Introduction: Short sleep duration and reduced sleep efficiency are two dimensions of sleep health that are associated with adverse effects on overall health including mortality, coronary heart disease, hypertension, and diabetes. However, we have limited knowledge on the efficacy of interventions (sleep extension) to improve sleep and if improving sleep can mitigate these adverse health outcomes. In this research, we will define the effects of a sleep extension intervention on multiple dimensions of sleep health in people who report habitual short sleep duration. Methods: Data collection is still ongoing. To date, 12 healthy participants (8 male, 4 female), aged 20.7± 2.5 y (mean+SD), BMI 21.8 ± 2.3 kg/m2 with reported habitual short sleep duration (<6.5h per night) have completed the study. For the study protocol, participants complete 2 weeks of baseline at-home monitoring followed by 4 weeks of sleep extension, where participants are asked to extend their time in bed to 8 hours per night. Sleep is measured by self-report sleep diaries and wrist-actigraphy. The dimensions of sleep health measured are sleep duration, timing (midpoint of sleep), efficiency (percent of sleep time out of total time in bed), and regularity (standard deviation of sleep duration during baseline and sleep extension segments). Results: Sleep duration was 5.7±0.2 (mean±SEM) hours at baseline and significantly increased (p<0.001) by 38.4±5.4 (mean±SEM) minutes during sleep extension. Sleep midpoint was 4:58 am±17 minutes (mean±SEM) at baseline and shifted significantly earlier (p<0.05) to 4:38 am±7 minutes (mean±SEM) during sleep extension. No statistically significant differences were detected between baseline and sleep extension for sleep regularity and efficiency. Conclusion: Short average sleep duration and reduced sleep efficiency are linked to a range of health problems such as mortality, coronary heart disease, hypertension, and diabetes. Data show our sleep extension intervention where participants were asked to extend their nightly time in bed to 8 hours has the capacity to increase sleep duration and shift the timing of sleep earlier in the night. These changes are considered positive changes to sleep and future studies are needed to understand if these changes can lead to improved health outcomes. Our findings also show sleep extension did not influence sleep regularity or efficiency, and thus different interventions are likely needed that target these dimensions of sleep health. Support: NIH-UL1TR002538, NIH-K01HL145099, Colorado Clinical Translational Science Institute Pilot (CO-J-20-119), University of Utah Seed Grant-10060570, Margolis Foundation, LEAP Program