Rafael Lazar

PhD student, Psychologist

“How does light influence human physiology, mental health and performance?” My main interests lie in the spectral composition of light, how it can be used (or not used) to enhance sleep, performance, and well-being and what we can do to live a healthy, sustainable lifestyle in a post-modern world.

Publications

2023

Siraji, Mushfiqul Anwar; Lazar, R.; van Duijnhoven, Juliëtte; Schlangen, Luc J M; Haque, Shamsul; Kalavally, Vineetha; Vetter, Céline; Glickman, Gena L; Smolders, Karin C H J; Spitschan, Manuel

An inventory of human light exposure behaviour Journal Article

In: Sci Rep, vol. 13, no. 1, pp. 22151, 2023, ISSN: 2045-2322.

Abstract | Links | BibTeX

@article{pmid38092767,

title = {An inventory of human light exposure behaviour},

author = {Mushfiqul Anwar Siraji and R. Lazar and Juliëtte van Duijnhoven and Luc J M Schlangen and Shamsul Haque and Vineetha Kalavally and Céline Vetter and Gena L Glickman and Karin C H J Smolders and Manuel Spitschan },

doi = {10.1038/s41598-023-48241-y},

issn = {2045-2322},

year  = {2023},

date = {2023-12-01},

urldate = {2023-12-01},

journal = {Sci Rep},

volume = {13},

number = {1},

pages = {22151},

abstract = {Light exposure is an essential driver of health and well-being, and individual behaviours during rest and activity modulate physiologically relevant aspects of light exposure. Further understanding the behaviours that influence individual photic exposure patterns may provide insight into the volitional contributions to the physiological effects of light and guide behavioural points of intervention. Here, we present a novel, self-reported and psychometrically validated inventory to capture light exposure-related behaviour, the Light Exposure Behaviour Assessment (LEBA). An expert panel prepared the initial 48-item pool spanning different light exposure-related behaviours. Responses, consisting of rating the frequency of engaging in the per-item behaviour on a five-point Likert-type scale, were collected in an online survey yielding responses from a geographically unconstrained sample (690 completed responses, 74 countries, 28 time zones). The exploratory factor analysis (EFA) on an initial subsample (n = 428) rendered a five-factor solution with 25 items (wearing blue light filters, spending time outdoors, using a phone and smartwatch in bed, using light before bedtime, using light in the morning and during daytime). In a confirmatory factor analysis (CFA) performed on an independent subset of participants (n = 262), we removed two additional items to attain the best fit for the five-factor solution (CFI = 0.95, TLI = 0.95, RMSEA = 0.06). The internal consistency reliability coefficient for the total instrument yielded McDonald's Omega = 0.68. Measurement model invariance analysis between native and non-native English speakers showed our model attained the highest level of invariance (residual invariance CFI = 0.95, TLI = 0.95, RMSEA = 0.05). Lastly, a short form of the LEBA (n = 18 items) was developed using Item Response Theory on the complete sample (n = 690). The psychometric properties of the LEBA indicate the usability for measuring light exposure-related behaviours. The instrument may offer a scalable solution to characterise behaviours that influence individual photic exposure patterns in remote samples. The LEBA inventory is available under the open-access CC-BY license. Instrument webpage: https://leba-instrument.org/ GitHub repository containing this manuscript: https://github.com/leba-instrument/leba-manuscript .},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

Light exposure is an essential driver of health and well-being, and individual behaviours during rest and activity modulate physiologically relevant aspects of light exposure. Further understanding the behaviours that influence individual photic exposure patterns may provide insight into the volitional contributions to the physiological effects of light and guide behavioural points of intervention. Here, we present a novel, self-reported and psychometrically validated inventory to capture light exposure-related behaviour, the Light Exposure Behaviour Assessment (LEBA). An expert panel prepared the initial 48-item pool spanning different light exposure-related behaviours. Responses, consisting of rating the frequency of engaging in the per-item behaviour on a five-point Likert-type scale, were collected in an online survey yielding responses from a geographically unconstrained sample (690 completed responses, 74 countries, 28 time zones). The exploratory factor analysis (EFA) on an initial subsample (n = 428) rendered a five-factor solution with 25 items (wearing blue light filters, spending time outdoors, using a phone and smartwatch in bed, using light before bedtime, using light in the morning and during daytime). In a confirmatory factor analysis (CFA) performed on an independent subset of participants (n = 262), we removed two additional items to attain the best fit for the five-factor solution (CFI = 0.95, TLI = 0.95, RMSEA = 0.06). The internal consistency reliability coefficient for the total instrument yielded McDonald's Omega = 0.68. Measurement model invariance analysis between native and non-native English speakers showed our model attained the highest level of invariance (residual invariance CFI = 0.95, TLI = 0.95, RMSEA = 0.05). Lastly, a short form of the LEBA (n = 18 items) was developed using Item Response Theory on the complete sample (n = 690). The psychometric properties of the LEBA indicate the usability for measuring light exposure-related behaviours. The instrument may offer a scalable solution to characterise behaviours that influence individual photic exposure patterns in remote samples. The LEBA inventory is available under the open-access CC-BY license. Instrument webpage: https://leba-instrument.org/ GitHub repository containing this manuscript: https://github.com/leba-instrument/leba-manuscript .

Stampfli, J. R.; Schrader, B.; di Battista, C.; Häfliger, R.; Schälli, O.; Wichmann, G.; Zumbühl, C.; Blattner, P.; Cajochen, C.; Lazar, R.; Spitschan, M.

The Light-Dosimeter: A new device to help advance research on the non-visual responses to light Journal Article

In: Lighting Research & Technology, 2023.

Links | BibTeX