Existing knowledge gap

Based on the above literature review, the significant findings of light-related research in connection with hospital patients for last 20 years were separated to identify the existing knowledge gap, and presented in Table 2.1. The impact of light on patients have been categorised in three groups: psychological impact of light; impact on diseases related to bones and cancers and impact on physiological diseases.

It is evident from Table 2.1 that the relationship between daylight and psychological benefit of hospital patients (e.g. reducing depression and SAD), and the impact of daylight on some specific physical diseases related to bones and cancers (e.g. rickets and breast cancer) are well established and supported by robust research. Research on the impact of daylight on physiological diseases (diseases originated from the malfunctions of physiological organs of human body e.g. heart, lungs, stomach, kidney, spinal cord, and not generated from psychological pressure) are few in number; three out of 23 articles listed in Table 2.1. Among 16 empirical research on psychological impact of light on patients (e.g. depression and SAD) presented in Table 2.1, six research identified the impact under bright artificial light sources. In a cohort study, Wirz-Justice et al. (1996) get evidence for the use of outdoor daylight exposure as a potential alternative or adjuvant to conventional bright artificial light therapy for SAD patients, for the first time. It is expected that the impact of daylight exposure on patients

28

Impact Author Year Findings

Psychological impact of

light

Burgess et al. 2006 Daylight exposure at morning determines human circadian phase. Lahti et al. 2006 Daylight influences the duration of sleep.

Roenneberg et al. 2003 Duration of daylight exposure influences the timing of sleep.

Ljubicic et al. 2007 Duration of daylight exposure is associated with depression of patients.

Beauchemin et al. 1996 Patients hospitalised for severe depression reduced their LoS by an average of 2.6 days if assigned to a sunny rather than a dull room overlooking spaces in shadow.

Oren et al. 2002 Light (artificial) treatment in morning has an antidepressant effect during pregnancy Kecskes et al. 2003 Daylight exposure reduces LoS of female patients with unipolar major depressive episode.

Benedetti et al. 2001 Bipolar patients randomly assigned to the brighter, eastern rooms had a mean 3.67-day shorter LoS in hospital than patients in west-facing rooms.

Someren et al. 1997 Exposure to bright light (artificial) improves rest activity rhythm disturbances in demented patients. Lovell et al. 1995 Exposure to bright light (artificial) reduces agitated behaviour in institutionalized elderly patients. Lewy et al. 1998 Light (artificial) treatment in morning is twice as effective as evening light treatment for SAD patients.

Wirz-Justice et al. 1996 This is the first study to provide evidence for the use of outdoor daylight exposure as a potential alternative or adjuvant to conventional artificial light therapy in SAD.

Bauer et al. 1994 Bright light (artificial) impact on patients‟ mood and behaviour.

Kripke et al. 1992 Bright light (artificial) is beneficial for patients with non-seasonal depression. Impact on

diseases related to bones and cancers

Lim et al. 2006 Exposure to daylight reduced mortality from breast and lung cancer patients.

Whyte et al. 2005 Deficiencies of UV-B can increase the risks of rickets in childhood and of osteomalacia and fractures in adults. Holick 2004 Deficiencies of UV-B have been associated with increased risks of rheumatoid arthritis.

Hughes et al. 2004 Exposure to daylight reduced the risk of non-hodgkin lymphoma (NHL). Freedman et al. 2002 Exposure to sunlight reduces mortality from prostate and colon cancer. Lefkowitz et al. 1994 Exposure to sunlight reduces mortality from ovarian cancer.

Impact on physiological

diseases

Choi et al. 2012 Daylight reduces average LoS for hospital patients in different wards: internal, otolaryngology, surgery, and gynecology wards. Walch et al. 2005 Elective cervical and lumbar spinal surgery patients exposed to an increased intensity of daylight (46% higher) experienced less

perceived stress, marginally less pain, took 22% less analgesic medication per hour and 21% less pain medication costs. Beauchemin et al. 1998 Daylight reduced hospital mortality and LoS for women MI patients (2.3 days in sunny rooms compared to 3.3 days in dull

rooms) in CICU.

29 psychological health will be similar to the impact of bright artificial light which will help to reduce patient LoS in hospitals. Table 2.1 shows that, there are at least five evidences confirmed that higher daylight intensities reduce patient LoS. Three of the studies examined LoS related to patients with psychological problems e.g. SAD (Beauchemin et al., 1996), unipolar (Kecskes et al., 2003) and bipolar (Benedetti et al., 2001) disorders; the other two research studied LoS related to patients with physiological problems e.g. myocardial infarction (Beauchemin et al., 1998) and other (e.g. internal, otolaryngology, surgery, and gynecology) diseases (Choi et al., 2012). Research on the impact of daylight on physiological diseases, that could be measured objectively (i.e. LoS of hospital patients), are necessary for the incorporation of the therapeutic benefit of daylight in the design of in-patient rooms, as it is applicable for most of the hospitals. The researcher identified that some parts of the methodologies, as well as the outcome of the two research, studied LoS related to patients with physiological problems (i.e. Beauchemin et al., 1998 and Choi et al., 2012), are questionable (discussed in Section 3.4). Defined knowledge about the impact of daylight on patients physiological developments was identified as weak and controversial from the outcome of the review of the literature related to therapeutic environment, conducted by previous researchers such as Devlin et al. (2003) and Edwards et al. (2002), and the results are well debated (HBN-04, 1997; Loftness et al., 2006); therefore, suggests that it is necessary to further investigate the impact of daylight on patient LoS in a general hospital environment scientifically. The particular interest of this PhD research is to quantify the impact of daylight intensity on LoS of patients with physiological diseases.