Sleep Quality in Spanish Adult Women: Associations with Sociodemographic Variables and Pre-Sleep Habits

Background/Objectives: Sleep health is a key determinant of physical and psychological well-being, yet poor sleep quality remains common, particularly among women. Sociodemographic inequalities and culturally patterned pre-sleep behaviours may contribute to sleep disturbances, but their combined role in Mediterranean populations is still insufficiently understood. This study aimed to examine sleep quality and its associations with sociodemographic characteristics and pre-sleep habits among adult women living in Spain. Methods: A cross-sectional online survey was conducted among 785 Spanish adult women aged 18–64 years. Sleep quality was assessed using the Spanish version of the Pittsburgh Sleep Quality Index (PSQI). Additional questionnaire items collected information on sociodemographic variables and pre-sleep habits, including meal timing, stimulant consumption, physical activity, bedtime routines, screen exposure, and sleeping alone or with company. Data were analysed using chi-square tests, Mann–Whitney U tests, Kruskal–Wallis tests, Spearman’s correlations, and principal component analysis. Results: The mean global PSQI score was 7.5 (SD = 3.01), indicating mildly impaired sleep quality overall. Age showed the largest association with global PSQI score (ε2 = 0.052, p < 0.001), followed by income (ε2 = 0.010, p = 0.016). Frequent nocturnal awakenings were the most common sleep disturbance, whereas sleep medication use was uncommon. Older age and lower income were associated with poorer sleep outcomes, including shorter sleep duration, lower sleep efficiency, and higher global PSQI scores. Higher education and health-related training were generally associated with more favourable sleep profiles. Pre-sleep habits such as late dinners, stimulant use, and evening screen exposure were highly prevalent but showed weak and non-significant associations with global PSQI scores. Conclusions: In this cross-sectional sample, poorer sleep quality was associated with selected sociodemographic characteristics, whereas isolated pre-sleep behaviours showed weak or non-significant associations with global PSQI scores. Given the study design and non-probability sampling, these findings should be interpreted as associations and generalized with caution. They may inform future studies and support the development of gender-sensitive, non-pharmacological sleep-health strategies that consider socioeconomic and cultural context.