a study by Figueiro and colleagues suggests that
long wavelength (red) light, which LEDs can also
deliver, may help keep us alert and productive
at night and throughout the day, which may be
helpful during a postlunch dip (Behavioral Brain
Research, 2014).
Light and the aging body
Those relationships aren’t as clear-cut in older
adults, however. As people age, their sleep-wake
patterns often make unwelcome shifts, with up
to 70 percent of older adults experiencing sleep
disturbances or disorders. That may be because
of underlying changes in the circadian system.
Researchers have found that older adults have
less activity in the suprachiasmatic nucleus, the
brain area that controls circadian cycles. Blue
light has less of a stimulating effect on areas
of their brains involved with alertness and
cognition, according to a 2014 fMRI study in
Sleep by Véronique Daneault of the University of
Montreal, and colleagues. Older adults produce
less melatonin overall than younger ones, and it
can take longer for older adults to fall and stay
asleep. In addition, lifestyle changes, such as cutting back on
work, exercise and social activity can also contribute to sleep
differences, and physical changes to the eye such as cataracts
and macular degeneration can make it harder to receive light.
People with Alzheimer’s or other types of dementia are even
more likely than other older adults to have disrupted sleep
schedules, including night wanderings. Studies suggest their
circadian rhythms become less regular and more delayed —
meaning they may have trouble falling asleep — and melatonin
levels decrease. They are also more likely to suffer from
degeneration of their ganglion cells.
A number of studies suggest that disordered sleep may
contribute to developing disease. Scientists who disturbed sleep
cycles in mice, similar to what humans experience during jet lag,
discovered that the animals’ brains produced less glutathione,
an antioxidant that helps protect against neuron damage and
brain inflammation (Journal of Alzheimer’s Disease, 2015).
Sleep problems are also associated with the buildup of beta-
amyloid, the protein that can form clumps and kill brain cells
— a hallmark of Alzheimer’s disease. A 2013 JAMA study by
Adam P. Spira, PhD, of the Johns Hopkins Bloomberg School
of Public Health used PET to show that poor and short sleep
were associated with an increase of beta-amyloid. Another study
Mander, PhD, of the University of California, Berkeley, showed
that healthy older adults with the highest buildup of the protein
had poorer sleep quality and performed worse on memory tests.
Some scientists suspect that sleep helps flush away beta-amyloid
proteins and other potentially toxic buildups (Science, 2013).
Living in a long-term care center can also make sleep
challenging for patients. They may spend more time in bed, and
encounter noise and light at inopportune times. They may also
have difficulty getting outside for a daily dose of sunlight that
would signal their brains that is it daytime and that it is time to
be awake. In addition, many care centers are dimly lit, Figueiro
says, adding that older people in care homes are often in “the
worst possible environment” for alertness during the day and
sleeping at night.
One way to help jump-start circadian cycles is sitting in
front of a simple light box. However, getting anyone — let alone
seniors with dementia — to regularly bask in the sometimes
uncomfortably bright light can be challenging.
“When we’re talking about using light to benefit health,
we’re not talking about simply immediate effects. We’re talking
about the total daily pattern of light,” says Jennifer Veitch, PhD,
a psychologist at the National Research Council of Canada who
researches how light affects human well-being and productivity.
That’s where measured doses of indoor light come in,
Dr. Mariana Figueiro of Rensselaer Polytechnic Institute with
the table she invented to provide light therapy to dementia
patients. Photo courtesy of Rensselaer Polytechnic Institute.
