Light for health                                                                                                               

Beth SolomonBlog

Today, our home environments have become more relevant than ever as we have all been forced to “stay at home” to reduce our interactions with one another, and consequently decrease disease transmission. As such, it has become even more critical that we understand how we can make our home a healthier environment that is conducive for both wellbeing and work.

While selecting a home involves a number of tradeoffs (How much does it cost? How far is it from my workplace or school? Where is the nearest tube station and grocery store?), for now we focus on housing quality.

Housing quality and health 

There is no single definition of housing quality. It is commonly described as a multidimensional concept that is construed, and consequently measured, by multiple phenomena simultaneously. Housing quality includes a variety of factors including: overcrowding, mould and dampness; thermal comfort; water and sanitation; indoor air and noise pollution; and lighting – to name a few.

Moreover, the impacts of housing quality on health are vast and wide-ranging – including infectious disease, non-communicable diseases and mental health. According to the World Health Organization, the health burden attributable to inadequate housing varies by exposure, ranging from 30% of excess deaths being attributable to indoor cold temperature and up to 47% of injury deaths attributable to a lack of window guards, to 15% of asthma deaths being attributable to damp conditions in the home. Moreover, many housing quality factors co-exist within the home, placing occupants at a greater risk of multiple health problems.

In my initial search of existing housing quality-health literature reviews, I found a bias in the literature. For instance, among the 82 reviews I identified, only 6 focused on low- and middle-income countries. One of the most interesting things, however, was the disproportionality of which housing quality factors (and health outcomes) were studied. Some, such as mould and dampness; crowding; and lead exposure, are widely studied. By far, indoor air pollution was the most prominent housing quality factor among the reviews, with more than double the number of reviews than the second highest housing quality factor, dampness and mould.

Having identified this significant gap, colleagues and I conducted a review of one of the less studied housing quality factors: lighting.

Lighting in the home and health 

In our recent review, we assessed the existing evidence on the relationship between lighting in the home and health and recommended areas for future research. Lighting is important for health through its role in, among others, visual performance and safety; regulation of bodily functions; function in the nervous and endocrine systems; and release of hormones such as melatonin.

Our search identified 28 relevant studies. Due to the diversity in the measurement of lighting in the home and health outcomes, studies were analysed qualitatively.

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 health (e.g. falls, burns, tuberculosis, cancer, and obesity), mental health (depression and anxiety) and sleep health (e.g. duration, quality and how long it takes to get to sleep).

Studies consistently showed that poor lighting in the home negatively impacts health – be it lack of sunlight exposure during the day or being exposed to bright lights during the nighttime. Though we were not able to establish links with specific health outcomes, due to the evidence being limited, this association was consistent across the different categories of lighting in the home and health domains. Only 4 studies found no association with at least a single health outcome.

Wider implications 

While lighting is sometimes included in housing quality assessments such as the UK Housing Health and Safety Rating System, the focus is narrow. The inclusion of lighting is primarily from a perspective of cost-saving (e.g. energy efficiency) or aesthetics; and the health considerations are often limited to the impact on injuries and depression. It is clear, however, that the intersection between lighting and health is much broader than this. As such, stronger consideration for health should be made when constructing and designing homes.

Until these policy changes, what can you and I do? We suggest taking simple measures around the home to ensure optimal lighting conditions for your health. For instance:

  • Keep your curtains open during the day
  • Make improvements to poor lighting at home (e.g. around stairs)
  • Sleep in darkness – maybe even use an eye mask!
  • If you use fuel-based lighting, placement of these lighting sources should be carefully selected; and where possible, safe and healthier alternatives (e.g., solar power) should be considered

Here is to brighter and healthier days ahead!