Physiological sleep measures predict time to 15-year mortality in community adults: Application of a novel machine learning framework

Abstract

Clarifying whether physiological sleep measures predict mortality could inform risk screening; however, such investigations should account for complex and potentially non-linear relationships among health risk factors. We aimed to establish the predictive utility of polysomnography (PSG)-assessed sleep measures for mortality using a novel permutation random forest (PRF) machine learning framework. Data collected from the years 1995 to present are from the Sleep Heart Health Study (SHHS; n = 5,734) and the Wisconsin Sleep Cohort Study (WSCS; n = 1,015), and include initial assessments of sleep and health, and up to 15 years of follow-up for all-cause mortality. We applied PRF models to quantify the predictive abilities of 24 measures grouped into five domains: PSG-assessed sleep (four measures), self-reported sleep (three), health (eight), health behaviours (four), and sociodemographic factors (five). A 10-fold repeated internal validation (WSCS and SHHS combined) and external validation (training in SHHS; testing in WSCS) were used to compute unbiased variable importance metrics and associated p values. We observed that health, sociodemographic factors, and PSG-assessed sleep domains predicted mortality using both external validation and repeated internal validation. The PSG-assessed sleep efficiency and the percentage of sleep time with oxygen saturation <90% were among the most predictive individual measures. Multivariable Cox regression also revealed the PSG-assessed sleep domain to be predictive, with very low sleep efficiency and high hypoxaemia conferring the highest risk. These findings, coupled with the emergence of new low-burden technologies for objectively assessing sleep and overnight oxygen saturation, suggest that consideration of physiological sleep measures may improve risk screening.

Keywords: hypoxaemia; rapid eye movement; risk screening; sleep efficiency.

Figure 1.

Importance of domains of predictors for all-cause mortality based on external validation (left panel) and internal validation (right panel). Significant pVIMPs have p-values < 0.01. Red/bold text indicates sleep domains. Abbreviations: SR = Self-Report; PSG = Polysomnography.

Figure 2.

Importance of individual predictors for all-cause mortality based on external validation (left panel) and internal validation (right panel). Significant pVIMPs have p-values < 0.05. Red/bold text indicates sleep predictors. Abbreviations: SR = Self-Report; PSG = Polysomnography; T90 = % total sleep time spent with arterial oxygen saturation [SpO₂] < 90%; REM % = % total sleep time in rapid eye movement sleep; Stage 3–4 % = % total sleep time in Stage 3–4 sleep; SF-36 PCS = SF-36 Physical Component Score; SF-36 MCS = SF-36 Mental Component Score; CVD = Cardiovascular Disease; BMI = Body Mass Index.