Abstract Background COVID-19 measures affected the lives of many older adults. Yet, little is known on changes in health among older adults, especially in periods when COVID-19 measures relaxed. We aimed to assess changes in health of older adults during multiple turning points of the COVID-19 pandemic and to analyse differences in changes in health between subpopulations of older adults. Methods This longitudinal study includes data from Dutch older adults (≥65 years) participating in the Lifelines COVID-19 Cohort and consists of seven questionnaires administered every 2-4 months between May ‘20 and October ‘21. The outcomes were quality of life (n = 14,682), physical fitness (n = 14,761) and feelings of isolation (n = 14,611). Changes in health and differences between subpopulations were analysed by multivariable linear mixed-effects models. Fluctuations in COVID-19 measures were described by the Government Stringency Index. Results Changes in quality of life and feelings of isolation of older adults coincided with fluctuations in the stringency of COVID-19 measures. In periods when measures were tightened, quality of life and feelings of isolation decreased and when measures relaxed, they improved. For example, when measures relaxed after the first lockdown in May ‘20, quality of life improved with 0.23 [95%CI: 0.16, 0.29] (p<.001). For physical fitness, changes were characterised by a slight decline of 0.26 [95%CI: 0.15, 0.37] (p=.001) during the study period. Differences in subpopulations were found for feelings of isolation for which differences between men and women congregated after a longer period of relaxed measures with 0.59 [95%CI: 0.49, 0.69] (p<.001). Conclusions Quality of life and feelings of isolation among older adults recover after periods of stringent measures. For physical fitness, the slight but continuing decline suggests a negative impact of COVID-19 measures. Our findings might indicate the need for health policy strategies to mitigate this effect. Key messages • Changes in quality of life and feelings of isolation of older adults coincided with fluctuations in stringency of COVID-19 measures and display recovery after periods of stringent measures. • Changes in physical fitness were characterized by slight decline and did not recover after stringent measures, suggesting an impact of COVID-19 measures on physical health of older adults.