A Population-Based Study of Physical Activity, Sedentary Behaviour, and Non-Communicable Disease Risk in Middle-Aged Adults in South West Nigeria

Non-communicable diseases represent the most rapidly growing component of Nigeria's disease burden, and population-based studies linking objectively measured physical activity and sedentary behaviour to non-communicable disease risk biomarkers in middle-aged Nigerian adults are absent from the literature. This dissertation presents a population-based study of physical activity, sedentary behaviour, and non-communicable disease risk among middle-aged adults aged 40 to 60 years in three states of the South West geopolitical zone. A stratified random sample of 600 adults was recruited from urban, peri-urban, and rural communities in Lagos, Ogun, and Osun States. Physical activity and sedentary behaviour were assessed using seven-day accelerometry combined with a validated contextual activity log. Non-communicable disease risk was characterised through blood pressure measurement, fasting blood glucose, total cholesterol, high-density lipoprotein cholesterol, waist circumference, and body mass index, generating a composite metabolic risk score. Multilevel regression examined the independent and interactive associations of physical activity and sedentary behaviour with metabolic risk after controlling for dietary intake, smoking, alcohol use, and sociodemographic confounders. Findings demonstrate that both physical inactivity and high sedentary time are independently associated with elevated metabolic risk, with their combined presence conferring the greatest risk. Rural residents demonstrate higher physical activity but higher metabolic risk from dietary factors, revealing the complex interplay of activity and diet. The dissertation provides original population-based evidence for non-communicable disease prevention policy targeting physical activity promotion in South West Nigeria. Keywords: physical activity, sedentary behaviour, non-communicable disease, middle-aged adults, South West Nigeria