Education comprehends far more than many suppose. Mind and body must both receive attention; and unless our youth are versed in the science of how to care for the body as well as the mind, they will not be successful students. It is essential that students exercise their physical powers in such a way that their physical strength shall not be disproportionate to their mental development, and therefore a judicious system of physical culture should be combined with school discipline, that there may be a harmonious development of all the powers of mind and body. Nothing that pertains to physical perfection should be looked upon as of little importance. In eating, drinking, and dressing, the laws of health should be diligently followed, and in regulating the hours for sleep, there should be no haphazard work. No student should form the habit of sitting up late at night to burn the midnight oil, and then take the hours of day for sleep. If they have been accustomed to doing this at home, they should seek to correct their habits and go to rest at a seasonable hour, and rise in the morning refreshed for the day’s duties. In our schools the lights should be extinguished at half past nine. (CE 124.1)

Progress in Brain Research

Volume 273, Issue 1, 2022, Pages 331-355

Chapter 16 – How can light be used to optimize sleep and health in older adults?

Globally, society is aging and changes to the timing and quality of sleep are often observed in older adults (aged ≥ 65 years). Good sleep quality, and sufficient sleep duration, is necessary to maintain good physical and psychological health, and strategies which optimize good sleep will be important in an aging society. Light has a very powerful effect upon sleep and circadian rhythms, and has specific advantages including the relative low cost, ease of administration and lack of interaction with other medications. For this reason, bright light treatment is a promising method for optimizing sleep and circadian rhythmicity in older adults. In this chapter, we examine whether bright light treatment could be used to optimize sleep, circadian rhythms, and health in older adults. We also outline a range of methodological considerations which need to be addressed to increase the feasibility, acceptability and effectiveness of light treatment in older adults.


Globally, people are living longer, and the speed at which society is aging is happening faster than ever before (World Health Organisation, 2018). By the year 2050, it is expected that one in six people worldwide (16%) will be aged 65 or older, equating to a global total of approximately two billion older adults (United Nations: Department of Economic and Social Affairs, 2019). Additionally, approximately 5% of the world’s population is expected to be 80 years of age or older by 2050 (United Nations: Department of Economic and Social Affairs, 2019). This significant societal change poses a number of challenges. In particular, maximizing good health in older age is a major public health challenge, as increases in longevity do not automatically translate to aging in good health (Wagg et al., 2021). More than 60% of older people (aged 65 years or over) demonstrate multi-morbidity, defined as having at least two chronic conditions such as hypertension, heart disease and diabetes, and the risk of multi-morbidity increases with advancing older age (Salive, 2013). Aging is, in itself, the primary risk factor for a range of chronic conditions including obesity, diabetes, cancer, cardiovascular disease and neurodegenerative disorders (Lopez-Otin et al., 2016). Given the projected increases in the prevalence of older adults, interventions and strategies which promote good health in older age will have significant individual, societal, and economic implications.


The timing and consolidation of sleep is regulated by the interaction between the homeostatic sleep drive and circadian rhythmicity (Borbely, 1982; Borbely and Achermann, 2000; Borbely et al., 2016). Circadian rhythms, including the sleep-wake cycle, are involved with several physiological systems and these have a significant direct relationship with physical and psychological health (Grandner, 2020). Key sleep parameters such as sleep duration, sleep continuity, sleep timing and sleep regularity, can have a major impact upon health outcomes (Buysse, 2014; Grandner, 2020). For example, insufficient sleep duration and poor sleep quality is associated with adverse health outcomes including mortality, weight gain, obesity, diabetes and cardiovascular disease (Grandner, 2020).


Sleep is also directly relevant to the mental health of an aging population. For example, sleep and depression are very closely linked, where insomnia, or insomnia symptoms, can predict the development of subsequent depressive disorders (Baglioni et al., 2011; Hertenstein et al., 2019; Palagini et al., 2019; Riemann et al., 2020). Insomnia will typically persist without proper treatment, and is a common treatment-resistant symptom in depressive patients (Carney et al., 2007; Morin et al., 2009). Ignoring sleep problems may thus lead to potential recurrence in people with depression. Late-life depression is common: one meta-analysis demonstrated that in older adults (≥ 75 years), the prevalence of major depression was 7.2%, and the prevalence of depressive disorder was up to approximately 17% (Luppa et al., 2012). Compared to younger adults, depression is more frequent and prevalent in older adults (Mitchell et al., 2010), and is associated with reduced quality of life, cognitive and physical impairment (Allan and Ebmeier, 2013; Koenig et al., 2014). Of interest is the fact that in older adults who have pre-existing physical healthy conditions, depression is associated with a range of negative outcomes including physical and mental deterioration, poor recovery, worse outcomes and increased morbidity (Allan and Ebmeier, 2013). In addition to individual suffering, this is associated with an economic cost: older adults with depression have a higher level of healthcare costs compared to older adults without depression, even when chronic illness is considered (Katon et al., 2003); additionally, chronic disease is in itself a risk factor for depression in older adults (Chang-Quan et al., 2010). Therefore, strategies which improve sleep are likely to benefit this population.


There are other conditions, which are common in older adults and which might also be relevant when considering the link between sleep and health. This includes sleep-related breathing disorders such as obstructive sleep apnea (OSA), which has an increasing prevalence with age and is in turn associated with negative health outcomes such as cardiovascular disorders (Chowdhuri et al., 2018; Edwards et al., 2010; Gosselin et al., 2019). For instance, one study demonstrated that the prevalence of mild-to-severe OSA may be as high as 68% in adults aged 60 years or above (Fietze et al., 2019).


There is now increasing evidence to suggest that sleep may have a direct mechanistic role in the development of dementia. For example, one meta-analytic study has shown that individuals who displayed sleep disturbances had a greater risk of developing dementia, compared to individuals without sleep disturbances (Shi et al., 2018); moreover, both short and long sleep durations, as well as changes to sleep durations (primarily assessed using self-report measures), also appear to be associated with cognitive impairments in older adults (Devore et al., 2016). Finally, one study found that objectively-measured sleep disruption (assessed using actigraphy) was associated with impaired cognition and cognitive decline (McSorley et al., 2019). This link is also supported by neuroimaging data: an association between self-reported sleep duration and β-amyloid burden, which is directly involved in the development of neurodegenerative dementia, has been reported in community-dwelling older adults (Spira et al., 2013). Experimental work in healthy volunteers has demonstrated that a single night of sleep deprivation is sufficient to increase β-amyloid levels in the brain (Shokri-Kojori et al., 2018).


Overall, the optimization of sleep has direct relevance to an aging population, both from a treatment and a preventative perspective. Techniques which optimize sleep in this population will therefore result in an individual benefit, as well as wider economic and societal benefits.

Can light improve sleep in older adults?

As outlined, sleep has a significant direct relationship with both physical and psychological health (Buysse, 2014). Sleep disturbances and complaints are common in older age (Crowley, 2011; Foley et al., 2004; Ohayon, 2002; Patel et al., 2018; Vitiello et al., 2002) and can occur alongside other illnesses and co-morbidities (Edwards et al., 2010; Foley et al., 2004; Lavoie et al., 2018). Given the bi-directional links between sleep and conditions such as depression, which are common in older


Methodological considerations for the use of light in sleep and health

BLT is highly likely to be useful in the treatment and optimization of sleep and circadian rhythmicity of older adults. However, before this can be translated to clinical and non-clinical environments with the aim of improving sleep and health, rigorous, well-controlled studies are needed. These are required to assess the feasibility and tolerability of BLT with specific consideration to the needs and wishes of a diverse and heterogeneous older adult population. In addition, studies are needed


Can light be used to treat clinical problems?

There are several potential health applications of BLT, both in the treatment and prevention of physical and psychological health.



Overall, light therapy is a very promising therapeutic technique to promote sleep and health in older adults. As well as the treatment of sleep and circadian rhythm problems, and mood disturbances such as depression, light therapy may have a role in the optimization of sleep, and the prevention of sleep disturbances, and this may have a subsequent benefit upon brain health. Specific advantages of light therapy include the low cost, ease of administration, and lack of interaction with….


Those who have the aged to provide for should remember that these especially need warm, comfortable rooms. Vigor declines as years advance, leaving less vitality with which to resist unhealthful influences; hence the greater necessity for the aged to have plenty of sunlight and fresh, pure air. (AH 149.1)                                

Seek to Understand Nature’s RemediesPure air, sunlight, abstemiousness, rest, exercise, proper diet, the use of water, trust in divine power—these are the true remedies. Every person should have a knowledge of nature’s remedial agencies and how to apply them. It is essential both to understand the principles involved in the treatment of the sick and to have a practical training that will enable one rightly to use this knowledge.

The use of natural remedies requires an amount of care and effort that many are not willing to give. Nature’s process of healing and upbuilding is gradual, and to the impatient it seems slow. The surrender of hurtful indulgences requires sacrifice. But in the end it will be found that nature, untrammeled, does her work wisely and well. Those who persevere in obedience to her laws will reap the reward in health of body and health of mind. (GC 366.2)                           



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