The name of this study design is longitudinal study.
Step-by-step explanation:
To study about ageing, cross-sectional and longitudinal and studies based on a lower animal are done Gerontology. These are done to know about various facts about the chronological and physiological age and their relation with the biological ageing process.
A longitudinal study or research is done by observing the same individual spanning or over time in order to observe and measure specific details or variables.
The BLSA study was based on longitudinal study design and hence used volunteers and followed them regularly until their death. It proved that longitudinal studies were less effective in identifying the biomarker for ageing process.