Nocturnal pulse wave amplitude attenuations are associated with long-term cardiovascular events

Objectives: Photoplethysmography (PPG) is an established technology for detecting pulse rate and pulse wave irregularities. However, whether temporal variations in pulse wave amplitudes, reflecting a combination of acute hemodynamic or autonomic responses to changes in overall vascular function, carry prognostic information remains unclear. To quantify nocturnal temporal pulse wave amplitude (PWA) attenuations and evaluate its association with long-term cardiovascular (CV) events in a large, racially diverse sample of men and women. Methods: Temporal PWA attenuations were determined based on the slopes between the upper and lower en-velopes of PPGs derived from overnight polysomnography of 1957 participants (899 men, 1058 women, mean age 68.2 & PLUSMN; 9.1 years) of the Multi-Ethnic Study of Atherosclerosis. The nocturnal PWA attenuation index was defined as the cumulative duration of all PWA attenuation events relative to total sleep duration. Results: Nocturnal PWA attenuation index was greater in men than in women by almost 13% (16.3 & PLUSMN; 8.9% vs. 14.4 & PLUSMN; 7.9%, p < 0.001). The nocturnal PWA attenuation index was highest in Chinese-American participants (17.9 & PLUSMN; 9.2%) and lowest in African-Americans (13.5 & PLUSMN; 8.1%). During a median follow-up of 4.9 years, 94 CV events occurred. In multivariable Cox proportional hazard analysis adjusted for typical confounders, the nocturnal PWA attenuation index <15.2% was associated with CV events (HR = 1.58 [1.02-2.45], p = 0.042). Conclusions: Nocturnal PWA attenuation index is inversely associated with the risk of CV events, particularly in men and African-Americans. The PPG-derived nocturnal PWA attenuation index could be simply obtained from smart wearable consumer devices and may provide a low-cost, accessible and scalable CV risk marker.