Narrow-band ultraviolet B (NB UV-B) exposures improve mood in healthy individuals differently depending on chronotype

ABSTRACT

The evening chronotype is associated with psychological symptoms such as depressed mood, while skin exposure to ultraviolet radiation (UVR) may affect mood and behavior through neural and humoral routes. This pilot study aimed to investigate the impact of whole-body narrow-band (NB) UV-B exposure on current mood state and circulating 25-hydroxyvitamin D3 (25(OH)D₃), interleukin-6 (IL-6), cortisol and β-endorphin (β-END) levels in healthy participants. Here, eleven healthy women received full-body NB UV-B exposures on four afternoons, and the chronotype was assessed with a shortened version of Horne and Östberg’s Morningness-Eveningness Questionnaire (MEQ). Perceived mood was evaluated using the Visual Analogue Scale (VAS), and serum 25(OH)D₃, IL-6, cortisol and β-END concentrations were monitored daily. Decreasing VAS values showed mood to improve significantly over the five days after the four suberythematous NB UV-B exposures (p = .038), and the more the circadian preference was inclined toward eveningness, the greater the improvement in the mood dimension of wellbeing (p = .021). Baseline mood state was correlated with baseline 25(OH)D₃ (r = −0.54, 95% CI: −0.86 to −0.09) and with baseline cortisol (r = −0.57, 95% CI: −0.87 to −0.04). During the NB UV-B exposures, 25(OH)D₃ increased significantly, as expected, and IL-6 declined significantly by −0.35 (95% CI: −0.69 to −0.07) pg/mL from the initial values of 1.12 ± 0.66 pg/mL (p = .025). In conclusion, in our pilot study, NB UV-B exposure improved mood, especially among those with evening preference for their daily activities, as well as circulating 25(OH)D₃ levels, whereas circulating IL-6 levels decreased.

Abbreviations: UVR: Ultraviolet radiation; NB UV-B: narrow-band UV-B; VAS: Visual Analogue Scales; β-END: β-endorphin; IL-6: Interleukin-6

KEYWORDS:

• Chronotype
• mood
• vitamin D
• β-endorphin
• cortisol
• interleukin-6
• UV-B

Acknowledgments

This study was supported financially by Competitive State Research Financing for this expert responsibility area of Tampere University Hospital. The authors AT and TK implemented the study; MEM, JL and OV performed the biochemical analyses; LY performed the UVR dosimetry; HK performed the statistical analyses; and all the authors took part in writing the manuscript.

Disclosure of interest

The authors report no conflicts of interest.

Additional information

Funding

This work was supported by the Competitive State Research Financing, Finland [grants #9P065 and #9T061], within the relevant expert responsibility area of Tampere University Hospital.