BackgroundRetirement is a major life transition which may influence health behaviours and time use. Little is known about how sedentary behaviour changes as a result of increased time availability after retirement. The aim of this study was to examine changes in non-occupational sedentary behaviours across the retirement transition. In addition, we examined which preretirement characteristics were associated with these changes.MethodsThe study population consisted of 2011 participants from the Finnish Retirement and Aging Study. Repeated postal survey including questions on sedentary behaviour domains (television viewing, computer use at home, sitting in a vehicle and other sitting) were conducted once a year across the retirement transition, covering on average 3.4 study waves. Linear regression with generalised estimating equations was used for the analyses.ResultsTotal sedentary time increased by 73 (95% CI 66 to 80) min/day during the retirement transition. Of the domain-specific sedentary behaviours, television viewing time increased by 28 (95% CI 25 to 32) min/day, computer use at home by 19 (95% CI 17 to 22) min/day and other sitting time by 37 (95% CI 33 to 41) min/day, while time sitting in a vehicle decreased by 6 (95% CI 4 to 9) min/day. Highest increase in total sedentary time was among women and persons who had high occupational sitting time, low physical activity level, sleep difficulties, mental disorders or poor health before retirement (all p values for interaction <0.03).ConclusionTotal and domain-specific sedentary time, except sitting in a vehicle, increased during the retirement transition.