Summary Sleep duration is an important concept in epidemiological studies. It characterizes a night’s sleep or a person’s sleep pattern, and is associated with numerous health outcomes. In most large studies, sleep duration is assessed with questionnaires or sleep diaries. As an alternative, actigraphy may be used, as it objectively measures sleep parameters and is feasible in large studies. However, actigraphy and sleep diaries may not measure exactly the same phenomenon. Our study aims to determine disagreement between actigraphic and diary estimates of sleep duration, and to investigate possible determinants of this disagreement. This investigation was embedded in the population‐based Rotterdam Study. The study population consisted of 969 community‐dwelling participants aged 57–97 years. Participants wore an actigraph and kept a sleep diary for, on average, six consecutive nights. Both measures were used to determine total sleep time (TST). In 34% of the participants, the estimated TST in the sleep diaries deviated more than 1 h from actigraphically measured TST. The level of disagreement between diary and actigraphic measures decreased with subjective and actigraphic measures of sleep quality, and increased with male gender, poor cognitive function and functional disability. Actigraphically measured poor sleep was often accompanied by longer subjective estimates of TST, whereas subjectively poor sleepers tended to report shorter TST in their diaries than was measured with actigraphy. We recommend, whenever possible, to use multiple measures of sleep duration, to perform analyses with both, and to examine the consistency of the results over assessment methods.

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Objective: The epidemiological evidence for the association between sleep duration and obesity in the elderly is inconsistent and has not been investigated with objective measures. Furthermore, the role of sleep fragmentation in this relationship is unknown. Our aim was to investigate the association of sleep measures with body mass index (BMI) and obesity in a normal elderly population. Design: Cross-sectional study. Subjects: A total of 983 community-dwelling elderly (mean age 68.4±6.9 years, range, 57-97). Measurements: Weight and height were measured, and sleep duration and fragmentation were assessed with on average six nights of actigraphy.Results: A quadratic model adequately described the association between continuous measures of sleep duration and BMI. Actigraphic sleep duration had a significant U-shaped relationship with BMI (b of quadratic term ¼ 0.30, 95% confidence interval (CI): 0.08, 0.52). Both short sleepers (o5 h: OR, 2.76 (95% CI: 1.38, 5.49), 5 to o6 h: OR, 1.97 (95% CI: 1.26, 3.08)) and long sleepers (X8 h: OR, 2.93 (95% CI: 1.39, 6.16)) were more likely to be obese, compared to participants who slept 7 to o8 h. BMI increased with 0.59 kg m À2 per standard deviation of sleep fragmentation (95% CI: 0.34, 0.84). After adjustment for sleep fragmentation, the association between short sleep and obesity was no longer significant. Exclusion of participants with probable sleep apnea only marginally changed these associations. Self-reported habitual sleep duration was not associated with BMI or obesity. Conclusions: Sleep duration, as measured with actigraphy, had a U-shaped relationship with BMI and obesity in an elderly population. A highly fragmented sleep is associated with a higher BMI and a higher risk of obesity, and may explain why short sleep is related to obesity. To preclude bias that can be introduced by self-report measures of sleep duration, using multiple measures of sleep parameters is recommended in future research.

Low MMSE score and high creatinine level prior to surgery as well as increased ECC time are important independent predictors of delirium. In addition, delirium is an important predictor of 30-day mortality. Patients with a substantial risk for delirium should be candidates for interventions to reduce postoperative delirium and to potentially improve overall surgical outcomes.

Objective-To assess fatigue in relation to depression, blood pressure, and plasma catecholamines in patients with primary Sjögren's syndrome (SS), in comparison with healthy controls and patients with rheumatoid arthritis. Methods-For the assessment of fatigue the Multidimensional Fatigue Inventory (MFI) was used, a 20 item questionnaire, covering the following dimensions: general fatigue, physical fatigue, mental fatigue, reduced motivation, and reduced activity. Furthermore, the Zung depression scale was used to quantify aspects of depression. Forty nine female primary SS patients, 44 female patients with rheumatoid arthritis (RA), and 32 healthy women filled in both questionnaires. In addition, supine values of blood pressure and plasma catecholamines were measured in the patients with primary SS. Results-Primary SS patients were more fatigued compared with the healthy controls on all the five dimensions of the MFI. When the analyses were repeated using depression as a covariate, group diVerences disappeared for the dimensions of reduced motivation and mental fatigue. In the primary SS patients, significant positive correlations between depression and the dimensions of reduced motivation and mental fatigue were found. Comparing patients with primary SS with those with RA, using depression as covariate, no statistically significant diVerences were found between these groups. No relation between fatigue and blood pressure was found, but a negative correlation was observed between the general fatigue subscale of the MFI and plasma noradrenaline. Conclusion-Patients with primary SS report more fatigue than healthy controls on all the dimensions of the MFI and when controlling for depression significant differences remain on the dimensions of general fatigue, physical fatigue, and reduced activity. The negative correlations between levels of noradrenaline and general fatigue in patients with primary SS may imply the involvement of the autonomic nervous system in chronic fatigue.