Bryan Johnson has a $275 wireless gadget that scores each of his nighttime erections on his phone. His girlfriend, Kate Tolo, has a $15,723.68 probe, a wire taped to her leg and a laptop that, he wrote, cannot be allowed to fall asleep.
According to Health and Me, the tech entrepreneur is monitoring Tolo's nighttime clitoral engorgement as part of his longevity experiments. The goal is to see whether genital blood flow offers clues about female sexual function and cardiovascular health.
Johnson laid out his reasoning in an Oct. 9 post on X: "Women have erections too. This is news for most women," he wrote. "The clitoris is erectile tissue, same as men. During REM sleep, blood flow spontaneously increases."
Tolo's setup is lab equipment: a 5-centimeter probe with a light sensor, one of 1,900 biomarkers she is tracking across her menstrual cycle.
Johnson argues that nighttime erections reflect whole-body health, including blood vessels, nerves, hormones, sleep stages, stress, glucose and cardiovascular health. He also claims that in men, erectile dysfunction typically shows up two to five years before heart symptoms.
Tolo explained the reasoning in an interview, per Health and Me. "Because the penis has smaller blood vessels than the rest of the body, and so it's the first thing to show up when problems happen. So it's all about blood flow," she said. "That's why it should work for women just as well as it works for men, because we have blood vessels too."
Health and Me notes that the evidence linking male erectile dysfunction with cardiovascular risk is more established than the evidence for using female genital blood flow as a cardiovascular monitoring tool. It adds that tracking changes during sleep may not be an established way to screen for heart disease.
There is some research connecting genital blood flow to sexual function. A small pilot study in the International Journal of Impotence Research measured clitoral tissue oxygen levels in 27 healthy, heterosexual, sexually active women of reproductive age, with a mean age of about 31. After adjusting for age, BMI and smoking, higher oxygen levels correlated with higher scores on a standard sexual function questionnaire, including for arousal, lubrication, orgasm and satisfaction. Women with sexual dysfunction had lower levels than those without: 28.4 mmHg versus 48.1 mmHg.
That is a correlation in a small sample, and it measured tissue oxygen, not nighttime engorgement. The authors called for larger studies and suggested the measure could be tested as a potential predictor of cardiovascular and metabolic conditions in women.
A 2024 review in the European Journal of Preventive Cardiology, included 54 studies and nearly 149,000 participants and found that women with cardiovascular disease had a higher risk of female sexual dysfunction. The outlet says the review supports a relationship between cardiovascular and sexual health but does not validate Johnson's tracking method.
Researchers would first need to establish what a normal pattern looks like, how measurements shift with sleep and hormonal cycles, and whether particular changes reliably predict disease, ideally in much larger groups, the outlet adds.
Tolo said, per Brit Brief, that men's nighttime erections have been studied extensively for decades while women's are "barely measured." "If the data turns out to matter the way it matters for men, someone should build the device," she said.