Abstract / Summary
Abstract Background. Arterial stiffness, measured as carotid–femoral pulse wave velocity (cfPWV), is an established independent predictor of cardiovascular events. Since 2024 the Oura Ring has reported a “Cardiovascular Age” (CVA), derived from nocturnal finger photoplethysmography (PPG). The ring describes CVA as an estimate of “how your heart and large arteries are aging compared to your chronological age” and classifies each user as below, aligned with, or above that age. Cardiovascular disease is the leading cause of death in women. Women’s arterial stiffness also follows a sex-specific trajectory, accelerating around the final menstrual period. A consumer metric of this kind therefore carries particular consequences for women. Objective. To set out how arterial stiffness and vascular age are properly measured and validated, to examine what a finger PPG waveform can and cannot represent, and to appraise Oura’s CVA claims and evidence. Particular attention is given to women and to statements by Oura’s Chief Executive filed with the US Securities and Exchange Commission (SEC). Findings. The ring does not measure pulse wave velocity, and Oura says so. Its only reference-standard validation is a company white paper. In 99 participants (63 women), it reported a correlation of r = 0.83 between estimated PWV and cfPWV, with no Bland–Altman analysis, no error metric and no results by sex. The ARTERY Society validation standard requires agreement statistics, which a correlation coefficient cannot supply. The only peer-reviewed study is an academic one in 160 mostly young adults. It did not use Oura’s algorithm, had no sex-stratified results and used chronological age rather than measured stiffness as its target. The ring-derived model had a mean absolute error of 7.25 years, which is wider than Oura’s ±5-year “aligned” band. Models trained to predict chronological age have a known regression-to-the-mean bias. That bias makes younger users appear older and older users younger, independent of their arteries. For women, the evidence is absent rather than adverse. No analysis addresses menstrual-cycle phase, pregnancy, the menopausal transition, hormone therapy, the effect of shorter stature on wave-reflection timing, or the higher prevalence of Raynaud’s phenomenon. CVA also cannot register women-specific risk enhancers such as pre-eclampsia or premature menopause. In a Rule 433 filing, Oura’s Chief Executive described the finger as “the first stop” of the pulse and claimed the ring’s accuracy allows it “to be right” about its predictions. The finger is the most distal site of the arterial tree, and no such accuracy has been demonstrated for CVA. Conclusions. CVA is an unvalidated, PPG-derived age-prediction residual. It is presented to consumers in the language of arterial ageing and cardiovascular risk. It should not be used to reassure or alarm patients, and least of all women in midlife, whose cardiovascular risk rises as their stiffness trajectory changes. Risk should continue to be assessed with validated risk equations, blood pressure, lipids and women-specific history, and cfPWV where arterial stiffness itself is the question.