Does temperature alter the relationship between sleep behaviour and non-communicable diseases in five different populations?

Marekerah, Queen Marvelous

Does temperature alter the relationship between sleep behaviour and non-communicable diseases in five different populations?

Thesis / Dissertation

2025

Publisher

University of Cape Town

Department

Department of Public Health and Family Medicine

Faculty

Faculty of Health Sciences

Abstract

Non-communicable diseases (NCDs) account for 71% of global deaths, with over 15 million annual fatalities occurring between the ages of 30 and 69. Emerging evidence links climate change, particularly rising temperatures, to disrupted sleep behaviours. However, the potential role of temperature in modifying the relationship between sleep disruption and NCDs remains underexplored, especially in low- and middle-income countries (LMICs). This study examines whether ambient nighttime temperatures alter the relationship between sleep behaviours and NCDs, focusing on African-origin populations across five diverse geographic locations. A case study approach was used, utilizing clinical data from the longitudinal Modelling the Epidemiologic Transition Study (METS, 2008-2013) and its ancillary studies, including METS-Microbiome (2017-2022) and METS-Sleep (2019-2024). Objective sleep measurements were obtained using actigraphy, while temperature data were sourced from the Iowa Environmental Mesonet (IEM) database. Sleep parameters included sleep onset time, wake-up time, sleep duration, wake after sleep onset (WASO), and sleep efficiency. Data from 809 African-origin adults (aged 35-55 years, 63% women) across Ghana, South Africa, Jamaica, Seychelles, and the US revealed significant variations in nighttime temperatures, ranging from 5°C to 32°C across the sites. Higher nighttime temperatures were associated with longer sleep duration but poorer sleep quality, as indicated by decreased sleep efficiency (-0.05, p < 0.001) and increased WASO (-0.005, p < 0.02). Poor sleep quality was linked to elevated risks of obesity, hypertension, and diabetes. Temperature minimally mediated the relationship between sleep and hypertension, with no significant mediation for obesity and diabetes. The project is structured into five sections: Part A (Protocol) reviews existing literature on NCDs, sleep, and climate change in LMICs, outlines the study population, and describes methodologies. Part B (Literature Review) explores how climate change-induced temperature variations may alter the relationship between sleep behaviours and NCDs. Part C (Journal-Ready Article) presents the study's findings, highlighting the complex interplay between temperature, sleep quality, and NCDs. Part D (Appendices) includes supplementary analyses, ethics approvals, and research permissions. Part E (Editorial/Policy Brief) discusses public health policy implications, emphasizing the need to consider temperature and sleep quality in addressing the global NCD burden. This study highlights the influence of nighttime ambient temperatures on sleep behaviours and their association with NCDs across diverse African-origin populations. The findings underscore the need to integrate climate variables into public health strategies aimed at mitigating the growing burden of NCDs.