[Figure 1 here]
Description of included studies (Table 1) : Most studies were
conducted in the United States (103 studies, 82%), followed by Europe
(16 studies, 13%), six which were conducted in Norway. The number of
studies escalated over time, with 86 studies (68%) published between
2015 and 2019, of which 26 (20.6%) were published in 2019 (Jan-Jul).
Cohort studies were the most common (92 studies, 73%), followed by
cross-sectional studies (32 studies, 25%).
Data sources (Table 1): Data on opioid use was retrieved from
pharmacy dispensing records for 108 studies (86%), with almost half (58
studies, 46%) using data from nationwide administrative systems.
Pharmacy dispensing claims or prescription records were used with one
(70 studies, 56%) or multiple data sources (42 studies, 33%), such as
medical health records, medical claims, hospitals separations, surveys,
census, and surveillance registries (e.g., mortality, cancer).
Study Populations (Table 1): One-quarter of studies did not
impose age restrictions, 64% included adults only and 9% focused
exclusively on the elderly (aged 65+ years);[20-30] two studies focused on adolescents and
young adults (13-29 years old). [31, 32]
Study populations varied
substantially in size, ranging from 121 [33] to 48
million people. [34] One-fifth of studies included
only opioid-naïve individuals (27 studies), defined as the absence of
opioid use in the six or 12 months prior to the index date. Studies
investigated opioid use among patients with various specific health
conditions, such as CNCP (42 studies, 33%), musculoskeletal conditions
(15 studies, 12%), injuries or trauma (13 studies, 10%) or the
infectious diseases HIV or hepatitis C (8 studies, 6%). Six studies
(5%) included patients with both cancer pain and CNCP without reporting
stratified results [35-40] and six studies (5%)
evaluated patients with cancer [26, 41, 42] or
cancer survivors. [27, 43, 44]