Browsing by Author "Rae, Dale"

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    Circadian rhythm, activity level, training habits and sports performance : the molecular and subjective components
    (2013) Stephenson, Kim Jenna; Rae, Dale; Roden, Laura
    Circadian rhythmicity, which is driven by a circadian clock, is a property of a biological process that displays an oscillation of approximately 24-hours even in the absence of external time cues. Individual differences in the preferred times of waking, activity and rest (sleep) are known as chronotype or diurnal preference; which arise due to differences in circadian rhythmicity due to the fact that rhythms are not exactly 24-hours. Various polymorphisms of certain genes involved in circadian rhythm generation have been associated with extreme chronotype. Of interest to this study is the PER3 gene as it has a variable number tandem repeat (VNTR) polymorphism in the coding region, which is repeated either four of five times, encoding proteins of different lengths.
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    Diurnal preference and sports performance : a subjective and genetic view
    (2011) Kunorozva, Lovemore; Roden, Laura; Rae, Dale
    [T]he purpose of this study was to describe the distribution of morning- or evening-preferring individuals (measured using the Horne-Östberg morningness-eveningness personality questionnaire) and PER3 VNTR polymorphism (from genomic DNA products extracted from human buccal cell samples amplified and digested with NcoI) within male Caucasian, trained cyclists (CYC, n=138), Ironman triathletes (IM, n=301) and an active, but non-competitive control population of Caucasian males (CON, n=120). In addition, performance was assessed in trained cyclists strongly preferring mornings or evenings at various times of day.
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    Perceived and objective neighborhood support for outside of school physical activity in South African children
    (BioMed Central, 2016-06-01) Uys, Monika; Broyles, Stephanie T; Draper, Catherine E; Hendricks, Sharief; Rae, Dale; Naidoo, Nirmala; Katzmarzyk, Peter T; Lambert, Estelle V
    Background: The neighborhood environment has the potential to influence children’s participation in physical activity. However, children’s outdoor play is controlled by parents to a great extent. This study aimed to investigate whether parents' perceptions of the neighborhood environment and the objectively measured neighborhood environment were associated with children's moderate-to-vigorous intensity physical activity (MVPA) outside of school hours; and to determine if these perceptions and objective measures of the neighborhood environment differ between high and low socio-economic status (SES) groups. Methods: In total, 258 parents of 9–11 year-old children, recruited from the South African sample of the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE), completed a questionnaire concerning the family and neighborhood environment. Objective measures of the environment were also obtained using Geographic Information Systems (GIS). Children wore an Actigraph (GT3X+) accelerometer for 7 days to measure levels of MVPA. Multilevel regression models were used to determine the association between the neighborhood environment and MVPA out of school hours. Results: Parents’ perceptions of the neighborhood physical activity facilities were positively associated with children’s MVPA before school (β = 1.50 ± 0.51, p = 0.003). Objective measures of neighborhood safety and traffic risk were associated with children’s after-school MVPA (β = −2.72 ± 1.35, p = 0.044 and β = −2.63 ± 1.26, p = 0.038, respectively). These associations were significant in the low SES group (β = −3.38 ± 1.65, p = 0.040 and β = −3.76 ± 1.61, p = 0.020, respectively), but unrelated to MVPA in the high SES group. Conclusions: This study found that several of the objective measures of the neighborhood environment were significantly associated with children’s outside-of-school MVPA, while most of the parents’ perceptions of the neighborhood environment were unrelated.
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    The role of chronotype in the participation and performance of South African and Dutch marathon runners
    (2014) Henst, Rob; Rae, Dale; Roden, Laura
    Introduction: Our circadian rhythms are internal biological rhythms of approximately (circa) 24 - hours (dies) allowing us to synchronize our internal biological “clock” with external time cues. Many innate biological functions are dependent on time-of-day, such as secreting adrenaline and cortisol in the mornings and melatonin in the evenings. The time-of-day at which these and other physiological functions are active, change or reach a certain level may influence a person’s diurnal preference, i.e. preference for mornings (morning-types) or evenings (evening-types), and is referred to as ‘chronotype’. Many different factors may affect a person’s chronotype, including age, sex, physical activity, ethnicity and geographical location. Certain clock-related genotypes have also been shown to be associated with chronotype. For example, some studies have found that the 5-repeat allele of the PER3 variable number tandem repeat (VNTR) polymorphism (PER35) is associated with a preference for mornings. Recent research has shown a high prevalence of morning-types and PER35VNTR allele carriers in trained South African runners, cyclists and triathletes. It was proposed that the early morning start-times of these endurance events might select people with a preference for mornings, since morning-types may cope better with rising early and being physically active in the early morning. Alternatively, the habitual early waking for training or endurance events may have conditioned the athletes to adapt to become morning-types. However, the geographical location of South Africa (i.e. climate and day length) and the fact that each group was physically active may also have contributed to this finding. Comparison of South African and Dutch runners would allow us to explore the effects of race start time and geography on this observation, since marathons in The Netherlands on average start at 11:41, and since the two countries differ significantly in latitude and as such have noticeable differences in daylight exposure. Aims: The aims of this study were 1) to compare the PER3VNTR genotype and chronotype distribution of South African and Dutch recreational marathon runners and active but non-competitive controls; 2) to investigate the relationship between the PER3VNTR genotype and chronotype in both the Dutch and South African samples; and 3) to determine whether marathon race time is associated with chronotype and PER3VNTR genotype in Dutch and South African marathon Methods: Ninety-five trained South African male marathon runners, 97 South African male active but non-competitive controls, 90 trained Dutch male marathon runners and 98 Dutch male active but non-competitive controls completed a questionnaire capturing demographics, training and race history, including personal best and most recent full and half-marathon race time (if applicable) and the Horne-Östberg morningness-eveningness personality questionnaire (HÖ-MEQ, a tool to assess a person’s chronotype). Each participant provided a buccal cell swab from with total genomic DNA was extracted to determine his PER3VNTR polymorphism genotype. The official race time from each runner who completed the designated marathons in South Africa or the Netherlands was collected from the event websites. Results: The South African and Dutch runners were more morning-orientated than their respective control groups and the South African runners were more morning-orientated than the Dutch runners. The PER3 VNTR polymorphism distribution was similar between the four groups and was not associated with chronotype. The marathon performance of the morning-type South African runners was better than the evening-types, and a higher HÖ-MEQ score (morningness) correlated with better personal best and most recent half-marathon race time. Similar observations were not found in the Dutch runners. Discussion: Since a higher prevalence of morning-types in South African marathon runners compared to Dutch marathon runners was found, it is proposed that the early marathon start-times in South Africa may favour morning-types, who are able to cope with those early morning start times. Alternatively, one could argue that through repetitive early-morning racing (i.e. participating in competitive running events), the chronotype of South African runners may be conditioned to that of a morning-type over time. It is proposed that this ability to cope with early morning marathon start times may lead to better marathon performances for morning-types than neither-types and evening-types in the South African running group. This effect does not occur in the Netherlands, where marathons start later in the morning and do thus not favour a certain chronotype. The difference in daylight exposure between the two countries as a function of latitude does not seem to affect chronotype, since the active but non-competitive control groups did not differ significantly between South Africa and the Netherlands. Unlike the findings from a previous study, the PER35allele was not more prevalent among the South African runners, but rather the distribution wasi n line with what has been described in most, but not all, other populations. No association between the PER35VNTR xpolymorphism and chronotype was found in any of the four groups. Since the four groups investigated in this study comprised physically active individuals, it is proposed that this lack of association may be due to the habituation effects of physical activity and early morning start times of marathon events(for only the South African runners). Conceivably,this habituation may even shift the diurnal preference of those with the PER34/5 and PER34/4VNTR genotypes towards morningness, disassociating any relationship between chronotype and the PER3VNTR genotype. Conclusion: The early morning start time of South African marathon events may favour morning-types, due to their ability to cope with being physically active in the early morning. We propose that the PER3VNTR genotype cannot solely explain the higher prevalence of morning-types in the South African runners in this study, however, it is very likely that the PER3VNTR genotype does play an important role in the chronotype distributions found in the study of Kunorozva et al.(2012). Since the PER3VNTR genotype was not associated with chronotype in any of the four groups, it is proposed that habituation to early-morning marathon racing may be the causal effect of the high number of morning-types in the South African runners group, and the apparent disassociation between chronotype and the PER3VNTR genotype. We also propose that the habituation effect of physical activity and training time-of-day on chronotype in the other groups may dissociate the PER3VNTR genotype with chronotype in a similar manner to which the early-morning start times of South African endurance events dissociates the two. No effect of geographical location on chronotype was found when comparing the Dutch and the South African groups. The morning-orientated South African runners seem to perform better in marathon running than the more evening-orientated runners do, which may be caused by their ability to cope with these early-morning marathon events. Further studies may explore whether marathon performance in later chronotypes can be improved by training-based habituation.
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    Sleep characteristics and cardiometabolic disease risk factors in corporate executives
    (2024) Pienaar, Paula; Rae, Dale; Lambert Vicki
    Hours spent in work and sleep comprise the majority of time in a typical day of working adults. As a result, the workplace is a key setting for public health action. Among working adults, 71% of deaths globally are related to non-communicable diseases (NCDs), most of which are attributed to cardiometabolic diseases (CMD). While there is clear evidence linking short sleep duration with CMD risk in the general population, similar data in a unique subset of the workforce, namely corporate executives, remains largely unexplored. The purpose of this thesis was to investigate the associations between sleep health and CMD risk in corporate executives. A systematic review and meta-analysis examined associations between selfreported sleep duration, all-cause mortality (ACM) and cardiovascular disease mortality (CVDM) in employed adults. Sleeping
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    The development of an exercise intervention framework as a modality of treatment for individuals with obstructive sleep apnea, in the South African public healthcare setting
    (2023) Jaffer, Zakirah; Rae, Dale; D'alton Caroline
    Introduction: Obstructive sleep apnoea (OSA) is described as a breathing-related sleep disorder wherein your ventilation is impaired during sleep, due to the narrowing and collapse of the upper airway. Untreated OSA has been shown to increase the number of severe cardiovascular and cerebrovascular events. Common treatment modalities for OSA, including surgical intervention and continuous positive airway pressure therapy are effective but remain extremely expensive. It is thus often inaccessible to those in a low-income, under-resourced setting, or those without access to healthcare, as is the case for the majority of South Africans. Since addressing weight loss is a key component of OSA treatment, exercise may provide the benefits of addressing both weight loss and inflammation in OSA patients, as well as lowering the risk of cardiovascular disease, depression, and comorbidities that arise from obesity. Aims: The aims of this study were to understand the nature of, and perception to, current physical activity (PA) habits as well as barriers to exercise, faced by individuals with obstructive sleep apnoea (OSA group) compared to a control group of individuals without OSA (CON group). This information was then used to design an exercise intervention framework for OSA patients which can be implemented in an under-resourced setting, such as in the public healthcare system in South Africa. Methods: This is a secondary analysis of data already collected as part of a larger study investigating “Physical activity and sedentary behavior among patients with obstructive sleep apnoea in South Africa” (HREC Ref: 142/2021). The parent observational study made use of custom and validated questionnaires answered by adults diagnosed with moderate to severe OSA and control participants with no OSA. Participants were asked to report on current and past exercise habits, perceptions, enablers, and barriers to PA, as well as preferred modes of exercise, which were further analyzed. Results: A total of thirty-seven adults were included in the current study; eighteen of whom had been diagnosed with OSA, matched with nineteen CON adults for age, BMI, neck circumference, waist circumference, and blood pressure (all p>0.050). Self-reported current participation in PA was lower in the OSA group (61%) compared to the CON group (74%), although not significantly different (p=0.410), with lower levels of PA between the two groups reported as being due to time constraints, dark/unsafe environment, laziness, covid restrictions, a lack of interest, motivation, and illness/injury/surgery within the OSA group specifically, There was a high presence of structural pain within the OSA group (83%) compared to the CON group (58%), although not significantly different (0.091), which was aggravated by PA (33% and 36% respectively). Frequency of PA was most commonly recorded as four to seven days per week by both the CON and OSA group (p=0.975, with a self-reported medium intensity ranging between 4-7 out of 10 (p=0.281) based on a subjectively designed 10-point scale (1: very low intensity, 10: very high intensity). Walking was the preferred form of PA within the OSA group (72%), as well as within the CON group (63%) (p=0.556), and both groups identified the ‘lack of motivation' as a barrier to participation in PA (p=1.000). Conclusion: Taking into account the observations 7 from evidence-based reviews in Chapter 1 and the results from Chapter 2, the proposed framework should include an exercise intervention that considers a moderate frequency of three to five times/week, a medium and building up to a higher intensity of 40-80% HRR, shorter sessions of 25-40 minutes per session but building up to 60 minutes where possible, and inclusion of aerobic and resistance exercises with a focus on walking as well as lower body activities. Group sessions should be considered to allow space for social interactions through physical activity which may help work around the barrier of motivation. Patient education on OSA and its consequences, the role of sleep, sleep hygiene, and disease management should also be included as part of the exercise intervention. Importantly, our results provide a basis for further development on this framework to establish an exercise Intervention as an adjunct therapy for OSA patients, specifically in lower income settings. Future studies can explore the efficacy of these exercise interventions in the management of OSA in adults from low income settings.