One slope does not fit all: longitudinal trajectories of quality of life in older adulthood

Purpose Maintaining or improving quality of life (QoL) in later life has become a major policy objective. Yet we currently know little about how QoL develops at older ages. The few studies that have modelled QoL change across time for older adults have used 'averaged' trajectories. However, this ignores the variations in the way QoL develops between groups of older adults. Methods We took a theoretically informed 'capabilities approach' to measuring QoL. We used four waves of data, covering 6 years, from the New Zealand Health, Work and Retirement Study (NZHWR) (N = 3223) to explore whether distinct QoL trajectories existed. NZHWR is a nationally representative longitudinal study of community-dwelling adults aged 50 + in New Zealand. Growth mixture modelling was applied to identify trajectories over time and multinomial regressions were calculated to test baseline differences in demographic variables (including age, gender, ethnicity, education and economic living standards). Results We found five QoL trajectories: (1) high and stable (51.94%); (2) average and declining (22.74%); (3) low and increasing (9.62%); (4) low and declining (10.61%); (5) low and stable (5.09%). Several differences across profiles in baseline demographic factors were identified, with economic living standards differentiating between all profiles. Conclusions The trajectory profiles demonstrate that both maintaining and even improving QoL in later life is possible. This has implications for our capacity to develop nuanced policies for diverse groups of older adults.