In an ageing global population, understanding the dynamics of late-life impairment is crucial, especially in developing countries where rapid demographic changes surpass the preparedness of health and care systems. This PhD thesis examines the patterns and drivers of functional limitations in Indonesians aged 50 and above, using 21 years of longitudinal data to address this important gap.

The research is conveyed via three interconnected investigations:

• The first research investigates differences in functional limitation trajectories based on sex and birth cohort, emphasising the influence of socio-economic and biological determinants on ageing outcomes.
• The second research used Group-Based Trajectory Modelling (GBTM) to detect unique sub-population patterns of functional limitations over time, offering a deeper comprehension of the variability in ageing experiences.
• The third research examines the correlation between objective physical performance indicators (handgrip strength, lung capacity, and timed sit-to-stand) and self-reported functional limitations, connecting clinical assessments with subjective functional health experiences.

Collectively, this research provides essential insights into the complex dynamics of ageing and disability within a resource-limited context, with substantial implications for health policy and treatments designed to enhance the quality of life for elderly individuals in Indonesia and other developing nations.

Nur Cahyadi is a PhD candidate at the School of Demography, ANU. He completed a Master of Social Research (advanced) in 2017 at the ANU School of Demography and a Master of Economics in 2015 at the Bogor Agricultural University in Indonesia. He contributed to the Ageing in Rural Indonesia Study (ARIS), a collaboration between ANU and Indonesian universities. Nur has extensive professional experience in the design, monitoring and evaluation of social assistance programs for low-income families, including elderly populations, through his work with the National Team for the Acceleration of Poverty Reduction (TNP2K) in Indonesia under the Coordinating Ministry for Human Development and Cultural Affairs and the Vice President Office of the Government of Indonesia. His work integrates research and policy to address critical challenges in ageing and poverty alleviation in resource-constrained settings.