Between October 9 and 12, 2026, biohacker Kate Tolo, partner of longevity entrepreneur Bryan Johnson, published results from tracking her own nocturnal genital blood flow, the female equivalent of the nighttime erections men experience during REM sleep. LADbible covered it on October 9 and the Daily Star on October 12. The couple's framing, posted on X and quoted by both outlets, is that the clitoris is erectile tissue and that spontaneous blood-flow increases during REM sleep are "a non-sexual, normal sleep function." In men, nocturnal erections are an established clinical signal. Johnson calls them "a tier 1 longevity marker," and their presence helps separate physical from psychological causes of erectile dysfunction. ED also tends to precede cardiovascular symptoms, which Johnson put at "2–5 years" in his post. Whether the same holds for women is barely studied.

Why It Matters

Take away the celebrity and there is a real product and research gap. The male side of this market is consumer-grade: Bluetooth tumescence rings, at-home ED tracking, and telehealth platforms built on the ED-as-cardiovascular-canary story. The female equivalent still depends on research-lab photoplethysmography that almost nobody outside a sexology lab can use. That leaves women's sexual-arousal disorders (FSIAD, the HSDD market [Acrux is now targeting](/stories/acrux-female-testosterone-fda-phase3)) without an objective at-home physiological endpoint, which is one reason female sexual-dysfunction trials still rely on questionnaires like the FSFI. For device makers this is a white space. The pleasure-tech industry already makes body-safe, app-connected, insertable devices with sensors. Lovense, Kegel trainers from Elvie and Perifit, and [Freyya's tampon-style pelvic-floor monitor](/stories/freyya-preseed-pelvic-floor-monitor) all have most of the hardware stack. A validated, consumer-grade overnight genital blood-flow sensor would sit between sexual wellness and cardiovascular screening. Whether women's nocturnal arousal predicts heart disease the way men's erections do is unproven. Johnson's audience will keep asking, so expect someone to try building one.

The equipment gap is the story. Per both reports, Johnson tracks his own nighttime erections with a wireless consumer sensor costing about $275 (£207) that connects to his phone over Bluetooth. Tolo's setup is lab equipment costing about $15,700 (£11,800–11,900): a 5cm internal light-sensor probe on a wire taped to her leg, streaming into a bedside laptop that has to stay awake all night or the data is lost. LADbible reports the device design dates from 1975 and has not been updated. "Men's nighttime erections have been studied extensively for decades... Women's are barely measured," Tolo said. "If the data turns out to matter the way it matters for men, someone should build the device." Per the Daily Star, the probe is one of about 1,900 biomarkers Tolo is tracking across her menstrual cycle for Johnson's Blueprint project.

This is an n-of-1 self-experiment by people who sell longevity products, published on social media, not a study. Neither outlet reports any peer review, and no results beyond the existence of measurable nighttime episodes have been published in a form we can verify. Treat it as a provocation rather than evidence.

Sources

Update — 2026-10-13

Initial entry — story first created.