We read with interest the manuscript “The International Incidence of Traumatic Brain Injury: A Systematic Review and Meta-Analysis” by Nguyen et al. (2016).Reference Nguyen, Fiest and McChesney ¹ The authors mentioned that their search was developed by study authors with expertise in traumatic brain injury (TBI) and/or epidemiology, in consultation with a research librarian with extensive systematic review expertise, and that the search was conducted on May 23, 2014, in the MEDLINE and EMBASE databases. From Asia, only the study from Taiwan by Chiu et al is included.

A simple search with the key word of “TBI in Iran” shows different local and nationwide studies performed by our colleagues, all done to serve as a base for design prevention strategies and epidemiological studies to reduce the number of patients with head trauma.Reference Aghakhani, Azami, Jasemi, Khoshsima, Eghtedar and Rahbar ^{2 -} Reference Rahimi-Movaghar, Saadat and Rasouli ⁴ Iran is almost 1,648,195 km² in size and the province of West Azerbaijan, including Urmia as its main city, is 37,437 km², whereas the entire area of Taiwan is 36,193 km². Accordingly, the study of TBIs occurring in the more than 200,000 km of roads all around IranReference Aghakhani, Azami, Jasemi, Khoshsima, Eghtedar and Rahbar ^{2 ,} Reference Vafaee, Vafaei and Forouzanfar ³ might be of value for inclusion in a systematic review. Respectfully, we would say that, unfortunately, not one of them is included in the authors’ review. We checked the inclusion and exclusion criteria, variables, and outcomes, and all matched. Even though the results are almost in the same range and agree with the outputs, it might not change them remarkably but it is worth such valuable research being included in the data of a systematic review such as this.