Good overhead lighting is an effective substitute for sunlight during an assessment

When you switch to energy-efficient lighting, you can light your home using the same amount of light for less money. Lighting accounts for around 15% of an average home's electricity use, and the average household saves about $225 in energy costs per year by using LED lighting. if you are still using incandescent light bulbs, switching to energy-efficient lighting is one of the fastest ways to cut your energy bills. For high-quality products with the greatest energy savings, choose bulbs that have earned the ENERGY STAR.

In addition to efficient lighting, consider using controls such as timers and dimmers to save electricity.  Timers automatically turn lights off when not in use by turning lights off when not in use, and dimmers can be used to lower light levels. Be sure to select products that are compatible with the energy-efficient bulbs you want to use.

If you have outdoor lighting that is left on for a long time, using LEDs or CFLs in these fixtures can save a lot of energy. LEDs and CFLs are available as flood lights, and have been tested to withstand the rain and snow so they can be used in exposed fixtures. For high quality products with the greatest savings, look for ENERGY STAR-qualified fixtures that are designed for outdoor use and come with features like automatic daylight shut-off and motion sensors.

LEDs

Light emitting diodes [LEDs] are a type of solid-state lighting -- semiconductors that convert electricity into light. Although once known mainly for indicator and traffic lights, LEDs in white light, general illumination applications are today's most energy-efficient and rapidly-developing lighting technology. LEDs use up to 90% less energy and last up to 25 times longer than traditional incandescent bulbs. 

LED technology is available in many lighting product types including replacements for 40W, 60W, 75W, and 100W traditional incandescent bulbs, reflector bulbs used in recessed fixtures, and track lights, task lighting, undercabinet lighting, and outdoor area lights. LEDs come in a variety of colors, and some bulbs can be tuned to different colors or different hues of white light.  Some are dimmable or offer convenient features such as daylight and motion sensors. LEDs work well indoors and outdoors because of their durability and performance in cold environments. Look for LED products such as pathway lights, step lights, and porch lights for outdoor use. You can also find solar-powered LED outdoor lighting. 

The cost of LED light bulbs has decreased dramatically since they entered the market and prices are expected to come down further as more products become available. While LEDs are more expensive than traditional incandescent bulbs, they still save money because they last a long time and have very low energy use. 

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• References

Int J Environ Res Public Health. 2021 Jan; 18[2]: 609.

Abstract

Poor housing is an important determinant of poor health. One key aspect of housing quality is lighting. Light is important for visual performance and safety, and also plays a vital role in regulating human physiological functions. This review aims to synthesise existing evidence on the relationship between lighting in the home and health and recommends areas for future research. Three databases were searched for relevant literature using pre-defined inclusion criteria. Study quality was assessed using the Newcastle Ottawa Scale. Extracted data were qualitatively synthesised according to type of lighting [natural light, artificial light and light at night] and stratified by broad health domains [physical, mental and sleep health]. Of the 4043 records retrieved, 28 studies met the inclusion criteria. There was considerable heterogeneity in light exposure metrics used and specific health outcome assessed by the studies. Lighting in the home can negatively affect health but the current evidence base is limited to a small number of studies in different domains of light and health. Further research surrounding specific health outcomes is required to better inform housing quality assessments and lighting practises in the home.

Keywords: light, illumination, housing, residential, home, health

1. Introduction

The right to adequate housing is a recognized international human right [1]. The World Health Organisation [WHO] defines healthy housing as one that encourages a state of complete physical, mental and social well-being [2]. People living in inadequate housing are at greater risk of ill health [3,4,5] and inadequate housing conditions are one of the main drivers of health inequalities [2]. Adequate housing is commonly assessed based on housing quality [4,5] which encompasses a wide variety of factors including: crowding and home safety, mould and dampness; temperature and humidity; ventilation and insulation; sanitation; indoor air and noise pollution; radon, asbestos and lead exposure; and lighting [2,4]. Many housing quality factors co-exist within the home, placing occupants at a greater risk of multiple health problems. Housing quality is associated with different health outcomes including developmental, chronic and acute conditions [5,6]. Many housing quality factors are widely studied, for example, mould and dampness [7]; crowding [8]; and lead exposure [5]. Others, however, are understudied despite their potential to impact health. One of the less studied housing quality factors is lighting in the home.

Adequate lighting is needed for visual performance and safety, and to reduce falls and injuries. Light is also highly essential for health and well-being [9,10,11] through the regulation of bodily functions [12]. Light plays an important role in the function of the nervous and endocrine systems and the secretion of hormones such as melatonin. Melatonin is released by the pineal gland in a 24-h cycle according to how much light is received, regulating the body’s circadian rhythm. In regular sleep-wake cycles, the hormone is highest at night in the dark promoting healthy sleep and lowest during daylight promoting alertness. Disruption to these rhythms caused by a lack of daylight exposure during the day and exposure to bright lights during the night constitutes as improper light exposure which affects health [9,13].

The importance of light on health is further demonstrated through its therapeutic effects. Symptoms of seasonal affective disorder and other types of depression have been shown to be effectively reduced by both natural and artificial light therapy [14,15,16,17]. Before the discovery of antibiotics, sunlight played a significant role in infection control and preventing the spread of disease in buildings [18,19]. Even today, forms of artificial light are effectively being used in hospital settings to reduce infection transmission [20,21].

Lighting within the home encompasses different types of light. For instance, homes may be illuminated by natural light through windows and supplemented with artificial light sources during the day, with artificial lighting continuing into the night. As such, there is a need to understand the impact of the various types of lighting in the home on the health of residents. A limited number of systematic reviews have previously explored the impact of lighting on the elderly [22] and the effects of sunlight [23] and light at night [24] on health in certain settings such as care homes. A systematic review that synthesises the evidence of health impacts from different types of lighting in the home is lacking.

This study aims to systematically review the literature and synthesise the existing evidence on associations of lighting in the home from natural light, artificial light and light at night with a broad range of health outcomes. Light is defined in its broadest sense to gather evidence on different aspects of lighting in the home and its effect on health, including lack of light, different types of illuminance and light as potential hazard source, for example, from indoor air pollution and burns. This allows identifying areas for further research and implications for policy development.

2. Materials and Methods

2.1. Protocol

This systematic review on lighting in the home and health was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA] reporting guidelines.

2.2. Search Strategy

Three databases [Embase, MEDLINE and Scopus] were searched for published literature from inception till February 2020 with no language restriction. The search strategy combined search terms for light exposure, health outcome and study setting. Keywords were identified following a preliminary screening of relevant literature in MEDLINE and relate to sunlight, nightlight, daylight, natural light, artificial light, illumination, residential light, domestic light, health, mental health, and falls. The full search strategy is outlined in Supplementary Table S1.

2.3. Eligibility Criteria

2.3.1. Study Type

Observational and intervention studies were included. Case reports and systematic reviews were excluded.

2.3.2. Population

No restrictions were applied to population characteristics. Studies carried out in a home setting [e.g., domestic, student and nursing homes] were included, those in institutional [e.g., hospital, prison] and experimental settings were excluded. Studies with mixed settings [e.g., nursing homes and hospitals] that do not differentiate the results between the two settings were excluded.

2.3.3. Exposure

Any lighting exposure within the home, including sunlight, artificial light and light at night using subjective or objective exposure metrics [e.g., lighting perception versus measurements] were included. Lighting outside of the home [e.g., streetlights] as well as lighting from electronic devices [e.g., televisions and mobile phone devices] were excluded. Intervention studies that prescribe light treatment for certain time periods were excluded as these reflect therapeutic lighting which is not the exposure of interest.

2.3.4. Outcome Measures

Studies including at least one health outcome in relation to the exposure, either self-reported or measured were included. Studies reporting on melatonin, used as a biomarker for circadian dysregulation [25], were also included.

2.3.5. Publication Type

Peer-reviewed studies published in academic journals were included. Conference abstracts, editorials and letters as well as studies not available in the English language were excluded.

2.4. Study Selection

Title and abstracts were screened for eligibility based on the inclusion criteria by the first author [OO], with a random sample of 16% independently screened by the second author [BS]. Acceptable concordance was predefined as agreement on at least 90% of ratings, a concordance of 95% was achieved. Full text was independently screened by OO and BS based on the eligibility criteria. At both stages, any discrepancies were resolved by discussion and consensus with the last author [DF].

2.5. Data Extraction

Information was extracted from eligible studies relating to study characteristics [including author, year, study design, and sample size], participant characteristics, lighting exposure [including type, assessment and measurement] and the health outcome [including data collection method and measure of association] using a customised data collection form.

2.6. Study Quality Assessment

Studies were evaluated using the Newcastle-Ottawa Scale for assessing the quality of non-randomised studies [e.g., cohort and case-control] [26]. The scale was adapted for assessment of intervention studies, as the success of the intervention was not the interest of this review but the association with the outcome at the different lighting environments, and cross-sectional studies. The scale awards stars in three categories: selection of the groups of study [maximum four stars], comparability [maximum two stars] and assessment of the outcome [maximum three stars], for a maximum score of nine. An overall score of 0–3 was defined as poor quality, 4–6 as fair quality, and 7–9 as good quality.

2.7. Data Analysis

There was considerable heterogeneity in the types of lighting, the exposure metrics used to quantify light and health outcomes across studies, thus it was not feasible to summarise findings via meta-analysis. Instead, studies were qualitatively synthesised, stratifying by type of lighting exposure and health outcomes. Type of lighting was categorised into: [i] natural light: light produced naturally by the sun; [ii] artificial light: fuel-based [e.g., kerosene lamps] and electric lighting; and [iii] light at night: lighting occurring specifically during the evening and night-time period within the home.

Specific health outcomes were categorised into broad health domains: physical, mental and sleep health. In studies where the reported health outcome was overall health or personal health, these were reported under general health.

3. Results

The PRISMA flow diagram [Figure 1] outlines the process of the literature search on lighting in the home and health and consequent screening. The search initially yielded 4043 potentially relevant studies, of which 3120 were unique. 2866 studies that did not meet the inclusion criteria were excluded during title and abstract screening. The full text of the remaining 254 studies were sought for further assessment, 226 studies were excluded, most commonly due to incorrect publication type such as posters and abstracts. Twenty-eight studies were eligible for inclusion in the review based on the pre-defined criteria.

Preferred Reporting Items for Systematic Reviews and Meta Analyses flow diagram.

3.1. Study Characteristics

Key characteristics of studies included in the review are outlined in Table 1. Of the included studies, 20 focused on high income countries, including 11 studies from Japan; eight studies were carried out in Low-Middle Income Countries [LMIC]. Combined, studies included a total of 965,056 participants, with sample sizes ranging from 17 to 932,341 [27] participants. Included studies varied substantially in study design ranging from cross-sectional studies [n = 14] case-control studies [n = 8], to cross-over studies [n = 2], longitudinal studies [n = 2] and randomised trials [n = 2].

Table 1

Key characteristics of studies included in the systematic review.