Annual transition probabilities of overweight and obesity in older adults: Evidence from World Health Organization Study on global AGEing and adult health

Overweight/obesity is becoming increasingly prevalent in sub-Saharan Africa including Ghana. However, transition probabilities, an essential component to develop cost-effective measures for weight management is lacking in this population. We estimated annual transition probabilities between three body mass index (BMI) categories: normal weight (BMI >=18.5 and <25.0 kg/m2), overweight (BMI >=25.0 and <30.0 kg/m2), and obesity (BMI >=30.0 kg/m2), among older adults aged >=50 years in Ghana. Data were used from a nationally representative, multistage sample of 1496 (44.3% females) older adults in both Waves 1 (2007/8) and 2 (2014/15) of the Ghana WHO SAGE. A multistage Markov model was used to estimate annual transition probabilities. We further examined the impact of specific socio-economic factors on the transition probabilities. At baseline, 22.8% were overweight and 11.1% were obese. The annual transition probability was 4.0% (95% CI: 3.4%, 4.8%) from normal weight to overweight, 11.1% (95% CI: 9.5%, 13.0%) from overweight to normal weight and 4.9% (95% CI: 3.8%, 6.2%) from overweight to obesity. For obese individuals, the probability of remaining obese, transitioning to overweight and completely reverting to normal weight was 90.2% (95% CI: 87.7%, 92.3%), 9.2% (95% CI: 7.2%, 11.6%) and 0.6% (95% CI: 0.4%, 0.8%) respectively. Being female, aged 50-65 years, urban residence, having high education and high wealth were associated with increased probability of transitioning into the overweight or obese categories. Our findings highlight the difficulty in transitioning away from obesity, especially among females. The estimated transition probabilities will be essential in health economic simulation models to determine sustainable weight management interventions.