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40 The Open Sleep Journal, 2008, 1, 40-51
1874-6209/08 2008 Bentham Open
Open Access
Developing Architectural Lighting Designs to Improve Sleep in Older
Adults
Mariana G. Figueiro*
,1
, Elyse Saldo
2
, Mary S. Rea
2
, Karen Kubarek
2
, Julie Cunningham
3
and Mark
S. Rea
1
1
Lighting Research Center, Rensselaer Polytechnic Institute, Troy, NY, USA
2
Department of Biology, The Sage Colleges, Troy, NY, USA
3
Department of Psychology, The Sage Colleges, Troy, NY, USA
Abstract: This paper discusses a proposed 24-hr lighting scheme for older adults that can positively impact the aging vis-
ual, circadian and perceptual systems. New lighting was installed in eight private rooms in an assisted living facility.
Measurements of residents’ sleep quality and circadian rest-activity patterns were obtained, before and after the new light-
ing was installed. Consistent with predictions based upon previous research, the subjects who completed the study showed
an improvement in sleep quality and rest/activity rhythms under the new 24-hr lighting scheme. In addition, all study par-
ticipants reported a strong preference for the 24-hr lighting. The new lighting not only provides older adults with good
lighting for performing their routine visual tasks, but also promotes high circadian light stimulation during the day and
low circadian light stimulation at night. Although not studied here, but also discussed as part of the 24-hr lighting scheme,
is the impact of a previously studied, novel night-light system that provides older adults with enhanced perceptual cues for
nighttime navigation within the room. The new 24-hr lighting scheme appears to have important practical implications for
improving the quality of life for seniors and will hopefully be adopted by architects, lighting specifiers and engineers.
Keywords: Senior housing, lighting, visual system, circadian system, sleep quality.
INTRODUCTION
Light reaching the retina allows us to see [1] and it syn-
chronizes our circadian rhythms to the 24-hr solar day [2].
Lighting also affects the perceptual system enabling us to
orient ourselves to the spatial environment and to help main-
tain postural control and stability [3]. There are two major
problems with residents in all senior health care facilities:
poor sleep quality and falls. New approaches to lighting de-
sign can be used to address these two major problems. This
paper discusses an integrated, 24-hr lighting design strategy
for older adults that takes into account the needs of the aging
visual, circadian and perceptual systems [4]. Original results
are presented from a demonstration project designed to test
the effectiveness of light in improving sleep quality in older
adults. A recent study of a novel night-light system that de-
monstrably improved postural stability in older adults is also
summarized [5]. It is the authors’ hope that a deeper under-
standing of the physiological changes to the aging visual,
circadian and perceptual systems and how lighting affects
these systems will result in wider use of light as a non-
pharmacological tool to help improve the quality of life of
older adults.
BACKGROUND
The Human Visual System
The eye consists of optical and neural parts. The function
of the optical parts of the eye is to place a focused, clear im-
*Address correspondence to this author at the Lighting Research Center,
Rensselaer Polytechnic Institute, Troy, NY, USA; E-mail: figuem@rpi.edu
age of the outside world on the retina. The optical parts of
the eye assure that light is transmitted through the eye with
minimal absorption and scattering. The function of the retina
is to absorb light signals and convert them to electrical sig-
nals. The human eye has photoreceptors that convert radiant
energy into neural signals for processing by the brain, a phe-
nomenon called phototransduction. Until recently, four types
of photoreceptors had been identified: rods and short, mid-
dle, and long wavelength cones. Rods allow us to see at
night and cones allow us to see during the day, discriminate
details and see colors. The human visual system can process
information over a large range of luminances (about 12 log
units). In order to cope with a wide range of retinal illumi-
nances from nighttime light levels (0.000001 cd/m
2
) to out-
door light levels (100,000 cd/m
2
), the human visual system
changes its sensitivity continuously, a process called adapta-
tion. As confirmed by many studies (reviewed in [1]), at
typical office illuminance levels (500 lux on the task surface
or approximately100 lux at the eye), visual performance is
near maximum for young adults (for targets of high contrast
and large size). The process of adaptation also influences the
spectral sensitivity of the visual system because different
combinations of photoreceptors are operating at different
retinal illuminances. At photopic light levels (adaptation
luminances higher than approximately 1 cd/m
2
), typical of
building interiors, retinal response is dominated by cone
photoreceptors in the fovea and periphery. The luminous
efficiency function for the CIE Standard Photopic Observer
has a maximum sensitivity at 555 nm. At scotopic light lev-
els, (adaptation luminances below 0.001 cd/m
2
) only rod
photoreceptors respond to light stimulus and the fovea is not
Developing Architectural Lighting Designs The Open Sleep Journal, 2008, Volume 1 41
operating. The luminous efficiency function for the CIE
Standard Scotopic Observer has a maximum sensitivity at
507 nm [6, 7]. At mesopic light levels, (adaptation lumi-
nances between approximately 0.001 and 1 cd/m
2
), both rods
and cone photoreceptors are active. There is no official lu-
minous efficiency function for the Standard Mesopic Ob-
server. Spatial distribution of light on the retina is critical to
vision. Through optical refraction by the cornea and lens in
the eye and by neural-optical enhancements by the retina, the
spatial distribution of objects and textures in the environment
can be processed with high fidelity by the visual system. The
visual system can fully process light pulses as short as 80
milliseconds, so the temporal characteristics of light are gen-
erally not considered in the lighting design process for the
visual system [1].
The Human Circadian System
The world rotates around its axis and as a result, all crea-
tures exposed to daylight on earth experience 24-hour cycles
of light and dark. Biological rhythms are self-sustaining os-
cillations with a set of species-specific characteristics, in-
cluding amplitude, phase, and period [8]. Living organisms
have adapted to this daily rotation of the earth by developing
biological rhythms that repeat at approximately 24 hours.
These are called circadian rhythms (Latin: circa, about; dies,
a day). Circadian rhythms are generated endogenously (in-
ternal to the body) and are constantly aligned with the envi-
ronment by zeitgebers, factors exogenous or external to the
body. In mammals, circadian rhythms are regulated by an
internal biological clock (pacemaker) located in the su-
prachiasmatic nuclei (SCN) of the hypothalamus of the brain
[8]. The SCN is a self-sustaining oscillator that maintains its
daily activities for weeks when isolated and cultured. The
SCN in humans has a natural period that is slightly greater
than 24 hours and environmental cues can reset and syn-
chronize the SCN daily, ensuring that the organism’s behav-
ioral and physiological rhythms are in synchrony with the
daily rhythms in its environment. The light/dark cycle is the
main synchronizer of the SCN to the solar day [9] and
reaches the SCN via the retinohypothalamic tract (RHT). In
2002, the intrinsically photosensitive retinal ganglion cell
(ipRGCs), a novel photoreceptor type in the retina was dis-
covered [10]. The ipRGCs are central to the “non visual”
responses to light by the retina, most notably the regulation
of circadian rhythms. It has been suggested that a combina-
tion of classical photoreceptors and the ipRGCs participate
in how the retina converts light signals into neural signals for
the circadian system [11, 12]. The exact amount of light
needed to activate the circadian system is still under debate,
especially outside laboratory conditions. Based on studies
that have been conducted under controlled conditions, it is
now accepted that light levels needed to activate the cir-
cadian system are higher than those needed to activate the
visual system, so one can see well in the environment, but
may not be getting enough light to stimulate the circadian
system. The circadian system is a “blue-sky detector,”
maximally sensitive to wavelengths shorter than 470 nm [12-
14]. Unlike the visual system, the circadian system simply
detects changes in overall irradiance, that is, the circadian
system does not care about pattern information or image
forming [15]. Perhaps the largest difference between the
visual and circadian systems is associated with when light is
registered on the retina [15, 16]. Light can either advance or
delay the SCN, that is, light applied after wake-up time will
cause one to go to bed earlier and wake up earlier while light
applied before bed times will cause one to go to bed later and
wake up later [16]. The circadian system takes longer to re-
spond than the visual system. It takes approximately 5-10
minutes for a measurable effect of light on markers of the
circadian system to be seen [17]. Finally, the circadian sys-
tem is concerned with changes in light levels, rather than
absolute light levels [18]. For example, an older person who
stays in a dim room all day long will suppress more mela-
tonin when exposed to a given light at night than would a
farmer, who has experienced very high outdoor light levels.
Contrast in light exposure during the day and night is impor-
tant to maintain a healthy and synchronized circadian sys-
tem.
The Human Perceptual System
There are many theoretical models of how people per-
ceive the three-dimensional world around them. Previc [19]
describes a comprehensive model that incorporates all of
these models into one. This model consists of four behav-
ioral realms: peripersonal (visuomotor operations in near-
body space), focal extrapersonal space (visual search and
object recognition), action extrapersonal (orienting in a to-
pographically defined space), and ambient extrapersonal
(orienting in earth-fixed space). All of these areas together
combine for a total 3-D perception of space; however, the
ambient extrapersonal realm is the area that is most impor-
tant for the perception of surface planes and orienting one’s
self to these planes. Its three main functions are spatial orien-
tation, postural control, and locomotion. All of these func-
tions are necessary to navigate changes in the world such as
inclines, obstacles, and edges.
Gibson [3] describes the senses as perceptual systems.
There are five main perceptual systems: the orienting sys-
tem, the auditory system, the haptic (cutaneous or touch)
system, the taste-smell system, and the visual system. These
systems use information gathered from the environment to
enable humans to perform activities such as spatial orienta-
tion, postural control, and locomotion. The sensory systems
involved with the ambient extrapersonal realm are visual
perception (ambient motion, slant), vestibular, and somato-
sensory/proprioceptive (orientation). However, the visual
system is the dominant system involved. The environment
surrounding an individual is the source of all stimulation for
perception. A person gains perspective by the many inter-
secting planes that make up the environment. When these
planes are illuminated, they reflect light and project struc-
ture. The different ways these planes are connected offer
further information about the environment. For example, one
plane in front of another represents an edge, while two plane
surfaces joining one another represents a corner. Horizontal
cues are obtained both from visual sensations of horizontal-
ity and by vestibular feedback cues. Architectural features
can be used to provide information about the environment
and therefore improve navigation in the space. Light is a
stimulus to the visual system and visual information provides
a spatial reference for self-position and location of obstacles
within a person’s surroundings. Removal of visual cues by
closing the eyes has been shown to result in increased body
sway. Therefore, lighting schemes that enhance architectural
42 The Open Sleep Journal, 2008, Volume 1 Figueiro et al.
features should be used to help with navigation and orienta-
tion in a space.
Changes to the Aging Visual System
Although visual capabilities decline from the age of 20
years, the human visual system can often be considered
“young” until about the age of 40 years [20]. Then, changes
to the aging eye become more noticeable as visual capabili-
ties decrease. Trouble focusing on objects at different dis-
tances (known as presbyopia) is particularly common after
age 45. Hardening of the crystalline lens capsule and, per-
haps, atrophy of the ciliary muscles are the primary causes of
lost accommodation. By age 65, variable accommodation is
nearly impossible and multi-focal lenses are required. As a
person grows older, less light reaches the back of the eyes
because the pupil gets smaller and the crystalline lens inside
the eye becomes thicker, absorbing more light. A 60-year old
receives about 1/3 of as much light at the retina as a 20-year
old. The lens also begins to scatter more light as one ages,
adding a “luminous veil” over images on the retina, which
reduces the distinctness (or contrast) of objects and the viv-
idness of colors. Reds begin to look like pinks, for example.
Moreover, the older eye loses some sensitivity to short-
wavelengths (blue light) due to progressive yellowing of the
crystalline lens. Because of neural changes that occur to the
aging eye, older adults take longer to adapt to changes in
brightness (e.g., transitioning from indoors to outdoors).
Last, but not least, chances of having age-related eye dis-
eases (cataract, glaucoma, macular degeneration, and dia-
betic retinopathy) are greater after age 60 to 65 years. Be-
cause of these changes to the aging eye, more light on the
task is required for older adults to perform visual tasks, es-
pecially those of low contrast and small size. The aging vis-
ual system is also more sensitive to glare, so lighting that
meets the need of the aging eye should be glare free (i.e., no
direct or reflected view of the light source is acceptable).
Because the older adult’s visual system cannot completely
adapt to dim conditions, light levels in transitional spaces
(such as hallways and entrance foyers) should be balanced
with those of the adjacent spaces. Intermediate light levels in
transitional spaces that lead from bright to dim areas should
be created [21]. This will enable older adults to adapt more
completely as they move through the different spaces. Re-
flecting light off of light color surfaces will reduce the likeli-
hood that pools of light and dark are formed in the space
while increasing light uniformity.
Changes to the Aging Circadian System
Sleep disturbances increase as we age and disruption of
the circadian system is one important reason. Surveys indi-
cate that 40 to 70 percent of the oldest members of the popu-
lation (over 65 years old) suffer from chronic sleep distur-
bances [22]. In general, this group of adults tends to go to
bed earlier in the evening and wake earlier in the morning
than younger adults. Frequent nocturnal awakenings, diffi-
culty falling asleep, and an increased number of naps during
the day are also more common in the oldest adults. Sleep
disturbances are associated with decreased physical health,
including increased cardiovascular problems, disruption of
endocrine functions, and decline of immune functions [23].
Studies of the circadian pacemaker, the central compo-
nent of the circadian system, have shown reduced neuronal
activity in the SCN of the elderly, especially after the age of
80 [24], and a reduced circadian rhythm amplitude after the
age of 50 [25]. This suggests that, at a molecular level, the
SCN becomes less responsive to entrainment stimuli such as
light-induced neural signals from the retina. Further, it is
hypothesized that some of the neural processes involved in
entrainment might be dysfunctional or less effective as we
age [26]. Light information travels from the retina to the
SCN through the RHT. Disturbances in circadian rhythms
leading to poor sleep in older adults can be the result of dys-
functional circadian pathways or a pathway that cannot proc-
ess light information with as much fidelity. Also, the first
stage of phototransduction (when light signals are converted
into neural signals) is negatively affected: older adults not
only have reduced optical transmission at short wavelengths,
which is maximally effective for the circadian system, they
also lead a more sedentary indoor lifestyle, with less access
to bright light during the day. In fact, research has demon-
strated that middle-aged adults are exposed to approximately
58 minutes of bright light per day [27] while older adults in
assisted living facilities were exposed to bright light for only
35 minutes a day [28]. Moreover, adults in nursing homes
see as little as 2 minutes a day [29]. Finally changes in the
amplitude and timing of melatonin and core body tempera-
ture rhythms may occur in older adults. Lower amplitude of
melatonin rhythms may be associated with reduced sleep
efficiency and deterioration of internal circadian rhythms,
affecting hormone production, alertness, and performance
[30]. Furthermore, earlier timing of melatonin rhythms peaks
may induce earlier drops in core body temperature. Waking
typically occurs about two hours after the minimum core
body temperature, so the early waking times of older adults
may be a result of earlier core body temperature troughs (re-
viewed in [31]. In addition, the time interval between the
core body temperature minimum and waking time is reduced
in elderly subjects [32].
Changes to the Aging Perceptual System
In addition to reductions in retinal illumination due to the
aging eye, the quality of the retinal image is also compro-
mised in older adults, possibly contributing to falls. Age-
dependent changes in the crystalline lens lead, in particular,
to poorer spatial vision. As the crystalline lens ages it be-
comes less clear and scattered light reduces spatial resolu-
tion, not only reducing visual acuity but also elevating con-
trast threshold for all spatial frequencies [33]. Under low
light levels even high contrast objects, such as door frames
and objects on the floor, can go undetected, leading to dis-
orientation and falls [34].
Neural changes also become problematic for the oldest
people in our population. Gibson [3] describes a number of
higher-order perceptual phenomena that can be compromised
in seniors. In particular, an inability to orient oneself with
respect to the environment becomes more common with ag-
ing. This neural weakness is confounded and amplified by
optical changes in the eye (reduced retinal illuminance and
spatial resolution) and, together, may contribute significantly
to the increased incidence of falls found in older people.
Previous Studies
It is well established that lighting that is designed with
the aging visual system in mind can help increase independ-
Developing Architectural Lighting Designs The Open Sleep Journal, 2008, Volume 1 43
ence in older adults. The Lighting Research Center (LRC) at
Rensselaer Polytechnic Institute developed and published
guidelines for designing lighting for older adults sponsored
by AARP Andrus Foundation. The Illuminating Engineering
Society of North America (IESNA) published a Recom-
mended Practice with recommendations for lighting for older
adults that meet the needs of the aging eye.
A new area of investigation is the impact of light on sleep
efficiency of older adults. Studies using bright white light
have demonstrated that light treatment can help reduce the
negative impact of aging on circadian rhythms of sleep and
wake, and thus, improve the quality and quantity of sleep in
older adults, including those with Alzheimer’s disease (AD).
Bright white light exposure in the morning improved sleep in
institutionalized older adults. Fetveit and colleagues [35]
demonstrated that exposure to 2 hours of bright light in the
morning for at least 2 weeks substantially improved sleep
efficiency of older adults living in nursing homes. Alessi
et al. [36] showed that five consecutive days of 30-minute
exposure to sunlight, increased physical activity, structured
bedtime, and control of light and noise at night resulted in a
significant decrease in daytime sleeping in intervention par-
ticipants compared to controls. Further, they showed that
intervention participants had increased participation in social
and physical activities as well as social conversation. Mur-
phy and Campbell [37] have shown that light exposure in the
evening can delay the circadian clock and help older adults
sleep better at night and be more awake during the day.
Fontana Gasio et al. [38] investigated the effectiveness of a
3-week exposure to a low intensity (approximately 200 lux
at the eye level) dawn-dusk simulation in improving distur-
bances of circadian rest-activity cycle, nocturnal sleep and/or
cognitive functions in 13 demented patients. There were no
significant changes in cognition, nor there was a modifica-
tion of circadian rest-activity cycle. However, the main sleep
episode was 1:14h earlier during treatment compared with
before and after dusk-dawn simulation. Further, patients who
underwent treatment tended to have shortened sleep latency,
longer sleep duration, and less nocturnal activity than the
control group. In parallel, nighttime light exposure tended to
be reduced.
Studies have also demonstrated that bright white light
exposure during the morning improves nighttime sleep, in-
creases daytime wakefulness, reduces evening agitation be-
havior, and/or synchronizes rest/activity patterns of people
with AD. These studies have used bright white light (at least
2500 lux and as high as 8000 lux) for at least 1 hour in the
morning, and treatment was carried on for at least 2 weeks.
Results showed greater sleep efficiency at night, decreased
sleep during daytime hours and, in some cases, reduced agi-
tation behavior [39-44]. Unattended exposure to bright white
light during the entire day improved rest/activity rhythms of
people with AD. Van Someren and colleagues [45] demon-
strated that exposing 22 dementia patients to continuous
bright indirect light (average of 1136 lux) over 4 weeks con-
solidated rest/activity rhythms of people with AD. Bright
white light exposure in the evening has also been shown to
improve quality of sleep and/or decrease nocturnal activity
and severity of sundowning (evening agitation). Satlin and
colleagues [46] demonstrated that evening exposure to bright
light (1500 to 2000 lux) for 2 hours decreased nocturnal ac-
tivity and severity of sundowning of AD patients. Figueiro
and colleagues have conducted two studies showing the im-
pact of blue light from light emitting diodes (LEDs) on sleep
quality in elderly persons with varying AD symptoms [47,
48]. The first six-week study was conducted in February and
March 2002 in a senior health care facility in Clifton Park,
NY. During the evening from 18:00 to 20:00, four AD pa-
tients were exposed to light from tabletop light fixtures (~ 30
lx at the cornea of red LEDs) for 10 days. The red light ex-
posure (RLE) condition was introduced as a control, because
red light at this intensity should not activate the circadian
system [12, 13, 49]. RLE was followed by 10 days of ~ 30 lx
of blue light exposure (BLE) using a similar fixture. Blue
light was expected to activate the circadian system. All indi-
a
b
Fig. (1). a). Motion-sensor controlled amber LEDs installed under
bed.* b). Motion-sensor controlled amber LEDs installed around
doorway.*
* Notes: 1) photosensors were disconnected for the photos; 2)
overhead fluorescent luminaire was kept off after installation of
night-lighting.
44 The Open Sleep Journal, 2008, Volume 1 Figueiro et al.
cators obtained in the study following BLE were consistent
with theoretical expectations. The percentages of sleep re-
vealed a statistically significant time by lighting conditions
interaction (p=0.003). The percentages of time that subjects
were asleep at 02:00 and at 04:00 were significantly greater
(p=0.046 and p=0.013, respectively) after BLE than after
RLE. Wrist-worn actigraphic recordings for two subjects
found a greater consolidation of activity to the daytime rela-
tive to the nighttime. For the patients with the most advanced
stage of AD, the estimated time of peak activity shifted from
04:00 during RLE to 11:40 after BLE. A similar protocol
was used two years later, and the study was expanded to in-
clude older adults without dementia but who had sleep com-
plaints. Similar results were obtained. Older adults with and
without AD slept significantly better after two-hour exposure
to 30 lux of blue light at the cornea than after exposure to the
same 30 lux of red light at the cornea [48].
Researchers at the LRC also conducted a small study to
verify the acceptance of the lighting solution that provides
visual information as well as vertical and horizontal percep-
tual cues [48]. In four bedrooms in a long-term care facility
in Clifton Park, NY, researchers mounted linear arrays of
amber-colored LEDs to the underside of the bed frame,
around the adjacent bathroom door frame, and under the mir-
ror and handrail in the bathroom (Figs. 1 and 2). The LED
array under the bed provided general, low-level ambient light
at night; illuminance levels between 10 and 15 lux were
measured on the floor next to the bed. The LED array fram-
ing the bathroom door contributed approximately 2 to 10 lux
on the floor near the door and when standing at the door
frame, 10.5 lux was measured at the plane of the cornea. The
array of LEDs in the bathroom provided 5 to 10 lux at the
center of the bathroom floor and about 2 to 4 lux at the cor-
nea when standing at the sink. Amber lights were selected
because they are more efficient and less expensive than
white LEDs, emit enough light to see, and are still relatively
close in color to the very familiar incandescent light source.
Each system was controlled by a photosensor to ensure that
the LED lighting did not come on during the day or when the
overhead lights were on. A motion sensor slowly turned the
lights on when the residents put their feet on the floor and
when nurses walked into the room. The new lighting mini-
mized waking the residents while allowing the nursing staff
to perform their mandatory nighttime bed checks. If the resi-
dents were awakened by the nurse, however, they no longer
had to experience discomfort from bright overhead lights.
Before-and-after surveys of residents and staff were used
to evaluate the bedroom and bathroom lighting. The after-
intervention survey was conducted two weeks following the
installation. Seventeen night staff members completed sur-
veys about the pre-existing lighting conditions. Sixteen staff
members completed surveys about the newly installed light-
ing. Twelve residents were interviewed about the pre-
existing lighting. The four residents who participated in the
study completed surveys about the lighting installed in their
bedrooms after the lighting intervention. Table 1 shows the
results of the survey regarding the bedroom and bathroom
lighting.
The results of the survey showed highly positive re-
sponses from both the staff and the residents to the novel
nightlighting, except for the responses of the staff to the
bathroom lighting who suggested that the bathroom lighting
was too dim. Indeed, in confirmation of these responses, the
bathroom did appear too dim to the experimenters as well.
Nevertheless, the novel nightlighting was well accepted by
both staff and residents in the long-term care facility. Most
of the dissatisfaction was related to the amount of light
available for staff to perform their tasks. In the next installa-
tion, it is proposed that either the amount of light be in-
creased or a task light be provided to the staff to perform
their rounds. Finally, Figueiro and colleagues [5] showed
that the novel nightlighting system that provides horizontal
and vertical perceptual cues has potential to impact postural
stability and control in older adults. In a laboratory setting,
Figueiro and colleagues were able to demonstrate that night-
lights that provide perceptual cues can significantly reduce
sway velocity in the critical, early phase of a sit-to-stand test.
A Proposed 24-hr Lighting Scheme
Based on the different studies investigating the impact of
light on the visual, circadian and perceptual systems of older
adults, researchers at the LRC proposed a 24-hr lighting
scheme that meets older adults needs [4]. The proposed
lighting scheme was designed to provide 1) high circadian
stimulation during the day and low circadian stimulation at
night, 2) good visual conditions during waking hours, and 3)
nightlights that provide perceptual cues to increase lighting
for nighttime navigation as well as increased postural stabil-
ity and control while transitioning from a sitting to a stand-
a
b
Fig. (2). a). Motion-sensor controlled amber LEDs installed at
sink. b). Motion-sensor controlled amber LEDs installed at toilet.
Developing Architectural Lighting Designs The Open Sleep Journal, 2008, Volume 1 45
ing position. High circadian stimulation (CS) by light can be
achieved by providing at least 400 lx at the cornea of a cir-
cadian effective white light source (i.e., more short-
wavelength energy) during the daytime. This white light
source can be daylight or any high correlated color tempera-
ture (CCT) light source, such as a 6500 K lamp. The use of
higher CCT lamps is recommended if available in the mar-
ket.
Light levels may need to be increased if the duration of
exposure is shorter (i.e., two hours), but this dose/temporal
relationship is yet to be established in real life applications,
so the light levels recommended here are high enough and
long enough to assure an effect on the circadian system of
older adults. The recommended dose also takes into account
the normal changes to the aging eye. No more than 100 lux
at the cornea of a circadian-ineffective white light source
(i.e., less short wavelength energy), such as a 2700 K lamp,
is recommended for evening hours. The light levels were
selected on the basis of estimated melatonin suppression as a
function of CS after one hour exposure [12, 50]. It should be
noted that the relationship between melatonin suppression
and consolidation of rest/activity rhythms remains unclear. It
must be true, however, that the proposed lighting scheme
will provide a better light and dark pattern for the circadian
system than the dim unvarying ones commonly found in
senior care facilities. Moreover, the proposed lighting solu-
tion will provide older adults with a high contrast between
daytime and nighttime light stimulation. When taking into
account the light levels and the spectra of the light sources
used during the day and at night, contrast between day and
night circadian light can be as much as 15:1, while the visual
light contrast is 4:1. The proposed lighting solution should
also be glare free and shadow free, and therefore, it should
satisfy the needs of the visual system of older adults. Figs. (3
to 7) show examples of how to implement the proposed
lighting solutions. If addition of new lighting systems in the
space is not possible (e.g., retrofit application or energy
codes), the designer should consider the use of supplemental
Table 1. Survey results. Sixteen staff members completed surveys about the newly installed lighting. Twelve residents were inter-
viewed about the pre-existing lighting. The four residents who participated in the study completed surveys about the
lighting installed in their bedrooms after the lighting intervention
Before Installation Surveys – Staff Yes No Not available
Do you turn on the room lights for performing checks on the residents at night? 100% 0% 0%
When checking on the residents at night, are they likely to wake up? 94% 6% 0%
Do the residents find the room lights uncomfortably bright at night? 82% 0% 18%
Before Installation Surveys – Residents Yes No Not available
Does the staff turning on the lights at night wake you up? 83% 0% 17%
Do you find the overhead lighting bright or glaring at night? 91% 0% 9%
Is it difficult to find or reach the lighting controls at night? 83% 8% 9%
After Installation Surveys – Staff Yes No Not available
There is enough light for performing checks on residents during the night. 81% 19% 0%
The (colored) lighting is useful. 93% 0% 7%
There is enough light in the bathroom without having to turn on overhead lighting. 62% 38% 0%
It is convenient to have the lighting on a motion sensor. 100% 0% 0%
After Installation Surveys – Residents Yes No Not available
Does the colored light wake you up at night when the nurses come in? 0% 100% 0%
Is the colored light uncomfortable at night if you get up to go to the bathroom? 0% 100% 0%
Do you like the colored light? 100% 0% 0%
Fig. (3). Daytime view (use of high CCT lamps).
46 The Open Sleep Journal, 2008, Volume 1 Figueiro et al.
lighting using blue LED luminaires or light boxes (peak at
470 nm) providing at least 30 lux at the cornea. This sup-
plemental lighting can be placed on dining tables, television
screens, or wheelchairs during morning hours. Finally, the
designer should plan on a nightlighting system that provides
sufficient illumination for the older adults to navigate in the
space without disrupting their sleep as well as perceptual
cues to help with balance. It is recommended that a night-
lighting system such as the one described above be adopted
in senior care facilities.
Fig. (4). Nighttime view (use of low CCT lamps).
Fig. (5). View of the kitchen (low CCT lamps).
Fig. (6). View of bedroom at night (low CCT lamps).
Fig. (7). View of nightlighting system.
MATERIALS AND METHODOLOGY
The Demonstration Project
The research project presented here was conducted to test
the effectiveness of the proposed 24-hr lighting scheme on
sleep quality of older adults. The study was approved by
Rensselaer’s Institute Review Board (IRB). The focus of the
demonstration project was to evaluate how the use of light-
ing with high circadian stimulation during the day and low
circadian stimulation at night would impact subjects’ sleep
quality. The secondary goal was to probe the subjects’ over-
all acceptance of the new lighting in an assisted living resi-
dential setting.
Location
The demonstration project was conducted at The Terrace
at Eddy Memorial, an assisted living facility in Troy, NY.
The Terrace is a multi-level care residence, where most of
the residents live independently but can have assistance with
bathing, dressing and medication management. The rooms
were private studio apartments with kitchenettes and resi-
dents spent part of their days in their rooms watching televi-
sion, napping or reading books.
Subjects
Subjects were recruited by the facility’s director of resi-
dent services. She identified subjects with sleep problems
and asked them if they were willing to participate in a light-
ing study. None of the subjects were informed about the
goals of the study; they were simply told that it was a light-
ing study. Ten female subjects were recruited for the ex-
periment, but one subject decided to withdraw from the ex-
periment prior to baseline data collection, one subject did not
want to add the new light fixtures to in her room, and one
subject had to be hospitalized during the study. A total of
seven subjects completed the study. Out of the seven sub-
jects who completed the study, one subject was legally blind
(which reduces the effectiveness of the light stimulus), one
subject did not stay in the room often because her husband
was staying at the adjacent nursing home and she would
spend most of the day with him, and one subject continu-
ously unplugged the lamps from the wall. Because of that,
we also looked at the results for the four subjects who com-
pleted the experiment without restrictions. Subjects’ age
ranged from 80 to 98 years old. Except for one subject, all
Developing Architectural Lighting Designs The Open Sleep Journal, 2008, Volume 1 47
had sleep complaints and three subjects were on sleep medi-
cation. Other than the subject who was legally blind, no
other subjects reported any eye disease, other than normal
presbyopia and reduction in contrast sensitivity due to age.
Lighting Conditions
The rooms were all illuminated with plug in table and/or
floor lamps and there were no ceiling lights in the room, ex-
cept for the entrance of the room (by the kitchenette) and the
bathroom. All of the table and floor lamps were outfitted
with incandescent lamps ranging from 60 to 150 watts (W).
Light levels in the rooms were measured during the daytime
using a commercial light meter. The measured daytime light
levels (including daylight) in the living rooms before the
lighting intervention ranged from 13 to 300 lux at plane of
the cornea.
The new lighting system had to be selected to comply
with the installation requirements of the facility, that is, the
luminaires had to be plug-ins. The new lighting was selected
to increase circadian stimulation during daylight hours. This
was achieved in two ways: 1) by increasing overall daytime
light levels by at least two to four times the existing light
levels by adding three to four table and floor lamps in each
room and 2) by using a 6500K lamp, which has more short-
wavelength content and was estimated to have twice the cir-
cadian stimulation as an incandescent lamp [12]. Their exist-
ing low-level incandescent table lamps were used during the
evening hours. The measured daytime light levels (including
daylight) in the living rooms after the lighting intervention
ranged from 200 to 475 lux at the cornea. Combined, the
cooler light source and the higher light levels gave a ratio
between daytime and nighttime circadian stimulation of at
least 4:1 and in some cases we were able to achieve a 6:1
ratio. The floor and table lamps were donated by Hunter
Lighting (three models were used: Greenwich table lamp,
Greenwich swing arm lamp, and Greenwich club floor
lamp). The screwbase compact fluorescent lamps were do-
nated by OSRAM SYLVANIA (CF23EL/MINI, 6500K).
The new table and floor lamps were used with a SYLVANIA
lamp and appliance indoor timer. The timer was set to turn
on the lights as soon as residents woke up (it varied among
subjects, but all lights were turned on between 06:45 and
08:00 hr). All the lights were programmed to be turned off at
18:00 hr. One subject “played” with the timers and her lamps
were continuously found off when experimenters were visit-
ing the facility to check on residents. One week after the new
lighting was installed, she asked to change the timer so that
lights were off at 16:00 hr instead of 18:00 hr. Even after the
timer change, the lights were found off during period visits
by the experimenters.
Dependent Measures
Two outcome measures were used to assess sleep quality
before and after the lighting intervention. The first outcome
measure was the Pittsburgh Sleep Quality Index (PSQI),
which is widely accepted as a useful instrument for measur-
ing sleep quality in various groups of patients. The question-
naire can be filled out in 5-10 minutes and has been shown to
have good validity for patients with psychiatric and sleep
disorders. The PSQI contains 19-item self-report questions
that yield seven component scores: subjective sleep quality,
sleep latency, duration, habitual sleep efficiency, sleep dis-
turbances, use of sleep medication, and daytime dysfunction.
A Global PSQI score of 5 or higher has been associated with
sleep disturbance. The second outcome measure was the use
of the actigraph, which is a small wrist activity monitor that
is widely accepted as useful instrument for measuring
rest/activity rhythms. The actigraph is used to obtain objec-
tive assessment of sleep quality in the field and has been
shown to correlate well with more traditional measures of
sleep quality, such as polysomnography [51]. A question-
naire probing their subjective assessment of the lighting in
their room before and after the intervention was also ob-
tained.
Procedures
The experiment ran from August 2007 to November
2007. Baseline data were collected between August 13 and
August 27, 2007. Upon arrival in their rooms, researchers
interviewed the subjects and asked them questions from the
PSQI and the lighting assessment questionnaire. Once the
interview was complete (about 15 minutes), subjects were
given the actigraphs and asked to wear them all the times
except when they were bathing or showering. Researchers
also performed light measurements in each room to docu-
ment baseline lighting conditions. Researchers stopped by
the facility every other day to check on the subjects, but none
of them had problems wearing the actigraphs and, in general,
they kept them on at all times. The actigraphs were worn for
2 weeks, after which researchers went back to the facility to
collect them and download the baseline data. During the
weeks of September 12 and September 24, the new lighting
was installed in each of the rooms. All the rooms had their
new lights controlled by timers to assure that lights were
turned on and off at specific times during the experiment.
The lights were kept on for 4 weeks (from September 24 to
October 22). During the last two weeks of the lighting inter-
vention period (between October 8 and October 22), subjects
were asked to wear the actigraphs once again. Between Oc-
tober 22 and October 24, researchers went back to the facil-
ity to collect the actigraphs and perform another interview to
assess their sleep quality (PSQI) and probe their acceptance
of the new lighting. At that time, the new lighting was turned
off and researchers came back a week later to put the acti-
graphs on for another 2 weeks. Ideally, a period of at least 2
weeks should have been used to allow their circadian sys-
tems to go back to baseline, but due to the deadline of the
project, this was not possible. Researchers performed a sec-
ond baseline data collection to check whether their sleep
quality would go back to the baseline values obtained prior
to the lighting intervention.
RESULTS
Two analyses were performed on the data. The first
analysis (analysis 1) included data from all seven subjects
who completed the experiment, regardless of the problems
during the study that may have led to less light exposure
during the day. The second analysis (analysis 2) included
only the subjects who, through observations made by the
researchers, were perceived to be in their rooms more often
during the intervention period, and therefore, were more
likely to have received more circadian light during the day.
We also compared the two sets of baseline data (the one col-
lected in August and the one collected in November). Al-
though the levels collected during the second baseline data
48 The Open Sleep Journal, 2008, Volume 1 Figueiro et al.
were not exactly the same as the levels during baseline 1,
there was no statistical significant difference between the
dependent measures for baseline 1 and 2 therefore, baseline
2 was not used in the analyses.
Data Analyses
The 19 self-rated items of the PSQI questionnaire were
combined to form seven component scores, each of which
has a range of 0-3 points. In all cases, a score of “0” indi-
cates no difficulty, while a score of “3” indicates severe dif-
ficulty. The seven component scores are added to give the
Global PSQI score that ranges from 0-21 points, with “0”
indicating no difficulty and “21” indication severe difficulty
in all areas. As mentioned above, a PSQI of 5 or above indi-
cates sleep problems. As an indication of consolidation of
circadian rest/activity rhythms [45], the following measures
were calculated from the actigraph data: 1) inter-daily stabil-
ity (IS), a ratio indicating the strength of coupling between
the light/dark cycle and rest-activity rhythm over a 24-hour
period (an increase in IS suggests an improvement); 2) intra-
daily variability (IV), an indication of the fragmentation of
the rest/activity rhythm; i.e., the frequency of the transitions
between rest and activity (a decrease in IV suggests im-
provement); 3) amplitude of the rest-activity rhythm, calcu-
lated as the difference between the means of the most active
10-hour period (M10) and the least active 5-hr period (L5) in
the 24-hr pattern (an increase in amplitude suggests im-
provement); 4) light/dark ratio, calculated from the quotient
of the average activity in the light period divided by the av-
erage activity in the dark period. A high light/dark ratio sug-
gests that subjects are more awake and active during the day
and more asleep and inactive at night; and 5) sleep effi-
ciency, which is an index of the amount of time in bed that is
actually spent sleeping and is calculated by dividing the ac-
tual sleep time by the time in bed and multiplying it by 100.
Finally, we compared the average rating given for each ques-
tion in the lighting assessment questionnaire. One tail paired
Student’s t-tests were used to determine whether there were
significant differences between the measurements obtained
before and after the lighting intervention.
PSQI
In analysis 1, there was no significant difference between
PSQI scores given after lighting intervention and baseline 1.
The average score for all the seven subjects who completed
the experiment was 6.35 before and after the lighting inter-
vention. The average score of the four subjects in analysis 2
showed a slight, but not statistically significant reduction in
PSQI scores (from 6.75 to 6). It is important to note, how-
ever, that the greatest improvements in PSQI score were with
subjects who had more significant sleep problems, as shown
by their high score at baseline. One subject had a score of 12
before the intervention and her score went down to 7 after
the lighting intervention and the other subject had a score of
11 before the intervention and her score went down to 9 after
the intervention. Nevertheless, on average, there was no sta-
tistical significant difference between the Global PSQI score
given before and after the lighting intervention.
Actigraph
In analysis 1, there was no statistical significant differ-
ence between IS, IV and amplitude values obtained before
and after the lighting intervention Although the light/dark
ratio was not statistically significantly higher after the light-
ing intervention in analysis 1, it did show a statistical signifi-
cant increase (p=0.04) in analysis 2 (Fig 8 and 9). This sug-
gests that the four subjects who had exposure to the light
were spending more time awake during the daytime hours
and more time asleep during the nighttime hours. Sleep effi-
ciency increased after light intervention in both analyses, but
did not reach statistical significant difference.
Fig. (8). Light/dark ratio for analysis 1 (seven subjects) before and
after light exposure.
Fig. (
9). Light/dark ratio for analysis 2 (four subjects) before and
after intervention.
Lighting Assessment
The lighting assessment survey had questions probing
daytime and nighttime lighting. Because no intervention was
made in their nighttime lighting, these questions served as
calibration for the subjective scale, i.e., it was expected that
no significant difference between the responses would be
obtained. In fact, there was no significant difference in rat-
ings given to the nighttime lighting questions. As shown in
Figs. (10 and 11), residents overwhelmingly preferred the
new lighting over the existing lighting. A statistically sig-
nificant higher rating (p=0.008) was given to the new light-
ing compared to their existing lighting. Moreover, subjects
agreed they could read well under the new lighting and did
not find the new lighting too bright. It is interesting to point
out that the only subject who found the new lighting too
bright was the one who “played” with the lights during the
study and turned them off continuously throughout the study.
DISCUSSION
The lighting demonstration project presented here was
designed to passively deliver high circadian light stimulation
Light/Dark Ratio
0
0.5
1.0
1.5
2.0
2.5
3.0
Average ratio
Baseline1
After intervention
Light/Dark Ratio
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
903 1004 1015 1019 2001 2014 2023
Subject number
Light/dark ratio
Baseline 1
After intervention
Developing Architectural Lighting Designs The Open Sleep Journal, 2008, Volume 1 49
during the day and low circadian light stimulation in the
evening to older adults, while always maintaining good visi-
bility, so as to improve both their objective and subjective
measures of sleep. Seven subjects between the ages of 80
and 98 living in an assisted living facility in upstate New
York were recruited for the demonstration project. The data
from four of the seven subjects could be analyzed because
they were consistently present during the 4-week lighting
intervention. The other three subjects were, unfortunately,
occupied with personal and family crises during the interven-
tion project and their data could not be unambiguously
evaluated. All four of the subjects who could be studied
showed that the lighting demonstration had some positive
benefits for sleep as measured through subjective reports and
through wrist-actigraphic analysis. Moreover all subjects,
including the subjects with personal and family crises, pre-
ferred the lighting intervention over their present lighting
scheme. The present results are consistent with the results
from previous studies and with theoretical expectations.
Figueiro et al. [47, 48], van Someren et al. [45], Sloane
et al. [52] and Riemersma-van der Lek [53], demonstrated
that light of the right spectrum and of sufficient amount ap-
plied at the proper circadian time can positively impact sleep
efficiency and sleep consolidation in older adults, including
those with AD. The present results are also consistent with
the knowledge that the circadian system is maximally sensi-
tive to short wavelength radiation (blue light) and minimally
sensitive to long wavelength radiation (yellow and red). In
principle, when high level blue-white light (at least 400 lux
at the plane of the cornea) is applied during the day and dim
level yellow-white light (less than 100 lux at the plane of the
cornea) is applied during the evening, the circadian system
has a sufficient contrast in daily light levels to entrain to a
24-h period. The entrainment to a consistent light-dark pat-
tern discourages random naps and intermittent sleep and
supports consolidated sleep at night and activity and atten-
tion during the day, as revealed by the higher light-dark ratio
observed after the light exposure.
The present findings are important for architectural prac-
tice. It is essential that theoretical research be demonstrated
in the field and thereby transferred to architectural practice.
There have been too few studies looking at the impact of
architectural lighting on sleep quality and rest/activity
rhythms of older adults in a real-life setting. The fact is that
field studies are inherently difficult to conduct because (a)
sites with cooperative administrators and subjects are hard to
find, (b) subjects drop out of the study, and (c) funding for
field demonstrations of scientific concepts is limited. With
regard to the problems of the type investigated here, van
Someren and colleagues were the first to demonstrate that
lighting could be a non-pharmacological treatment to im-
prove rest/activity disturbances in patients with AD [45]. At
that time, less was known about the spectral and absolute
sensitivities of the circadian system, and the light levels used
in their study were probably unnecessarily high. Today, due
to tuning the spectrum to the maximum sensitivity of the
circadian system, light levels can be reduced and still have
the same impact on rest/activity rhythms. The results of this
study build upon those from van Someren [45] and Figueiro
[47, 48] and further reinforce the call to improve lighting in
senior housing based upon scientific principles.
CONCLUSIONS
This paper discusses a proposed 24-hr lighting scheme
for older adults that can positively impact the aging visual,
circadian and perceptual systems [4]. The new 24-hr lighting
scheme discussed here appears to have important practical
implications for improving the quality of life for seniors and
will hopefully be adopted by architects, lighting specifiers
and engineers. The authors understand that architects and
designers will face challenges to implement the proposed 24-
h lighting solution due to initial costs and energy codes and
regulations. These challenges should not, however, stop ar-
chitects and designers from building public awareness and
lobbying code officials to recognize how important lighting
can be to improve the quality of life for seniors who run high
risk of falls and poor sleep quality. These efforts will ulti-
mately promote the changes we need to facilitate the adop-
tion of superior lighting solutions in senior facilities. Moreo-
ver, the proposed lighting scheme is intended to replace inef-
ficient incandescent light sources with more efficient light
sources. The careful tuning of the spectrum of the light to the
range where the circadian system is maximally sensitive
(blue light) and the use of lighting controls to apply and re-
move the light at the right timing will reduce the need for
higher energy consumption. Finally, it must be emphasized
again that demonstrations of integrated, yet quantitative,
lighting solutions based upon basic principles of circadian
entrainment, vision and perception are essential for trans-
forming architectural practice to serve society.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the American
Institute of Architects for funding the research project pre-
Fig. (10). Ratings given by each subject to the question: “I like the
current lighting in my room.”
Fig. (11). Average rating given to the question: “I like the current
lighting in my room.”
Likes Current Lighting in Room
0
1
2
3
4
5
6
5 = strongly agree
1 = strongly disagree
Baseline
After intervention
Likes Current Lighting in Room
0
1
2
3
4
5
6
903 1004 1015 1019 2001 2014 2023
Subject number
5 = strongly agree
1 = strongly disagree
Baseline
After intervention
50 The Open Sleep Journal, 2008, Volume 1 Figueiro et al.
sented here. The authors would also like to acknowledge the
subjects, Kim Shepee-LaBombard, The Terrace staff,
Patricia Rizzo, Rui Qi, Chris Munson, Howard Ohlhous,
Conan O’Rourke, Xiang Wei, Dan Wang, Martin Overing-
ton, Dennis Guyon, Sandhya Parameswaran, and Russ Leslie
of the Lighting Research Center for their contributions to
this project. The authors would like to thank Todd Langner
from Hunter Lighting for his personal support to this project
and for donating all the floor and table lamps and Pamela
Horner from OSRAM SYLVANIA for donating the light
bulbs. EJ Van Someren is also acknowledged for his assis-
tance with actigraphy data analyses.
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Received: May 07, 2008 Revised: June 30, 2008 Accepted: July 03, 2008
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