The role of serum lipids and BMI in China patients with primary pterygium

Abstract

To study the role of Body Mass Index (BMI) and serum lipid profile molecules, as well as their derivative indexes in primary pterygium patients. The patient group consisted of 110 patients with primary pterygium diagnosed in our center between January 2019 and December 2020, while the control group consisted of 144 healthy persons of similar age and sex diagnosed during the same time period. The BMI, serum lipid profile molecules and their derivative indexes of both groups were analyzed retrospectively. In the patient group, 62 patients were overweight or obesity and 104 patients with dyslipidemia. Among them, body mass index (BMI), serum triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and apolipoprotein B (Apo-B) levels were significantly higher than those in the control group (p < 0.05). The difference in Apo-B/ApoAl ratio, TC/LDL-C ratio, HDL-C/LDL-C ratio was statistically significant (p < 0 .05), while the serum high-density lipoprotein cholesterol (HDL-C), apolipoprotein A1 (ApoA1) and TG/LDL-C ratio were not significantly different in the patient group compared with control group (p > 0.05). Logistic analysis indicated that obesity, TC and HDL-C/LDL-C ratio are independent risk factors influencing the onset of pterygium (p < .05). BMI and serum lipid level are both significantly associated with primary pterygium. Obesity and abnormal serum lipid metabolism are independent risk factors for pterygium and play a critical role in the development of pterygium. Obesity and serum lipid level can significantly affect clinical management of pterygium. These characteristics are simple to use in clinical practice and may aid in the identification of pterygium high-risk populations.

BACKGROUND

Primary pterygium is a chronic disease of the abnormity hyperplasia of the conjunctival fibrovascular tissue which is a common ocular surface disease in ophthalmology.¹ As the pterygium tissue grows and invades the cornea, it will cause corneal astigmatism, affect visual function, and affect aesthetics.² Pterygium is a common proliferative ocular surface disease, which mainly cause is still unclear, and its occurrence and development are related to many factors.^3,4 It is believed that the damage of local limbal stem cell may be the basis of the pathogenesis of pterygium.⁵ At present, the treatment of pterygium is surgery, but the recurrence rate after surgery is relatively high. Therefore, studying the related risk factors of pterygium and exploring the pathogenesis of pterygium are great significance to the prevention and treatment of pterygium. Although the pathogenesis of pterygium is still not clarified, recently, despite increasing evidence that the pathogenesis and development of pterygium may be related to ultraviolet radiation, inflammation, viral infection, oxidative stress, DNA methylation, extracellular matrix regulators, apoptosis, oncogene proteins, epithelial-mesenchymal cell transformation, changes in cholesterol metabolism and so on,^6–8 but there are few studies on the correlation between obesity, serum lipid profile molecules, especially, serum lipid derivative indexes and pterygium. Studies have found that there was a intermarriage correlation between pterygium and cholesterol metabolism, and the changes in cholesterol homeostasis in cells may be related to the occurrence of pterygium.^8–12 For example, Kilic et al. found that reduction of high-density lipoprotein levels may indicate that systemic oxidative stress is closely related to pterygium⁸; Pan Zhoxian et al. reported a cross-sectional study in a large population of Hebei Province and found that the elevated serum HDL-C level in the fasting state is the cause of pterygium in the Han population⁹; Peiretti et al. discovered the prominent expression of low-density lipoprotein receptor (LDL-R) and hydroxymethylglutaryl-coenzyme A reductase (HMG-CoA-R) in pterygium tissue cells, which are related to cholesterol metabolism¹⁰; Wu Mengliang et al. found that LDL-R was positively related to the subconjunctival fibroblasts (PSFs) proliferation, which related to the pathogenesis of pterygium¹¹; Studies have confirmed that two drugs which name everolimus and pioglitazone alter cholesterol metabolism, can inhibit the proliferation of pterygium fibroblasts and participate in the regulation of intracellular cholesterol homeostasis.¹² However, there are few studies on the correlation between serum lipid derivative indexes and pterygium.

With the improvement of living standards, the number of obesity and dyslipidemia people are increasing. Obesity and dyslipidemia are risk factors for many diseases, such as chronic cardiovascular and cerebrovascular diseases, lung diseases, liver and kidney dysfunction, and cancer.^13,14 Therefore, we hypothesized that the pathogenesis and development of pterygium may be related to Obesity and dyslipidemia. However, the comprehensive interview with an association of primary pterygium relate obesity, serum lipid profile molecules and serum lipid derivative indexes has not been studied in depth. This study aims to analyze the level of BMI, serum lipid profile molecules, especially, serum lipid derivative indexes in primary pterygium patients to prove that obesity and dyslipidemia plays an important role in the development of pterygium.

RESEARCH OBJECTS AND METHODS Research objects

One hundred and ten patients with primary pterygium diagnosed in Sun Yat-sen University Cancer Center from January 2019 to December 2020 were selected as the patient group. A total of 144 healthy individuals with age and sex matching during the same period were selected as control group. There was no statistical difference in the age and sex of both groups. The research was approved by the Ethics Committee of Sun Yat-sen University Cancer Center, and written informed consent was obtained from each patient involved in the study. Clinical data of the patients were retrospectively analyzed, including gender, age, serum lipid profile molecules and their derivative indexes. The individual serum lipid profile molecules include triglycerides (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A1 (ApoA1) and apolipoprotein B (ApoB), and their derivative indexes including LDL-C/HDL-C ratio, TC/HDL-C ratio, TG/HDL-C ratio, HDL-C/ApoA1 ratio and ApoB/ApoA1 ratio.

The inclusion criteria of patients included the following: (1) clinically diagnosed primary pterygium; (2) have no prior history of eye surgery; (3) have no history of hypertension, diabetes, etc.; (4) have no primary lipid metabolism-related diseases with intake of lipid-regulating drugs and other drugs that might affect serum lipid profile molecules in the past 3 months; (5) have no severe cardiovascular dieases, brain diseases, hepatic or renal function.

Pterygium examination method

All patients were examined by the same experienced ophthalmologist through a structured slit-lamp to assess the anterior segment of their eyes. In this study, all patients with pterygium had at least 2 mm length measuring from the limbus to the corneal vertex.

Measurement and evaluation criteria of body mass index

The height, weight, and other parameters of the patients are measured by skilled nurse. Body mass index (BMI) is calculated by weight (kg)/height (m²) that were measured to the nearest 0.1 kg and 0.1 cm. According to the standard in the “Guidelines for the Prevention and Control of Overweight and Obesity in Adults in China” by the Ministry of Health, normal BMI was defined as 18.5 ≥ BMI ≤ 23.9 kg/m², overweight was defined as 24 ≥ BMI ≤ 27.9 kg/m², and obesity was defined as BMI ≥ 28 kg/m².¹⁵

Serum lipid testing

Three milliliters blood was obtained from patients and control after fasting for 8–12 h. After plasma separation, serum lipid molecules were measured using an automatic biochemical analyzer. The range of serum lipid profile molecules reference value is TC: 3.1–5.69 mmol/L, TG: 0.2–1.7 mmol/L, HDL-C: 1.16–1.42 mmol/L, LDL-C: 2.2–3.1 mmol/L, Apo-A1: 1.2–1.6 g/L, Apo-B: 0.6–1.0 g/L. Serum lipid derivative indexes was calculated according to the results of the above serum lipid profile molecules.

Statistical analysis

SPSS 25.0 statistical software (IBM Inc., Armnok, USA) was used for all analysis. The descriptive data were calculated as mean ± standard deviation (SD). The comparison between two groups and subgroups was analyzed by independent sample t test for continuous variables respectively according to the presence of pterygium. The independent risk factors of pterygium were analyzed by multivariate regression logistic analyses. p < .05 indicates that the difference was statistically significant.

We confirm that during this research, all applicable institutional and governmental rules regarding the ethical use of human volunteers were followed. The Sun Yat-sen University Cancer Center granted ethics approval for patient recruiting and data analysis.

RESULTS Characteristics of study subjects

Table 1 lists the characteristics of individuals by age, gender, and others. In the patient group, there were 60 males and 50 females, with an average age of 51.54 ± 9.16 years old. The incidence of pterygium was 40 cases of right eye, 34 cases of left eye, and 36 cases of both eyes. There were 62 cases of abnormal weight, with an incidence rate of 56.4%, including 47 cases of overweight and 15 cases of obesity. In the control group, there were 63 males and 81 females, with an average age of 50.86 ± 6.89 years old. There were 69 cases of abnormal weight, and the incidence of abnormal weight was 47.9%, including 56 cases of overweight and 13 cases of obesity.

TABLE 1 Characteristic of study subjects and ratio (%).

Characteristics	N (%)
Patient group	110 (100.0)
Pterygium
In the right eye	40 (36.4)
In the left eye	34 (30.9)
In both eyes	36 (32.7)
Sex
Males	60 (54.5)
Females	50 (45.5)
Age
≤45	44 (40.0)
>45	66 (60.0)
Body mass index
Normal	48 (43.6)
Overweight	47 (42.7)
Obesity	15 (13.7)
Dyslipidemia	104 (94.5)
Control group
Sex	144 (100.0)
Males	63 (43.8)
Females	81 (56.2)
Age
≤45	52 (36.1)
>45	92 (63.9)
Body mass index
Normal	75 (52.1)
Overweight	56 (38.9)
Obesity	13 (9.0)
Dyslipidemia	129 (89.5)

The relationship between pterygium and body mass index

A comparison of the two groups' BMI findings revealed that the BMI of patient group was much higher than the control, and the difference was statistically significant (p < .05) (Table 2), indicated that overweight or obesity related to pterygium. Among men, the patient group's BMI was substantially higher than the control group (p < .05) (Table 3). However, there was no significant difference in BMI among females (Table 4).

TABLE 2 Univariate analysis of patient group and control group $\left(\overline{x}\pm s\right).$

Parameters	Patient group (n = 110)	Control group (n = 144)	T value	p Value
Age (year)	51.54 ± 9.16	50.86 ± 6.89	−0.593	0.554
TC (mmol/L)	5.13 ± 0.98	5.71 ± 0.95	4.288	0.000
TG (mmol/L)	1.30 ± 0.56	1.67 ± 1.76	2.018	0.045
HDL-C (mmol/L)	1.45 ± 0.38	1.44 ± 0.36	−0.105	0.916
LDL-C (mmol/L)	3.09 ± 0.85	3.63 ± 0.74	4.743	0.000
ApoAl (g/L)	1.49 ± 0.22	1.49 ± 0.24	−0.079	0.937
Apo-B (g/L)	1.03 ± 0.20	1.13 ± 0.25	3.007	0.003
Apo-B/ApoAl ratio	0.71 ± 0.18	0.78 ± 0.20	2.460	0.015
TC/LDL-C ratio	1.75 ± 0.45	1.60 ± 0.22	−2.966	0.003
TG/LDL-C ratio	0.45 ± 0.24	0.47 ± 0.54	0.337	0.736
HDL-C/LDL-C ratio	0.51 ± 0.21	0.42 ± 0.15	−3.567	0.000
BMI	23.87 ± 2.72	24.75 ± 3.05	2.176	0.031

Abbreviations: ApoA1, apolipoprotein A1; ApoB, apolipoprotein B; HDL-C, high-density lipoprotein-cholesterol; LDL-C, low-density lipoprotein-cholesterol; TC, total cholesterol; TG, triglycerides.

TABLE 3 Univariate analysis of patient group and control group in male $\left(\overline{x}\pm s\right)$

Parameters	Patient group in male (n = 110)	Control group in male (n = 144)	T value	p Value
Age (year)	51.22 ± 9.47	50.27 ± 7.91	−0.569	0.571
TC (mmol/L)	4.97 ± 0.97	5.79 ± 0.95	4.489	0.000
TG (mmol/L)	1.16 ± 0.42	1.78 ± 1.68	2.650	0.009
HDL-C (mmol/L)	1.35 ± 0.37	1.30 ± 0.30	−0.650	0.517
LDL-C (mmol/L)	3.07 ± 0.84	3.68 ± 0.72	4.090	0.000
ApoAl (g/L)	1.41 ± 0.23	1.41 ± 0.21	−0.052	0.959
Apo-B (g/L)	1.10 ± 0.17	1.11 ± 0.24	0.202	0.840
Apo-B/ApoAl ratio	0.80 ± 0.16	0.81 ± 0.20	0.210	0.834
TC/LDL-C ratio	1.69 ± 0.33	1.59 ± 0.17	−1.928	0.056
TG/LDL-C ratio	0.40 ± 0.17	0.50 ± 0.56	1.265	0.209
HDL-C/LDL-C ratio	0.48 ± 0.20	0.37 ± 0.11	−3.572	0.001
BMI	24.15 ± 2.73	25.66 ± 2.67	2.931	0.004

Abbreviations: ApoA1, apolipoprotein A1; ApoB, apolipoprotein B; HDL-C, high-density lipoprotein-cholesterol; LDL-C, low-density lipoprotein-cholesterol; TC, total cholesterol; TG, triglycerides.

TABLE 4 Univariate analysis of patient group and control group in female $\left(\overline{x}\pm s\right)$

Parameters	Patient group in female (n = 110)	Control group in female (n = 144)	T value	p Value
Age (Year)	51.93 ± 8.87	51.58 ± 5.42	−0.230	0.819
TC (mmol/L)	5.33 ± 0.96	5.62 ± 0.94	1.456	0.149
TG (mmol/L)	1.47 ± 0.67	1.55 ± 1.87	0.249	0.804
HDL-C (mmol/L)	1.57 ± 0.34	1.61 ± 0.37	0.514	0.608
LDL-C (mmol/L)	3.11 ± 0.87	3.56 ± 0.78	2.564	0.012
ApoAl (g/L)	1.59 ± 0.17	1.59 ± 0.24	−0.070	0.945
Apo-B (g/L)	0.95 ± 0.20	1.15 ± 0.25	4.163	0.000
Apo-B/ApoAl ratio	0.60 ± 0.14	0.74 ± 0.20	3.803	0.000
TC/LDL-C ratio	1.83 ± 0.56	1.62 ± 0.27	−2.298	0.024
TG/LDL-C ratio	0.52 ± 0.31	0.44 ± 0.51	−0.881	0.381
HDL-C/LDL-C ratio	0.55 ± 0.21	0.48 ± 0.18	−1.714	0.090
BMI	23.52 ± 2.70	23.65 ± 3.15	0.212	0.832

Abbreviations: ApoA1, apolipoprotein A1; ApoB, apolipoprotein B; HDL-C, high-density lipoprotein-cholesterol; LDL-C, low-density lipoprotein-cholesterol; TC, total cholesterol; TG, triglycerides.

The relationship between pterygium and abnormal serum lipid levels

In the patient group, 109 cases of dyslipidemia, accounting for 90.8%, and 103 cases of dyslipidemia in the control group, accounting for 85.8%. Comparing and analyzing the serum lipids of the patient group and the control group, it was found that the serum TC, TG, LDL-C, and Apo-B levels of the patient group were higher than those of the control group, and the difference was statistically significant (p < .05). The differences of Apo-B/ApoAl ratio, TC/LDL-C ratio, HDL-C/LDL-C ratio between the two groups were statistically significant (p < .05); however, there was no statistical difference in serum HDL, ApoA1 levels and serum lipid ratio TG/LDL-C ratio between the two groups Academic significance (p > .05) (Table 2). Among males, there were statistically significant differences in TC, TG, LDL-C, Apo-B, HDL-C/LDL-C ratio, and BMI between the two groups (p < .05) (Table 3). Among females, there were statistically significant differences in TC, TG, LDL-C, Apo-B, Apo-B/ApoA1 ratio, TC/LDL-C ratio and HDL-C/LDL-C ratio between the two groups (p < .05) (Table 4). The TC, LDL-C, TC/LDL-C ratio between the two groups were statistically significant among subjects aged <45 years old (p < .05) (Table 5). Serum lipid profile molecules and their derivative indexes showed no significant differences between those aged ≥45 years old (p > .05) (Table 6).

TABLE 5 Univariate analysis of patient group and control group in age ≤ 45 years old $\left(\overline{x}\pm s\right)$

Parameters	Patient group in age ≤ 45 years old (n = 23)	Control group in age ≤ 45 years old (n = 52)	T value	p Value
TC (mmol/L)	5.71 ± 1.00	5.11 ± 1.09	2.217	0.030
TG (mmol/L)	1.46 ± 0.81	1.29 ± 0.80	0.851	0.397
HDL-C (mmol/L)	1.44 ± 0.33	1.39 ± 0.38	0.550	0.584
LDL-C (mmol/L)	3.61 ± 0.76	3.03 ± 0.91	2.643	0.010
ApoAl (g/L)	1.50 ± 0.23	1.44 ± 0.25	0.897	0.372
Apo-B (g/L)	1.10 ± 0.32	0.99 ± 0.23	1.703	0.093
Apo-B/ApoAl ratio	0.76 ± 0.26	0.72 ± 0.23	0.681	0.498
TC/LDL-C ratio	1.59 ± 0.11	1.73 ± 0.23	−2.827	0.006
TG/LDL-C ratio	0.40 ± 0.17	0.45 ± 0.30	−0.830	0.409
HDL-C/LDL-C ratio	0.42 ± 0.12	0.49 ± 0.20	−1.733	0.087
BMI	24.1 ± 4.00	23.9 ± 3.06	0.183	0.855

Abbreviations: ApoA1, apolipoprotein A1; ApoB, apolipoprotein B; HDL-C, high-density lipoprotein-cholesterol; LDL-C, low-density lipoprotein-cholesterol; TC, total cholesterol; TG, triglycerides.

TABLE 6 Univariate analysis of patient group and control group in age > 45 years old $\left(\overline{x}\pm s\right)$

Parameters	Patient group in age > 45 years old (n = 87)	Control group in age > 45 years old (n = 92)	T value	p Value
TC (mmol/L)	5.71 ± 1.05	5.73 ± 1.16	−0.129	0.898
TG (mmol/L)	1.64 ± 1.85	1.86 ± 3.58	−0.523	0.602
HDL-C (mmol/L)	1.49 ± 0.53	1.44 ± 0.38	0.853	0.395
LDL-C (mmol/L)	3.49 ± 0.86	3.40 ± 0.89	0.742	0.459
ApoAl (g/L)	1.51 ± 0.29	1.50 ± 0.23	0.121	0.904
Apo-B (g/L)	1.07 ± 0.24	1.12 ± 0.23	−1.207	0.229
Apo-B/ApoAl ratio	0.73 ± 0.19	0.77 ± 0.22	−1.149	0.252
TC/LDL-C ratio	1.71 ± 0.51	1.82 ± 1.21	−0.834	0.405
TG/LDL-C ratio	0.56 ± 1.11	0.93 ± 4.45	−0.741	0.459
HDL-C/LDL-C ratio	0.47 ± 0.36	0.46 ± 0.20	0.275	0.783
BMI	24.5 ± 2.86	24.0 ± 2.71	1.315	0.190

Abbreviations: ApoA1, apolipoprotein A1; ApoB, apolipoprotein B; HDL-C, high-density lipoprotein-cholesterol; LDL-C, low-density lipoprotein-cholesterol; TC, total cholesterol; TG, triglycerides.

Analysis of independent risk factors for pterygium

The findings of multivariate logistic regression analysis of BMI, serum lipids and their derivative indexes (TG, TC, HDL, LDL-C, ApoA1, Apo-B, Apo-B/ApoAl ratio, TC/LDL-C ratio, TG/LDL-C ratio, HDL-C/LDL-C), revealed that obesity (OR = 2.615), TC (OR = 50.047) and HDL-C/LDL-C ratio (OR = 27.04) were independent risk factors for the onset of pterygium (p < .05) (Table 7).

TABLE 7 Multivariate regression logistic analysis of BMI, serum lipid profile molecules and their derivative indexes

Parameters	B	Standard error	Wald	p Value	OR	95% CI
Sex	0.112	0.351	0.101	0.750	1.118	0.562–2.227
Age	−0.005	0.020	0.057	0.811	0.995	0.956–1.036
TC	3.913	1.317	8.829	0.003	50.047	3.788–661.189
TG	−0.822	0.817	1.014	0.314	0.439	0.089–2.178
HDL-C	−3.577	2.128	2.827	0.093	0.028	0.000–1.809
LDL-C	−3.093	1.373	5.070	0.024	0.045	0.003–0.670
ApoAl	−0.421	1.298	0.105	0.746	0.656	0.052–8.351
Apo-B	−1.494	1.285	1.353	0.245	0.224	0.018–2.783
TC/LDL-C ratio	−14.520	5.347	7.373	0.007	0.000	0.000–0.018
TG/LDL-C ratio	4.266	3.468	1.513	0.219	71.201	0.080–637.435
HDL-C/LDL-C ratio	14.818	6.719	4.864	0.027	27.040	5.200–142.180
Overweight group	0.596	0.317	3.546	0.060	1.815	0.976–3.377
Obesity group	0.961	0.487	3.902	0.048	2.615	1.000–6.778

Abbreviations: ApoA1, apolipoprotein A1; ApoB, apolipoprotein B; HDL-C, high-density lipoprotein-cholesterol; LDL-C, low-density lipoprotein-cholesterol; TC, total cholesterol; TG, triglycerides.

DISCUSSION

This is the study investigating the association between obesity, serum lipids, serum lipids derivative indexes and pterygium. In the present study, comprehensively analyzed the role of BMI, serum lipids and the ratio of serum lipids in the pterygium, and found that high BMI and dyslipidemia were positively associated with the risk of pterygium. Study finding that TC, TG, LDL-C, and Apo-B levels of the patient group were higher than those of the control group, and the difference was statistically significant, indicated dyslipidemia was underlying related to the pathogenesis process of pterygium. Consistent with the previous study, which reported by H Cajucom-Uy et al. indicated that the pterygium is correlated with serum triglyceride levels, especially in severe pterygium, the serum triglyceride level is higher in the non-fasting state.¹⁶ However, there was no statistical difference in serum HDL and ApoA1.

Obesity measured by standard systemic examination included height (cm) and weight (kg), is a prominent cause of many diseases.^17–19 The correlation between obesity or serum lipid levels and pterygium has rarely been reported. In a cross-sectional study in South Korea, it was found that the prevalence of pterygium only increased with the increase of BMI in women, and there was no obvious association between obesity and pterygium in men.²⁰ Our study also found that the BMI of patient group was much higher than the control group, which indicated that the overweight and obesity were related to the occurrence of pterygium. Interestingly, there was no significant association between BMI and pterygium among females.

The multiple regression logistic analysis found that overweight, obesity and dyslipidemia were independent risk factors for the abnormal proliferative process of pterygium, which was consistent with the results of previous study. This study also analyzed the relationship between multiple ratios of serum lipids and pterygium disease. The previous studies have shown that the ratio of serum lipids has clinical significance in cardiovascular and cerebrovascular diseases, diabetes and other diseases.^21,22 Despite the single index of serum lipids is normal, but in fact the serum lipid ratio has changed already. Serum lipid ratios maybe reflect disease conditions earlier than a single serum lipid indexes.²¹ Dong Shiqi et al. found that the TG/HDL ratio, TC/HDL ratio, LDL/HDL ratio were critical factors in the development of pterygium.²² For the first time, this study comprehensively analyzed the relationship between various serum lipid ratios and pterygium, and found that the HDL-C/LDL-C ratio was an significant risk factor for the process of pterygium, and explored more potentially significant serum lipid indexes for the pterygium.

Obesity and dyslipidemia are involved in the pathogenesis of pterygium is unclear. Previous studies have suggested that obesity and dyslipidemia can induce systemic oxidative stress, which causes the complications.²³ Oxidative stress was considered to be an important pathogenic factor for many chronic diseases, including many diseases of the eye.²⁴ Emine et al. proposed that increased systemic oxidative stress may be a susceptible factor for the development of pterygium.²⁵ To the best of our knowledge, ultraviolet (UV) light damage is the most important risk factor for pterygium. UV can cause more reactive oxygen species to be produced, leading to lipid peroxidation, which turns lipid molecules in cell membranes into lipid peroxides, causing oxidative stress in the body. Lead to tissue damage, which indicates that oxidative stress is related to lipid peroxidation, and lipid peroxide levels are significantly related to serum cholesterol and triglycerides.²⁶ Obesity leads to increased ROS, increased expression of NADPH oxidase, and oxidative stress.²³ Therefore, oxidative stress is correlated with obesity and serum lipid levels. In this study, we suggested that TG, TC, LDL-C and Apo-B, which related to oxidative stress, were significantly higher in patients with pterygium. Our findings also shown that obesity and dyslipidemia were closely related to pterygium and were independent risk factors for the development of pterygium. These results indicate that obesity and dyslipidemia are likely to develop in primary pterygium through oxidative stress which play a primary role in the pathogenesis of pterygium. At the same time, there is evidence that pterygium has the histological characteristics of tumors.²⁷ The important feature of tumor tissue is that the normal cell out of control leads to excessive cell proliferation and the formation of tumor cells. Since cholesterol which required by the cell proliferation process is the main component of cell membranes,^28,29 indicates that cholesterol was inseparable from cell proliferation in the progress of pterygium.

In summary, this study found that overweight, obesity and dyslipidemia which related oxidative stress may play an important role in the occurrence and development of primary pterygium, and they are independent risk factors for the development of pterygium. The individual serum lipids indexes and serum lipid ratios can indicate the occurrence and progress of pterygium, and promptly intervention in weight and dyslipidemia can prevent the occurrence of pterygium or inhibit the progress of pterygium. The results of serum lipid profile molecules and their derivative indexes can be obtained only through simple inspection methods, which have the advantages of convenient, fast, easy to repeat, and low price. The changes of these indicators maybe reflect the progress of pterygium, which can be used as a beneficial supplement for the occurrence and progression of pterygium is worthy of clinical promotion. Obesity, pterygium, sex differences, and oxidative stress all have interrelationships that need to be investigated further in prospective investigations.

AUTHOR CONTRIBUTIONS

Yu-ying Sun, Wei-peng Liang, and Yu-ying Liu participated in the whole study design. The manuscript was drafted by Yu-ying Sun and revised by Wei-peng Liang. All the authors read and approved the final manuscript.

ACKNOWLEDGMENTS

This work was supported by Medical Scientific Research Foundation of Guangdong Province [grant number A202136911]; Guangdong Esophageal Cancer Institute Science and Technology Program [grant number M202013].

CONFLICT OF INTEREST STATEMENT

The authors declare no conflict of interest.

ETHICS STATEMENT

The study protocol was approved by the ethics review committees of all participating institutions.