Sleep needs vary significantly across different life stages, according to Dr. Pradeep Bajad. While eight hours is often cited, individual requirements change due to neurological, hormonal, and biological shifts. Infants and children need more deep and REM sleep for brain development. Teenagers experience a biological shift in their circadian rhythm, leading to later sleepiness. Adults generally have consolidated sleep, but older adults experience lighter, shorter, and more fragmented sleep as deep and REM sleep decline with age.