A higher female (51.7%) to male (48.3%) gender ratio was found among the study population which mostly consisted of young and middle-aged adults (67.8%). Consistent with this study, Wang et al  reported a study population comprising 68.8% females and 31.2% males (age range: 11- 24 years; mean: 16 years) in a study to measure the scoliosis Cobb angle by end vertebra tilt method. In a Hungrarian study comparing angle values of patients with adolescent idiopathic scoliosis (AIS) determined by the ZEBRIS spine examination method with the angle values defined by the standard Cobb method on biplanar X-ray images, Takács et al  also reported a higher female (89.5%) to male (10.5%) gender ratio among the 19 children.
Lumbar Lordotic Angles
On a lateral lumbar radiograph, the Cobb angle is the angle between the perpendiculars from the superior endplate of the first lumbar vertebra (L1) and the superior endplate of the first sacral vertebra (S1). It is associated with the spinous process angle of the coronal plane and rotation of the apical vertebra, and hence measured on the coronal or sagittal plane of imaging. The average L1-L5 and L1-S1 LLAs of 27.18o (SD=13.05o) and 43.56o (SD=14.58o) are similar to other findings reported in the literature. In particular, Benditz et al  reported that the L1-S1 angle for lumbar lordosis on radiographs obtained in erect position was 44.99° (range: 29° to 59°), and 47.91° (range: 36° to 78°) on supine MRI images. Using the ZEBRIS spinal examination method, Takács et al  obtained a sagittal LLA of 43.0o (SD= 9.00).
It has been suggested that degenerative changes as well as disc herniation start at the lower lumbar segments with aging . Furthermore, it is obvious that with aging, the loss of trunk muscles balance, along with an increase in LLA (decrease in lordosis), would lead to an increase in intervertebral disc stresses with an eventual change in pressure points along the lumbar spine. Furthermore, this study found that the LLAs, particularly to the L1-S1 angle measured among the adolescent group consisting of 7 individuals (mean age: 16.29±2.43 years) was 49.29o (SD=10.69o) and comparable to other findings reported in the literature. In particular, in a study conducted to assess the effect of corrective exercises on lumbar lordosis using the spinal mouse method on 40 male students (mean age: 17.24 ± 2.84 years), Yazici & Mohammadi  measured LLAs of 48.23o (SD=1.74o) (pre-test) and 43.56o (SD= 0.97o) (post-test) in the experimental group and 48.51o (SD=2.18o) (pre-test) and 49.63o (SD=1.85o) (post-test) in the control group. Ko et al  also reported pre-intervention and post-intervention LLAs of 40.0o (SD=2.4o) and 40.1o (SD=2.4o) among a control group in a study to assess the effect of lumbar stabilization exercise and sling exercise on LLA and other parameters on patients with chronic back pain.
The findings of this study are also in agreement with the results of other studies which measuring LLAs using the Cobb method. In particular, this study found the measured L1-S1 lordotic angle for young adults (20 to 39 years) as 46.58o (SD=14.54o), while Takács et al  and Castillo et al  measured similar sagittal lumbar Cobb angles of 47.3o (SD=16.80) in children (8-16 years), and of 49.4o (SD=9.5o) among a cohort of young adults (age range: 18 to 35 years). Skaf et al  also found that LLA was significantly correlated with age (R= 0.341, p < 0.0001) and showed a tendency to decrease from the third decade onwards, to become relatively constant after the sixth decade. Lee  also reported similar findings.
It has been previously hypothesized that an imbalance of the trunk muscle can increase the LLC of the lumbar spine due to weakness of abdominal muscles, along with aging . Per this study’s finding, the observed decrease in the Cobb-measured LLAs with age parallels an increase in lumbar lordosis. Moreover, with aging, the loss of trunk muscles balance with associated decrease in lordosis, and consequent increases in LLA results in increased intervertebral disc stresses with subsequent changes in pressure points along the lumbar spine, inducing upward motion. In general, symmetrical facets distribute a given load evenly and bilaterally. In asymmetrical facet joints, the loading force is unevenly distributed and shifted to the side of the facet joint. Subsequently, the induced eccentric stress affects the disc, resulting in disc degeneration or herniation moving cranially with age, according to Karacan . Contrary to the findings of this study, higher LLAs have been reported in other studies. Sparrey et al  found an angle 51° (SD=11o) as lordotic angles of modern humans compared to 60.9° (SD=12.0o) (range: 31° to 88°) reported in a much older study after analyzing lumbar lordosis angles of 100 asymptomatic adult volunteers . The range of LLA is however, agreeable with the findings of this study.
Lumbar Lordotic Angles and Gender Dimorphism
This study established that LLAs and the lumbar spine are gender dimorphic with increased lumbar lordosis in adult females than males. In line with this finding, Bailey et al  reported higher LLAs in females and stated that the lumbar spine is sexually dimorphic with increased lumbar lordosis in adult females than males. A probable reason for this could be explained by the fact that pregnancy is associated with increased lumbar lordosis in women. From the viewpoint of biomechanics, variations in the load distribution in the lumbar spine could also account for this. Matsumoto et al  and Sparrey et al  reiterated similar observations and same reasons for the gender dimorphism associated with LLAs. According to Porto & Okazaki , there is no evidence that effectively proves the association of LLA with gender and age.
However, other studies found no evidence of gender-based differences in the LLAs. In a review, De Carvalho et al  also demonstrated that even though gender differences were assessed, existing tests showed controversy in the literature regarding differences in the association or relationship between LLAs and gender. In particular, whereas some studies have shown no difference in lumbar lordosis, others have found larger angles in females and few found larger angles in males .