Blepharoptosis among Korean adults: age-related prevalence and threshold age for evaluation

This study used data from the Korean National Health and Nutrition Examination Survey (KNHANES-V), which was performed in 2010–2012 by the Korean Centers for Disease Control and Prevention and the Korean Ministry of Health and Welfare, Sejong, Republic of Korea. A total of 25,534 individuals in KNHANES-V were identified as candidates for this study. Participants aged less than 19 years (n = 5935) were excluded, as were adults with a previous history of eyelid or intraocular surgery, or with a medical condition that might affect the position of the eyelid or motility, including thyroid disease, systemic collagen disease, myopathy, cerebrovascular and cardiovascular disease (n = 1721). Non-operated adult patients with congenital blepharoptosis were included in this study. In total, 17,878 adults were included in the final analyses. All participants provided written consent forms prior to enrollment. The Institutional Review Board of the Korea Centers for Disease Control and Prevention (KCDC) reviewed and approved this nationally representative data study.

Trained interviewers from the KNHANES-Vadministered standardized health examinations and questionnaires. Current smokers were defined as participants who currently smoked and had smoked more than 100 cigarettes in their lifetime. Participants were also categorized based on the quantity of alcohol consumed per day for the month prior to the interview; participants were considered heavy drinkers if they had consumed more than 30 g per day. Participants who performed moderate exercise at least five times per week for 30 min or more per session, or who performed vigorous exercise at least three times per week for 20 min or more per session, were considered regular exercisers. The educational level was classified as high if the respondent had completed a high school education. A monthly household income of less than 1092.40 United Sates dollars (USD) corresponded to the lowest income quartile.

Anthropometric measurements were performed by specially trained examiners. Body weight and height, measured with participants barefoot and wearing light clothing, were used to calculate the body mass index (BMI). Waist circumference (WC) was estimated to the nearest 0.1 cm in a horizontal plane at the midpoint from the iliac crest to the costal margin at the end of a normal expiration. Blood pressure was checked every 8 h via the right arm while the participant was in a sitting position, after about 5 min of relaxation, by a mercury sphygmomanometer (Baumanometer; Baum, Copiague, NY, USA). The definitive blood pressure was determined using mean values of the second and third measurements. A participant was classified as hypertensive if the systolic blood pressure was more than 140 mmHg or the diastolic blood pressure was more than 90 mmHg, or if the participant had been diagnosed with high blood pressure and was taking high blood pressure medication. The percent body fat (fat mass/total mass × 100, %) and sum of the lean soft tissue mass of the arms and legs were obtainedby dual-energy X-ray absorptiometry (DXA, QDR 4500 A; Hologic, Waltham, MA, USA) at mobile examination centers.

The eyelid positions of all participants were examined by specially trained opticians who were resident physicians. The qualitycontrol of the ophthalmic survey was performed by the Epidemiologic Survey Committee of the Korean Ophthalmologic Society. Marginal reflex distance 1 (MRD1) was defined as the distance from the upper eyelid margin to the corneal light reflex in the primary position [13, 14]. The ophthalmic resident physicians with over 3 years of experience participated in this survey by directly measuring with a ruler. A differential diagnosis of blepharoptosis was made with particular attention paid to pseudoptosis associated with eyebrow ptosis and dermatochalasis. MRD1 values were obtained and sorted into five subclassifications: (1) ≥ 4.0 mm, (2) 3.0–3.9 mm, (3) 2.0–2.9 mm, (4) 1.0–1.9 mm, and (5) <  1.0 mm. Before data analyses, we defined blepharoptosis as an MRD1 of less than 2 mm for either eye. The levator function test (LFT) was also evaluated by measuring the upper eyelid excursion from downgaze to upgaze, excluding any influence of frontalis muscle function, and sorted into four subclassifications: (1) ≥ 12 mm, (2) 8–11 mm, (3) 5–7 mm, and (4) <  4 mm.

Statistical analyses were conducted using the survey procedure of SAS Windows software (version 9.3; SAS Institute, Cary, NC, USA) to account for the complex sampling design from the KNHANES, which supplies nationally representative blepharoptosis prevalence estimated values. A two-sided P value less than 0.05 was considered statistically important. Fundamental characteristics of participants with and without blepharoptosis were expressed as proportions (% standard error, SE) for categorical variables and as means ± SE for continuous variables. The chi-square test or independent two-sample t-test was performed to compare differences in participant characteristics with or without the presence of blepharoptosis. The cutoff age in the prediction of blepharoptosis was defined as the point of largest statistical value by the Rao-Scott chi-square test.

The baseline characteristics of the study participants are presented in Table 1. The cross-sectional analyses included data on 17,878 adults (15,178 participants without blepharoptosis and 2160 participants with blepharoptosis). Among the eligible participants, the incidence of blepharoptosis was 12.08%. Table 1 shows the results of univariate analyses of the associations between blepharoptosis and demographic characteristics, lifestyle and medical factors, and obesity parameters. Based on univariate analyses, factors associated with the composite outcome of blepharoptosis were less drinking, less exercise, less income, less education, more metabolic syndromes, more hypertension, more severe diabetes, more cataracts, less employment, higher age, a higher BMI, and a greater WC. After adjusting for confounders, age, and obesity parameters including BMI and WC were closely related with blepharoptosis.

Table 2 shows the mean MRD1 (mm) and mean levator function test (LFT, mm) results for both eyes and for all age groups, as well as the blepharoptosis prevalence (%) according to age group. Both mean the MRD1 and mean LFT decreased, while blepharoptosis prevalence (%) increased, with increasing age. These relationships were especially apparent in the group over 60 years of age. Figure 1 shows the prevalence (%) of blepharoptosis for male, female, and all participants according to age group. Generally, blepharoptosis prevalence increased with increasing age, and increased more rapidly between the 50–59 and 60–69 years of age groups, and between the 60–69 and 70–79 years of age male, female, and total participants, because the slope of line was steeper in these sections compared to the other sections.

Figure 2 shows blepharoptosis prevalence (%) according to age and obesity parameters, including BMI and abdominal obesity (WC). The blepharoptosis prevalence was higher among participants with a BMI more than and equal to 25 versus those with a BMI less than 25. Blepharoptosis prevalence was also higher in the participants with a WC more than and equal to 90 cm (males) and more than equal to 80 cm (females) versus those with a WC less than 90 cm (males) and less than 80 cm (females). Figure 3 shows the association between blepharoptosis and BMI according to age group. In the 50–59 and 60–69 years age groups, blepharoptosis incidence was higher, and the participants had higher BMI scores. The association between blepharoptosis incidence and obesity severity in these groups was stronger than that in the other groups. However, in the 70–79 and 80–89 years age groups, extremely obese participants (BMI more than 30) showed a sudden decrease in the prevalence of blepharoptosis.

Finally, we investigated the cutoff age of for recommending blepharoptosis evaluation. The cutoff age in the prediction of blepharoptosis was defined as the point of largest statistical values using the Rao-Scott chi-square test. Figure 4 shows that the optimal cutoff age was 66 years for all participants, 63 years for males, and 71 years for females.