A cervical lordosis curvature decline in Chinese asymptomatic populations from 2016 to 2024: a comparative analysis

Abstract

Background

There is increasing concern regarding the effects of contemporary lifestyles on spinal health. This study aimed to evaluate recent trends in cervical lordosis (CL) curvature over the past eight years.

Methods

Asymptomatic individuals who underwent cervical spine radiography at four hospitals were randomly selected from hospital databases for a comparative analysis of data spanning from 2016 to 2024. The curvature of CL was assessed using three methods: the C2-C7 Cobb angle (Cobb A), the C2-C7 Harrison posterior tangent angle (Harrison A), and Borden’s method for evaluating CL depth. Measurements of CL curvature were performed using the previously described methodologies by two authors, employing a Picture Archiving and Communication System. The selected participants were categorized into two cohorts: young adults (aged < 40 years) and older adults (aged ≥ 40 years).

Results

In the 2016 and 2024 cohorts, no significant age differences based on gender were observed. Females in these cohorts exhibited significantly lower CL curvature measurements, as assessed by the Cobb A and CL depth indices, in comparison to their male counterparts. Furthermore, within these cohorts, older adults demonstrated a reduction in CL depth compared to younger adults. The assessment of CL curvature in the 2024 cohort, utilizing the Cobb A and Harrison A methods, revealed a reduction in measurements compared to the 2016 cohort. This decrease was observed across both genders and all age groups.

Conclusions

The findings of this study indicate a decline in CL curvature over the past eight years. Further investigation is warranted to understand the etiology and clinical significance of this observed trend.

Introduction

Concurrently, advancements in technology have markedly improved personal convenience through electronic devices. Nonetheless, this technological progress has resulted in heightened dependency on these devices. The pervasive use of handheld electronics and mobile phones, notwithstanding their numerous advantages, has elicited concerns. In recent years, there has been an increasing concern among the public and academic communities regarding spinal health in the context of widespread digital device usage [1–5].

A recent community-based cross-sectional study reported a prevalence of cervical spondylosis of 13.76% within the Chinese population [1]. In this context, the term text neck has been coined to describe postural changes associated with prolonged handheld device use, sparking debate about its potential long-term effects on cervical alignment [1]. This is attributed to the continuous exposure to electronic devices and the sustained forward flexion of the neck, which impose increased biomechanical loads on the cervical spine in progressively flexed postures [2]. Scholars extensively acknowledge the significant correlation between text neck and excessive mobile phone usage, identifying text neck as an emerging global health epidemic [3–8].

While smartphones were already prevalent in China by 2016, the intensity and duration of usage may have further increased in subsequent years. Excessive use of mobile phones is increasingly recognized as a potential factor influencing alterations in cervical lordosis (CL) curvature [9]. Simultaneously, modifications in CL curvature within the cervical sagittal balance have been demonstrated to substantially affect cervical spine stability [10–12]. Research indicates that changes in cervical sagittal balance are closely associated with cervical degenerative diseases [13]. As a result, it has become essential to objectively document temporal trends in cervical alignment within the general population as an initial step.

This study aimed to examine secular trends in cervical lordosis curvature among asymptomatic adults over an eight-year period (2016–2024) and to quantify any observable changes in radiographic parameters.

Materials and methods

Participants

This study conducted a retrospective analysis of a cohort of East Asian individuals who had undergone cervical spine digital radiography (DR) during routine physical examinations in the medical examination departments of four hospitals. These radiographs were voluntarily requested by individuals concerned about cervical health, who were retrospectively confirmed to be asymptomatic at the time of imaging, based on medical records showing no active neck pain or neurological symptoms. Participants were randomly selected from hospital databases using a computer-generated random number sequence applied to a list of all eligible individuals who met the initial inclusion criteria (adults with cervical spine DR). Informed consent was waived due to the retrospective nature of the study. The cohorts from 2016 to 2024 consist of independent sets of individuals. The study protocol was approved by the institutional review board (Approval No. K295-1). Cervical spine DR images acquired in 2016 and 2024 were analyzed. Exclusion criteria included patients with a history of cervical spine surgery, those under the age of 18, and individuals presenting with scoliotic deformity or cervical spondylolisthesis. Parameters were independently assessed twice by two authors using a Picture Archiving and Communication System (PACS), with the mean value used for further analysis. The reporting of this study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines [14].

Figure 1 illustrates the participant selection flowchart. Participants were categorized into two cohorts based on the year of participation: the 2016 cohort and the 2024 cohort. The 2016 cohort included 89 male and 79 female participants, while the 2024 cohort comprised 94 male and 84 female participants. The mean age of male participants in the 2016 cohort was 43.78 years with a standard deviation of 12.14 years, spanning an age range of 22 to 72 years. Female participants in the same cohort had a mean age of 43.18 years with a standard deviation of 11.98 years, and an age range of 24 to 73 years. In the 2024 cohort, the mean age of male participants was 43.65 years with a standard deviation of 13.76 years, within an age range of 23 to 73 years. Female participants in the 2024 cohort had a mean age of 41.64 years with a standard deviation of 13.65 years, and an age range of 21 to 75 years. Table 1 provides a detailed demographic breakdown of participants by age decade for both cohorts.

Fig. 1.

Flowchart of Participant Population Selection

Table 1.

Detailed age distribution of participants by decade

Age (y)	2016 (n = 168)	2024 (n = 178)
18–29	28 (17%)	32(19%)
30–39	35 (21%)	36 (20%)
40–49	48 (28%)	50 (28%)
50–59	42 (25%)	43 (24%)
≥ 60	15 (9%)	17 (10%)

Participants were stratified into two age-based cohorts: the young adult cohort (Young), which included individuals younger than 40 years, and the older adult cohort (Older), comprising individuals aged 40 years and above.

Measurements

A consistent radiologic protocol was employed throughout the study duration. Lateral radiographs were acquired with each participant standing in a natural posture, shoulders relaxed, and the auditory-nasal line parallel to the horizontal plane. The hips and knees were fully extended. The radiographs extended to the external occipital convexity, with the X-ray tube centered at the C4 vertebra.

In each of the lateral radiographs, the CL angle was assessed using the following methodologies (Fig. 2).

Fig. 2.

Three methods used for measuring cervical lordosis curvature in lateral digital radiographic images

C2-C7 Cobb angle measurement method (Cobb A) [15–18]. The angle between the horizontal line of the C2 lower endplate and the horizontal line of the C7 lower endplate.

C2–C7 Harrison posterior tangent angle method (Harrison A) [15, 16, 19, 20]. The angle between the line along the posterior margin of the C2 vertebra and the posterior margin of the C7 vertebra.

For all angle parameters, lordosis was assigned positive values, while kyphosis was assigned negative values.

The CL depth was measured by Borden’s method [13, 21]. In this method, Line a is delineated by connecting the posterior edges of all vertebral bodies, while Line b extends from the posterior superior margin of the odontoid process to the posterior inferior margin of the C7 vertebra. The CL depth (c) is defined as the maximum perpendicular distance between Line b and Line a. A negative value is recorded when Line b is anterior to Line a.

Measurements were independently evaluated by two observers, each of whom performed two separate assessments. The mean of these assessments was recorded. Subsequently, both intra-rater and inter-rater reliability were calculated using the Intraclass Correlation Coefficient (ICC).

Statistical analyses

The results are expressed as mean ± standard deviation. Statistical analyses were conducted utilizing SPSS software, version 29.0 (Chicago, IL). The Shapiro-Wilk test was employed to assess the normality of data distribution. Comparisons of measurements based on gender were performed using the independent samples t-test, which was also applied to evaluate differences across various years and age groups. A significance threshold of P < 0.05 was established for all statistical tests.

Results

The detailed age distribution by decade is presented in Table 1.

No statistically significant age differences were identified between males and females within the 2016 and 2024 cohorts. Furthermore, no significant age differences were detected between participants of the 2016 and 2024 cohorts, irrespective of gender. (Table 2)

Table 2.

Age comparison

	2016			2024			2016 vs. 2024
	M	F	M vs. F	M	F	M vs. F	M	F
n	89	79		94	84
Age (y)	43.78±12.14	43.18±11.98	0.948	43.65±13.76	41.64±13.65	0.448	P = 0.749	P = 0.331

Data are expressed as mean ± standard deviation

M Male, F Female, 2016 data from the year 2016, 2024 data from the year 2024

In the analysis of Cobb A, females exhibited significantly smaller angles compared to males in both the 2016 and 2024 cohorts. This trend was similarly observed for CL depth in both cohorts, as well as for Harrison A in the 2024 cohort, with females displaying significantly smaller measurements than their male counterparts. In the 2024 cohort, both male and female participants exhibited significantly reduced Cobb A and Harrison A measurements compared to the 2016 cohort. (Table 3)

Table 3.

Cervical lordosis curvature across gender groups from 2016 to 2024

	2016			2024			2016 vs. 2024
	M	F	M vs. F	M	F	M vs. F	M	F
Cobb A (°)	24.20±11.67	20.08±13.43	0.035	19.30±11.70	13.31±11.04	< 0.001	P = 0.005	P < 0.001
Harrison A (°)	25.58±11.60	23.38±13.51	0.257	21.59±11.45	17.03±11.15	0.008	P = 0.020	P = 0.001
CL depth (mm)	10.81±4.98	8.86±4.93	0.012	10.56±6.23	7.81±5.49	0.002	P = 0.772	P = 0.202

Data are expressed as mean ± standard deviation

M Male, F Female, 2016 data from the year 2016, 2024 data from the year 2024, Cobb A C2-C7 Cobb angle, Harrison A C2–C7 Harrison posterior tangent angle, CL depth Cervical Lordosis depth

In the analysis of CL depth, older adults exhibited significantly smaller measurements than young adults in both the 2016 and 2024 cohorts. In the 2024 cohort, both young and older adult groups demonstrated significantly smaller Cobb A and Harrison A measurements compared to those in the 2016 cohort. (Table 4)

Table 4.

Cervical lordosis curvature across age groups from 2016 to 2024

	2016			2024			2016 vs. 2024
	Young	Older	Young vs. Older	Young	Older	Young vs. Older	Young	Older
n	63	105		84	94
Cobb A (°)	24.73±13.69	20.78±11.82	0.050	15.87±11.38	17.02±12.11	0.257	P < 0.001	P = 0.028
Harrison A (°)	26.08±13.46	23.63±11.93	0.221	19.17±11.52	19.68±11.56	0.385	P = 0.001	P = 0.019
CL depth (mm)	11.30±5.25	9.05±4.73	0.002	10.28±5.53	8.36±6.34	0.033	P = 0.263	P = 0.381

Data are expressed as mean ± standard deviation

Young the young adult group (< 40 years), Older the older adult group (≥ 40 years), 2016 data from the year 2016, 2024 data from the year 2024, Cobb A C2-C7 Cobb angle, Harrison A C2–C7 Harrison posterior tangent angle, CL depth Cervical Lordosis depth

The intra-rater ICC for evaluating the CL parameters ranged from 0.87 to 0.95, whereas the interobserver ICC ranged from 0.85 to 0.94. These values suggest a high degree of measurement reliability, indicating both good to excellent consistency.

Discussion

The primary objective of this research was to ascertain whether a secular trend in CL curvature could be identified in the population between 2016 and 2024. The findings of the present study confirm that CL curvature measurements are indeed smaller in the 2024 cohort than they were eight years ago, affecting both males and females across all age groups.

Studies have indicated gender differences in cervical spine morphology, consistently finding that females exhibit smaller CL curvature measurements compared to males [22–25]. Our study corroborated these findings, demonstrating that the C2-C7 Cobb angles are indeed smaller in females than in males. We hypothesized that the reduced CL curvature in females may be associated with their generally lower levels of outdoor physical activity.

Our findings regarding age-related changes in cervical lordosis diverge from previous normative studies, which have reported an increase in angular CL with advancing age [18–29]. In contrast, our study identified a decrease in CL depth among older adults, while the C2–C7 Cobb and Harrison angles did not exhibit a significant decline with age. This discrepancy is likely attributable to methodological differences. Firstly, the spinal segments assessed differ: our study focused on C2–C7, whereas other studies examined C3–C7 [29] or C1–C7 [28], complicating direct comparisons. Secondly, CL depth, a linear measurement, and global angles represent distinct geometric characteristics of the cervical curve. The lack of significant angular change in our cohorts suggests that the relationship between aging and cervical alignment is complex and may not conform to a universal pattern.

Previous research has demonstrated that individuals exhibit significantly increased cervical spine flexion during smartphone use compared to periods of non-use [30, 31]. Furthermore, the mechanical load on the spine intensifies with increasing degrees of neck flexion [2]. Although smartphones were widely used by 2016, the cumulative exposure and potential increase in daily usage intensity between 2016 and 2024 might contribute to the observed progressive decrease in CL curvature. Consequently, habitual long-term smartphone use is hypothesized to lead to a progressive decrease in CL curvature. Biomechanical studies have indicated that Cobb angles are correlated with various parameters of cervical sagittal alignment [12]. Considering the persistence of contemporary lifestyle habits, it is essential to investigate the impact of alterations in CL on other cervical structures, including intervertebral discs.

A longitudinal study with a minimum follow-up period of 10 years has demonstrated that CL significantly affects the progression of degenerative changes in the cervical spine. The study found a markedly higher incidence of posterior disk protrusion progression in individuals lacking CL [13]. Additionally, research conducted by Zhuang L et al., which included a cohort of 2,438 young patients, indicates a potential association between cervical disc degeneration and excessive smartphone use [32]. The dominant hypothesis posits that excessive smartphone usage may lead to a gradual decrease in CL, thereby elevating stress on the intervertebral discs and potentially inducing their degeneration. This process could contribute to a heightened incidence of degenerative cervical spondylosis. However, additional empirical research is necessary to substantiate this relationship.

Cuéllar JM et al. have posited that “text neck,” a condition linked to the contemporary prevalence of smartphone usage, could be considered an epidemic [33]. They emphasized the need for additional clinical research to evaluate whether this condition might expedite the progression of cervical kyphosis. A comprehensive review revealed that the incidence of degenerative cervical spine disorders is increasing worldwide, irrespective of economic status [34]. A population-based study has concurrently demonstrated a 74.1% increase in annual surgical rates for these conditions between 2008 and 2014, underscoring the rising incidence and prevalence [35]. Our study demonstrated that the increasing incidence of degenerative cervical spine diseases could potentially be linked to the progressive reduction in CL curvature. This reduction not only could exacerbate the prevalence of degenerative cervical spondylosis but also might correspond with the heightened annual surgical rates.

Notably, while the Cobb and Harrison angles demonstrated a significant decline from 2016 to 2024, the CL depth did not exhibit a corresponding significant reduction. This discrepancy may be attributed to the fundamental differences in the parameters measured. The Cobb and Harrison angles assess the global angular alignment between C2 and C7, whereas Borden’s method measures the maximal linear distance of the posterior vertebral line from a reference chord. A reduction in overall angular lordosis may result from a more gradual curvature or a shift in the apex of the curve, which may not proportionally affect the maximum depth measurement. Consequently, these indices, although related, capture distinct geometric aspects of cervical lordosis, and their trends may not necessarily align. The clinical relevance of the observed reduction in CL curvature, while statistically significant, requires further investigation. The mean differences, though consistent, may fall within a range of natural variation for some individuals. Future longitudinal studies are needed to determine if these small, population-level changes over time translate to an increased individual risk for pain or functional impairment, and to establish clinically significant thresholds for such declines.

This study is subject to several limitations that warrant consideration when interpreting the findings. Firstly, the relatively small sample size may compromise the statistical power and limit the generalizability of the results. Secondly, the retrospective design inherently restricted data availability; notably, we lacked individual metrics on electronic device usage duration (daily screen time) and other potential confounding variables such as smoking history, occupational ergonomics, and detailed medical comorbidities, which precludes the establishment of direct causal relationships. Thirdly, the analysis was confined to radiographic alignment parameters and did not encompass other pertinent cervical spine changes, such as disc degeneration, muscle quality, or osteophyte formation. Fourthly, there is potential for selection bias, as participants were individuals who voluntarily underwent cervical spine imaging during health check-ups, which may not fully represent the general asymptomatic population. Lastly, the generalizability of our findings may be restricted to East Asian adults in similar clinical contexts, as genetic, lifestyle, and ergonomic factors in other populations could produce different trends.

Conclusions

In this study, we demonstrated that individuals currently exhibit a significant decline in CL curvature and deviate more from the ideal cervical alignment compared to data from eight years prior. Future research incorporating detailed device usage metrics should investigate the underlying causes of this decline in cervical curvature and examine the potential implications of this trend.

Abbreviations

CL

Cervical Lordosis

Cobb A

C2-C7 Cobb angle

Harrison A

C2-C7 Harrison posterior tangent angle

DR

Digital Radiography

PACS

Picture Archiving and Communication System

STROBE

Strengthening the Reporting of Observational Studies in Epidemiology

ICC

Intraclass Correlation Coefficient

Authors’ contributions

X.L. and W.Z. conceived and designed the study. X.L. and Z.S. performed formal analysis. Z.S., W.Z and P.L. contributed to data acquisition and investigation. X.L. and Z.X. developed the methodology. H.L. and L.Y. supervised the project. X.L. and L.Y. wrote the original draft. L.Y. and H.L. reviewed and edited the manuscript. All authors reviewed and approved the final version of the manuscript. X.L., W.Z., Z.S. and Y.B. contributed equally to this work and share first authorship. L.Y. and H.L. contributed equally to this work.

Funding

This study was supported by the 2022 Joint Funding Scheme for Scientific Research Projects (FDCT-GDST Projects) of the Science and Technology Development Fund of Macau, the Department of Science and Technology of Guangdong Province (2022A0505020019 &0056/2021/AGJ), the Project of the Administration of Traditional Chinese Medicine of Guangdong Province of China (NO. 20241046), and the National Natural Science Foundation of China (NO. 82302035).

Data availability

All datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Ethics Committee of the Fifth Affiliated Hospital of Sun Yat-sen University (Approval No. K295-1). The study was conducted in accordance with the principles of the Declaration of Helsinki. The need for informed consent was waived by the Ethics Committee of the Fifth Affiliated Hospital of Sun Yat-sen University because of the retrospective nature of the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.