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Sleep Fragmentation Index

Meaning

The Sleep Fragmentation Index (SFI) is a quantitative polysomnographic metric used in sleep medicine to measure the degree of sleep discontinuity, reflecting the number of arousals and awakenings per hour of sleep. A high SFI indicates poor sleep quality, where the individual repeatedly shifts from deeper to lighter stages of sleep or wakes up briefly, even if they do not recall the events. This fragmentation prevents the sustained periods of deep, restorative sleep necessary for optimal hormonal secretion and metabolic regulation.