Study Objectives: To describe sleep duration patterns of adults over a 20-year period; to compare sociodemographic, lifestyle, and health characteristics across these patterns; and to relate the patterns to sleep quality. Methods: The study population consisted of 3695 adults aged 20 to 59 years at baseline. Five measurements of self-reported sleep duration were used to compose seven patterns from 1987 to 2012: persistent short (≤6 hours), moderate (7-8 hours), or long (≥9 hours) sleep duration and several changing patterns (varying and became short, moderate, or long sleepers). Multinomial logistic regression analyses were used to compare characteristics across sleep duration patterns. Results: About 56% of the adults had persistent moderate sleep duration over 20 years. This group had a better sleep quality than the other groups. Of the adults who changed in their sleep duration (40%), 43% became a short sleeper. Sleep duration patterns that deviate from persistent moderate sleep duration were associated with physical inactivity during leisure time (odds ratios [ORs] and 95% confidence intervals [95% CIs] varied between 1.26 [1.04-1.53] and 1.58 [1.06-2.37]) and with poor self-rated health (ORs [95% CIs] varied between 1.50 [1.20-1.87] and 2.15 [1.48-3.12]). Conclusions: Nearly half of the adults did not have persistent moderate sleep duration over a 20-year period and more than one-sixth became short sleeper. This is reason for concern considering the adverse health status associated with short and long sleep duration. Leisure-time physical activity is a potential important target to prevent unfavorable changes in sleep duration over the life course.