired, such as in research, the longer form is recommended
where the subscales can be utilized to characterize the nature
of the limitation independently within specific domains as well
as provide a global assessment. In conclusion, the FOSQ-10 is
a psychometrically strong instrument that shows promise as a
valid and reliable measure for the clinical evaluation of disor-
ders of excessive daytime sleepiness and the effectiveness of
related interventions.
the FOSQ-10 was robustly associated with the FOSQ-30 Total
score (r = 0.96, P < 0.0001), explaining 92% of the variance
in the longer version. The subscale scores of the 2 instruments
were also highly related and statistically reliable (see Table 3)
with a similar range of pre-treatment scores.
Following CPAP treatment, both the FOSQ-30 and the
FOSQ-10 detected a large,
clinically meaningful change
in the Total score (P < 0.0001). The correlation between the
post-treatment FOSQ-10 Total score and the same score for the
FOSQ-30 was r = 0.97 (P < 0.0001, 94% of the variance). As
illustrated in Table 3, the post-treatment and change scores of
the 2 instruments were also highly related.
In evaluating the utility of the FOSQ-10 to distinguish be-
tween known groups, we compared scores on the short form
for patients with OSA (Sample 2) to normal values for the
As expected, the baseline Total score on the
FOSQ-10 for the OSA group (mean = 12.48 ± 3.23) statisti-
cally differed (t = 8.65, P < 0.0001) from the normal values
(mean = 17.81 ± 3.10). This suggests that the FOSQ-10 can
successfully discriminate between normal individuals who do
not experience sleepiness-related impairment from those suf-
fering limitations in daily activities related to excessive day-
time sleepiness.
The degree to which impairment related to sleepiness is
evaluated and the benefit of treatment documented within the
context of routine practice depends on the convenience and
psychometric strength of outcome measures. We have met the
objectives of this study by developing a short, easily applied
measure with strong psychometric properties of reliability and
validity that adequately assesses how the symptom of daytime
sleepiness affects daily activities.
The FOSQ-10 captures the content of the original FOSQ
domains and related operational definitions as demonstrated
by the high proportion of the variance of the FOSQ Total score
explained by the shorter instrument and the robust relation-
ship between the FOSQ-30 and FOSQ-10 subscale pre-treat-
FOSQ-10—Chasens et al
Table 3—Baseline and Post-Treatment Means, Ranges and Correlations for FOSQ-30 and FOSQ-10 Subscales for Sample 2
Scale Baseline Post 90-days Follow Up Treatment Δ
Possible Mean Min Max Pearson r P Value Mean Min Max Pearson r P Value Pearson r P Value
Productivity 1-4 2.85 ± 0.70 1.3 4 0.83 < 0.0001 3.58 ± 0.43 2.6 4 0.90 < 0.0001 0.73 < 0.001
FOSQ-10 General
Productivity 1-4 2.41 ± 0.92 1 4 3.31 ± 0.71 2.0 4
Activity Level 1-4 2.31 ± 0.73 1 4 0.91 < 0.0001 3.33 ± 0.54 2.0 4 0.93 < 0.0001 0.91 < 0.001
FOSQ-10 Activity Level 1-4 2.14 ± 0.83 1 4 3.33 ± 0.58 2.0 4
Vigilance 1-4 2.40 ± 0.73 1 3.9 0.84 < 0.0001 3.38 ± 0.56 1.6 4 0.91 < 0.0001 0.85 < 0.001
FOSQ-10 Vigilance 1-4 2.65 ± 0.73 1 4 3.53 ± 0.51 1.7 4
Social Outcomes 1-4 2.84 ± 0.86 1 4 0.97 < 0.0001 3.62 ± 0.62 1.0 4 0.95 < 0.0001 0.95 < 0.001
FOSQ-10 Social Outcomes 1-4 2.84 ± 0.86 1 4 3.70 ± 0.61 1.0 4
Intimacy and Sexual
Relationships 1-4 2.54 ± 0.96 1 4 0.89 < 0.0001 3.26 ± 0.85 1.0 4 0.93 < 0.0001 0.89 < 0.001
FOSQ-10 Intimacy and
Sexual Relationships 1-4 2.32 ± 1.02 1 4 3.25 ± 0.93 1.0 4
Total Score 5-20 13.04 ± 3.04 7.03 19.7 0.96 < 0.0001 17.7 ± 2.50 9.5 20 0.97 < 0.0001 0.95 < 0.001
FOSQ-10 Total Score 5-20 12.48 ± 3.23 6 19.3 17.1 ± 2.57 9 20

SLEEP, Vol. 32, No. 7, 2009
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This research was supported by grants from the National
Institutes of Health, National Heart Lung and Blood Institute
HL53991 (T. Weaver); P50-HL60287 (A. Pack, G. Maislin, D.
Dinges, and T. Weaver), Respironics, Inc., Nellcor Puritan Ben-
nett Inc., DeVilbiss Health Care Inc., and Healthyne Technolo-
gies, Inc. We wish to thank Respironics, Inc. for providing the
Sample 2 data.
dIsClosure stAteMent
This was not an industry supported study. Dr. Weaver has
received research support from Respironics; has consulted for
Jazz, Sanofi-Aventis, Apnex Medical, and Cephalon; has had
the use of research equipment form Respironics and Protech;
and has FOSQ license agreements with Jazz, Sanofi-Aventis.
Merck, Sleep Solutions, RTI Health Solutions, NV Organon,
and Aspire Medical. The other authors have indicated no finan-
cial conflicts of interest.
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