This study examined the associations between reported quantitative sleep measures and multiple daytime impairment domains. We collected data from a subsample of adults (n = 513) from the Colorado Longitudinal Twin Study and Community Twin Study. Results revealed that greater insomnia symptom frequency (days per week) significantly predicted greater global sleep-related functional impairment and depressive symptoms. Sleep onset latency was also positively associated with depressive symptoms. Receiver operating characteristic curve analyses indicated 3-4 nights per week and 36-40 min provided optimal sensitivity and specificity for impairment. Thus, insomnia frequency and sleep latency are critical in understanding the impact of insomnia on multiple impairment domains. Using functional impairment as criterion, these findings also support the use of specific quantitative cutoffs for sleep measures in diagnostic systems.