Combined association of clinical and lifestyle factors with non-restorative sleep: The Nagahama Study

BACKGROUND Non-restorative sleep (NRS) was suggested to be associated with cardiovascular outcomes. However, causative factors for NRS have not been fully elucidated. This study aimed to clarify factors and their relationships with NRS to better understand the clinical and epidemiological implications of NRS and to develop a score that can objectively evaluate NRS status. METHODS Study subjects consisted of 9,788 community residents (age 53.6 ± 13.4 y). Subjective NRS as well as possible clinical and lifestyle factors for NRS were investigated by questionnaires. Other clinical parameters were obtained from personal records of information obtained at the baseline examination. RESULTS A total of 3,261 participants complained of NRS. Factors independently associated with subjective NRS were younger age (odds ratio = 1.43), use of a hypnotic drug (2.04), irregular sleep schedule (2.02), short sleep duration (<5 h, 11.7; 5-6 h, 4.81; 6-7 h, 2.40), frequent sleepiness (2.33), routine stress (4.63), no habitual exercise (1.61), nocturia symptoms (1.43), symptoms of gastroesophageal reflux disease (1.44), and depression (1.46) (all P <0.001). The NRS score comprised of these 10 factors was linearly associated with the frequency of subjective NRS (Ptrend <0.001). Frequency of individuals with a high NRS score was greater in women (52.3%) than in men (42.1%, P<0.001), while no clear association was observed with common risk factors for cardiovascular diseases. CONCLUSIONS NRS was a phenomenon representing various clinical and lifestyle features. Careful attention should be paid to individuals with a high NRS score who might be at risk for mental fatigue and have unfavorable lifestyle factors.