Some attacks or spells can damage an Investigator's attribute score.
For example, in the module. Dead light, the titular creature has an attack:
Consume (fight maneuver): If it succeeds, it melts into its victim. The victim suffers 1D10 + 5 NO damage per turn until he dies, dying in agony as a deadly light pulses from within his flesh and boils from his eyes and mouth, and his flesh begins to burn and turns to ash. Light consumption of a victim is 1 / 1D6 of loss).
If the investigator survives in some way to this attack, will they ever recover the lost NOC from this horrible assault?