Effect of Sleep, Sleep Apnoea and Insomnia Symptoms on Depressive Symptoms in Combined harmonised Community-Based Cohorts-A Cross-Sectional Analysis.

Depressive symptoms were present in 17% of the combined community-based sample.

• Total sample size was n=1238 participants from two harmonised population-based cohorts.
• Sample was 68% male with mean age 57 ± 12 years and mean BMI 28.0 ± 4.2 kg/m2.
• Cohorts were the Sleep and HEalth in women (SHE) study and the Men Androgen Inflammation Lifestyle Environment and Stress (MAILES) study.
• Both cohorts were community-based, avoiding clinical referral bias.

Objective measures of intermittent hypoxia (AHI and ODI) were not significantly associated with depressive symptoms.

• Apnoea-hypopnoea index (AHI) and oxygen desaturation index (ODI) were used as objective measures of OSA-related hypoxia.
• No statistically significant link was found between these hypoxia variables and depressive symptoms.
• This finding held after adjusting for age, sex, BMI, alcohol, and physical activity.
• The result addresses the question of whether hypoxia or sleep fragmentation is the primary mechanism linking sleep apnoea to depression.

Reduced sleep efficiency (SE%) was significantly associated with increased odds of depressive symptoms before adjustment for insomnia.

• OR for SE% and depressive symptoms was 0.84 (95% CI: 0.72–0.98), indicating lower SE% was associated with higher odds of depressive symptoms.
• This association was statistically significant in models adjusting for age, sex, BMI, alcohol, and physical activity.
• When insomnia symptoms were added to the model, this association was no longer statistically significant.
• Sleep efficiency was measured objectively as part of the polysomnographic or actigraphic assessment.

Increased wake after sleep onset (WASO) was significantly associated with increased odds of depressive symptoms before adjustment for insomnia.

• OR for WASO and depressive symptoms was 1.26 (95% CI: 1.06–1.51), indicating greater WASO was associated with higher odds of depressive symptoms.
• This association was statistically significant in models adjusting for age, sex, BMI, alcohol, and physical activity.
• When insomnia symptoms were included in the model, this association was no longer statistically significant.
• WASO is an objective measure of sleep fragmentation.

Insomnia symptoms appeared to be a key factor in the relationship between sleep fragmentation and depressive symptoms, as adjusting for insomnia eliminated the significant associations.

• Both SE% and WASO associations with depressive symptoms became non-significant after adjustment for insomnia symptoms.
• Pathway analyses were used to further explore potential mediating relationships between sleep variables, insomnia, and depression.
• Subjective insomnia symptoms and subjective depressive symptoms were both collected alongside objective sleep measures.
• The authors suggest insomnia symptoms may mediate or confound the relationship between objective sleep fragmentation and depression.

The study used a cross-sectional design with harmonised data from two population-based cohorts to assess sleep and depressive symptom associations.

• Objective OSA measures (AHI, ODI) and sleep fragmentation variables (SE%, WASO) were measured alongside subjective insomnia and depressive symptom data.
• Logistic regression models adjusted for age, sex, BMI, alcohol, and physical activity.
• Pathway analyses were conducted to explore mediating relationships.
• The cross-sectional design precludes causal inference.