Major organizations warn against lifestyle polyphasic sleep for the general population. Documented/likely risks: chronic sleep deprivation; hormonal disruption (GH, melatonin); circadian misalignment; social/occupational interference; higher accident risk; impaired immunity and athletic recovery; potential severe psychiatric effects in case reports.

Some controlled recordings show shifts (e.g., small REM decreases, slight SWS increases) alongside overall total sleep reduction; many participants cannot sustain regimens for more than weeks, citing fatigue, mood issues, cognitive deficits, and social disruption. A small Uberman experiment saw 9/10 drop within a month; the lone finisher stopped at week five with ongoing issues.

Fragmented/restricted sleep links to increased daytime sleepiness, lapses in attention/vigilance, poorer academic performance, and higher occupational accident risk. Evidence suggests suppressed growth hormone when sleep is heavily fragmented/restricted, with potential implications for recovery, memory, and brain waste clearance.

Frequent, irregular sleep bouts can desynchronize circadian rhythms, disrupting melatonin, cortisol, ghrelin/leptin and other hormones; can weaken immune responses and alter inflammation markers. Short naps may show plasticity (faster entry to SWS/REM) under pressure, but this reflects adaptation to deprivation, not an optimal chronic state.