Table 1 shows the quality status of the articles. If any articles scored less than 3, they were considered weak in the group and excluded from the study. Also, in the case of obtaining a score of 4 to 6, it was considered to mean average quality and a score of 6 and above was considered to mean high quality. In the initial search, 183 articles were found, 90 articles were removed in the initial review, and finally, 22 articles were included in the meta-analysis stage. In the 22 reviewed articles, the time of publication of the articles was between 2008 and 2022, and the total sample size was equal to 99,306. Also, in relation to the method of conducting studies, two studies were conducted using a retrospective method, two articles were conducted using a prospective method, and other articles were conducted using a cross-sectional method (
Table 2). Moreover, the sample size ranged from 264 patients in the study by Yadollahi and Sahmeddini (
23) to 47,295 patients in the study by Bolandparvaz et al. (
24). The HT prevalence also ranged from 0.3% in the study by Rahimi-Movaghar et al. (
25) to 77.2% in the study by Yousefzadeh et al. (
26) (
Table 2). Also,
Figure 1 shows flowcharts for systematic review (
Figure 1).
Figure 2 shows that the overall HT prevalence was 20.9 (95% CI, 14.4 - 29.2) in Iran. Also,
Figure 3 shows the funnel plot diagram, and
Figures 4 and
5 show the meta-regression of the prevalence of HT based on the year and number of patients of publication of the articles. Also, there was no relationship between the year of publication of articles (P = 0.96, Z-value = 0.05) and sample size (P = 0.41, Z-value = -0.82) with the prevalence of HT.
Diseases related to the head and nervous system can seriously threaten the patient’s life (
45-
47). Trauma has many types, and its prevalence is high (
48,
49). According to the results, the overall prevalence of HT in Iran is 20.9 (95% CI, 14.4 - 29.2). Various studies have been conducted on traumatic brain injury (TBI) prevalence in different age groups. For example, in a study on 42,412 children and adolescents, Nigrovic et al. reported that the TBI prevalence was 42,099 (99%) (
16). Aoki et al. also stated that out of 15,441 trauma children in Japan, 6,386 (41.35%) patients had HT (
50). Langlois et al. also reported that the TBI prevalence in children aged 0 - 14 years was reported to be about 475,000 (
51), which is much more than the results of the present study.
This discrepancy seems to be due to the study population. Further, the TBI prevalence in Thurman's study was 74 per 100,000 people in the emergency department (
52). Haarbauer-Krupa et al. also reported that the TBI prevalence was 2.5% (95% CI, 2.3% - 2.7%) during the years 2011 - 2012 (
53), which was lower than the results of the present study. This discrepancy may be due to differences in age groups and also the type of study. The current study is a meta-analysis study that was carried out on all age groups, while the aforementioned studies were original and were performed on children.
The TBI prevalence has also been investigated among the adult population in other countries. For example, Gerritsen et al. found that the HT prevalence was equal to 22.1 per 1,000 patients (
54), Baiden et al. also concluded that out of 6,314 patients, the TBI prevalence was equal to 208 cases (3.3%) (
55), which is much lower than the present study. This discrepancy may be due to the fact that the current study was a meta-analysis, while the above-mentioned studies were original.