National Health and Nutrition Examination Survey, 2017-March 2020 Prepandemic File: Sample Design, Estimation, and Analytic Guidelines.

Objectives This report describes the creation of the NHANES 2017-March 2020 prepandemic data files, including the selection of the appropriate NHANES sample design (2015-2018) to create sample weights and variance units for public-use data files. Additionally, the development of a factor applied to the primary sampling units to adjust the 2017-March 2020 data to fit the NHANES 2015-2018 sample design is described. Analyses to assess representativeness of the target population were performed, and a simulation to replicate the impact of interrupted data collection using earlier NHANES cycles was undertaken. Analytic guidance specific to use for prepandemic data files is also included. .

National Health and Nutrition Examination Survey 2017-March 2020 Prepandemic Data Files-Development of Files and Prevalence Estimates for Selected Health Outcomes.

Background and objectives: In March 2020, the coronavirus disease 2019 (COVID-19) pandemic halted National Health and Nutrition Examination Survey (NHANES) field operations. As data collected in the partial 2019-2020 cycle (herein referred to as 2019-March 2020) are not nationally representative, they were combined with previously released 2017-2018 data to produce nationally representative estimates. This report explains the creation of the 2017-March 2020 prepandemic data files, provides recommendations for and limitations of the files' use, and presents prevalence estimates for selected health outcomes based on the files. Methods: The 2019-2020 primary sampling units (PSUs) were reassigned to the 2015-2018 sample design strata and combined with the 2017-2018 data to create a data set that could be used to calculate nationally representative estimates. A PSU-level adjustment factor was created to equalize the contribution of each stratum to the total survey sample and applied to participant base weights. Interview and examination weights were calculated from the adjusted base weights. The performance of final interview weights was assessed by comparing the demographic characteristics of the weighted NHANES 2017-March 2020 prepandemic sample with nationally representative estimates from the 2018 5-year American Community Survey. Prevalence estimates and 95% confidence intervals were calculated for selected health outcomes. Results: Among children and adolescents aged 2-19 years, the prevalence of obesity was 19.7% and the prevalence of untreated or restored dental caries in one or more primary or permanent teeth was 46.0%. Among adults aged 20 and over, the age-adjusted prevalence of obesity was 41.9%, severe obesity was 9.2%, and diabetes was 14.8%. Among adults aged 18 and over, the age-adjusted prevalence of hypertension was 45.1%. Among adults aged 65 and over, the age-adjusted prevalence of complete tooth loss was 13.8%. Conclusion: A PSU-level adjustment factor and additional weighting adjustments made nationally representative estimates from the 2017-March 2020 prepandemic data files possible; this was the last NHANES data collected before widespread transmission of COVID-19.