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Epidemiologic study of age-related cataracts among an elderly chinese population in Shih-Pai, Taiwan
Epidemiologic Study of Age-related Cataracts Among an Elderly Chinese Population in Shih-Pai, Taiwan Su-Ying Tsai, BS,1 Wen-Ming Hsu, MD,2 Ching-Yu Cheng, MD, MPH,2 Jorn-Hon Liu, MD,2 Pesus Chou, DrPH1 Purpose: The purpose of this study was to determine the prevalence and risk factors for age-related cataracts in a metropolitan elderly Chinese population in Shihpai, Taipei, Taiwan. Design: Population-based cross-sectional study. Participants: A total of 2045 subjects at least 65 years of age were invited to participate, and 1361 (66.6%) participated in the survey. Methods: An eye examination, including lens opacity grading, was conducted by ophthalmologists using the Lens Opacity Classification System III (LOCS III). A structured questionnaire was used for data collection. Interviewers also collected information on subjects’ blood pressure, lifestyle (cigarette smoking and alcohol intake), medical history, and waist and hip circumferences. Main Outcome Measures: Subjects were defined as having age-related cataracts if there was any type of lens opacity with an LOCS III grade of more than 2 in one or both eyes. When both eyes of an individual had age-related cataracts, the more affected eye was used for analysis. Results: Among the 1361 participants, 806 were diagnosed with age-related cataracts. The prevalence was 59.2% (95% confidence interval, 56.6%– 61.8%). Women had a higher prevalence of cataracts than men (64.0% vs. 56.1%, P ⫽ 0.004). The prevalence of age-related cataracts increased with age (P ⫽ 0.001). Nuclear opacity was the most prevalent type (38.9%), followed by cortical opacity (21.9%) and posterior subcapsular opacity (9.2%). On the basis of the final logistic regression model, after controlling for all other covariates, increased age and female gender were factors that were associated with an increased risk for all types of cataracts. Besides age and gender, the most significant risk factor for nuclear cataracts was current cigarette smoking; the significant predictors for cortical cataracts were higher systolic blood pressure, a history of cigarette smoking in the past, and history of diabetes; the significant predictor for posterior subcapsular cataracts was higher systolic blood pressure. Conclusions: The increasing prevalence of age-related cataracts with age highlights the need to seek appropriate medical services and for preventative interventions. Elderly people often ignore the importance of seeking vision services and care to prevent blindness or visual impairment. These findings suggest that the elderly need to be educated regarding the importance of eye care by physicians and hygiene authorities in Taiwan. Ophthalmology 2003;110:1089 –1095 © 2003 by the American Academy of Ophthalmology.
Age-related cataracts are the main cause of blindness throughout the world.1 Because of the success of modern surgical intervention, cataract extraction surgery is the most Originally received: April 16, 2001. Accepted: October 29, 2002. Manuscript no. 210259. 1 Community Medicine Research Center and Institute of Public Health, National Yang-Ming University, Taipei, Taiwan. 2 Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan. Presented in part at the 18th Congress of the Asia-Pacific Academy of Ophthalmology, March 2001, Taipei, Taiwan. Supported by a grant from Taipei Veterans General Hospital (VGH89-4041), Taipei, Taiwan. The authors have no proprietary interest in any aspect of the study. Reprint requests to Pesus Chou, DrPH, Institute of Public Health, National Yang-Ming University, Shih-Pai, Taipei 112, Taiwan. © 2003 by the American Academy of Ophthalmology Published by Elsevier Inc.
commonly performed ophthalmic procedure in eye health care services.2 The importance of early detection and early treatment and identification of risk factors for age-related cataracts is evident. Although age-related cataracts are not fatal, cataracts have a negative impact on daily and social activities3 and the quality of life of the elderly.4 Moreover, lens opacities lead directly to visual impairment and loss of vision.1 Loss of vision is associated with a reduced quality of life5 and functional status,6 predisposition to falls and hip fractures,7 and clinical depression.8 Advanced age is the most reliable independent risk factor for the occurrence of lens opacities, but the role of other possible contributing or inhibiting factors is not clear.9 There were few data on the epidemiology of age-related cataract in the Asian population. The purpose of this study was to determine the prevalence of age-related cataracts in a metropolitan elderly Chinese population in Shihpai, TaiISSN 0161-6420/03/$–see front matter doi:10.1016/S0161-6420(03)00243-4
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Ophthalmology Volume 110, Number 6, June 2003 pei, Taiwan, and to identify factors associated with agerelated cataracts, including demographic variables, lifestyle, medical history, and waist-to-hip ratio.
Material and Methods Selection of Subjects A population-based survey on eye diseases among subjects 65 years of age and older in Shihpai, Taipei, Taiwan, was conducted between July 1, 1999, and December 31, 2000. The Shihpai community is located in the Peitou district, Taipei. The Peitou district has a population of approximately 247,100 and a land area of approximately 56.8 km2, making it the second largest district in Taipei City. The Shihpai community is the Peitou district’s prosperous commercial hub. The study hospital, one of the largest medical centers in Taiwan, has the most complete equipment and provides advisory medical services. Shihpai was chosen as the study community after taking population stability, metropolitan area, and local support into consideration. Residents 65 years of age and older were identified by the household registration system. The household registration system in Taiwan is designed to collate and supply demographic information and to officially recognize personal status and relations. These household registration data are provided as a reference for the government to effect administrative and socioeconomic development programs and to assist scholars in academic research. According to the official household registration in 1999, the total number of residents at least 65 years of age in Shihpai was 4750. Excluding vacant households (658 persons), residents who died before they were interviewed (48 persons), and inpatient, paralyzed, and disabled (298 persons), 3746 residents were eligible for the study. Residents (n ⫽ 2045) were randomly selected from the eligible subjects and were invited to participate in the study. A structured questionnaire was used to obtain information based on demographic data (age, gender, locality, marital status, and education), personal medical history, and lifestyle (smoking and alcohol intake). Participants’ self-reported demographic data were assessed. Level of education was used as a proxy measure for social class (no school or primary school without diploma, primary school with diploma, secondary school, higher education, and higher education or above) and was categorized as follows: (1) no school or primary school without diploma; (2) primary school with diploma or secondary school or higher education; (3) higher education or above. Subjects were asked about martial status (married and living with spouse, cohabiting, divorced, separated, widowed, and not married), and marital status was simply categorized as the experience of marriage (including married and living with spouse, cohabiting, divorced/separated, and widowed) and no marriagelike experience in this analysis. Personal medical history was investigated by means of a checklist. The participants were asked whether they had been diagnosed with a chronic disease such as diabetes (yes/no) by a physician. Cigarette smoking history and alcohol intake were used as indices of lifestyle. The participants were asked questions about their cigarette smoking history (smoker, ex-smoker, and never-smoker); alcohol intake was limited to wine and hard alcohol and was categorized as no habit of alcohol consumption (or frequency of alcohol consumption was only once a week) and a habit of alcohol consumption (frequency of alcohol consumption was more than once a week). The women were also asked whether they ever used estrogen replacement therapy or other hormones (yes/no). Before data collection, the interviewers were intensively trained to conduct a household interview based on the structured questionnaire and to measure blood pressure, weight, height, and
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waist and hip circumferences. Three consecutive seated blood pressure readings, at least 5 minutes apart, were taken from the right arm and averaged. Waist girth was measured at the minimum circumference, whereas hip girth was measured at the maximum circumference. The definition of obesity was follows. Regional or central obesity by waist-to-hip ratio (WHR) was a WHR greater than 0.92 for men or greater than 0.88 for women.10 Those who were interviewed were invited to the Taipei Veterans General Hospital for an eye examination, including bestcorrected visual acuity, tonometry, slit-lamp biomicroscopy, and ophthalmoscopy. Ophthalmologists conducted the eye examination by according to a standardized protocol. This study was approved by the Institutional Review Board of the Taipei Veterans General Hospital (VGHIRB No.: 89-11-01A).
Definitions The study aimed at estimating the prevalence of age-related cataracts. Subjects with congenital or traumatic cataracts in one eye were excluded from this analysis, and the condition of the other eye was recorded in the survey. Three major types of age-related cataracts (nuclear, cortical, and posterior subcapsular) were assessed by use of the Lens Opacity Classification System III (LOCS III)11,12 by senior ophthalmologists. Subjects were categorized as having an age-related cataract if any type of opacity with an LOCS III grade of greater than 2 was present in one or both eyes. We chose the grade of greater than 2 as the cutoff, because this grade in the LOCS III is close to a grade of 2 or greater in the LOCS II, which is the definition of cataracts adopted by previous major population-based studies.13 When both eyes of a subject had age-related cataracts, the more affected eye was analyzed. Subjects with previous cataract surgery performed after they were 50 years of age were included for prevalence estimation and identification of risk factors if they had no history of ocular trauma and the onset of poor vision was after adulthood.
Pilot Study A pilot study was performed approximately 1 month before the beginning of the main fieldwork to provide a field test of lens grading procedures. For convenience, the pilot study was performed on 78 eyes from 78 subjects other than the study subjects. Interobserver reproducibility of lens grading (grade ⬎2 versus grade ⱕ2) between two study ophthalmologists was assessed using statistics. For cataract diagnosis, agreement was high with a statistic of 0.86 for cortical opacity (51 of 78 eyes rated as not having opacity by both observers) and 0.82 for posterior subcapsular opacity (63 of 78 eyes rated as not having opacity by both observers). The statistic for interobserver reproducibility was 0.85 for nuclear opacity (35 of 78 eyes rated as not having opacity by both observers). Intraobserver statistics for reproducibility of grading cataracts (grade ⬎2 vs. grade ⱕ2) were 0.83 (58 of 78 eyes rated as not having cortical opacity), 0.80 (66 of 78 eyes rated as not having posterior subcapsular opacity), and 0.86 for (47 of 78 eyes rated as not having nuclear opacity) for one ophthalmologist. ⌲ statistics were 0.87 (cortical opacity), 0.85 (posterior subcapsular opacity), and 0.84 (nuclear opacity) for the other ophthalmologist for agreement on reproducibility of grading cataracts.
Statistical Analysis Dependent variables in the analysis were the three types of cataracts versus nonadvanced lens opacity to an LOCS III grade of 2 or more. The independent variables tested were gender (female vs. male), age (ⱖ75 years vs. 65–74 years), WHR (high: WHR ⱖ 0.92
Tsai et al 䡠 Age-related Cataracts in Taiwan Table 1. Prevalence of Age-related Cataracts by Age and Gender in Shihpai, Taipei, Taiwan, 1999 –2000 Male
Female
Cataract Age (yrs)
Examined No.
Without Surgery No.
65–69 70–74 75–79 80⫹ Total
283 314 150 75 822
113 134 80 42 369
Total
Cataract
With Without With Surgery Total PrevaExam- Surgery Surgery Total No. No. lence (%) ined No. No. No. No. 20 31 23 18 92
133 165 103 60 461
47.0 52.6 68.7 80.0 56.1
198 178 118 45 539
86 99 58 19 262
for males; WHR ⱖ 0.88 for females vs. normal: WHR ⬍ 0.92 for males; WHR ⬍ 0.88 for females), cigarette smoking (current smoking vs. nonsmoking; ex-smoking vs. nonsmoking), alcohol intake (yes vs. no), systolic blood pressure (SBP ⱖ 160 mmHg vs. SBP ⬍ 160 mmHg), and history of diabetes (yes vs. no). For statistical analyses, 2 tests were performed to test for an association between each independent variable and dependent variable for univariate analysis. A P value of less than 0.05 was considered to be statistically significant. Multiple logistic regression analyses were used to fit the best model for independent variables and their interactions. Statistical analysis was performed by use of the Statistical Analysis System (SAS 6.12; SAS Institute, Cary, NC) software.
Results Of the 2045 subjects, 1361 (66.6%) participated in the study and received both the questionnaire and eye examination. Of the 684 nonexamined subjects, 677 (33.1%) subjects cooperated only for the household interview, and 7 (0.03%) subjects could not be contacted during three visits for the household interview. The main reasons for nonexamination were refusal to participate, lack of time, or inability to contact the subjects. Consequently, the analysis of this study was based on the data gathered from the 1361 participating subjects. A comparison of demographic information and some of the variables in the subjects with and without the eye examination revealed that the participating subjects were younger than those who refused (72.2 years vs. 74.3 years, P ⬍ 0.001); they were also more likely to be male (P ⫽ 0.001), with a higher level of education (P ⫽ 0.001) than those who refused. There was no significant difference in the other variables (cigarette smoking, alcohol intake, history of diabetes, and hypertension) between the two groups. A total of 806 subjects were diagnosed with age-related cataracts as listed in Table 1. The overall prevalence was 59.2% with a 95% confidence interval (CI; 56.6%– 61.8%). The higher prevalence in women was statistically significant (64% vs. 56.1%, P ⫽ 0.004). The prevalence of cataracts increased with age (P ⫽ 0.001). The rate for age-related cataracts increased rapidly from 57.1% for ages 70 to 74 years to 72.8% for ages 75 to 79 years. Among the 175 participants who had cataract surgery before the survey, there were more women than men (15.4% vs. 11.2%; P ⫽ 0.025). The rate of cataract surgery significantly increased with age (2 test for trend; 2 ⫽ 8.116, P ⫽ 0.001) but did not differ between education level and marriage status. The subjects who had prior surgery were significantly older than the subjects who had no prior surgery (75.6 years vs. 72.3 years, P ⫽ 0.002). The age-specific prevalence of the three types of cataracts are shown in Table 2. Nuclear cataracts were the most prevalent type
12 17 34 20 83
98 116 92 39 345
Cataract Prevalence (%)
Examined No.
Without Surgery No.
49.5 65.2 77.9 86.7 64.0
481 492 268 120 1361
199 233 138 61 631
With Surgery Total PrevaNo. No. lence (%) 32 48 57 38 175
231 281 195 99 806
48.0 57.1 72.8 82.5 59.2
(38.9%), followed by cortical cataracts (21.9%) and posterior subcapsular cataracts (9.2%). Of the 631 subjects with cataracts shown in Table 1 (without surgery), subjects with nuclear, cortical, posterior subcapsular cataracts, and mixed cataracts are shown in Figure 1. Separate univariate analyses of nuclear, cortical, and posterior subcapsular cataracts were performed, and their odds ratios (OR) and 95% CI are shown in Table 3. Stratified by age (ⱖ 75 and ⬍75), there was only one significant interaction. Age and gender had a significant interaction effect on posterior subcapsular cataracts. The interaction (age– gender) effect on nuclear cataracts and cortical cataracts was not significant. Because the interaction term was significant, stratified analysis by age older than 75 was examined to explore the relationship between gender and posterior subcapsular cataracts in multivariate analyses as shown in Table 4. For those 75 years of age or older, women had a 2.4-fold higher rate (95% CI, 1.1–2.9) of posterior subcapsular cataracts. There were no significant differences between gender and posterior subcapsular cataracts, however, for those 65 to 74 years old. The results of three separate multivariate logistic regression analyses after controlling for all covariates and considering the interaction assessment are presented in Table 4. Older age and female gender were factors associated with an increased risk for all types of cataracts. Besides age and gender, the significant risk factor for nuclear cataracts was current smoking (OR ⫽ 1.6; 95% CI ⫽ 1.1–2.2); significant predictors for cortical cataracts were higher SBP (OR ⫽ 1.5; 95% CI ⫽ 1.1–2.1), history of cigarette smoking (OR ⫽ 1.4; 95% CI ⫽ 1.1–2.0), and history of diabetes (OR ⫽ 1.4; 95% C I⫽ 1.1–1.9); higher SBP (OR ⫽ 1.5; 95% CI ⫽ 1.1–2.3) was also significantly related to posterior subcapsular cataracts. We examined the relationship between history of hormone use and the three types of cataracts, using multivariate logistic regression among women (data not shown). After controlling for all covariates, a history of hormone use was associated with a decreased risk of nuclear cataracts (OR ⫽ 0.59; 95% CI ⫽ 0.38 – 0.93). A history of hormone use among women was not significantly associated with cortical cataracts and posterior subcapsular cataracts using a multivariate logistic regression.
Discussion The National Health Insurance Program in Taiwan was implemented in 1994. Lack of utilization of ophthalmologic care for prevention and treatment, however, has created the impression that loss of vision is expected in senior life and the idea that nothing can be done to improve the situation among elderly people,14 particularly in less-educated elderly people.15 This could be an explanation for the 66.6%
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Ophthalmology Volume 110, Number 6, June 2003 Table 2. Prevalence of Age-related Cataracts by Age and Gender in Shihpai, Taipei, Taiwan, 1999 –2000 2 Test
Cataract (without Surgery)
Cataract
No.
Male
Female
Total
Prevalence
Prevalence
Prevalence
(%)
No.
(%)
No.
(%)
Nuclear opacity Age 65–69 70–74 75–79 80⫹ Total Cortical opacity Age 65–69 70–74 75–79 80⫹ Total Posterior subcapsular opacity Age 65–69 70–74 75–79 80⫹ Total
88 108 68 36 300
45 57 41 16 159
12 28 16 7 63
31.1 34.4 45.3 48.0 36.5
15.9 18.2 27.3 21.3 19.3
4.2 8.9 10.7 9.3 7.7
72 87 53 18 230
48 53 27 11 139
19 20 18 5 62
36.4 48.9 44.9 40.0 42.7
24.2 29.8 22.9 24.4 25.8
9.6 11.2 15.3 11.1 11.5
response rate. In our survey, the unexamined subjects were more likely to be female and illiterate, those with a higher risk. Therefore, the unexamined subjects remain a potential source of bias in our estimates. Nevertheless, in this study we observed a high prevalence of age-related cataracts (59.2%) among the elderly in Taiwan, particularly of the nuclear type, and the prevalence increased with age and was higher among women than men in the older age group. Of 1361 participants, 175 (12.9%) had previous cataract surgery. The rate of surgery increased
Figure 1. Venn diagram for 631 subjects (without surgery) with nuclear, cortical, posterior subcapsular cataracts, and mixed cataracts.
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160 195 121 54 530
93 110 68 27 298
31 48 34 12 125
Gender Difference
Age Difference
P ⫽ 0.022
2 (trend) ⫽ 3.422 P ⫽ 0.001
P ⫽ 0.005
2 (trend) ⫽ 1.593 P ⫽ 0.056
P ⫽ 0.016
2 (trend) ⫽ 2.422 P ⫽ 0.008
33.3 39.6 45.1 45.0 38.9
19.3 22.4 25.4 22.5 21.9
6.4 9.8 12.7 10.0 9.2
significantly with age but did not differ with respect to education level or marriage status. All participants who had undergone surgery were asked when they had surgery for cataracts (1994 or before vs. after 1994), and only 33.1% (58 of 175) were operated on before the National Health Insurance Program was implemented in 1994, whereas most of the subjects (approximately 66.9%; 117 of 175) had surgery after implementation of the National Health Insurance Program. In fact, among a generally old and retired population, cost might be an impetus to use the health services, because free-of-charge surgery was not available before 1994. Relative to other deadly and/or chronic diseases, the elderly population ignored eye treatment and improvement of vision. Although the surgery rate was relatively higher than the 1994 levels because of the initiation of the Nation Health Insurance Program, increased attention to the treatment of tractable vision disease to prevent blindness is still an important public health task in Taiwan. Although there was a low percentage (12.9%) of cataract surgery in the elderly in our study, the Salisbury Eye Evaluation (SEE) project revealed a similarly low percentage in black and white elderly16 (Table 5). Table 2 shows the prevalence of three types of cataracts, excluding subjects with prior cataract surgery. Among the 175 participants who have had cataract surgery before the survey, there were more women than men (83 of 539 ⫽ 15.4% vs. 92 of 822 ⫽ 11.2%; P ⫽ 0.025). The rate of cataract surgery significantly increased with age (P ⫽ 0.001), and the rate for cataract surgery among women was 6% of those aged 65 to 69 years, 9.6% of those aged 70 to
Tsai et al 䡠 Age-related Cataracts in Taiwan Table 3. Univariate Analysis on Age-related Cataracts among Residents 65 of Age and Older in Shihpai, Taipei, Taiwan, 1999 –2000 Type of Cataract Nuclear Variable Gender Female vs. male Age (yrs) ⱖ 75 vs. 65–74 Waist-to-hip ratio* High vs. normal Systolic blood pressure SBP ⱖ 160 mmHg vs. SBP ⬍ 160 mmHg Smoking Current smoking vs. nonsmoking Ex-smoking vs. nonsmoking Alcohol Yes vs. no History of diabetes Yes vs. no History of hormone use among women Yes vs. no
Cortical
Posterior Subcapsular
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
1.6
1.3–2.0
1.6
1.2–2.0
1.5
1.2–2.0
2.8
2.2–3.6
2.4
1.9–3.0
3.0
2.3–3.9
1.1
0.9–1.4
1.2
0.9–1.5
1.1
0.8–1.4
1.2
0.8–1.7
1.7
1.2–2.4
1.8
1.2–2.6
1.2 0.9
0.9–1.6 0.7–1.2
0.9 1.1
0.7–1.3 0.8–1.5
0.8 1.1
0.5–1.1 0.8–1.6
0.9
0.7–1.2
0.8
0.5–1.1
0.8
0.6–1.1
1.2
0.9–1.6
1.5
1.1–2.1
1.4
1.1–2.0
0.6
0.4–0.9
0.8
0.5–1.2
0.7
0.4–1.1
*High waist-to-hip ratio group: (male) waist-to-hip ratio ⱖ 0.92; (female) waist-to-hip ratio ⱖ 0.88. SBP ⫽ systolic blood pressure.
75 years, 28.8% of those aged 75 to 79 years, and 44.4% of people aged 85 years or older. Information about the type of cataract for those having had prior surgery was unavailable. One possible reason why the prevalence of nuclear or cortical cataract in women is unsteady could be that there was a relatively higher rate of cataract surgery in the latter two groups (ages 80⫹ years and ages 75–79 years). Although variable, age-related increase in prevalence of nuclear or cortical cataract for women and the total prevalence of cataracts among women on Table 1 (including those with
prior cataract surgery) showed a steady, age-related increase. A comparison of the prevalence rates with those from the SEE project16 for each type of cataract is shown in Table 5. The SEE project16 included two racial groups (blacks and whites) and determined the prevalence of cataracts in each. The SEE project reported that nuclear cataract and posterior subcapsular cataracts were lower among blacks than among whites; however, cortical opacity was higher among blacks than among whites. Further comparison with three races
Table 4. Logistic Regression Analysis on Age-related Cataracts among Residents 65 years of Age and Older in Shihpai, Taipei, Taiwan, 1999 –2000 (n ⫽ 1361) Type of Cataract Nuclear Variable Gender (women vs. men) Age (ⱖ75 vs. 65–74) Waist-to-hip ratio (high vs. normal) Systolic blood pressure (SBP ⱖ 160 mmHg vs. SBP ⬍ 160 mmHg) Cigarette smoking Current smoking vs. nonsmoking Ex-smoking vs. nonsmoking Alcohol (yes vs. no) History of diabetes (yes vs. no) Interaction: age*gender† Age ⱖ 75 year. (women vs. men) Age 65–74 years (women vs. men) †
Cortical
Posterior Subcapsular
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
1.8 2.7 0.9 1.0
1.3–2.3 2.1–3.6 0.7–1.1 0.7–1.5
1.7 2.2 0.9 1.5
1.3–2.3 1.7–2.9 0.7–1.2 1.1–2.1
0.9 1.5
— — 0.6–1.2 1.1–2.3
1.6 1.1 1.0 1.1
1.1–2.2 0.8–1.6 0.7–1.3 0.8–1.5
1.3 1.4 0.8 1.4
0.9–1.9 1.1–2.0 0.6–1.2 1.1–1.9
1.0 1.3 0.8 1.3
0.7–1.6 0.8–2.0 0.5–1.2 0.9–1.8
— —
2.4 1.3
1.1–2.9 0.6–1.8
— —
Interaction term (age*gender) was examined in the logistic regression for the three types of cataracts.
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Ophthalmology Volume 110, Number 6, June 2003 Table 5. Comparison of the Prevalence of Age-related Cataracts among Elderly in Salisbury Eye Evaluation (SEE) Project and Shihpai Study Three types of Cataract Rate %†
Study Shihpai Study Salisbury Eye-Evaluation Project (SEE) Black White
Cortical
Posterior Subcapsular Cataracts
Cataract Surgery rate %
38.9
21.9
9.2
12.9
31.0 46.3
54.5 23.9
2.6 5.4
4.8 12.2
Examined No.
Prevalence %*
Nuclear
1361
59.2
621 1772
68.0 55.1
*Inclusion of cataract surgery data. Exclusion of cataract surgery data.
†
(blacks, whites, and Asians) revealed that whites have a higher rate (46.3%) than blacks and Asians for nuclear cataracts, and blacks have the lowest rate of nuclear cataracts (31.0%). For cortical cataracts, blacks have a significantly higher rate (54.5%) than whites and Asians, and Asians had the lowest rate of cortical cataracts (21.9%). For posterior subcapsular cataracts, Asians had the highest rate (9.2%), and blacks had the lowest rate (2.6%). In Taiwan, common eye medications can be obtained without a prescription. Unfortunately, many elderly people have the erroneous impression that over-the-counter eye medications provide economical protection against age-related cataracts or other ocular diseases. For this reason, the high rate of posterior subcapsular cataracts might be related to high steroid use. Most studies indicate that cataracts are more common in women than in men.2,13,17–21 In our study, women had a higher prevalence than men for all three cataract types. Women using hormones, however, had a lower prevalence of nuclear cataracts as determined by univariate and multivariate analyses in our study. Univariate analysis also indicated a protective effect of hormone replacement therapy against cortical cataracts.22 The Blue Mountains Eye Study23 reported that current users of hormone replacement therapy aged 65 years and older had a lower prevalence of cortical cataracts than did those who never used hormone replacement therapy (OR ⫽ 0.4; 95% CI ⫽ 0.2– 0.8). A protective association between the use of hormone replacement therapy and nuclear and posterior subcapsular cataracts is reported from the SEE.24 The findings of the Beaver Dam Eye Study, however, indicated that there is little evidence of an association between hormone exposure and the incidence of age-related cataracts in women 5 years later.25 The association between cigarette smoking and age-related cataracts was investigated in several studies.26 –30 A prospective study29 reported that cigarette smoking increases the risk of developing both nuclear and posterior subcapsular cataracts. A study in Maryland30 reported that the risk of nuclear cataracts increased with increasing cigarette use and decreased if the subject had quit smoking. The Blue Mountains Eye Study28 also reported that people who smoked cigarettes had a higher prevalence than nonsmokers of more severe nuclear (OR ⫽ 1.3; 95% CI ⫽ 1.1–1.6) and posterior subcapsular (OR ⫽ 1.5; 95% CI ⫽
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1.1–2.1) cataracts. Multivariate analyses revealed a significantly increased risk between current cigarette smoking and nuclear cataracts (OR ⫽ 1.6; 95% CI ⫽ 1.1–2.2). Even ex-smokers had 1.4 times the risk for cortical cataracts compared with people who never smoked. Thus, these results support a role for cigarette smoking as a risk factor for cataracts. Multivariate analyses revealed an association between blood pressure and age-related cataracts in our study. Blood pressure and hypertension with age-related cataracts, however, were equivocal factors in previous studies.9,19,22,29,31,32 Some studies9,19,29,31 reported an association between hypertension (or blood pressure) and agerelated cataracts, but other studies22,32 did not. We found a significantly increased risk between high SBP and cortical and posterior subcapsular cataracts. Further etiologic studies are needed to clarify the relation between blood pressure and age-related cataracts. There is a consistent positive association between diabetes and age-related cataracts in epidemiologic studies, and diabetes is associated with cortical cataracts.2,19,33–35 Similar findings from our study indicated that diabetic individuals are 1.4 times more likely to have cortical opacity. In summary, the findings of this study indicate a high prevalence of age-related cataracts among the Chinese elderly in Taiwan. As noted earlier, elderly people tend to believe that visual loss is expected in senior life and often ignore the importance of seeking vision services and care to prevent blindness or impairment. These findings suggest that the elderly need to be educated regarding the importance of eye care by physicians and hygiene authorities. For a more meaningful comparison of age-related cataract rates in different populations, future surveys should use comparable diagnostic criteria or classifications.
References 1. Thylefors B. The World Health Organization’s programme for the prevention of blindness. Int Ophthalmol 1990;14:211–9. 2. Cheng CY, Liu JH, Chen SJ, Lee FL. Population-based study on prevalence and risk factor of age-related cataracts in Peitou, Taiwan. Zhonghua Yi Xue Za Zhi (Taipei) 2000;63: 641– 8.
Tsai et al 䡠 Age-related Cataracts in Taiwan 3. Zhao J, Sui R, Jia L, et al. Visual acuity and quality of life outcomes in patients with cataract in Shunyi County, China. Am J Ophthalmol 1998;126:515–23. 4. Fletcher AE, Ellwein LB, Selvaraj S, et al. Measurements of vision function and quality of life in patients with cataracts in southern India. Report of instrument development. Arch Ophthalmol 1997;115:767–74. 5. Lee PP, Spritzer K, Hays RD. The impact of blurred vision on functioning and well-being. Ophthalmology 1997;104:390 – 6. 6. Scott IU, Schein OD, West S, et al. Functional status and quality of life measurement among ophthalmic patients. Arch Ophthalmol 1994;112:329 –35. 7. Ivers RQ, Cumming RG, Mitchell P, Attebo K. Visual impairment and falls in older adults: The Blue Mountains Eye Study. J Am Geriatr Soc 1998;46:58 – 64. 8. Rovner BW, Ganguli M. Depression and disability associated with impaired vision: The Movies Project. J Am Geriatr Soc 1998;46:617–9. 9. Hirvela H, Luukinen H, Laatikainen L. Prevalence and risk factors of lens opacities in the elderly in Finland. A population-based study. Ophthalmology 1995;102:108 –17. 10. Chou P, Liao MJ, Tsai ST. Associated risk factors of diabetes in Kin-Hu, Kinmen. Diabetes Res Clin Pract 1994;26:229 –35. 11. Chylack LT Jr, Wolfe JK, Singer DM, et al. The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group. Arch Ophthalmol 1993;111:831– 6. 12. Karbassi M, Khu PM, Singer DM, et al. Evaluation of lens opacities classification system III applied at the slitlamp. Optom Vision Sci 1993;70:923– 8. 13. Leske MC, Connell AM, Wu SY, et al. Prevalence of lens opacities in the Barbados Eye Study. Arch Ophthalmol 1997; 115:105–11. 14. Smeeth L, Iliffe S. Effectiveness of screening older people for impaired vision in community setting: systematic review of evidence from randomised controlled trials. BMJ 1998;316: 660 –3. 15. Zhao J, Jia L, Sui R, Ellwein LB. Prevalence of blindness and cataract surgery in Shunyi County, China. Am J Ophthalmol 1998;126:506 –14. 16. West SK, Munoz B, Schein OD, et al. Racial differences in lens opacities: the Salisbury Eye Evaluation (SEE) project. Am J Epidemiol 1998;148:1033–9. 17. Klein BE, Klein R, Linton KL. Prevalence of age-related lens opacities in a population: the Beaver Dam Eye Study. Ophthalmology 1992;99:546 –52. 18. Mitchell P, Cumming RG, Attebo K, et al. Prevalence of cataract in Australia: the Blue Mountains eye study. Ophthalmology 1997;104:581– 8. 19. Leske MC, Wu SY, Hennis A, et al. Diabetes, hypertension, and central obesity as cataract risk factors in a black popula-
20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32.
33. 34. 35.
tion. The Barbados Eye Study. Ophthalmology 1999;106:35– 41. Sperduto RD, Seigel D. Senile lens and senile macular changes in a population-based sample. Am J Ophthalmol 1980;90:86 –91. Sperduto RD, Hiller R. The prevalence of nuclear, cortical, and posterior subcapsular lens opacities in a general population sample. Ophthalmology 1984;91:815– 8. McCarty CA, Mukesh BN, Fu CL, et al. The epidemiology of cataract in Australia. Am J Ophthalmol 1999;128:446 – 65. Cumming RG, Mitchell P. Hormone replacement therapy, reproductive factors, and cataract: The Blue Mountains Eye Study. Am J Epidemiol 1997;145:242–9. Freeman EE, Munoz B, Schein OD, et al. Hormone replacement therapy and lens opacities: the Salisbury Eye Evaluation project. Arch Ophthalmol 2001;119:1687–92. Klein BE, Klein R, Lee KE. Reproductive exposures, incident age-related cataracts, and age-related maculopathy in women: the beaver dam eye study. Am J Ophthalmol 2000;130:322– 6. Klein BE, Klein R, Linton KL, et al. Cigarette smoking and lens opacities: the Beaver Dam Eye Study. Am J Prev Med 1993;9:27–30. Klein BE, Klein R, Lee KE. Incident cataract after a five-year interval and lifestyle factors: the Beaver Dam eye study. Ophthalmic Epidemiol 1999;6:247–55. Cumming RG, Mitchell PG. Alcohol, smoking, and cataracts: The Blue Mountains Eye Study. Arch Ophthalmol 1997;115: 1296 –303. Christen WG, Manson JE, Seddon JM, et al. A prospective study of cigarette smoking and risk of cataract in men. JAMA 1992;268:989 –93. West S, Munoz B, Emmett EA, et al. Cigarette smoking and risk of nuclear cataracts. Arch Ophthalmol 1989;107:1166 –9. Szmyd L Jr, Schwartz B. Association of systemic hypertension and diabetes mellitus with cataract extraction. A casecontrol study. Ophthalmology 1989;96:1248 –52. Klein BE, Klein R, Lee KE. Diabetes, cardiovascular disease, selected cardiovascular disease risk factors, and the 5-year incidence of age-related cataract and progression of lens opacities: The Beaver Dam Eye Study. Am J Ophthalmol 1998; 126:782–90. Leske MC, Chylack LT, Wu SY. The Lens Opacities CaseControl Study. Risk factors for cataract. Arch Ophthalmol 1991;109:244 –51. Rowe NG, Mitchell PG, Cumming RG, et al. Diabetes, fasting blood glucose and age-related cataract: the Blue Mountains Eye Study. Ophthalmic Epidemiol 2000;7:103–14. The Framingham Offspring Eye Study Group. Familial aggregation of lens opacities: The Framingham Eye Study and the Framingham Offspring Eye Study. Am J Epidemiol 1994;140: 555– 64.
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Age-related cataracts are the main cause of blindness throughout the world.1 Because of the success of modern surgical intervention, cataract extraction surgery is the most Originally received: April 16, 2001. Accepted: October 29, 2002. Manuscript no. 210259. 1 Community Medicine Research Center and Institute of Public Health, National Yang-Ming University, Taipei, Taiwan. 2 Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan. Presented in part at the 18th Congress of the Asia-Pacific Academy of Ophthalmology, March 2001, Taipei, Taiwan. Supported by a grant from Taipei Veterans General Hospital (VGH89-4041), Taipei, Taiwan. The authors have no proprietary interest in any aspect of the study. Reprint requests to Pesus Chou, DrPH, Institute of Public Health, National Yang-Ming University, Shih-Pai, Taipei 112, Taiwan. © 2003 by the American Academy of Ophthalmology Published by Elsevier Inc.
commonly performed ophthalmic procedure in eye health care services.2 The importance of early detection and early treatment and identification of risk factors for age-related cataracts is evident. Although age-related cataracts are not fatal, cataracts have a negative impact on daily and social activities3 and the quality of life of the elderly.4 Moreover, lens opacities lead directly to visual impairment and loss of vision.1 Loss of vision is associated with a reduced quality of life5 and functional status,6 predisposition to falls and hip fractures,7 and clinical depression.8 Advanced age is the most reliable independent risk factor for the occurrence of lens opacities, but the role of other possible contributing or inhibiting factors is not clear.9 There were few data on the epidemiology of age-related cataract in the Asian population. The purpose of this study was to determine the prevalence of age-related cataracts in a metropolitan elderly Chinese population in Shihpai, TaiISSN 0161-6420/03/$–see front matter doi:10.1016/S0161-6420(03)00243-4
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Ophthalmology Volume 110, Number 6, June 2003 pei, Taiwan, and to identify factors associated with agerelated cataracts, including demographic variables, lifestyle, medical history, and waist-to-hip ratio.
Material and Methods Selection of Subjects A population-based survey on eye diseases among subjects 65 years of age and older in Shihpai, Taipei, Taiwan, was conducted between July 1, 1999, and December 31, 2000. The Shihpai community is located in the Peitou district, Taipei. The Peitou district has a population of approximately 247,100 and a land area of approximately 56.8 km2, making it the second largest district in Taipei City. The Shihpai community is the Peitou district’s prosperous commercial hub. The study hospital, one of the largest medical centers in Taiwan, has the most complete equipment and provides advisory medical services. Shihpai was chosen as the study community after taking population stability, metropolitan area, and local support into consideration. Residents 65 years of age and older were identified by the household registration system. The household registration system in Taiwan is designed to collate and supply demographic information and to officially recognize personal status and relations. These household registration data are provided as a reference for the government to effect administrative and socioeconomic development programs and to assist scholars in academic research. According to the official household registration in 1999, the total number of residents at least 65 years of age in Shihpai was 4750. Excluding vacant households (658 persons), residents who died before they were interviewed (48 persons), and inpatient, paralyzed, and disabled (298 persons), 3746 residents were eligible for the study. Residents (n ⫽ 2045) were randomly selected from the eligible subjects and were invited to participate in the study. A structured questionnaire was used to obtain information based on demographic data (age, gender, locality, marital status, and education), personal medical history, and lifestyle (smoking and alcohol intake). Participants’ self-reported demographic data were assessed. Level of education was used as a proxy measure for social class (no school or primary school without diploma, primary school with diploma, secondary school, higher education, and higher education or above) and was categorized as follows: (1) no school or primary school without diploma; (2) primary school with diploma or secondary school or higher education; (3) higher education or above. Subjects were asked about martial status (married and living with spouse, cohabiting, divorced, separated, widowed, and not married), and marital status was simply categorized as the experience of marriage (including married and living with spouse, cohabiting, divorced/separated, and widowed) and no marriagelike experience in this analysis. Personal medical history was investigated by means of a checklist. The participants were asked whether they had been diagnosed with a chronic disease such as diabetes (yes/no) by a physician. Cigarette smoking history and alcohol intake were used as indices of lifestyle. The participants were asked questions about their cigarette smoking history (smoker, ex-smoker, and never-smoker); alcohol intake was limited to wine and hard alcohol and was categorized as no habit of alcohol consumption (or frequency of alcohol consumption was only once a week) and a habit of alcohol consumption (frequency of alcohol consumption was more than once a week). The women were also asked whether they ever used estrogen replacement therapy or other hormones (yes/no). Before data collection, the interviewers were intensively trained to conduct a household interview based on the structured questionnaire and to measure blood pressure, weight, height, and
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waist and hip circumferences. Three consecutive seated blood pressure readings, at least 5 minutes apart, were taken from the right arm and averaged. Waist girth was measured at the minimum circumference, whereas hip girth was measured at the maximum circumference. The definition of obesity was follows. Regional or central obesity by waist-to-hip ratio (WHR) was a WHR greater than 0.92 for men or greater than 0.88 for women.10 Those who were interviewed were invited to the Taipei Veterans General Hospital for an eye examination, including bestcorrected visual acuity, tonometry, slit-lamp biomicroscopy, and ophthalmoscopy. Ophthalmologists conducted the eye examination by according to a standardized protocol. This study was approved by the Institutional Review Board of the Taipei Veterans General Hospital (VGHIRB No.: 89-11-01A).
Definitions The study aimed at estimating the prevalence of age-related cataracts. Subjects with congenital or traumatic cataracts in one eye were excluded from this analysis, and the condition of the other eye was recorded in the survey. Three major types of age-related cataracts (nuclear, cortical, and posterior subcapsular) were assessed by use of the Lens Opacity Classification System III (LOCS III)11,12 by senior ophthalmologists. Subjects were categorized as having an age-related cataract if any type of opacity with an LOCS III grade of greater than 2 was present in one or both eyes. We chose the grade of greater than 2 as the cutoff, because this grade in the LOCS III is close to a grade of 2 or greater in the LOCS II, which is the definition of cataracts adopted by previous major population-based studies.13 When both eyes of a subject had age-related cataracts, the more affected eye was analyzed. Subjects with previous cataract surgery performed after they were 50 years of age were included for prevalence estimation and identification of risk factors if they had no history of ocular trauma and the onset of poor vision was after adulthood.
Pilot Study A pilot study was performed approximately 1 month before the beginning of the main fieldwork to provide a field test of lens grading procedures. For convenience, the pilot study was performed on 78 eyes from 78 subjects other than the study subjects. Interobserver reproducibility of lens grading (grade ⬎2 versus grade ⱕ2) between two study ophthalmologists was assessed using statistics. For cataract diagnosis, agreement was high with a statistic of 0.86 for cortical opacity (51 of 78 eyes rated as not having opacity by both observers) and 0.82 for posterior subcapsular opacity (63 of 78 eyes rated as not having opacity by both observers). The statistic for interobserver reproducibility was 0.85 for nuclear opacity (35 of 78 eyes rated as not having opacity by both observers). Intraobserver statistics for reproducibility of grading cataracts (grade ⬎2 vs. grade ⱕ2) were 0.83 (58 of 78 eyes rated as not having cortical opacity), 0.80 (66 of 78 eyes rated as not having posterior subcapsular opacity), and 0.86 for (47 of 78 eyes rated as not having nuclear opacity) for one ophthalmologist. ⌲ statistics were 0.87 (cortical opacity), 0.85 (posterior subcapsular opacity), and 0.84 (nuclear opacity) for the other ophthalmologist for agreement on reproducibility of grading cataracts.
Statistical Analysis Dependent variables in the analysis were the three types of cataracts versus nonadvanced lens opacity to an LOCS III grade of 2 or more. The independent variables tested were gender (female vs. male), age (ⱖ75 years vs. 65–74 years), WHR (high: WHR ⱖ 0.92
Tsai et al 䡠 Age-related Cataracts in Taiwan Table 1. Prevalence of Age-related Cataracts by Age and Gender in Shihpai, Taipei, Taiwan, 1999 –2000 Male
Female
Cataract Age (yrs)
Examined No.
Without Surgery No.
65–69 70–74 75–79 80⫹ Total
283 314 150 75 822
113 134 80 42 369
Total
Cataract
With Without With Surgery Total PrevaExam- Surgery Surgery Total No. No. lence (%) ined No. No. No. No. 20 31 23 18 92
133 165 103 60 461
47.0 52.6 68.7 80.0 56.1
198 178 118 45 539
86 99 58 19 262
for males; WHR ⱖ 0.88 for females vs. normal: WHR ⬍ 0.92 for males; WHR ⬍ 0.88 for females), cigarette smoking (current smoking vs. nonsmoking; ex-smoking vs. nonsmoking), alcohol intake (yes vs. no), systolic blood pressure (SBP ⱖ 160 mmHg vs. SBP ⬍ 160 mmHg), and history of diabetes (yes vs. no). For statistical analyses, 2 tests were performed to test for an association between each independent variable and dependent variable for univariate analysis. A P value of less than 0.05 was considered to be statistically significant. Multiple logistic regression analyses were used to fit the best model for independent variables and their interactions. Statistical analysis was performed by use of the Statistical Analysis System (SAS 6.12; SAS Institute, Cary, NC) software.
Results Of the 2045 subjects, 1361 (66.6%) participated in the study and received both the questionnaire and eye examination. Of the 684 nonexamined subjects, 677 (33.1%) subjects cooperated only for the household interview, and 7 (0.03%) subjects could not be contacted during three visits for the household interview. The main reasons for nonexamination were refusal to participate, lack of time, or inability to contact the subjects. Consequently, the analysis of this study was based on the data gathered from the 1361 participating subjects. A comparison of demographic information and some of the variables in the subjects with and without the eye examination revealed that the participating subjects were younger than those who refused (72.2 years vs. 74.3 years, P ⬍ 0.001); they were also more likely to be male (P ⫽ 0.001), with a higher level of education (P ⫽ 0.001) than those who refused. There was no significant difference in the other variables (cigarette smoking, alcohol intake, history of diabetes, and hypertension) between the two groups. A total of 806 subjects were diagnosed with age-related cataracts as listed in Table 1. The overall prevalence was 59.2% with a 95% confidence interval (CI; 56.6%– 61.8%). The higher prevalence in women was statistically significant (64% vs. 56.1%, P ⫽ 0.004). The prevalence of cataracts increased with age (P ⫽ 0.001). The rate for age-related cataracts increased rapidly from 57.1% for ages 70 to 74 years to 72.8% for ages 75 to 79 years. Among the 175 participants who had cataract surgery before the survey, there were more women than men (15.4% vs. 11.2%; P ⫽ 0.025). The rate of cataract surgery significantly increased with age (2 test for trend; 2 ⫽ 8.116, P ⫽ 0.001) but did not differ between education level and marriage status. The subjects who had prior surgery were significantly older than the subjects who had no prior surgery (75.6 years vs. 72.3 years, P ⫽ 0.002). The age-specific prevalence of the three types of cataracts are shown in Table 2. Nuclear cataracts were the most prevalent type
12 17 34 20 83
98 116 92 39 345
Cataract Prevalence (%)
Examined No.
Without Surgery No.
49.5 65.2 77.9 86.7 64.0
481 492 268 120 1361
199 233 138 61 631
With Surgery Total PrevaNo. No. lence (%) 32 48 57 38 175
231 281 195 99 806
48.0 57.1 72.8 82.5 59.2
(38.9%), followed by cortical cataracts (21.9%) and posterior subcapsular cataracts (9.2%). Of the 631 subjects with cataracts shown in Table 1 (without surgery), subjects with nuclear, cortical, posterior subcapsular cataracts, and mixed cataracts are shown in Figure 1. Separate univariate analyses of nuclear, cortical, and posterior subcapsular cataracts were performed, and their odds ratios (OR) and 95% CI are shown in Table 3. Stratified by age (ⱖ 75 and ⬍75), there was only one significant interaction. Age and gender had a significant interaction effect on posterior subcapsular cataracts. The interaction (age– gender) effect on nuclear cataracts and cortical cataracts was not significant. Because the interaction term was significant, stratified analysis by age older than 75 was examined to explore the relationship between gender and posterior subcapsular cataracts in multivariate analyses as shown in Table 4. For those 75 years of age or older, women had a 2.4-fold higher rate (95% CI, 1.1–2.9) of posterior subcapsular cataracts. There were no significant differences between gender and posterior subcapsular cataracts, however, for those 65 to 74 years old. The results of three separate multivariate logistic regression analyses after controlling for all covariates and considering the interaction assessment are presented in Table 4. Older age and female gender were factors associated with an increased risk for all types of cataracts. Besides age and gender, the significant risk factor for nuclear cataracts was current smoking (OR ⫽ 1.6; 95% CI ⫽ 1.1–2.2); significant predictors for cortical cataracts were higher SBP (OR ⫽ 1.5; 95% CI ⫽ 1.1–2.1), history of cigarette smoking (OR ⫽ 1.4; 95% CI ⫽ 1.1–2.0), and history of diabetes (OR ⫽ 1.4; 95% C I⫽ 1.1–1.9); higher SBP (OR ⫽ 1.5; 95% CI ⫽ 1.1–2.3) was also significantly related to posterior subcapsular cataracts. We examined the relationship between history of hormone use and the three types of cataracts, using multivariate logistic regression among women (data not shown). After controlling for all covariates, a history of hormone use was associated with a decreased risk of nuclear cataracts (OR ⫽ 0.59; 95% CI ⫽ 0.38 – 0.93). A history of hormone use among women was not significantly associated with cortical cataracts and posterior subcapsular cataracts using a multivariate logistic regression.
Discussion The National Health Insurance Program in Taiwan was implemented in 1994. Lack of utilization of ophthalmologic care for prevention and treatment, however, has created the impression that loss of vision is expected in senior life and the idea that nothing can be done to improve the situation among elderly people,14 particularly in less-educated elderly people.15 This could be an explanation for the 66.6%
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Ophthalmology Volume 110, Number 6, June 2003 Table 2. Prevalence of Age-related Cataracts by Age and Gender in Shihpai, Taipei, Taiwan, 1999 –2000 2 Test
Cataract (without Surgery)
Cataract
No.
Male
Female
Total
Prevalence
Prevalence
Prevalence
(%)
No.
(%)
No.
(%)
Nuclear opacity Age 65–69 70–74 75–79 80⫹ Total Cortical opacity Age 65–69 70–74 75–79 80⫹ Total Posterior subcapsular opacity Age 65–69 70–74 75–79 80⫹ Total
88 108 68 36 300
45 57 41 16 159
12 28 16 7 63
31.1 34.4 45.3 48.0 36.5
15.9 18.2 27.3 21.3 19.3
4.2 8.9 10.7 9.3 7.7
72 87 53 18 230
48 53 27 11 139
19 20 18 5 62
36.4 48.9 44.9 40.0 42.7
24.2 29.8 22.9 24.4 25.8
9.6 11.2 15.3 11.1 11.5
response rate. In our survey, the unexamined subjects were more likely to be female and illiterate, those with a higher risk. Therefore, the unexamined subjects remain a potential source of bias in our estimates. Nevertheless, in this study we observed a high prevalence of age-related cataracts (59.2%) among the elderly in Taiwan, particularly of the nuclear type, and the prevalence increased with age and was higher among women than men in the older age group. Of 1361 participants, 175 (12.9%) had previous cataract surgery. The rate of surgery increased
Figure 1. Venn diagram for 631 subjects (without surgery) with nuclear, cortical, posterior subcapsular cataracts, and mixed cataracts.
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160 195 121 54 530
93 110 68 27 298
31 48 34 12 125
Gender Difference
Age Difference
P ⫽ 0.022
2 (trend) ⫽ 3.422 P ⫽ 0.001
P ⫽ 0.005
2 (trend) ⫽ 1.593 P ⫽ 0.056
P ⫽ 0.016
2 (trend) ⫽ 2.422 P ⫽ 0.008
33.3 39.6 45.1 45.0 38.9
19.3 22.4 25.4 22.5 21.9
6.4 9.8 12.7 10.0 9.2
significantly with age but did not differ with respect to education level or marriage status. All participants who had undergone surgery were asked when they had surgery for cataracts (1994 or before vs. after 1994), and only 33.1% (58 of 175) were operated on before the National Health Insurance Program was implemented in 1994, whereas most of the subjects (approximately 66.9%; 117 of 175) had surgery after implementation of the National Health Insurance Program. In fact, among a generally old and retired population, cost might be an impetus to use the health services, because free-of-charge surgery was not available before 1994. Relative to other deadly and/or chronic diseases, the elderly population ignored eye treatment and improvement of vision. Although the surgery rate was relatively higher than the 1994 levels because of the initiation of the Nation Health Insurance Program, increased attention to the treatment of tractable vision disease to prevent blindness is still an important public health task in Taiwan. Although there was a low percentage (12.9%) of cataract surgery in the elderly in our study, the Salisbury Eye Evaluation (SEE) project revealed a similarly low percentage in black and white elderly16 (Table 5). Table 2 shows the prevalence of three types of cataracts, excluding subjects with prior cataract surgery. Among the 175 participants who have had cataract surgery before the survey, there were more women than men (83 of 539 ⫽ 15.4% vs. 92 of 822 ⫽ 11.2%; P ⫽ 0.025). The rate of cataract surgery significantly increased with age (P ⫽ 0.001), and the rate for cataract surgery among women was 6% of those aged 65 to 69 years, 9.6% of those aged 70 to
Tsai et al 䡠 Age-related Cataracts in Taiwan Table 3. Univariate Analysis on Age-related Cataracts among Residents 65 of Age and Older in Shihpai, Taipei, Taiwan, 1999 –2000 Type of Cataract Nuclear Variable Gender Female vs. male Age (yrs) ⱖ 75 vs. 65–74 Waist-to-hip ratio* High vs. normal Systolic blood pressure SBP ⱖ 160 mmHg vs. SBP ⬍ 160 mmHg Smoking Current smoking vs. nonsmoking Ex-smoking vs. nonsmoking Alcohol Yes vs. no History of diabetes Yes vs. no History of hormone use among women Yes vs. no
Cortical
Posterior Subcapsular
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
1.6
1.3–2.0
1.6
1.2–2.0
1.5
1.2–2.0
2.8
2.2–3.6
2.4
1.9–3.0
3.0
2.3–3.9
1.1
0.9–1.4
1.2
0.9–1.5
1.1
0.8–1.4
1.2
0.8–1.7
1.7
1.2–2.4
1.8
1.2–2.6
1.2 0.9
0.9–1.6 0.7–1.2
0.9 1.1
0.7–1.3 0.8–1.5
0.8 1.1
0.5–1.1 0.8–1.6
0.9
0.7–1.2
0.8
0.5–1.1
0.8
0.6–1.1
1.2
0.9–1.6
1.5
1.1–2.1
1.4
1.1–2.0
0.6
0.4–0.9
0.8
0.5–1.2
0.7
0.4–1.1
*High waist-to-hip ratio group: (male) waist-to-hip ratio ⱖ 0.92; (female) waist-to-hip ratio ⱖ 0.88. SBP ⫽ systolic blood pressure.
75 years, 28.8% of those aged 75 to 79 years, and 44.4% of people aged 85 years or older. Information about the type of cataract for those having had prior surgery was unavailable. One possible reason why the prevalence of nuclear or cortical cataract in women is unsteady could be that there was a relatively higher rate of cataract surgery in the latter two groups (ages 80⫹ years and ages 75–79 years). Although variable, age-related increase in prevalence of nuclear or cortical cataract for women and the total prevalence of cataracts among women on Table 1 (including those with
prior cataract surgery) showed a steady, age-related increase. A comparison of the prevalence rates with those from the SEE project16 for each type of cataract is shown in Table 5. The SEE project16 included two racial groups (blacks and whites) and determined the prevalence of cataracts in each. The SEE project reported that nuclear cataract and posterior subcapsular cataracts were lower among blacks than among whites; however, cortical opacity was higher among blacks than among whites. Further comparison with three races
Table 4. Logistic Regression Analysis on Age-related Cataracts among Residents 65 years of Age and Older in Shihpai, Taipei, Taiwan, 1999 –2000 (n ⫽ 1361) Type of Cataract Nuclear Variable Gender (women vs. men) Age (ⱖ75 vs. 65–74) Waist-to-hip ratio (high vs. normal) Systolic blood pressure (SBP ⱖ 160 mmHg vs. SBP ⬍ 160 mmHg) Cigarette smoking Current smoking vs. nonsmoking Ex-smoking vs. nonsmoking Alcohol (yes vs. no) History of diabetes (yes vs. no) Interaction: age*gender† Age ⱖ 75 year. (women vs. men) Age 65–74 years (women vs. men) †
Cortical
Posterior Subcapsular
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
Odds Ratio
95% Confidence Interval
1.8 2.7 0.9 1.0
1.3–2.3 2.1–3.6 0.7–1.1 0.7–1.5
1.7 2.2 0.9 1.5
1.3–2.3 1.7–2.9 0.7–1.2 1.1–2.1
0.9 1.5
— — 0.6–1.2 1.1–2.3
1.6 1.1 1.0 1.1
1.1–2.2 0.8–1.6 0.7–1.3 0.8–1.5
1.3 1.4 0.8 1.4
0.9–1.9 1.1–2.0 0.6–1.2 1.1–1.9
1.0 1.3 0.8 1.3
0.7–1.6 0.8–2.0 0.5–1.2 0.9–1.8
— —
2.4 1.3
1.1–2.9 0.6–1.8
— —
Interaction term (age*gender) was examined in the logistic regression for the three types of cataracts.
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Ophthalmology Volume 110, Number 6, June 2003 Table 5. Comparison of the Prevalence of Age-related Cataracts among Elderly in Salisbury Eye Evaluation (SEE) Project and Shihpai Study Three types of Cataract Rate %†
Study Shihpai Study Salisbury Eye-Evaluation Project (SEE) Black White
Cortical
Posterior Subcapsular Cataracts
Cataract Surgery rate %
38.9
21.9
9.2
12.9
31.0 46.3
54.5 23.9
2.6 5.4
4.8 12.2
Examined No.
Prevalence %*
Nuclear
1361
59.2
621 1772
68.0 55.1
*Inclusion of cataract surgery data. Exclusion of cataract surgery data.
†
(blacks, whites, and Asians) revealed that whites have a higher rate (46.3%) than blacks and Asians for nuclear cataracts, and blacks have the lowest rate of nuclear cataracts (31.0%). For cortical cataracts, blacks have a significantly higher rate (54.5%) than whites and Asians, and Asians had the lowest rate of cortical cataracts (21.9%). For posterior subcapsular cataracts, Asians had the highest rate (9.2%), and blacks had the lowest rate (2.6%). In Taiwan, common eye medications can be obtained without a prescription. Unfortunately, many elderly people have the erroneous impression that over-the-counter eye medications provide economical protection against age-related cataracts or other ocular diseases. For this reason, the high rate of posterior subcapsular cataracts might be related to high steroid use. Most studies indicate that cataracts are more common in women than in men.2,13,17–21 In our study, women had a higher prevalence than men for all three cataract types. Women using hormones, however, had a lower prevalence of nuclear cataracts as determined by univariate and multivariate analyses in our study. Univariate analysis also indicated a protective effect of hormone replacement therapy against cortical cataracts.22 The Blue Mountains Eye Study23 reported that current users of hormone replacement therapy aged 65 years and older had a lower prevalence of cortical cataracts than did those who never used hormone replacement therapy (OR ⫽ 0.4; 95% CI ⫽ 0.2– 0.8). A protective association between the use of hormone replacement therapy and nuclear and posterior subcapsular cataracts is reported from the SEE.24 The findings of the Beaver Dam Eye Study, however, indicated that there is little evidence of an association between hormone exposure and the incidence of age-related cataracts in women 5 years later.25 The association between cigarette smoking and age-related cataracts was investigated in several studies.26 –30 A prospective study29 reported that cigarette smoking increases the risk of developing both nuclear and posterior subcapsular cataracts. A study in Maryland30 reported that the risk of nuclear cataracts increased with increasing cigarette use and decreased if the subject had quit smoking. The Blue Mountains Eye Study28 also reported that people who smoked cigarettes had a higher prevalence than nonsmokers of more severe nuclear (OR ⫽ 1.3; 95% CI ⫽ 1.1–1.6) and posterior subcapsular (OR ⫽ 1.5; 95% CI ⫽
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1.1–2.1) cataracts. Multivariate analyses revealed a significantly increased risk between current cigarette smoking and nuclear cataracts (OR ⫽ 1.6; 95% CI ⫽ 1.1–2.2). Even ex-smokers had 1.4 times the risk for cortical cataracts compared with people who never smoked. Thus, these results support a role for cigarette smoking as a risk factor for cataracts. Multivariate analyses revealed an association between blood pressure and age-related cataracts in our study. Blood pressure and hypertension with age-related cataracts, however, were equivocal factors in previous studies.9,19,22,29,31,32 Some studies9,19,29,31 reported an association between hypertension (or blood pressure) and agerelated cataracts, but other studies22,32 did not. We found a significantly increased risk between high SBP and cortical and posterior subcapsular cataracts. Further etiologic studies are needed to clarify the relation between blood pressure and age-related cataracts. There is a consistent positive association between diabetes and age-related cataracts in epidemiologic studies, and diabetes is associated with cortical cataracts.2,19,33–35 Similar findings from our study indicated that diabetic individuals are 1.4 times more likely to have cortical opacity. In summary, the findings of this study indicate a high prevalence of age-related cataracts among the Chinese elderly in Taiwan. As noted earlier, elderly people tend to believe that visual loss is expected in senior life and often ignore the importance of seeking vision services and care to prevent blindness or impairment. These findings suggest that the elderly need to be educated regarding the importance of eye care by physicians and hygiene authorities. For a more meaningful comparison of age-related cataract rates in different populations, future surveys should use comparable diagnostic criteria or classifications.
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