Kate Tolo is tracking vaginal blood flow during sleep with a probe that Bryan Johnson says costs $15,723.68, and she said it uses “the same kind smartwatches use to read your heart rate.” The project, he says, follows 1,900 biomarkers across her menstrual cycle.
Johnson, her partner and the entrepreneur behind the longevity company Blueprint, posted on October 9: “I am measuring my girlfriend’s erections.” He described a 5 cm probe with a light sensor.
The setup records to a laptop, and Tolo warned that if it falls asleep, “we lose the data.”
That project prompted Anna, who posts as @ArguablyAnna, to suggest it could be among the only funded research on the female reproductive system in decades or centuries. That overstates the gap. Research on this measurement alone goes back decades: a 1979 study recorded vaginal blood-flow changes during REM sleep in 8 women, and a 1985 study also documented changes linked to sleep stages.
The distinction between vaginal blood flow and clitoral erections matters here. UCLA psychophysiologist Nicole Prause said the intravaginal Biopac probe “does not measure the clitoris,” and called Johnson’s post “medical disinformation.”
Dr. Hillary Seger, a member of Tolo’s care team, said women have “no validated clinical equivalent” to men’s nighttime erection testing. She described Tolo’s recordings across a menstrual cycle as the first she’d personally seen.
Tolo argues that tracking nighttime vaginal blood flow could help distinguish physical from psychological causes of sexual problems and might offer clues about cardiovascular health. Those are proposed uses. Her self-tracking hasn’t established a validated diagnostic test.
Her broader project also comes from years of menstrual pain. At 13, Tolo’s first period caused pain that left her on the floor, she said. In her early 20s, she turned down a laparoscopy after a doctor suspected she had endometriosis.
On July 9, Johnson announced that she’d received a diagnosis without surgery. The sleep probe itself hasn’t been established as an endometriosis test.