Exercise and screen use may change during the transition to adulthood, but their prospective associations need to be distinguished from concurrent associations. This study examined whether baseline exercise predicted subsequent screen use and whether baseline screen use predicted subsequent exercise after accounting for both baseline behaviors. Data were drawn from a prospective cohort initially recruited at Northwestern University. Baseline assessments occurred from 2014–2018 and follow-up assessments from 2019–2026. Participants reported the frequency of heavy and light exercise and daily television, video, and computer or video game use using five-category items coded 0–4. Separate baseline-adjusted regression models included age, gender, individual follow-up duration, and follow-up calendar year. Fully adjusted analyses included 2139 participants for heavy exercise and 2144 for light exercise, with a mean follow-up of 6.6 years. Ordinal regression and additional sensitivity analyses assessed robustness. Each behavior showed positive continuity across assessments. Higher baseline heavy exercise predicted lower follow-up screen-use scores (b = −0.093, 95% CI [−0.124, −0.063]); the corresponding association for light exercise was smaller in numerical magnitude (b = −0.044, 95% CI [−0.075, −0.013]). Both associations remained significant after correction for four cross-behavior comparisons. Baseline screen use was not significantly associated with subsequent heavy or light exercise after adjustment. Ordinal and sensitivity analyses produced the same overall pattern. Exercise frequency was prospectively associated with later television, video, and gaming use, although effects were modest.
