Figure 1: The blue-light blocking (BLB) glasses. A. The Ultrahuman BLB glasses. The glasses are shown in their smart packaging, wherein the eye glass on the blue side appears black because it absorbs all the light reaching it through the blue cover. B. Transmission spectrum showing that the BLB glasses absorb almost all light between 430-530 nm (area enclosed by the white dotted line).
In the last quarter of 2024, Ultrahuman employees worked through a tremendous surge of orders coinciding with the global year-end-festival/holiday time. We conducted an in-house study, modeled around the case-control paradigm, to test worker recovery and sleep at this period. A key impediment in most lifestyle observational studies is that it is difficult to quantify the amount of screentime across participants in different organizations. This could be counteracted to some extent here by selecting 13 participants from various teams in-house and assigning them to two-groups - those who wore the BLB glasses (BLBG) a.k.a. the BLBG group and those who did not wear the BLBG glasses (the non-BLBG group). The BLBG participants wore the BLB glasses from 5:00 p.m. till bedtime daily for an average of 4 weeks between 15th September to 5th November 2024. The non-BLBG participants either did not wear any new glasses or continued with their own prescription glasses (if they had ones) during this period.
To determine impact on health biomarkers, all participants wore the Ultrahuman Ring AIR which tracks sleep, stress and recovery metrics.8, 9, 10, 11 A total of 1046 days of Ring AIR data were collected. Analysis of metrics was divided into three periods – weeks preceding the day of starting BLBG usage (before), during the days of BLBG usage (during) and the period since the last day of wearing the glasses (after) and done at an individual level first and then grouped later for graphs. We analysed the during and after periods on normalizing those values to the before period within the respective BLBG and non-BLBG groups of participants.
Given that blue light influences onset of melatonin production, BLBG usage was expected to show changes in the sleep scores of the participants. The Ultrahuman sleep score comprehensively aggregates across several metrics of sleep quantity and quality in a weighted manner. The overall sleep score of both groups showed a similar overall declining sleep health over time (Figure 2A). However, the non-BLBG group showed a steeper drop in the last period as compared to the BLBG group (Non-BLBG: Kruskal-Wallis (KW) test: p<0.05, Dunn’s post hoc test: During vs After: p<0.05; BLBG: KW: p=0.11, Before vs After: p=0.15). Since the participants were in the same teams and pulled comparable workloads, this statistically significant decline seems to have stemmed from wearing of the BLB glasses.
Figure 2: Box and whisker plots for a) sleep and b) stress scores of the BLBG (pink) and non-BLBG group (blue) for three time periods - before, during, and after the weeks of BLBG usage. Each distribution is represented as Median+1.5 times the inter-quartile range. *p<0.05, ***p<0.001, and ****p<0.0001 for Kruskal Wallis test. #p<0.05, ##p<0.01, and ####p<0.0001 for Dunn’s post hoc pair-wise comparison.
The sleep score results led us to next examine whether the BLBG usage was mitigating daytime stress or enhancing recovery at night. We studied this by comparing the daily stress rhythm score that measures the load on the cardiac system along with sympathetic activation. A higher score indicates better stress management. We found that the median stress scores of our non-BLBG participants declined steadily over the three time periods indicating a perhaps increasing or cumulative impact over these months (Figure 2B). There was a significant difference in the stress scores of before vs after periods for both groups (Non-BLBG: KW: p<0.0001, Before vs During: p<0.01, During vs After: p<0.0001, Before vs After: p<0.05; BLBG: KW: p<0.001, Before vs During: p=0.06, During vs After: p<0.0001, Before vs After: p=0.08) indicating that the BLBG usage did not help manage daytime stress on-line.
We then closely examined physiological parameters of the participants during sleep and recovery. First, the night-time resting heart rate (RHR) was compared across the three time periods. Lower RHR values are associated with better recovery outcome. We observed a significant decrease in the RHR of the non-BLBG group initially that later rose to higher median levels (Figure 3A). Whereas for the BLBG group, the RHR was consistently maintained during the BLBG usage period, even extending into the period after stopping the usage of the glasses.
Figure 3: Box and whisker plots for a) night time resting heart rate (RHR) and b) recovery scores of the BLBG (pink) and non-BLBG group (blue) for three time periods - before, during, and after the weeks of BLBG usage. Each distribution is represented as Median+1.5 times the inter-quartile range. ****p<0.0001 for Kruskal Wallis test. #p<0.05, and ####p<0.0001 for Dunn’s post hoc pair-wise comparison.
Next, we compared the recovery scores across the three periods for both the groups. Higher scores indicate efficient coping of the body with the preceding day’s demands in the following sleep session. We found that the scores were maintained for both the groups before and during the period of BLBG use, but declined when the participants stopped wearing the glasses (Figure 3B). The magnitude of decline was however lower in the BLBG group relative to the reduction in the non-BLBG group. These two metrics, the night time RHR and the recovery score, indicate a startling long-term effect of wearing BLBG lasting beyond the usage period.
Our findings thus present immediate as well as delayed benefits of wearing the blue-light glasses over an average of 4 weeks. Since this study was conducted during a time when the work demands were relatively higher, the decline in sleep and stress scores in the non-BLBG participants was explainable. However, unlike the non-BLBG group, the BLBG participants were able to maintain their sleep as usual even on the high-stress days. Wearing BLB glasses from evening to bed time kept the sleep scores unaltered.
Intense workdays not only hamper sleep but also impact recovery during sleep. We found that the night time RHR in the participants who wore the BLB glasses, was maintained despite the day-time stress. This was not the case with the non-BLBG participants. A low RHR has been linked to better sleep and higher recovery. This was reflected in the recovery scores of the two groups across the three periods of comparison. Overall wearing the BLB glasses and thereby cutting down on the blue light exposure evening onwards seems to lessen the impact of the day’s demands and helps wind down into a usual sleep progression. Additionally, three of our BLBG participants (two males and one female) reported that they fell asleep faster and more easily after finishing late night calls while using the glasses. Few of them therefore continued to use the glasses even after the end of the study period. Thus, besides the physiological impact of blocking the blue light, these glasses might also have conferred a perceived calming effect on the users. It could have been mediated by non-delayed secretion of melatonin thereby setting in an improved sleep schedule.
As this was a pilot study, our sample sizes were low and we could only control for the gender and team-category. We did not control for age, body-mass index, and meal timings. A more comprehensive analysis in the future could therefore help tease out the effects of additional factors impacting the circadian rhythms.
This study presents an initial assessment of short term as well as persisting long-term benefits of wearing the blue-light blocking glasses on the daily health metrics of the users.
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