Associations of smartphone addiction and physical activity with sleep quality and neck/shoulder symptoms in university students: a cross-sectional study

Objective To examine the associations of smartphone addiction, physical activity, and sedentary time with sleep quality and neck/shoulder symptoms during the previous 7 days in university students, and to assess the potential modifying role of physical activity in outcomes associated with smartphone addiction. Methods A cross-sectional survey was conducted among 585 students from a single university in Jilin Province, China. Smartphone addiction, physical activity, sedentary time, sleep quality, and neck/shoulder symptoms were assessed using validated questionnaires. Multivariable linear regression and Poisson regression with robust variance were used to examine adjusted associations and interaction terms. Results Of the participants, 43.8% were classified as having poor sleep, and 46.2% reported at least one neck/shoulder symptoms during the previous 7 days. After adjustment for covariates, higher smartphone addiction and longer sedentary time were both associated with higher PSQI scores, a higher prevalence of poor sleep, and a higher prevalence of neck/shoulder symptoms during the previous 7 days. Meeting physical activity recommendations was associated with lower PSQI scores and a lower prevalence of poor sleep, but showed no independent association with neck/shoulder symptoms. After further adjustment for PSQI, smartphone addiction, sedentary time, and PSQI score were still significantly associated with a higher prevalence of neck/shoulder symptoms. Interaction plots showed descriptively lower predicted PSQI scores and lower predicted probabilities of neck/shoulder symptoms among students who met physical activity recommendations at comparable levels of smartphone addiction; however, the formal interaction terms were not statistically significant. Conclusion Smartphone addiction and sedentary time were consistently associated with poorer sleep quality and more frequent neck/shoulder symptoms. Physical activity was more consistently associated with sleep outcomes than with neck/shoulder symptoms. These findings support considering smartphone use, sedentary behaviour, physical activity, and sleep management together in campus health promotion research.