Association of Sleep Pattern Objectively Measured by Smartphone App with Work Productivity Loss in Japanese Employees

Sleep disturbances are a major yet underrecognized contributor to reduced workplace productivity ("presenteeism"). Previous studies have largely relied on self-reported sleep data, limiting their scalability and objectivity. We examined the association between objectively measured sleep characteristics and presenteeism among Japanese workers, using real-world data from a smartphone sleep application. A total of 79,048 working adults (mean age: 42.1 years [range: 18-66 years]; women: 47.8%) provided informed consent and at least seven nights of valid sleep data across a 28-day period. Over 2.1 million nights of sleep data were analyzed. Sleep variables included total sleep time (TST), sleep latency, wake after sleep onset (%WASO), chronotype (MSFsc), and social jetlag. Generalized additive models revealed that both short and long TST were associated with increased presenteeism, forming a U-shaped relationship. Greater sleep latency, higher %WASO, delayed chronotype, and greater social jetlag were also independently linked to higher presenteeism scores. Unsupervised clustering using UMAP and the Leiden algorithm identified five sleep phenotypes: "Healthy Sleepers," "Long Sleepers," "Fragmented Sleepers," "Poor Sleepers," and "Social Jetlaggers." The latter two groups exhibited the highest levels of insomnia symptoms, excessive daytime sleepiness, and presenteeism. These findings suggest that not only sleep duration but also timing, quality, and regularity are critical factors influencing occupational functioning. Smartphone-based sleep tracking offers a scalable approach to identify at-risk individuals and may help inform personalized interventions to improve employee health and productivity.