Purpose
The aim of this study was to compare morning and evening time-trial performance, RPE and mood state of trained swimmers, taking into account chronotype, habitual training time-of-day and
...PERIOD3 (PER3)
variable number tandem repeat genotype.
Methods
Twenty-six swimmers (18 males, age: 32.6 ± 5.7 years) swam 200 m time trials (TT) at 06h30 and 18h30 in a randomised order.
Results
There was no difference between morning and evening performance when the swimmers were considered as a single group (06h30: 158.8 ± 22.7 s, 18h30: 158.5 ± 22.0 s,
p
= 0.611). However, grouping swimmers by chronotype and habitual training time-of-day allowed us to detect significant diurnal variation in performance, such that morning-type swimmers and those who habitually train in the morning were faster in the 06h30 TT (
p
= 0.036 and
p
= 0.011, respectively). This was accompanied by lower ratings of perceived exertion (RPE) scores post-warm-up, higher vigour and lower fatigues scores prior to the 06h30 TT in morning-type swimmers or those who trained in the morning. Similarly, neither types and those who trained in the evenings had lower fatigue and higher vigour prior to the 18h30 TT.
Conclusions
It appears that both chronotype and habitual training time-of-day need to be considered when assessing diurnal variation in performance. From a practical point of view, athletes and coaches should be aware of the potentially powerful effect of training time on shifting time-of-day variation in performance.
Antiretroviral therapy has significantly reduced morbidity and mortality in people living with HIV (PLWH). However, a direct consequence of higher survival is the development of ageing-related ...co-morbidities that have considerable potential to affect quality of life. Sleep disturbances in PLWH are a significant source of morbidity. A meta-analysis has estimated the prevalence of self-reported sleep disturbances in PLWH to be 58%, with commonly identified disturbances including insomnia, obstructive sleep apnoea and poor sleep quality. Not only do sleep disturbances impair daytime functioning, but chronic sleep disruption also associates with metabolic dysregulation and cardiometabolic disease. Therefore, an understanding of the pathogenesis of sleep disturbances in PLWH is important for reducing morbidity and improving quality of life. Several pathophysiological processes in HIV infection may cause sleep-wake dysregulation. In early infection stages, immunological changes such as expression of sleep-promoting cytokines could mediate sleep disturbances. Long term, chronic immune activation, in addition to side effects of antiretroviral therapy, may impact sleep homeostasis more severely, for example through increasing the risk of obstructive sleep apnoea. These sleep disturbances may further contribute to an inflammatory state, due to the bi-directional relationship between sleep and immunity. In summary, further elucidating the link between HIV, immune activation, and sleep is an underexplored avenue for minimising population morbidity and mortality.
Inter-individual variability exists in recovery from jetlag following travel across time zones. Part of this variation may be due to genetic differences at the variable number tandem repeat (VNTR) ...polymorphism of the
(
) gene as this polymorphism has been associated with chronotype and sleep, as well as sensitivity to blue light on melatonin suppression. To test this hypothesis we conducted a laboratory-based study to compare re-entrainment in males genotyped as
(n = 8) and
(n = 8) following simulated eastward travel across six time zones. The recovery strategy included morning blue-enriched light exposure and appropriately-timed meals during the first 24 h after simulated travel. Dim light melatonin onset (DLMO), sleep characteristics, perceived sleepiness levels (Stanford Sleepiness Scale), and resting metabolic parameters were measured during constant routine periods before and after simulated travel. While DLMO time was similar between the two groups prior to simulated eastward travel (p = .223), it was earlier in the
group (17h23 (17h15; 17h37)) than the
group (18h05 (17h53; 18h12)) afterwards (p = .046). During resynchronisation, perceived sleepiness and metabolic parameters were similar to pre-travel in both groups but sleep was more disturbed in the
group (total sleep time: p = .008, sleep efficiency: p = .008, wake after sleep onset: p = .023). The
VNTR genotype may influence the efficacy of re-entrainment following trans-meridian travel when blue-enriched light exposure is incorporated into the recovery strategy on the first day following travel.
Inter-individual variability exists in recovery from jetlag following travel across time zones. Part of this variation may be due to genetic differences at the variable number tandem repeat (VNTR) ...polymorphism of the PERIOD3 (PER3) gene as this polymorphism has been associated with chronotype and sleep, as well as sensitivity to blue light on melatonin suppression. To test this hypothesis we conducted a laboratory-based study to compare re-entrainment in males genotyped as PER3
4/4
(n = 8) and PER3
5/5
(n = 8) following simulated eastward travel across six time zones. The recovery strategy included morning blue-enriched light exposure and appropriately-timed meals during the first 24 h after simulated travel. Dim light melatonin onset (DLMO), sleep characteristics, perceived sleepiness levels (Stanford Sleepiness Scale), and resting metabolic parameters were measured during constant routine periods before and after simulated travel. While DLMO time was similar between the two groups prior to simulated eastward travel (p = .223), it was earlier in the PER3
5/5
group (17h23 (17h15; 17h37)) than the PER3
4/4
group (18h05 (17h53; 18h12)) afterwards (p = .046). During resynchronisation, perceived sleepiness and metabolic parameters were similar to pre-travel in both groups but sleep was more disturbed in the PER3
5/5
group (total sleep time: p = .008, sleep efficiency: p = .008, wake after sleep onset: p = .023). The PER3 VNTR genotype may influence the efficacy of re-entrainment following trans-meridian travel when blue-enriched light exposure is incorporated into the recovery strategy on the first day following travel.
Relationships between mental health and multiple health behaviours have not been explored in young South African women experiencing social constraints. The aim of this study was to identify ...associations between mental health indicators and risk factors with physical activity, sedentary behaviour, and sleep, amongst young women living in Soweto, a predominantly low-income, urban South African setting. For this cross-sectional study, baseline measurements for participants (n = 1719, 18.0-25.9 years old) recruited for the Healthy Life Trajectories Initiative were used including: physical activity, sedentary behaviour (sitting, screen and television time), sleep (duration and quality), depression and anxiety indicators, emotional health, adverse childhood experiences, alcohol-use risk; social vulnerability, self-efficacy, and social support. Multiple regression analyses showed that depression (beta = 0.161, p < 0.001), anxiety (beta = 0.126, p = 0.001), adverse childhood experiences (beta = 0.076, p = 0.014), and alcohol-use risk (beta = 0.089, p = 0.002) were associated with poor quality sleep. Alcohol-use risk was associated with more screen time (beta = 0.105, p < 0.001) and television time (beta = 0.075, p < 0.016). Social vulnerability was associated with lower sitting time (beta = - 0.187, p < 0001) and screen time (beta = - 0.014, p < 0.001). Higher self-efficacy was associated with more moderate- to vigorous-intensity physical activity (beta = 0.07, p = 0.036), better-quality sleep (beta = - 0.069, p = 0.020) and less television time (beta = - 0.079, p = 0.012). Having no family support was associated with more sitting time (beta = 0.075, p = 0.022). Binomial logistic regression analyses supported these findings regarding sleep quality, with anxiety and depression risk doubling the risk of poor-quality sleep (OR = 2.425, p < 0.001, OR = 2.036, p = 0.003 respectively). These findings contribute to our understanding of how mental health indicators and risk factors can be barriers to health behaviours of young women in Soweto, and that self-efficacy and social support can be protective for certain of these behaviours for these women. Our results highlight the uniqueness of this setting regarding associations between mental health and behaviours associated with non-communicable diseases risk.
South Africans living in low socioeconomic areas have self-reported unusually long sleep durations (approximately 9-10 h). One hypothesis is that these long durations may be a compensatory response ...to poor sleep quality as a result of stressful environments. This study aimed to investigate whether fear of not being safe during sleep is associated with markers of sleep quality or duration in men and women. South Africans (n = 411, 25-50 y, 57% women) of African-origin living in an urban township, characterised by high crime and poverty rates, participated in this study. Participants are part of a larger longitudinal cohort study: Modelling the Epidemiologic Transition Study (METS)-Microbiome. Customised questions were used to assess the presence or absence of fears related to feeling safe during sleep, and the Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index were used to assess daytime sleepiness, sleep quality and insomnia symptom severity respectively. Adjusted logistic regression models indicated that participants who reported fears related to safety during sleep were more likely to report poor sleep quality (PSQI > 5) compared to participants not reporting such fears and that this relationship was stronger among men than women. This is one of the first studies outside American or European populations to suggest that poor quality sleep is associated with fear of personal safety in low-SES South African adults.
The extent to which income setting or rural and urban environments modify the association between sleep and obesity in young children is unclear. The aims of this cross-sectional observational study ...were to (i) describe and compare sleep in South African preschool children from rural low-income (RL), urban low-income (UL) and urban high-income (UH) settings; and (ii) test for associations between sleep parameters and body mass index (BMI).
Participants were preschoolers (5.2 ± 0.7y, 49.5% boys) from RL (n = 111), UL (n = 65) and UH (n = 22) settings. Height and weight were measured. Sleep, sedentary behaviour and physical activity were assessed using accelerometery.
UL children had higher BMI z-scores (median: 0.39; interquartile range: - 0.27, 0.99) than the UH (- 0.38; - 0.88, 0.11) and RL (- 0.08; - 0.83, 0.53) children (p = 0.001). The UL children had later bedtimes (p < 0.001) and wake-up times (p < 0.001) and shorter 24 h (p < 0.001) and nocturnal (p < 0.001) sleep durations than the RL and UH children. After adjusting for age, sex, setting, SB and PA, for every hour less sleep obtained (24 h and nocturnal), children were 2.28 (95% CI: 1.28-4.35) and 2.22 (95% CI: 1.27-3.85) more likely, respectively, to belong to a higher BMI z-score quartile.
Shorter sleep is associated with a higher BMI z-score in South African preschoolers, despite high levels of PA, with UL children appearing to be particularly vulnerable.
Summary
Studies have shown bidirectional relationships between short‐ or long‐sleep duration and risk for obesity, non‐communicable diseases, all‐cause mortality and cardiovascular disease mortality. ...Increasing sleep duration may be an appropriate strategy to reduce cardiometabolic risk in short‐sleeping individuals. The aim is to review the effects of sleep extension interventions on cardiometabolic risk in adults. The PubMed and Scopus databases were searched for relevant, English, peer‐reviewed scientific publications (until August 2018). Seven studies that aimed to increase sleep duration in adults by any sleep extension intervention and described at least one cardiometabolic risk factor were included. These studies had a combined sample size of 138 participants who were either healthy (n = 14), healthy short‐sleeping (n = 92), overweight short‐sleeping (n = 10), or pre‐ or hypertensive short‐sleeping (n = 22) individuals. The durations of the sleep extension interventions ranged from 3 days to 6 weeks, and all successfully increased total sleep time by between 21 and 177 min. Sleep extension was associated with improved direct and indirect measures of insulin sensitivity, decreased leptin and peptide tyrosine‐tyrosine, and reductions in overall appetite, desire for sweet and salty foods, intake of daily free sugar, and percentage of daily caloric intake from protein. This review provides preliminary evidence for a role for sleep extension to improve cardiometabolic outcomes and directive towards future studies in the field of cardiometabolic health and sleep.
HIV has become a manageable chronic condition due to the success and scale-up of antiretroviral therapy (ART). Globally, South Africa has the highest number of people living with HIV (PLHIV) and ...research evidence indicates that countries with the highest burden of PLHIV have a substantial burden of obesity, hypertension (HPT) and type 2 diabetes (T2D). We sought to summarize the burden of these three common NCDs among PLHIV in South Africa.
In this systematic review, multiple databases were searched for articles reporting on the prevalence of obesity, HPT, and T2D among PLHIV in South Africa published since journal inception until March 2022. A meta-analysis was conducted using random-effects models to obtain pooled prevalence estimates of the three NCDs. Heterogeneity was assessed using X
test on Cochran's Q statistic.
We included 32 studies, with 19, 22 and 18 studies reporting the prevalence of obesity, HPT, and T2D among PLHIV, respectively. The overall prevalence of obesity, HPT, and T2D was 23.2% 95% CI 17.6; 29.9, 25.5% 95% CI 15.6; 38.7, and 6.1% 95% CI 3.8; 9.7 respectively. The prevalence of obesity was significantly higher among women (P = 0.034) compared to men, however the prevalence of HPT and T2D did not differ by sex. The prevalence of each of the three NCDs did not differ significantly between rural, urban, and peri-urban areas. The prevalence of obesity and T2D was higher in studies conducted between 2013 and 2022 compared to studies conducted between 2000 and 2012, while the prevalence of HPT was higher between 2000 and 2012 compared to between 2013 and 2022.
These findings suggest that South Africa is experiencing a syndemic of NCDs among people PLHIV highlighting the need to increase cost-effective interventions and management strategies that involve integrated HIV and NCD care in the South African setting.
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