https://orcid.org/0000-0003-1137-9274
Dear editor
We thanks Dr SMJ Mortazavi for interest in our recent publication.Citation1
Regarding to his first comments on “smartphone blue light filter”. We agree with his opinion in terms of blue light suppressing the secretion of melatonin, which possibly causes circadian rhythm disruption.Citation2 Though most applications are available in modern smartphones, people are mostly not aware of the dangers of the blue light, hence they usually do not apply the blue light filter for protection, especially in Taiwan and China.Citation3 That is why we did not consider this factor would affect our result. All participants stand on the same baseline.
The second concern was about the control of environmental light before bedtime. The environmental lights’ exposure intensity and frequency vary from the individual and complicated causal mechanisms in a naturalistic setting. Notably, Lin et al, discovered smartphone use has a mediator effect of circadian rhythm delay with daily and bedtime pre-sleep. They indicated that using a smartphone before bedtime mediated delayed circadian rhythm and reduced the total sleep time.Citation4 Furthermore, Chang et al also demonstrated that using the light-emitting device before bedtime increased the risk of delayed sleep-phase disorder and sleep-onset insomnia.Citation5 In addition it was reported that as smartphone light can suppress melatonin production, which is not only a sleep-promoting hormone, but also plays an important role in inhibiting the release of estrogen, resulting in a propensity for breast cancer.Citation4,Citation5 These illustrated that the light emitted by smartphones could be harmful to human well-being.
Thank you for your contributions and comments. This is a very important health issue, as smartphones become indispensable to life gradually, it already changes in the living styles of human beings. No study has investigated the relationship between smartphone use and breast cancer. This case–control study purposely investigated the relationship between smartphone use and breast cancer risk. However, the findings of this research are that excessive smartphone use significantly increased the risk of breast cancer. Particularly for participants with smartphone addiction, close distance between breasts and smartphones, and the habit of smartphone use before bedtime.
Therefore, we hope these findings may provide a basis for further scientific research and we will consider these confounding factors you mentioned in our future research.
Disclosure
The authors report no conflicts of interest in this communication.
References
- Shih YW, Hung CS, Huang CC, et al. The association between smartphone use and breast cancer risk among Taiwanese women: a case–control study. Cancer Manag Res. 2020;12:10799–10807. doi:10.2147/CMAR.S26741533149685
- Mortazavi SAR, Parhoodeh S, Hosseini MA, et al. Blocking short-wavelength component of the visible light emitted by smartphones’ screens improves human sleep quality. J Biomed Phys Eng. 2018;8(4Dec):375–380. doi:10.31661/jbpe.v8i4Dec.64730568927
- Shen Q, Xu L, Jiang Y, Zheng R, Zhang Y. Survey and statistical analysis of Hangzhou citizens’ awareness of harmful blue light and consciousness of protection against blue light. J Phys Conf Ser. 2020;1616:012074.
- Lin YH, Wong BY, Lin SH, Chiu YC, Pan YC, Lee YH. Development of a mobile application (App) to delineate “digital chronotype” and the effects of delayed chronotype by bedtime smartphone use. J Psychiatr Res. 2019;110:9–15. doi:10.1016/j.jpsychires.2018.12.01230611008
- Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci USA. 2015;112(4):1232–1237. doi:10.1073/pnas.141849011225535358