GBD provides comprehensive, and up-to-date, epidemiological information on 369 diseases and 87 risk factors for 204 countries. GBD 2019 includes global, regional, national, and subnational data that is developed by the Institute for Health Metrics and Evaluation (IHME) in Seattle, Washington, USA (19, 20).
GBD 2017 defines OA as a symptomatic arthritis at the hip or knee that has been confirmed radiologically based on the kellgren Lawrence grading (21) in which grade 0 shows no x-ray changes regarding OA,grade 1 has minimal joint space narrowing and possible osteophytes, grade 2, definite osteophytes and possible joint space narrowing, grade 3, moderate osteophytes, definite joint space narrowing, some sclerosis and possible deformity, and grade 4 also has large osteophytes, marked narrowing of joint space, severe sclerosis and definite deformity of bone. A definite diagnosis of OA is considered at grade 2 (22).
GBD 2019 adds two new sites for OA which have been included in current study: hand, and “other sites” (eg, foot, shoulder, wrist). Although spine is another common site for OA but, it is usually discussed in the studies covering estimates of low back pain and neck pain (19). Based on the tenth revision of the international classification of diseases (ICD), the codes used for OA include M16 -M16.9 for OA in the hip, M17-M17.9 for OA of the knee, and M18-M18.9 for hand OA (23). In this study, prevalence, incidence, and YLDs for OA overally and by hip, knee, hand, and other OA were extracted from GBD Results Tool (https://ghdx.healthdata.org/gbd-results-tool) and GBD Compare Tool (https://vizhub.healthdata.org/gbd-compare/).
Incidence, prevalence, remission, and cause of death were estimated with the use of DisMod-MR, a Bayesian meta-regression disease-modeling tool .The detailed methodology has been published previously (24, 25).
Additionally, GBD employs the comparative risk assessment (CRA) methodology to provides attributable mortality, YLLs, YLDs, and DALYs for 84 risk factors by multiplying population attributable fractions (PAFs). As high BMI is considered a modifiable risk factor attributed to OA in the GBD 2019, we also evaluated the estimates for high BMI (20).
Overall, results were reported for a total of 21 countries in the region (Afghanistan, Algeria, Bahrain, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Palestine, Qatar, Saudi Arabia, Sudan, Syrian Arab Republic, Tunisia, Turkey, United Arab Emirates, and Yemen) between 1990 and 2019 and were classified by sex, 5-year intervals age groups (30–34, 35–39, …, 65–69, and 70 + years of age), and metric (number and rate) were also reported. Estimates were reported as age-standardized values as well to compare countries'estimates. Socio-demographic index (SDI) is a combined indicator of the ranking of the income per capita, average educational attainment, and fertility rates.The variation of association between SDI and the aforementioned OA metrics with the level of SDI were also performed and reported.
Lastly, a decomposition analysis was also carried out to report contribution of population growth, age structure change, and incidence rate change to the overal new cases changes between 1990–2019 (26).
Such a study is designed to show the changes of OA burden and its related risk factor during past three decades and interpreted the changes with 95% uncertainty intervals (UIs) for every metric.