ObjectivesThe aim of this study was to develop an index to measure older adults’ exposure to the COVID-19 pandemic, and to study its association with various domains of functioning.DesignCross-sectional study.SettingThe Longitudinal Aging Study Amsterdam (LASA), a cohort study in the Netherlands.ParticipantsCommunity dwelling older adults aged 62-102 years (n=1089) who participated in the LASA COVID-19 study (June-September 2020), just after the first wave of the pandemic.Primary outcome measuresA 35-item COVID-19 exposure index with a score ranging between 0 and 1 was developed, including items that assess the extent to which the COVID-19 situation affected daily lives of older adults. Descriptive characteristics of the index were studied, stratified by several socio-demographic factors. Logistic regression analyses were performed to study associations between the exposure index and several indicators of functioning (functional limitations, anxiety, depression, and loneliness).ResultsThe mean COVID-19 exposure index score was 0.20 (SD 0.10). Scores were relatively high among women and in the southern region of the Netherlands. In models adjusted for socio-demographic factors and pre-pandemic functioning (2018-2019), those with scores in the highest tertile of the exposure index were more likely to report functional limitations (OR: 2.23; 95% CI: 1.48 to 3.38), anxiety symptoms (OR: 3.87; 95% CI: 2.27 to 6.61), depressive symptoms (OR: 2.45; 95% CI: 1.53 to 3.93) and loneliness (OR: 2.97; 95% CI: 2.08-4.26) than those in the lowest tertile.ConclusionsAmong older adults in the Netherlands, those with higher scores on a COVID-19 exposure index reported worse functioning in the physical, mental and social domain. The index may be used to identify persons for whom targeted interventions are needed to maintain or improve functioning during the pandemic or post-pandemic.Strengths and limitations of this studyThis study was based on a representative sample of older adults from three culturally different regions in the Netherlands.The Longitudinal Aging Study Amsterdam COVID-19 study provides unique data on functioning of older adults in various life domains during the COVID-19 pandemic.The items of the COVID-19 exposure index that was developed were based on self-report, more objective sources such as medical records were lacking.The study covered the first months of the pandemic in the Netherlands, longitudinal data is needed to monitor functioning of older adults in later stages of the pandemic.