Amount and patterns of physical activity accumulation during the transition from midlife to older adulthood: introducing the physical activity Bank

Objectives Previous studies have examined ‘trajectories' of physical activity, but few have investigated physical activity ‘accumulation'. In this study, we explored the ‘Physical Activity Bank' concept, incorporating both ‘accumulation amount' and ‘accumulation pattern'. The aims were to jointly describe the amount and patterns of physical activity accumulation in mid-to-older-adulthood and show how these vary by demographic characteristics. Design Prospective cohort study. Methods Data were collected from five mail surveys (2007–2016) of an Australian cohort transitioning from midlife to older adulthood. An individual Physical Activity Bank score was calculated as the total amount of physical activity across the five surveys. Patterns of accumulation were determined using group-based trajectory modelling. The resulting scores and patterns were compared against guideline-based cumulative thresholds (e.g., 2500 MET.mins across five surveys, 500 MET.mins/week on average) and stratified by gender, age, education, and weight status. Results Large variations were observed in Physical Activity Bank amounts over five surveys in nine years, from 0 to 21,479 MET.mins. Accumulation patterns were identified as low-stable (45.9%), moderate-stable (29.4%), moderate-increasing (11.7%), high-declining (7.5%), and high-stable (5.6%). Two contrasting patterns (moderate-increasing and high-declining) achieved a similar Bank amount; however, the former reflected more consistent accumulation, while the latter accumulated a large amount of activity only at baseline. Women, participants with lower education, or overweight/obese tended to have less active Bank amount and patterns. Conclusions This study demonstrates large variations in both the amount and accumulation patterns of the ‘Physical Activity Bank'. Future research may consider both dimensions, rather than a single metric, to assess long-term physical activity.