Use the labels in the right column to find what you want. Or you can go thru them one by one, there are only 34,134 posts. Searching is done in the search box in upper left corner. I blog on anything to do with stroke. DO NOT DO ANYTHING SUGGESTED HERE AS I AM NOT MEDICALLY TRAINED, YOUR DOCTOR IS, LISTEN TO THEM. BUT I BET THEY DON'T KNOW HOW TO GET YOU 100% RECOVERED. I DON'T EITHER BUT HAVE PLENTY OF QUESTIONS FOR YOUR DOCTOR TO ANSWER.
Changing stroke rehab and research worldwide now.Time is Brain!trillions and trillions of neuronsthatDIEeach day because there areNOeffective hyperacute therapies besides tPA(only 12% effective). I have 523 posts on hyperacute therapy, enough for researchers to spend decades proving them out. These are my personal ideas and blog on stroke rehabilitation and stroke research. Do not attempt any of these without checking with your medical provider. Unless you join me in agitating, when you need these therapies they won't be there.
What this blog is for:
My blog is not to help survivors recover, it is to have the 10 million yearly stroke survivors light fires underneath their doctors, stroke hospitals and stroke researchers to get stroke solved. 100% recovery. The stroke medical world is completely failing at that goal, they don't even have it as a goal. Shortly after getting out of the hospital and getting NO information on the process or protocols of stroke rehabilitation and recovery I started searching on the internet and found that no other survivor received useful information. This is an attempt to cover all stroke rehabilitation information that should be readily available to survivors so they can talk with informed knowledge to their medical staff. It lays out what needs to be done to get stroke survivors closer to 100% recovery. It's quite disgusting that this information is not available from every stroke association and doctors group.
Showing posts with label bright light therapy. Show all posts
Showing posts with label bright light therapy. Show all posts
Nursing Department, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, China
Abstract
Objective:
Sleep disturbances are common after stroke and may adversely affect neurological recovery. Although post-stroke sleep disturbances encompass insomnia symptoms, circadian rhythm sleep–wake disturbances, and sleep-disordered breathing, research has focused predominantly on obstructive sleep apnea. This review evaluated the effects of bright light therapy (BLT), a non-pharmacological intervention that may influence circadian regulation, on sleep outcomes after stroke.
Methods:
Ten electronic databases covering English-and Chinese-language literature were searched from inception to April 9, 2026. Randomized controlled trials involving adults with stroke that evaluated validated subjective or objective sleep outcomes were eligible. Data were pooled using random-effects models when studies were sufficiently comparable clinically and methodologically. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool. The primary outcomes were wake after sleep onset (WASO) and subjective sleep quality. The protocol was registered in PROSPERO (CRD420251111617).
Results:
Five randomized controlled trials involving 343 participants were included. Three trials involving 181 participants contributed to the WASO analysis; the pooled estimate was not statistically significant (MD = −39.17 min, 95% CI −115.34 to 36.99; P = 0.31), and heterogeneity was substantial (I2 = 96%). Four trials involving 300 participants contributed to the subjective sleep quality analysis; the pooled estimate favored BLT (SMD = −0.85, 95% CI −1.38 to −0.32; P = 0.002), although heterogeneity was substantial (I2 = 78%). After exclusion of Song Chang-yu, the pooled effect remained statistically significant but was attenuated, and heterogeneity decreased to 0% (SMD = −0.55, 95% CI −0.83 to −0.28).
Conclusion:
BLT may improve subjective sleep quality after stroke; however, evidence for objective sleep continuity remains uncertain because of the small evidence base and substantial heterogeneity. Larger, methodologically rigorous trials using standardized light parameters, standardized outcome measures, and direct circadian assessments are needed to clarify the clinical effects of BLT and identify optimal treatment protocols.
Of course your competent? doctor has been using bright light therapy for almost a decade already! NO? So, incompetence? And your board of directors is so incompetent they don't know what competence is in their hospital!
People exposed to brighter
daytime light were significantly less likely to develop dementia over
eight years, with the strongest associations seen in those already at
higher risk, highlighting light exposure as a promising avenue for
future prevention research.A large prospective study published in the journal General Psychiatryfound that greater exposure to bright daytime light was associated with a lower risk of developing dementia.
Circadian rhythms may influence dementia development
Dementia is the most common neurodegenerative disease worldwide and is rapidly increasing in prevalence with the aging of the global population. Withlimited effective treatments, prevention is a top priority.
The environmental light-dark cycle is key to aligning with natural circadian rhythms, which, in turn, are fundamental to normal physiological, behavioral, and cognitive functioning. People with dementia often show disrupted circadian rhythms, and conversely, these are linked to a higher risk of dementia.
More evidence of such associations comes from the promising use of bright light therapy (BLT) in patients with dementia to correct dysregulated circadian rhythms and improve cognitive symptoms. However, the modern lifestyle limits adequate exposure to natural bright light during the day, as most people spend this time indoors in buildings with insufficient lighting. This is worsened by excessive nighttime light exposure, which affects nearly 80% of the world’s population.
The current study aimed to investigate associations between daytime and nighttime light exposures and dementia risk.
Researchers measured daytime and nighttime light exposure using wrist-worn devices over seven days in a community cohort of 87,577 dementia-free adults (mean age 62 years). They then examined whether light exposure predicted future dementia diagnoses.
Brighter daytime light linked to lower dementia risk
Over a median follow-up period of eight years, 741 participants developed dementia. At baseline, participants who developed dementia were more likely to be older, male, less educated, less physically active, smokers, or to have hypertension, diabetes, or hearing loss.
The investigators found that exposure to daytime light levels brighter than 1,000 lux was associated with a 16% lower risk of dementia. Shorter durations of increasingly bright daytime light showed similar associations, suggesting a graded pattern across brighter-light thresholds.
Thus, 17% reductions in risk were observed with at least 1.4 hours of exposure to bright daytime light of 3000 lux or more, versus 0.7 hours at 5000 lux, and 0.45 hours at 7000 lux.
Greater effects among high-risk groups
The effects of higher average daytime light exposure and longer exposure to bright daytime light were most pronounced among certain groups. For instance, such exposures were associated with a 30% to 38% reduction in dementia risk among individuals exposed to higher nighttime light levels.
Smartphones shining at 3 a.m. feel harmless, yet the glow might be
training the body to expect daytime when it most needs sleep. New
research following more than 88,000 adults shows that brighter lights
are not just a nuisance, they are linked to a sharp rise in several
forms of heart disease.
Daniel Windred
of Flinders University and colleagues collected about 13 million hours
of wrist-sensor data, then checked health records for almost a decade.
Light steers the body’s circadian rhythms, the near-24-hour cycles that organize hormone release, blood pressure, and metabolism.
Even
brief exposure to a ceiling lamp at night can delay the internal clock
by hours, leaving the heart working out of phase with the rest of the
body.
The hormone melatonin
normally climbs after dusk and signals blood vessels to relax, which
lowers nighttime pressure. Ordinary indoor brightness, roughly 100 lux, can cut melatonin in half and keep vessels tighter for the rest of the night.
Shift-work studies add weight to the concern. A UK Biobank analysis of 238,661 participants reported that habitual night workers carried a higher risk of incident and fatal cardiovascular disease, partly through disrupted sleep timing.
Bright
outdoor lighting is also implicated. Residents of Ningbo, China, who
lived under the strongest street illumination had a 43 percent greater
chance of cerebrovascular disease compared with those in darker
neighborhoods, according to a 2024 American Stroke Association report.
Bedroom lights and heart disease
Windred’s
team asked volunteers to wear a light meter for one week between 2013
and 2016. The device counted every photon, whether from a bedside lamp,
phone screen, or passing headlights.
People in the brightest tenth
of the sample needed only about one hour of overhead lighting between
midnight and 6 a.m. to qualify for that category.
Their cardiovascular trouble began appearing within the eight-year follow-up, independent of age, smoking, genetics, or sleep length.
The
pattern held across five cardiovascular outcomes, suggesting a broad
effect on vascular tissue rather than one specific pathway.
Resting
blood pressure, blood sugar tolerance, and heart-beat timing all rely
on clock genes that switch activity by day and night.
“This is the biggest study of personal light exposure patterns and cardiovascular health to date,” says Windred.
Bright lights and women’s hearts
Women usually develop heart disease later than men because estrogen
protects artery walls. In this study, however, women exposed to bright
nights faced risks similar to men, erasing the usual gap.
Laboratory work hints at a reason. One experiment
found that women’s pineal glands suppress melatonin more readily than
men’s when exposed to the same intensity of light, showing a heightened
biological sensitivity.
He
notes that modern 24-hour society leaves many people under constant
light cues that keep the heart in daytime mode around the clock.
Young
adults in the dataset also showed stronger links between night light
and heart failure or atrial fibrillation, matching earlier reports that
younger shift workers accumulate risk faster than peers on regular schedules.
Impact of night light beyond the heart
Clock disruption changes how the body handles glucose, raising the odds of type 2 diabetes, itself a major cardiac risk.
Epidemiological
studies connect chronic light at night with higher obesity rates and
impaired insulin action, even after controlling for diet.
Animal experiments reveal that mice kept under constant light develop stiffer arteries and thicker heart walls within weeks.
Although
rodents run on a faster clock, the mechanisms, oxidative stress and
inflammatory signaling, mirror findings in human shift workers.
Stroke
researchers add cerebral concerns. Artificial illumination that
shortens sleep by an hour can elevate sympathetic nerve activity the
next morning, boosting clot formation potential.
Public-health groups now include healthy sleep in standard heart-fitness checklists. The American Heart Association’s “Life’s Essential 8” places regular, dark-room sleep on the same level as exercise and diet for protecting arteries.
Making your bedroom darker
Windred
advises selecting a fixed sleep interval and guarding its darkness each
night. If nature calls before dawn, use a dim red or amber night-light
rather than flipping the bathroom fixture.
Phone manufacturers offer night modes that lower blue wavelengths,
yet intensity still matters. Experts recommend setting screens below 10
percent brightness after sunset and keeping them an arm’s length away.
Blackout curtains or opaque blinds can block streetlamps
that pierce bedroom shades. For renters who cannot change window
dressings, an inexpensive sleep mask cuts ambient glow to near zero.
People
who work rotating nights can consolidate exposure by using bright,
white light during the shift to stay alert, then wearing dark glasses on
the ride home to help the brain wind down before bed.
Pushing for darker nights
Urban
planners are beginning to weigh health when designing street lighting.
Shielded fixtures that aim beams downward can maintain safety while
reducing bedroom spill and sky glow.
Hospital policies are
changing too. Some intensive-care units now switch to low-intensity,
warm lights overnight, helping patients maintain a circadian signal and
possibly recover faster.
Researchers call for cardiovascular
guidelines to list night lights avoidance alongside salt limits and
step counts. The evidence, they argue, shows that avoiding lights at
night is not a luxury but daily medicine for the heart.
If your doctor suggests this for your depression it means they have COMPLETELY FAILED YOU BY NOT PREVENTING DEPRESSION BY 100% RECOVERY PROTOCOLS! In my opinion that is not a competent doctor!
A 2024 research review suggests that PSD may affect up to 43.9% of older adults. So there should be 10s of thousands of doctors getting researchers to solve stroke to 100% recovery! And every single one of them is a complete failure for not doing that! Hope you are OK with such fucking failures in the stroke medical world!
Send me hate mail on this:
oc1dean@gmail.com. I'll print your complete statement with your name and my
response in my blog. Or are you afraid to engage with my stroke-addled
mind? I'm curious why you haven't engaged researchers to solve stroke to 100% recovery.
ContributorAnuradha writes about environmental health disparities & epidemiology10:21am EST
Updated Nov 5, 2024, 05:32am EST
... [+]Corbis via Getty Images
Major depressive disorder is a debilitating disability that impacts around 5% of adults
worldwide. While doctors commonly prescribe antidepressants to
patients, it has several side effects and might not always succeed in
preventing relapses of depressive episodes. A non-pharmacological
solution that could effectively treat depressive disorders is bright
light therapy. Patients with non-seasonal depression who were treated
with bright light therapy reported a 40% remission rate, according to a
recent study.
“The primary supportive argument in favor of using bright light as an
adjunctive treatment is the cost. Even though outpatient treatment
costs with antidepressants are widely variable, exposure to external
light generally involves no costs or limitations, which reinforces the
need to firm bright light therapy as an efficient adjunctive treatment
for non-seasonal depressive disorders,” the researchers wrote in their
study that was published in JAMA Psychiatry.
Prior studies have shown that light exposure can affect people’s mood
and cognitive functioning. Researchers say that happens when bright
light enters the inner surface of the retina where neurons called
retinal ganglion cells are located. These neurons transmit visual
information from the retina to brain areas responsible for mood regulation like the amygdala, suprachiasmatic nucleus, and the dorsal raphe nucleus.
To delve deeper into how bright light therapy could help in treating
non-seasonal depression, the researchers analyzed the data from studies
that included 858 participants who were diagnosed with depressive
disorders. The study participants were made to sit in front of a
fluorescent light box that produced extremely bright white light at an
intensity of 10,000 lux for at least 30 minutes daily. “Patients treated
with bright light therapy had a significantly higher remission rate
(40%) than the control groups who were only treated with
anti-depressants (23%),” the team observed. “These findings suggest that
bright light therapy was an effective adjunctive treatment for
non-seasonal depressive disorders, and the response time to the initial
treatment may be improved with the addition of bright light therapy.”
“Our results do not underscore the need for randomized clinical
trials with larger follow-up periods but strengthen the theory that
patients treated with bright light therapy acquire remission of symptoms
and response rate more rapidly than patients treated only with
antidepressants,” the authors added.
For three decades, bright light therapy has been used to treat sleep
disorders like delayed sleep phase syndrome, which is characterized by
people falling asleep only several hours after midnight and difficulties
waking up in the morning.
Bright light therapy works by slowly tweaking and shifting people's
sleep patterns. The light boxes are also used to treat seasonal
depression in the Global North during winters.
Your healthcare provider must determine the right duration of bright
light exposure and the correct light intensity for the therapy to have
tangible results. Studies have also found that bright light therapy
might work best along with antidepressants.
While these results are encouraging and show the potential of bright
light therapy, buying a light box and using it at home might not be that
effective. "Some devices advertised as '10,000-lux' devices produced
this intensity only at unreasonably close distances, over a restricted
field, or with unacceptable glare or unevenness of illumination. Device
selection is key to ensuring that patients receive evidence-supported
doses of light," researchers wrote in a 2019 study.
This from April 2017 should have already triggered this therapy for all the depression in survivors created by not having 100% RECOVERY PROTOCOLS, since it
produces BDNF. But your incompetent hospital didn't have enough brains
to extrapolate the benefits of this in rats to humans. Do you prefer your hospital incompetence NOT KNOWING OR NOT DOING?
Contributor: Anuradha writes about environmental health disparities & epidemiologyN10:21am EST
Updated Nov 5, 2024, 05:32am EST
... [+]Corbis via Getty Images
Major depressive disorder is a debilitating disability that impacts around 5% of adults
worldwide. While doctors commonly prescribe antidepressants to
patients, it has several side effects and might not always succeed in
preventing relapses of depressive episodes. A non-pharmacological
solution that could effectively treat depressive disorders is bright
light therapy. Patients with non-seasonal depression who were treated
with bright light therapy reported a 40% remission rate, according to a
recent study.
“The primary supportive argument in favor of using bright light as an
adjunctive treatment is the cost. Even though outpatient treatment
costs with antidepressants are widely variable, exposure to external
light generally involves no costs or limitations, which reinforces the
need to firm bright light therapy as an efficient adjunctive treatment
for non-seasonal depressive disorders,” the researchers wrote in their
study that was published in JAMA Psychiatry.
Prior studies have shown that light exposure can affect people’s mood
and cognitive functioning. Researchers say that happens when bright
light enters the inner surface of the retina where neurons called
retinal ganglion cells are located. These neurons transmit visual
information from the retina to brain areas responsible for mood regulation like the amygdala, suprachiasmatic nucleus, and the dorsal raphe nucleus.
To delve deeper into how bright light therapy could help in treating
non-seasonal depression, the researchers analyzed the data from studies
that included 858 participants who were diagnosed with depressive
disorders. The study participants were made to sit in front of a
fluorescent light box that produced extremely bright white light at an
intensity of 10,000 lux for at least 30 minutes daily. “Patients treated
with bright light therapy had a significantly higher remission rate
(40%) than the control groups who were only treated with
anti-depressants (23%),” the team observed. “These findings suggest that
bright light therapy was an effective adjunctive treatment for
non-seasonal depressive disorders, and the response time to the initial
treatment may be improved with the addition of bright light therapy.”
“Our results do not underscore the need for randomized clinical
trials with larger follow-up periods but strengthen the theory that
patients treated with bright light therapy acquire remission of symptoms
and response rate more rapidly than patients treated only with
antidepressants,” the authors added.
For three decades, bright light therapy has been used to treat sleep
disorders like delayed sleep phase syndrome, which is characterized by
people falling asleep only several hours after midnight and difficulties
waking up in the morning.
Forbes Daily: Join over 1 million
Forbes Daily subscribers and get our best stories, exclusive reporting
and essential analysis of the day’s news in your inbox every weekday.
Bright light therapy works by slowly tweaking and shifting people's
sleep patterns. The light boxes are also used to treat seasonal
depression in the Global North during winters.
Your healthcare provider must determine the right duration of bright
light exposure and the correct light intensity for the therapy to have
tangible results. Studies have also found that bright light therapy
might work best along with antidepressants.
Summary: A new study explores how different light
levels impact cognitive function by influencing hypothalamic activity in
the brain. The study utilized advanced 7 Tesla fMRI to show that higher
levels of light improve cognitive performance during complex tasks.
This link between light exposure and brain function suggests potential
for light-based therapies to enhance alertness and cognitive abilities
throughout the day. The findings pave the way for further investigation
into how light affects various brain structures and could inform the
development of non-invasive treatments for cognitive fatigue and sleep
disorders.
Key Facts:
Higher levels of
light exposure were correlated with increased activity in the posterior
hypothalamus and improved performance on cognitive tasks.
The study used 7 Tesla fMRI, providing high-resolution insights into how light influences hypothalamic activity.
While
increased light levels boosted cognitive performance, the exact neural
mechanisms and involved brain regions require further exploration.
Source: eLife
Exposure
to higher levels of light can help people feel more awake and increase
cognitive performance, probably by influencing the activity of parts of a
brain region called the hypothalamus, according to new research.
The study, published today as a Reviewed Preprint in eLife,
is described by the editors as of fundamental importance, and represents
a key advancement to our understanding of how different levels of light
affect human behaviour.
They
found that, during both tasks, higher levels of light triggered an
increase in activity over the posterior hypothalamus. In contrast, the
inferior and anterior hypothalamus followed a seemingly opposite
pattern, exhibiting decreased activity under higher levels of light.
Credit: Neuroscience News
The strength of
evidence is praised as compelling, supporting the authors’ analyses of
the complex interplay between light exposure, hypothalamic activity, and
cognitive function.
With
further research, the findings could be used to inform various light
therapy treatments to increase an individual’s quality of sleep and
affective state, and help them feel more awake and perform tasks better
throughout the day.
The biological effects of light exposure have been well documented in
recent years. Higher illuminance has been shown to stimulate alertness
and cognitive performance. These effects primarily rely on a subclass of
light-sensitive cells in the retina, called ipRCGs.
These cells
project to multiple areas of the brain, but projections are most densely
found within the hypothalamus, which is typically associated with the
regulation of circadian rhythms, sleep and alertness, and cognitive
functions.
However, this knowledge of the brain circuitry
underlying the biological effects of light has almost entirely stemmed
from studies in animals.
“Translating findings on how light
exposure affects the brain in animal models to humans is a difficult
process, as the later maturation of the cortex in human beings enables
much more complex cognitive processing,” explains lead author Islay
Campbell, former PhD student at the GIGA-CRC Human Imaging – now awarded
her doctorate – University of Liège, Belgium.
“In particular, the
question of whether hypothalamus nuclei contribute to the stimulating
impact of light on cognition is not established.”
To better
understand the impact of light on human cognition, Campbell and
colleagues recruited 26 healthy young adults to participate in their
study.
They asked each
participant to complete two auditory cognitive tasks; an executive task
modified from the ‘n-back task’ in which participants were asked to
determine whether a current sound was identical to the one they heard
two items earlier, or contained the letter ‘K’; and an emotional task,
in which participants were asked to identify the gender of a voice that
was either pronounced in a neutral tone or in an angry tone.
Each task was completed whilst the individuals were alternatively
placed in darkness, or exposed to short periods of light in four levels
of illumination.
The team used a technique called 7 Tesla
functional magnetic resonance imaging, which has a higher resolution and
signal-to-noise ratio compared with standard 3 Tesla MRI, to assess the
impact of the different light levels on the activity of the
hypothalamus during the tasks.
They found that, during both
tasks, higher levels of light triggered an increase in activity over the
posterior hypothalamus. In contrast, the inferior and anterior
hypothalamus followed a seemingly opposite pattern, exhibiting decreased
activity under higher levels of light.
Next, the team sought to
determine whether these changes in regional hypothalamus activity were
related to a change in cognitive performance. They focused on assessing
the participants’ performance during the executive task, as this
required a higher level of cognition to solve.
Their analysis
revealed that higher levels of light indeed led to better performance in
the task, indicating an increase in cognitive performance. Importantly,
the increase in cognitive performance under higher illuminance was
found to be significantly negatively correlated with the activity of the
posterior hypothalamus.
This makes it unlikely that the posterior
hypothalamus activity directly mediates the positive impact of light on
cognitive performance, and possibly hints at other brain regions being
involved, requiring further research.
On
the other hand, the activity of the posterior hypothalamus was found to
be associated with an increased behavioural response to the emotional
task. This suggests the association between cognitive performance and
the activity of the posterior hypothalamus may be context dependent – in
some tasks, certain hypothalamus nuclei or neuronal populations may be
recruited to increase performance, but not in others.
The authors call for future work in this area to assess the impact of
light on other structures, or entire networks of the brain to determine
how varying light levels modify their crosstalk and interactions with
the cortex to bring about behavioural changes.
“The questions
that remain from our study are important to answer, because acting on
light stands as a promising easy to implement means to reduce fatigue
throughout the day, improving cognitive defects and allowing a restful
night’s sleep with minimal cost and side effects,” says Campbell.
“Our
results demonstrate that the human hypothalamus does not respond
uniformly to varying levels of light while engaged in a cognitive
challenge,” says senior author, Gilles Vandewalle, co-director of the
GIGA-CRC Human Imaging , University of Liège.
“Higher levels of
light were found to be associated with higher cognitive performance, and
our results indicate that this stimulating impact is mediated, in part,
by the posterior hypothalamus.
“This region is likely to work
jointly with the decreased activity of the anterior and inferior
hypothalamus, along with other non-hypothalamus brain structures that
regulate wakefulness.”
“Targeted lighting for therapeutic use is
an exciting prospect. However, it will require a more comprehensive
understanding of how light affects the brain, particularly at the
subcortical level. Our findings represent an important step towards this
goal, at the level of the hypothalamus,” notes Campbell.
About this cognition research news
Author: Emily Packer Source: eLife Contact: Emily Packer – eLife Image: The image is credited to Neuroscience News
WHOM IN STROKE DO WE ASK to tell us what this means for survivors? Since nobody knows it means every stroke association is non functioning. My non-scientific takeaway is that maybe this might be used to address post stroke fatigue. Don't listen to me,I'm not medically trained.
Optimizing indoor lighting to be brighter during daytime hours and dimmer in the evening may provide cardiometabolic benefits, according to study findings published in Diabetologia.
In findings from a randomized controlled trial, participants who were
in an indoor environment with bright lighting during the day and dim
lighting in the evening had lower plasma glucose levels and increased in
energy expenditure compared with bright lighting in the evening and dim
lighting during the day, providing evidence that indoor lighting should
correspond to the natural day-night cycle.
Schrauwen is a professor of metabolic aspects of type 2
diabetes in the NUTRIM School of Nutrition and Translational Research at
Maastricht University in the Netherlands.
“Insulin resistant, prediabetic people have disturbances in their 24-hour energy and substrate metabolism and circadian clock, which may contribute to the development of diabetes,” Patrick Schrauwen, PhD,
professor of metabolic aspects of type 2 diabetes in the NUTRIM School
of Nutrition and Translational Research at Maastricht University in the
Netherlands, told Healio. “These may be due to — among other factors —
suboptimal light conditions, as many people spent most of their times
indoors. Optimizing the light condition may be able to reset some of
these metabolic disturbances.”
Schrauwen and colleagues conducted a randomized controlled crossover
trial with 14 adults aged 40 to 75 years with overweight who met one of
four criteria for insulin resistance. Only participants with a bedtime
around 11 p.m. and a sleep duration of 7 to 9 hours were enrolled.
Participants stayed in a respiration chamber for two seperate 40-hour
periods beginning at 6 p.m. on day 1 and ending at noon on day 3. In one
of the sessions, participants were exposed to bright lighting during
daytime from 8 a.m. to 6 p.m. and dim lights during the evening from 6
p.m. to 11 p.m. In the other session, separated by a washout of at least 4 days,
participants were in a dim lighting environment from 8 a.m. to 6 p.m.
and bright lights from 6 p.m. to 11 p.m. Volunteers wore an actigraph to
measure sleep patterns before and during the study. Energy expenditure,
sleep metabolic rate and substrate oxidation were calculated based on
oxygen consumption and carbon dioxide production. Wireless sensors were
used to measure skin temperature. Fasting blood samples were collected
at 7:45 a.m. on days 2 and 3 and at 5:45 p.m. on day 2, and postprandial
blood samples were taken every 30 minutes for 4 hours after breakfast
each day and dinner on day 2.
Lower glucose with bright daytime lighting
There were no changes in proximal skin temperature between the two
conditions, but distal skin temperature was lower at 6 p.m. for the
bright lighting during the day pattern compared with spending the day in
dim lighting (28.8°C vs. 29.9°C; P = .039). At 11 p.m., those
in the bright day light pattern had a higher distal skin temperature
compared with those in the bright evening light condition (30.1°C vs.
28.8°C; P = .006).
Participants in the bright day lightning pattern had a greater
increase in plasma triglycerides after breakfast on day 2 compared with
dim lighting during the day (P = .029). Plasma glucose was
lower just before dinner for those in the bright day light pattern
compared with bright light in the evening (5 mmol/L vs. 5.2 mmol/L; P = .02).
Energy expenditure improved with bright daytime lighting
Energy expenditure on day 2 and day 3 was not significantly different
between lighting patterns. There was also no difference in energy
expenditure in the postprandial phase of the day 2 breakfast. After
dinner, those in the bright day light condition had greater postprandial
energy expenditure compared with bright evening lighting. Sleeping
metabolic rate was lower in the night after the light intervention
compared with before the bright light intervention in the bright evening
light pattern only. Respiratory exchange ratio did not differ between
the conditions in any time interval.
“Optimizing light conditions, including bright light during the day
and dim light during the night, affects 24-hour metabolism in humans and
may be important to improving metabolic health in individuals at risk
for developing type 2 diabetes or insulin resistance,” Schrauwen said.
However, Schrauwen noted that the study cohort was small and the
study duration short at 40 hours. He said longer studies with more
participants are needed to determine whether the light conditions may
translate into clinically relevant improvements, and these first results justify such further studies.
