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Methodology

Read the NCD-RisC methodology

NCD RisC work has two key components. The first is data curation and management, which involves the sourcing, harmonisation, and organisation of studies that contain data on NCDs and their risk factors. The second is statistical analysis, which involves the use of bespoke statistical models to obtain estimates of patterns and trends in the data. The key aspects of our data curation and management are outlined below. For the details of our statistical analysis please see each specific studies' publications.


  • Inclusion/exclusion criteria - read more
    To ensure only high quality studies that are representative of general population are used, all studies in the NCD-RisC database are assessed against inclusion and exclusion criteria.

  • Data cleaning - read more
    NCD-RisC have developed a data cleaning procedure which removes data with values that are possible data entry errors. This process is done in three stages:
    1. Checking all variables against their respective univariate cleaning criteria;
    2. Checking that all data meet relevant multivariate constraints (e.g., systolic blood pressure should be higher than diastolic blood pressure);
    3. Detecting multivariate outliers by pairs of related variables (e.g., BMI and waist circumference) based on the relationship of the relevant variables in the entirely of dataset.

  • Conversion to metrics with standard definition
    For a small number of data sources in the NCD-RisC database, only a subset of metrics of interest are available. In such cases, conversion regression models have been developed to estimate other metrics of interest from the available data.
    1. Mean BMI - read more
    2. Prevalence of BMI categories - read more
    3. Prevalence of diabetes - read more

References:

  1. Worldwide trends in diabetes prevalence and treatment from 1990 to 2022: a pooled analysis of 1108 population-representative studies with 141 million participants. Lancet 2024
  2. Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 populationrepresentative studies with 222 million children, adolescents, and adults. Lancet 2024, 403:1027-1050
  3. Diminishing benefits of urban living for children and adolescents' growth and development. Nature 2023, 615:874-883
  4. Worldwide trends in hypertension prevalence and progress in treatment and control from 1990 to 2019: a pooled analysis of 1,201 population-representative studies with 104 million participants. Lancet 2021, 398:957-980
  5. Height and body-mass index trajectories of school-aged children and adolescents from 1985 to 2019 in 200 countries and territories: a pooled analysis of 2181 population-based studies with 65 million participants. Lancet 2020, 396:1511-1524
  6. Repositioning of the global epicentre of non-optimal cholesterol. Nature 2020, 582:73-77
  7. Rising rural body-mass index is the main driver of the global obesity epidemic in adults. Nature 2019, 569:260-264
  8. Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128.9 million children, adolescents, and adults. Lancet 2017, 390:2627-2642
  9. Worldwide trends in blood pressure from 1975 to 2015: a pooled analysis of 1479 population-based measurement studies with 19.1 million participants. Lancet 2017, 389:37-55
  10. Worldwide trends in diabetes since 1980: a pooled analysis of 751 population-based studies with 4.4 million participants. Lancet 2016, 387:1513-1530