#Sleep staging data — i.e., stats that say how long you were in light or deep sleep — should be interpreted with caution. Sleep studies in clinics use EEGs (electroencephalograms) to measure brain activity. Trackers instead rely on proxies like heart rate, temperature, and movement, which are far less accurate. While trackers can give a general sense of patterns, they’re far less precise than lab testing, and experts warn that for some people, trackers actually worsen sleep quality. For example, performance anxiety around sleep (sometimes called orthosomnia), leading to stress, over-checking, and ultimately worse sleep. Sleep thrives on letting go: obsessing over numbers keeps the brain in “performance mode,” making it harder to relax and drift off. nz.news.yahoo.com/experts..