Sleep and cognitive performance of African-Americans and European-Americans before and during circadian misalignment produced by an abrupt 9-h delay in the sleep/wake schedule

<div><p>We conducted two studies of circadian misalignment in non-Hispanic African and European-Americans. In the first, the sleep/wake (light/dark) schedule was advanced 9 h, similar to flying east, and in the second these schedules were delayed 9 h, similar to flying west or sleeping during the day after night work. We confirmed that the free-running circadian period is shorter in African-Americans compared to European-Americans, and found differences in the magnitude and direction of circadian rhythm phase shifts which were related to the circadian period. The sleep and cognitive performance data from the first study (published in this journal) documented the impairment in both ancestry groups due to this extreme circadian misalignment. African-Americans slept less and performed slightly worse during advanced/misaligned days than European-Americans. The current analysis is of sleep and cognitive performance from the second study. Participants were 23 African-Americans and 22 European-Americans (aged 18–44 years). Following four baseline days (8 h time in bed, based on habitual sleep), the sleep/wake schedule was delayed by 9 h for three days. Sleep was monitored using actigraphy. During the last two baseline/aligned days and the first two delayed/misaligned days, beginning 2 h after waking, cognitive performance was assessed every 3 h using the Automated Neuropsychological Assessment Metrics (ANAM) battery. Mixed model ANOVAs assessed the effects of ancestry (African-American or European-American) and condition (baseline/aligned or delayed/misaligned) on sleep and performance. There was decreased sleep and impaired cognitive performance in both ancestry groups during the two delayed/misaligned days relative to baseline/aligned days. Sleep and cognitive performance did not differ between African-Americans and European-Americans during either baseline/aligned or delayed/misaligned days. While our previous work showed that an advance in the sleep/wake schedule impaired the sleep of African-Americans more than European-Americans, delaying the sleep/wake schedule impaired the sleep and cognitive performance of African-Americans and European-Americans equally.</p></div

Performance on a simple response time task is sleep or work more important for miners? /

The purpose of the current study was to investigate the impact of work- and sleep-related factors on an objective measure of response time in a field setting

The effects of different roster schedules on sleep in miners

Shiftwork involving early morning starts and night work can affect both sleep and fatigue. This study aimed to assess the impact of different rostering schedules at an Australian mine site on sleep and subjective sleep quality

Cognitive performance during baseline/aligned and delayed/misaligned days.

<p>Performance was assessed on the simple reaction (RT) time task (A and B), procedural RT task (C), Go/No-Go task (D), and code substitution delayed task (E). Closed circles represent African-Americans and open circles represent European-Americans. Dark grey shading represents timing of scheduled sleep/dark episodes during both baseline/aligned and advanced (misaligned) days. Light grey shading on the right panels represents the previous baseline sleep episode. The last three cognitive performance tests (17, 20 and 23h after baseline wake time) during the delayed/misaligned days occurred when participants would normally be sleeping (i.e. during the scheduled baseline sleep/dark period). Lapses were defined as being RTs < 500ms, slow responses were responses exceeding the 90^th percentile of the cumulative distribution of each participant’s baseline responses, and d-Prime scores were the discriminability values indicating the overall ability to discriminate between the go and no-go stimuli. Data are mean ± SEM. Higher scores for A, B, and C represent worse cognitive performance. Lower scores for D and E represent worse cognitive performance. N = 20 African-Americans and 22 European-Americans (A and B). N = 23 African-Americans and 22 European-Americans (C, D and E). There were significant differences between baseline/aligned and delayed/misaligned days on all performance measures shown, but there were no significant differences between African-Americans and European-Americans on any of the cognitive performance measures.</p

Dim light melatonin onset (DLMO) and estimated temperature minimum (Tmin) for each participant.

<p>DLMO was measured after the four baseline days on Chicago time (baseline, aligned) and after the three days on Japan time (delayed, misaligned). Rectangles show the timing of the sleep/dark periods. Top: Circles show the DLMO relative to the baseline bedtime, with 0 representing the timing of the start of the scheduled baseline sleep period. Bottom: Triangles show the Tmin relative to baseline bedtime. The Tmin was calculated as the DLMO + 7 h. Filled symbols represent African-Americans and open symbols are European-Americans. The DLMOs and Tmins were properly aligned to the sleep/dark periods during baseline (DLMOs before sleep and Tmins within sleep), but were misaligned relative to the sleep/dark period during delayed days. The vertical symbol placement is for visualization purposes and has no relationship to days.</p

Subjective sleepiness and fatigue (low energy level) during baseline/aligned and advanced (misaligned) days.

<p>Closed circles represent African-Americans and open circles represent European-Americans. Dark grey shading represents timing of scheduled sleep/dark episodes during both baseline and advanced days. Light grey shading on right panels (advanced) represents the previous baseline sleep/dark episodes. Top panel shows subjective ratings on the fatigue mood dimension (low energy level) and the bottom panel shows subjective sleepiness (Stanford Sleepiness Scale). Data are mean ± SEM. Fatigue scores were on a scale of 0–6 and the Stanford Sleepiness Scale is a scale of 1–7. For both measures higher scores represent feeling more fatigue/sleepiness. N = 23 African-Americans and 22 European-Americans. * Significant difference (P≤0.05) between African-Americans and European-Americans as determined by mixed model ANOVAs. There were significant differences between baseline/aligned and delayed/misaligned days for both variables, and there were significant differences between African-Americans and European-Americans during baseline/aligned but not during delayed/misaligned days.</p

Total Sleep Time (TST), Early Morning Awakening (EMA), and Columbia Jet Lag Scale scores by study day.

<p>TST was measured using sleep logs (A) and actigraphy (B). EMA (C) was measured with actigraphy. Higher scores on the Columbia Jet Lag Scale (D) represent increased feelings of jet lag. Closed circles represent African-Americans and open circles represent European-Americans. Data are mean ± SEM. Baseline and delayed days (days 3–5 and days 6–8) were separated by a phase assessment period (refer to protocol, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0186843#pone.0186843.g001" target="_blank">Fig 1</a>). There were significant differences between baseline/aligned and delayed/misaligned days on all variables. There were no significant differences between African-Americans and European-Americans for any of the sleep measures, but there was one difference for Columbia Jet Lag Scale scores (p<0.05). N = 23 African-Americans and 22 European-Americans for sleep logs (A) and Columbia Jet Lag Scale (D) and N = 22 African-Americans and 21 European-Americans for actigraphy (B, C).</p

Protocol diagram.

<p>Time of day shown at the top is Chicago time and time of day shown on the bottom is Japan time (9-h earlier than Chicago time). Study day is shown on the left. Black shading shows timing of scheduled sleep periods. Schedules were individualized for each participant to best match their habitual sleep. This diagram shows the protocol for a participant on a 00:00–08:00 baseline sleep schedule. Days 1–5 were baseline during which participants remained on local, Chicago time (as indicated on the left). On days 7–9, the sleep schedule was shifted 9-h later (delayed), as though participants had traveled to Japan. The wall clocks in the bedrooms were changed to indicate the time in Japan. During baseline days the sleep schedule was aligned with each participant’s circadian rhythms, whereas during advanced days the sleep schedule was misaligned. “X” shows the timing of the Automated Neuropsychological Assessment Metrics (ANAM) performance battery and “Px” shows the timing of practice ANAM tests. Tests were given relative to each participants scheduled sleep times; 2 h after waking, and then every 3 h with a total of five tests per day. Light grey shading shows the timing of circadian phase assessments, during which the dim light melatonin onset (DLMO) was assessed.</p

Participant demographics.

<p>Participant demographics.</p

Risk factors of sleep-disordered breathing in haemodialysis patients.

BackgroundSleep-disordered breathing (SDB) is common in patients with kidney disease; but often underdiagnosed as it is infrequently assessed in clinical practice. The objective of this study was to assess the risk factors of SDB in haemodialysis patients, and to identify useful assessment tools to detect SDB in this population.MethodsWe used nocturnal oximetry, Epworth Sleepiness Scale (ESS) and STOPBANG questionnaire to screen for SDB in haemodialysis patients. Presence of SDB was defined by Oxygen desaturation index (ODI≥5/h), and further confirmed by apnoea-hypopnea index (AHI) from an in-laboratory polysomnography. Blood samples were collected prior to commencing a haemodialysis treatment.ResultsSDB was detected in 70% of participants (N = 107, mean age 67 years). STOPBANG revealed that 89% of participants were at risk of SDB; however, only 17% reported daytime sleepiness on the ESS. Of the participants who underwent polysomnography (n = 36), obstructive sleep apnoea was identified in 86%, and median AHI was 34.5/h. Oximetry and AHI results were positively correlated (r = 0.62, P = 0.0001), as were oximetry and STOPBANG (r = 0.48; PConclusionDialysis patients with a large neck circumference and anaemia are at risk of SDB; using nocturnal oximetry is practical and reliable to screen for SDB and should be considered in routine management of dialysis patients, particularly for those who demonstrate risk factors