Out of the total number of 42,595 hospitalized patients due to trauma during 2014-2018, 4562 (10.7%) cases were HI patients. AAIRHI was 429 cases (95% CI, 418,443) per 100,000 person, which was higher in men (80%) compared to women (20%) (671 cases (95% CI, 644,694) vs. 182 cases (95% CI, 170,194)). (Fig 2-B) The mean age of patients was 28.5±17.3 years, which was higher in women compared to men (29.4±19.4 years vs. 27.7±15.3 years). The mean Length of Stay (LOS) was 111.3±239.8 hours which was higher in men than in women (126 ± 265.8 hour vs 96.6±213.8 hour).
The incidence rate of HI was varied among different age groups (P<0.001). The highest incidence rate was observed in the age group of 15-29 years with a significant differences compared to other age groups (752 cases (95% CI, 720,786) per 100,000 person). The lowest mean LOS was observed in the age group of 0-4 years (79.3±131.4 hours), while the age group of 70-79 years had the highest mean LOS (221.1±528.9 hours). The incidence rate of HI was higher among men compared to women in all age groups and the ratio of man to women HI incidence rate was observed in the age group of 15-29 (8.7:1.3). (Table 1)
Table 1- The incidence rate of HI in different age groups in Zanjan province
Age group
|
Population
N (%)
|
Total
N (%)
|
Men
N (%)
|
Women
N (%)
|
Incidence rate
Per 100,000
(95% CI)
|
Age
Mean±SD
|
LOS
Mean±SD
|
0-4
|
96655 (9)
|
242 (5.3)
|
152 (62.8)
|
90 (37.2)
|
250 (220,284)
|
2.4±1.4
|
79.3±131.4
|
05-14
|
156269 (14.6)
|
552 (12.1)
|
397 (71.9)
|
155 (28.1)
|
353 (324,384)
|
9.6±3.1
|
95.9±227.5
|
15-29
|
269071 (25.2)
|
2024 (44.4)
|
1756 (86.7)
|
268 (13.2)
|
752 (720,786)
|
22.1±4.1
|
106.7±206.5
|
30-44
|
279653 (26.1)
|
1035 (22.7)
|
795 (76.8)
|
240 (23.2)
|
370 (348,393)
|
35.6±4.2
|
131.9±255.2
|
45-59
|
152362 (14.2)
|
464 (10.2)
|
342 (73.7)
|
122 (26.2)
|
305 (277,334)
|
50.8±4.2
|
178±419.3
|
60-69
|
55222 (5.2)
|
143 (3.1)
|
96 (67.1)
|
47 (32.9)
|
259 (218,305)
|
63.7±2.6
|
139.4±214
|
70-79
|
31428 (2.9)
|
74 (1.6)
|
50 (67.6)
|
24 (32.4)
|
235 (185,296)
|
73.8±2.6
|
221.1±528.9
|
+80
|
16801 (1.6)
|
28 (0.6)
|
18 (64.2)
|
10 (35.7)
|
167 (111,241)
|
83.3±4.2
|
119.5±165.7
|
N: Number, CI: confidence interval, SD: standard deviation, LOS: length of Stay
An increased trend of AAIRHI was observed in the study area from 2014-2018, which rose from 74 cases (95% CI, 69,80) in 2014 to 86 cases (95% CI, 80,92) in 2018 (an 18% increase, P<0.001). The highest incidence rate (22.3%) and the highest AAIRHI were observed in 2017 (95 cases (95% CI, 90,101) per 100,000 person). The mean LOS was increased from 101.3±196.4 hours in 2014 to 141.5±263.8 hours in 2018, a 40% increase. The incidence of HI was higher in men compared to women in all years with a ratio of ~ 8:2. (Table 2)
Table 2- HI incidence rate by years in Zanjan province from 2014-2018
Year
|
Population
N (%)
|
Total
N (%)
|
Men
N (%)
|
Women
N (%)
|
Incidence rate
Per 100,000
(95% CI)
|
AAIRHI
Per 100,000
(95% CI)
|
Age
Mean±SD
|
LOS
Mean±SD
|
2014
|
1039350
|
780 (17.1)
|
604 (77.4)
|
176 (22.6)
|
75 (70,81)
|
74 (69,80)
|
27.1±16.2
|
101.3±196.4
|
2015
|
1048366
|
913 (20.)
|
724 (79.3)
|
189 (20.7)
|
87 (82,93)
|
85 (80,91)
|
27.3±15.9
|
109.3±202.5
|
2016
|
1057461
|
917 (20.1)
|
753 (82.1)
|
164 (17.9)
|
87 (81,93)
|
87 (81,93)
|
28±16.3
|
130.9±362.4
|
2017
|
1066555
|
1018 (22.3)
|
813 (79.9)
|
205 (20.1)
|
95 (90,101)
|
95 (90,101)
|
28.8±16.2
|
113.7±211.1
|
2018
|
1075727
|
934 (20.5)
|
712 (76.2)
|
222 (23.8)
|
87 (81,93)
|
86 (80,92)
|
28.8±16.7
|
141.5±263.8
|
Mean
|
1057492
|
912.4
|
721.2 (79)
|
191.2 (21)
|
86.2 (81,93)
|
85 (80,91)
|
28±16.2
|
119.3±247.2
|
N: Number, CI: confidence interval, SD: standard deviation, AAIRHI: Age-adjusted incidence rate of head injuries, LOS: length of Stay
Out of the total number of 4,562 registered patients due to HI, nasal bones fractures had the highest incidence rate with 212 cases (95% CI, 203,221) per 100,000 person. The ratio of men to women was approximately 8:2 in all fractures types due to HI. Fracture of tooth was common in younger ages in the cohort (24.4 ± 15.3 years) and the highest mean LOS was observed in the fracture of base of skull (213.5 ± 323 hours). (Table 3)
Table 3- The incidence rate of fractures due to HI in Zanjan province
ICD 10
Code
|
Fracture of Skull and Facial bones subdivisions
|
Total
N (%)
|
Men
N (%)
|
Women
N (%)
|
Incidence rate
Per 100,000
(95% CI)
|
Age
Mean±SD
|
LOS
Mean±SD
|
S02.0
|
Vault of skull
|
307 (7)
|
250 (81)
|
57 (19)
|
29 (26,32)
|
25.4±18.9
|
219.1±374.1
|
S02.1
|
base of skull
|
378 (8)
|
306 (81)
|
72 (19)
|
36 (32,40)
|
26.9±19.4
|
214.5±323
|
S02.2
|
nasal bones
|
2242 (49)
|
1724 (77)
|
518 (23)
|
212 (203,221)
|
26.5±14.3
|
60.3±168.8
|
S02.3
|
orbital floor
|
110 (2)
|
90 (82)
|
20 (18)
|
10 (9,13)
|
31±14.4
|
200.8±235.6
|
S02.4
|
malar and maxillary bones
|
697 (15)
|
570 (82)
|
127 (18)
|
66 (61,71)
|
34±16.6
|
157±268
|
S02.5
|
tooth
|
126 (3)
|
100 (79)
|
26 (21)
|
12 (10,14)
|
24.4±15.3
|
121.1±306.6
|
S02.6
|
mandible
|
348 (8)
|
286 (82)
|
62 (18)
|
33 (30,37)
|
28.9±16.3
|
172.2±373.1
|
S02.7
|
Multiple skull and facial bones
|
17 (1)
|
16 (94)
|
1 (6)
|
2 (1,3)
|
34.7±18.1
|
142.7±141.2
|
S02.8
|
other skull and facial bones
|
197 (4)
|
154 (78)
|
43 (22)
|
19 (16,21)
|
31.3±16.4
|
163.2±212.6
|
S02.9
|
part unspecified
|
140 (3)
|
110 (79)
|
30 (21)
|
13 (11,16)
|
25.9±21.6
|
157.6±269.2
|
Total
|
4562 (100)
|
3606 (80)
|
956 (20)
|
431 (419,444)
|
28.55±17.35
|
111.3±239.8
|
N: Number, CI: confidence interval, SD: standard deviation, LOS: length of Stay
As figure 2 reveals, an increasing trend was observed in the incidence rate of fracture of Vault of skull, which increased from 4 cases in 2014 to 7 cases in 2018 per 100000 person-year, a 75% increase. The incidence rate of fracture of nasal bone increased from 38 cases in 2014 to 41 cases in 2018 per 100000 person-year. (Fig 2-A) The age group of 15-29 years was identified as the highest risk group for the incidence of malar and maxillary bones (108.1), mandible (60.2), nasal bones (419.2), orbital floor (20.1), other skull and facial bones (27.1) and tooth fractures (20.4) compared to other age group, while the highest incidence rates of basal skull (55.9) and part unspecified fractures (29) were in the age group of 0-4 years, the highest incidence rates of Multiple skull and facial bones fractures (3.2) were in the age group of 70-79 years and the highest incidence rate of Vault of skull fracture (53.8 cases per 100,000 person) was in the age group of 60-69 years. (Fig 2-B) An increasing trend of mean LOS was observed in the fracture of tooth, which increased from 77 hours in 2014 to 262 hours in 2018, while the mean LOS of Multiple skull and facial bones fractures was decreased from 546 hours in 2014 to 88 hours in 2018. (Fig 2-C)
Spatial analysis results
According to the graphical and numerical outputs of Global Moran' I statistic and given the P-value of 0.003004, the spatial distribution of overall AAIRHI appeared to be significantly different than random at rural district levels in Zanjan province with a 95% CI. The spatial distribution of AAIRHI can be regarded to be clustered among men in the study area, while it had random pattern among women (P=0.006473 and P=0.376282, respectively). (Fig 3)
The incidence rate of HI was not homogenous across rural areas in Zanjan province (P<0.001). (Fig 4-B) Spatial analysis showed that Qarebolagh (the east) and Qeshlaqat (the southwest) had the highest AAIRHI compared to other areas (1026 cases and 885 cases per 1,000,000 person, respectively). Among men, the highest AAIRHI was observed in Qarebolagh and Qeshlaqat (1705 and 1639 cases per 100,000 man, respectively), which was similar to the spatial distribution of overall AAIRHI. Among women, the highest AAIRHI was observed in Soltanieh, GezelGechilo respectively (374, 332 cases per 100,000 woman, respectively), which was different compared to the spatial distribution of AAIRHI among men. (Fig 4-C)
Hotspot analysis detected one hotspot with a 99% CI, two hotspots with a 95% CI and two hotspots with a 90% CI located in the east and the center. Six cold spots with a 99% CI and one coldspot with a 95% CI were determined in the southeast. (Fig 4-D) Anselin local Moran’s analysis identified seven Low-Low (LL) clusters in the southeast and two High-High (HH) cluster in the center of the study area, which was consistent to the results of hotspot analysis. Gilvan region was determined as a High-Low (HL) outlier, an area with high AAIRHI, which surrounded by regions with low AAIRHI. The hotspot patterns of AAIRHI was different among men compared to women. Six hotspot and eight coldspot were detected among men, while there were two hotspot and two coldspot among women. GezelGechilo was identified as a HL outlier among women in the study area, an area with high AAIRHI compared to its neighbors. (Fig 4-E)
The incidence of HI varied across the years and an ascending trend was observed in the study area from 2014-2018 (P<0001). (Fig 5-A) AAIRHI was increased approximately doubled at Bonab during a five-year period which known as the first populated region (from 52 cases in 2014 to 99 cases in 2018 per 100,000 person), while the highest increase of AAIRHI was occurred at Darasjin which increased from 0 case in 2014 to 142 cases in 2018 per 100,000 person. A significant increase in AAIRHI was also observed at QezeGechio which increased from 0 to 103. While AAIRHI was increased in most regions, a significant descending trend was detected at SaeedAbad which decreased from 57 cases in 2014 to 0 cases in 2018 per 100,000 person. (Fig 5-B)
Spatial autocorrelation analysis showed that the Moran's I statistic was significant (Moran's Index: 0.241111), and the spatial pattern of AAIRHI was clustered in the study area. As figure 5 reveals, three hotspots with a 99% CI were identified at the north of the study area in 2014 which was not detected again during 2015-2018. The southeast of the area was determined as a coldspot across all years. The number of hotspots was decreased from 5 in 2014 to 0 in 2018. The spatial pattern of hotspots was changed from 2014-2018 and shifted from the north to the center. (Fig 5-C) Anselin local Moran’s I analysis showed that different spatial clusters of AAIRHI was detected among various years during 2014-2018. The number of clusters was decreased from 2 HH cluster in 2014 to 0 cluster in 2018. One HL outlier was detected at Golabar, an area with high AAIRHI that surrounding by areas with low AAIRHI. (Fig 5-D)
The incidence of HI was not same among men across different years and an ascending trend was observed during 2014-2018 (P <0001). (Fig 6-A) It was increased from 114 cases in 2014 to 129 cases in 2018 per 100,000 man, a 14% increase. Among men, the highest AAIRHI was observed at QareBolaq with 1705 cases per 100,000 man. The highest increase of AAIRHI was detected at Khoramdareh which increased from 14 case in 2014 to 109 cases in 2018 per 100,000 man, while the highest decrease was observed at Qeshalaqat which decreased from 251 cases in 2014 to 0 case in 2018. A significant increase of AAIRHI also observed among men at Daram (form 87 to 542 cases), ChaiparehBala (from 50 to 297 cases) from 2014-2018. (Fig 6-B)
Spatial autocorrelation analysis showed that the Moran's I statistic was significant among men (Moran's Index: 0.219330), and the spatial pattern of AAIRHI was clustered among men in the study area. As figure 6 reveals, the spatial distribution of hotspots and coldspots was changed among men over a five years in Zanjan, which shifted south from center. Among men, three hotspot were recognized in the study area in 2018, which were different from those observed previously. The number of hotspots and coldspots was decreased from five hotspot and four coldspot in 2014 to three hotspot and three coldspot in 2018. (Fig 6-C) Anselin local Moran’s I analysis showed that the spatial clusters of AAIRHI was different among men across various years which consistent with the results of hotspots analysis. Two HL outlier and two LH outlier was observed among men in 2018 which were different from those observed previously. As figure 5 shows, different coldspots were detected at the southeast which most of them was same among various years. (Fig 6-D)
The incidence of HI was not homogenous also among women across different years and an ascending trend was observed from 2014-2018 (P<0001). (Fig 7-A) AAIRHI was increased from 34 cases in 2014 to 41 cases in 2018 per 100,000 woman, a 20% increase. Among women, Soltanieh had the highest AAIRHI with 374 cases per 100,000 woman. Darasjin had the highest increase of AAIRHI compared to other regions, which increased from 0 cases in 2014 to 349 cases in 2018 per 100,000 woman. A significant ascending trend also observed at Dolatabad (from 0 to 346), GezelGechilo (from 0 to 225) and Qeshalaqat (from 0 to 143) from 2014-2018. (Fig 7-B)
Moran's I statistic was not significant among women (Moran's Index: 0.058904), the spatial pattern of AAIRHI for women was random in the study area. As figure 7 shows, the spatial distribution of hotspots and coldspots was changed among women over a five years period which shifted from the north to the southwest. Among women, three hotspots were detected in 2018 which were different from those observed previously. (Fig 7-C) Anselin local Moran’s I analysis showed that the spatial clusters of AAIRHI was different among women across various years during 2014-2018, which consistent with the results of hotspots analysis. While no HH cluster was defined in 2014, one HH cluster detected in Darasjin located at the southeast. While AbharRoud was determined as HL outlier in 2014, it was detected as LH outlier in 2018 (Fig 7-D)