Biohacker Bryan Johnson sounds alarm on UV rays: 'Sun can damage skin indoors too'; shares protection protocol for youthful skinEven when you're sitting safely by a window or on a cloudy day, your skin could be silently taking damage, warn experts. While SPF ratings protect against sunburn-causing UVB rays, they often do not account for the deeper-penetrating UVA rays, which can accelerate aging and increase cancer risk, according to Dr. Adam Friedman, professor and chair of dermatology at GW School of Medicine and Health Sciences.
"SPF only refers to UVB, the type that burns," Friedman explains in a report from CNBC Make It. "UVA gets through clouds and windows, harming your skin without you even noticing." He emphasizes that a heart-healthy routine should also include a skin-healthy one, noting that prolonged UVA exposure can damage collagen and elastin, causing wrinkles, sagging, and increasing the likelihood of skin cancer.
Many people assume sitting indoors or behind glass prevents sun damage. Friedman warns this is a false sense of security. While UVB rays are largely blocked by windows, UVA rays pass through, creating what he calls a "silent killer" for the skin. He recommends broad-spectrum sunscreens with SPF 30 or higher, applied regularly, especially near windows or during extended outdoor activity.
Tech entrepreneur Bryan Johnson, known for his extreme anti-aging experiments, echoes this caution. In a recent post on X (formerly Twitter), Johnson stressed that sunlight can harm the skin even indoors. His protocol includes UV-tinted windows, monitoring UV levels, and minimizing sun exposure during peak hours to reduce cumulative damage, reinforcing the idea that standard sunscreen use alone may not be enough (Johns Hopkins Medicine).
Experts advise combining SPF use with physical barriers like UV-filtering glass and smart scheduling of sunlight exposure. Broad-spectrum protection ensures defense against both UVA and UVB rays, while monitoring the UV index can help plan safer times outdoors. Consistent awareness, rather than relying solely on SPF numbers, is key to preventing long-term skin damage.
Whether at home, in the office, or commuting by car, indoor UV exposure is real and cumulative. As Dr. Friedman notes, "You're getting exposed and being harmed, and don't even feel or know about it." SPF alone cannot fully protect you -- understanding UVA risks and adapting daily habits may be the missing step for truly sun-safe living.