Sleep characteristics associated with nocturnal blood pressure nondipping in healthy individuals: a systematic review.

OBJECTIVE: The current literature investigating nocturnal blood pressure (BP) nondipping has largely focused on clinical populations, however, conditions such as hypertension, obstructive sleep apnoea and insomnia are recognized confounding factors for BP dipping. The exact mechanisms responsible for BP nondipping remain unclear, therefore, there is a need to investigate BP nondipping in healthy individuals to better understand the underlying mechanisms. This review identifies sleep characteristics that may contribute to BP nondipping in healthy individuals. It is anticipated that an understanding of the sleep characteristics that contribute to BP nondipping may inform future sleep-related behavioral interventions to ultimately reducing the burden of cardiovascular disease. METHODS: The PubMed, Scopus and Web of Science databases were searched for relevant, English language, peer-reviewed publications (from inception to March 2022). The search identified 550 studies. After duplicates were removed, the titles and abstracts of the remaining 306 studies were screened. Of these, 250 studies were excluded leaving 56 studies to test for eligibility. Thirty-nine studies were excluded such that 17 studies fully met the inclusion criteria for the review. RESULTS: Findings from this review indicate that short sleep duration, more sleep fragmentation, less sleep depth and increased variability in sleep timing may be associated with BP nondipping in healthy individuals. CONCLUSION: While there is no evidence-based approach for the treatment of nocturnal BP nondipping, it seems promising that addressing one's sleep health may be an important starting point to reduce the prevalence of BP nondipping and perhaps the progression to cardiovascular disease.

Associations between self-reported sleep duration and cardiometabolic risk factors in young African-origin adults from the five-country modeling the epidemiologic transition study (METS).

OBJECTIVES: To investigate associations between self-reported sleep duration and cardiometabolic (CM) risk factors in African-origin adults residing in five countries spanning the epidemiologic transition. DESIGN: Cross-sectional. SETTING AND PARTICIPANTS: Ghanaian (n = 491), South African (n = 503), Jamaican (n = 508), Seychellois (n = 501) and American (n = 480) men and women. MEASUREMENTS: Self-reported sleep duration was obtained using questionnaires. Sex- and site-stratified logistic regression analyses investigated relationships between sleep duration, individual CM risk factors and a binary CM risk variable (presence of ≥3 CM risk factors), adjusting for age, physical activity and education. RESULTS: Sleep duration distributions varied by cohort: 44.5%, 41.4%, 35.9%, 16.8% and 2.5% of American, Jamaican, Seychellois, Ghanaian and South African men reported <7 h sleep per night respectively (p < 0.001). Similarly, 42.6%, 28.6%, 25.2%, 12.8% and 1.5% of American, Jamaican, Seychellois, Ghanaian and South African women reported <7 h sleep respectively (p < 0.001). American men reporting ≤6 h sleep were more likely to be in the elevated CM risk group (OR: 2.52, 95%CI: 1.02, 6.22, p = 0.045) and to have a high waist circumference (OR: 2.44, 95%CI: 1.07, 5.57, p = 0.034) compared to those reporting 8 h sleep. Jamaican women reporting ≤6 h sleep (OR: 2.53, 95%CI: 1.19, 5.36, p = 0.016) and American women reporting 7 h sleep (OR: 2.71, 95%CI: 1.17, 6.26, p = 0.002) were more likely to be obese than those reporting 8 h sleep. CONCLUSIONS: Associations between short sleep and CM risk factors were only evident in the American men and women and Jamaican women. Future interventions to address CM risk and sleep health may need to be country-specific when targeting high-risk populations.

Chronotype of South African adults is affected by solar entrainment.

Our daily lives are influenced by three different daily timers: the solar clock, our endogenous circadian clock and the societal clock. The way an individual's endogenous clock synchronises to the solar clock, through either advances or delays relative to sunrise and sunset, results in a phenomenon known as diurnal preference or chronotype. South Africa uses just one time zone, but in the most easterly regions of the country, the sun rises and sets up to an hour earlier than in the most westerly regions throughout the year. It was hypothesised first that South Africans living in the east of the country may have a greater preference for mornings (more morning chronotypes) than those living in the west; and second, that this difference would not be due to genetic differences in the populations, particularly a genetic polymorphism previously shown to influence chronotype. Here, we describe and compare the distribution of chorotype and PERIOD3 variable number tandem repeat (VNTR) polymorphism frequency in eastern (n = 129) and western (n = 175) sample populations. Using the Horne-Östberg Morningness, Eveningness Questionnaire we found that there was a significantly higher proportion of morning-types in the eastern population (56.6%) than in the western population (39.4%), and there were higher proportions of neither-types and evening-types in the western population (51.4% and 9.1%, respectively) than in the eastern population (37.2% and 6.2%, respectively) (p = 0.009). There were no significant differences in distribution of the PER3 genotype (p = 0.895) and allele (p = 0.636) frequencies. Although previous studies have shown associations between chronotype and PER3 VNTR genotypes, no significant associations were observed in either the eastern (p = 0.695) or the western (p = 0.630) populations. These findings indicate that, in South African populations, longitude influences chronotype independently of PER3 genotype. The impacts of the differences in chronotype whilst maintaining the same societal temporal organisation in the eastern and western regions were not assessed.