The Prevalence of Sleep Disturbances and Anxiety Among Croatian University Students: Possible Association with Lifestyle Factors and COVID-19

<b>Background/Objectives</b>: University students are particularly vulnerable to psychological distress and sleep disturbances, which may impair academic performance and overall well-being. Lifestyle changes, increased academic demands, and the COVID-19 pandemic may have further exacerbated these problems. This study aimed to assess the prevalence of insomnia and anxiety among students at the University of Rijeka and to examine their associations with COVID-19 infection, vaccination status, lifestyle habits, and sociodemographic characteristics. <b>Methods</b>: A cross-sectional online survey was conducted between October 2024 and April 2025 among 594 students from 14 faculties of the University of Rijeka. Data were collected using a self-administered questionnaire including sociodemographic variables, the Insomnia Severity Index (ISI), the Generalized Anxiety Disorder-7 (GAD-7), lifestyle behaviors, and COVID-19-related factors. Statistical significance was set at <i>p</i> < 0.05. <b>Results</b>: Insomnia was reported by 50.7% of students (36.9% mild, 12.1% moderate, 1.7% severe), while 49.6% reported elevated anxiety levels. Female sex, smoking, low physical activity, poor subjective sleep quality, and frequent nighttime awakenings were significantly associated with higher ISI and GAD-7 scores (all <i>p</i> < 0.05). COVID-19 infection and vaccination status showed weaker associations with insomnia compared to psychosocial and lifestyle factors. Students living in shared rental accommodation reported higher insomnia severity. In multivariable regression analysis, anxiety severity, sleep fragmentation (frequent nocturnal awakenings), and poor perceived sleep quality emerged as the strongest independent predictors of insomnia severity. <b>Conclusions</b>: Insomnia and anxiety are highly prevalent among University of Rijeka students and are primarily associated with psychosocial and lifestyle factors rather than COVID-19-related variables. University-based interventions focusing on stress reduction, sleep hygiene, and early mental health support are warranted, particularly for high-risk groups.