Contemporary '24/7' society requires many people to lose sleep. Despite numerous studies assessing sleepiness, there are aspects relevant to work settings that remain largely overlooked. Laboratory studies typically measure sleepiness within dull, controlled environments isolating participants from distractions. The key sign of sleepiness is a 'lapse' and failure to react to a stimulus, usually assumed to be a 'microsleep' (drooping eye-lids etc). However, sleep loss has other subtle effects, particularly a vulnerability to distraction and tendency to dwell on the distraction ('perseverate'). Both are due to failings of the frontal cortex ('executive centres') as sleep is critical for normal function here. Thus 'distractability' is a component of sleep loss, separate from 'microsleeps', and masked by usual laboratory procedures. Whereas distractability may be of little concern to sleepy people in an office environment, with background talking, telephones and movements in the visual periphery, for those monitoring surveillance screens, control rooms, driving at night etc, distractions are problematic. Moreover, older people are more likely to be 'caught off guard' in this manner. This research undertakes a series of studies with moderately sleep deprived young and older people, using contrived distractions in realistic settings (viewing security screens, mock control room, and office settings).