Novel Journal Metrics in Cardiothoracic Surgery: How Different Are Contemporary Metrics From the Impact Factor?

Objective: Despite shortcomings, impact factor (IF) remains the "gold standard" metric for journal quality. However, novel metrics including the h-index, g-index, and Altmetric Attention Score (AAS; mentions in mainstream/social media) are gaining traction. We assessed correlations between these metrics among cardiothoracic surgery journals.

Methods: For all cardiothoracic surgery journals with a 2021 Clarivate IF (N = 20), the 2-year IF (2019 to 2020) and 5-year IF (2016 to 2020), h-index, and g-index were obtained. Two-year journal-level AAS (2019 to 2020) was also calculated. Journal Twitter presence and activity was sourced from Twitter and the Twitter application programming interface. Correlations were assessed using Spearman correlation, and coefficients of determination were calculated.

Results: IF demonstrated a moderate-strong positive correlation with the h-index (r_s = 0.48 to 0.77) and g-index (r_s = 0.49 to 0.79) and a moderate correlation with AAS (r_s = 0.53 to 0.58). The 2-year IF accounted for 25% to 49% of variability in the h-index, 27% to 55% of variability in the g-index, and 32% of variability in the AAS. Among journals with a Twitter account (N = 10), IF was strongly correlated with Twitter following (r_s = 0.81 to 0.86), which was in turn strongly correlated with journal AAS (r_s = 0.79). Article-level AAS was moderately correlated with citation count (r_s = 0.47).

Conclusions: IF accounted for only between 25% and 55% of variability in the h-index and g-index, indicating that these newer metrics measure unique dimensions of citation-based impact. Thus, the academic community must familiarize itself with these newer journal metrics. Social media attention may be associated with scholarly impact, although further work is needed to understand these relationships.