Abstract
Photoplethysmography-derived arterial stiffness index (ASI) has been proven to be associated with various cardiovascular diseases. The present study aims to determine whether the predictive value of ASI varies between elderly and non-elderly and whether ASI improves the discrimination and reclassification ability of the updated Systematic Coronary Risk Evaluation (SCORE2) in different age groups. This retrospective study included UK Biobank participants with ASI recordings. Multivariable Cox proportional hazard models were used to estimate the associations between ASI and major adverse cardiovascular events (MACE) in different age groups. The difference in C-statistic, integrated discrimination improvement (IDI), and continuous net reclassification improvement (NRI) were calculated to test the predictive performance of ASI beyond SCORE2 in the elderly and non-elderly. A total of 127 045 participants were included in the primary analysis. During a median of 11.7 years, 2606 (10.7%) and 4408 (4.3%) MACE were identified in the elderly and non-elderly, respectively. The non-elderly exhibited a greater extent of increased risk for MACE with higher ASI (HR, 1.314 [1.280-1.350] vs. HR, 1.066 [1.026-1.107]). Furthermore, the IDI and continuous NRI of ASI beyond SCORE2 for MACE were more than two times higher for non-elderly individuals than their elderly counterparts (IDI, 0.0481% [0.0182%-0.0953%] vs. IDI, 0.0010% [-0.0052% to 0.0295%]; NRI, 8.76% [6.83% to 10.60%] vs. NRI, 3.27% [-3.92% to 5.97%]). Our findings suggested that ASI should primarily be utilized for primary cardiovascular prevention in individuals below 65.