Age-related cataract is the leading cause of mild to moderate visual impairment throughout the world.1–8 With longer life expectancies and an aging population, the worldwide burden and impact of age-related cataract are expected to increase, making it a global public health concern. Health economic studies in the United States and Australia have always shown that the medical costs of age-related cataract far exceeds those of other major eye conditions such as retinal diseases (e.g. age-related macular degeneration and diabetic retinopathy), glaucoma, and refractive errors.9,10 Thus, cataract imposes heavy economic burdens on individuals, communities, and countries.
Depression is a chronic and often recurrent psychiatric disorder among older people, and its association with cataract has not been well defined. A previous study has shown that depression is a prevalent mental health problem in ophthalmological practice and is often unrecognized or untreated.11 There have been a number of studies examining the association between visual impairment and depression with inconsistent findings. For example, in a study of 339 socially vulnerable older adults aged over 50 years in Armenia, the odds of having depression were higher among those with visual impairment compared to those without after adjusting for confounders (odds ratio [OR] = 2.75; 95% confidence interval [CI]: 1.29–5.87).12 Another study in Europe indicated that the prevalence of major depressive disorder and anxiety disorders were significantly higher in visually impaired older adults compared to their normally sighted peers (p < 0.05).13 On the contrary, other studies reported nonsignificant results. A population-based study of 2520 white and black individuals aged 65 to 84 years in the United States found neither baseline best-corrected visual acuity nor its change was associated with the development of depressive symptoms.14 Another study on young- and middle-age U.S. adults aged 20 to 39 years demonstrated that visual acuity was not associated with depression disorder (p = 0.20) after adjusting for age, gender, ethnicity, body mass index, mean arterial pressure, tobacco use, diabetes, and physical activity.15 In addition, cataract surgery has been linked with improvement in depression in some studies,16–20 but little has been known on the association between the presence of cataract and depressive symptoms, especially in Chinese population. Understanding the risk factors for depression in Chinese population may have great public health implications as Chinese is the world’s most populous ethnic group and may have the greatest burden of depression. In addition, there is also social stigma associated with mental health problems in Chinese cultures. Population-based studies assessing the potential relationship between cataract and depressive symptoms could guide clinical treatment of cataract and medical decision making in public health.
In this study, we aimed to assess the association of age-related cataract with the presence of depressive symptoms in a community-based cohort of older Chinese people aged 60 years or older. We also examined whether the association between cataract and depressive symptoms is explained by worse visual acuity.
The Weitang Geriatric Diseases study was a community-based survey conducted in the Weitang town located in Suzhou. The aim of the study was to estimate the patterns, predictors, and burden of common health outcomes of elderly people aged 60 years or older in eastern China. The study method has been reported elsewhere.21 Based on the official records, 6030 persons aged 60 years or older resided in the town. Before the study, an invitation was sent to each family explaining the nature of the study and inviting all adults 60 years of age or older to participate in this study. A person was considered “ineligible” to participate if he or she had moved from the residing address, had not been living there for more than 6 months, or was deceased. Of the 6030 names listed in the official records, 5613 subjects were considered to be eligible to participate in this study. Only eligible subjects were invited.
The Weitang Geriatric Diseases study was conducted following the tenets of the Helsinki Declaration and was approved by the Institutional Review Board of Soochow University. All participants gave written informed consent at the recruitment stage of the study.
Slit-lamp examination (model SL-1E; Topcon) was performed on both eyes in each study participant and included a clinical grading of lens opacity using the Lens Opacities Classification System (LOCS) III.22 LOCS III includes an assessment of nuclear opalescence (NO), cortical cataract (C), and posterior subcapsular cataract (PSC) (P). A LOCS III score of 4.0 or more for NO was defined as significant nuclear cataract, a score of 2.0 or more for C as significant cortical cataract, and a score of 2.0 or more for P as significant PSC.23 Any cataract was defined as the presence of any subtypes in at least one eye.
Measurement of Depressive Symptoms
We used the 9-item Patient Health Questionnaire (PHQ-9) depression scale to assess the frequency of symptoms experienced and reported by the study participants within the past 2 weeks.24 The PHQ-9 scores range from 0 to 27 and indicate the presence and severity of depression, with scores of 5 being the cut-points for having depressive symptoms. The validity and reliability of the PHQ and its 9-item depression module to establish depressive diagnosis and grade severity have been documented in a previous report.25 This instrument has also been validated in a general Chinese population. It was translated into Chinese by Wang et al. for the purposes of screening depression.26 In the present study, “any depressive symptoms” was defined as a PHQ-9 score from 5 to 27 and “no depressive symptoms” as a PHQ-9 score from 0 to 4. Investigators who performed the grading of cataract were blind to the subject’s answers to the PHQ-9.
Assessment of Covariates
Presenting visual acuity was measured monocularly with a Snellen vision chart with tumbling-E optotypes (Precision Vision, La Salle, IL) at an illumination of approximately 500 lux at a distance of 4 m, with the participants wearing their presenting optical correction (spectacles or contact lenses), if any. The light intensity of the examination room for the visual acuity test was measured by a light meter. A risk factor questionnaire asking about socioeconomic status, lifestyle-related factors, disease histories, and medication intake was administered verbally by trained research assistants. Diabetes mellitus was defined as fasting glucose levels of more than 7.0 mmol/L or physician diagnosis of diabetes and use of diabetic medications.27 Hypertension was defined as systolic blood pressure of 140 mm Hg or more or diastolic blood pressure of 90 mm Hg or more, or use of antihypertensive medication.
Study participants with previous cataract surgery in both eyes were excluded from analyses. Binary logistic regression models were fitted to calculate the ORs and 95% CIs for associations between the presence of age-related cataract and the presence of any depressive symptoms. For multivariate analysis, only age, gender, cataract, and factors that were significantly different in univariate comparison (p < 0.05) were retained in the model. The interactions between age-related cataract and other variables with depressive symptoms were determined using a likelihood-ratio test. Statistical analyses were performed using SPSS 16.0 (SPSS Inc., Chicago, IL), and a p value of less than 0.05 indicated statistical significance.
From August 2014 to February 2015, a total of 4611 subjects attended the clinic, representing an 82.1% response rate. Of the 4611 elderly adults who participated in this study, the PHQ-9 questionnaire was completed by 4579 participants. The prevalence of having any depressive symptoms (PHQ-9 score 5–27) in this cohort was 8.0% (95% CI 7.2–8.8). Women were more likely to have any depressive symptoms compared with men (10.7% vs. 5.0%; p < 0.001). Depressive symptoms were more prevalent in older age groups. For example, the prevalence of having any depressive symptoms was only 4.9% (95% CI 3.9–5.8) in people aged 60 to 64 years whereas it was 23.4% (95% CI 18.4–28.4) in those aged 80 year or older.
Among the 4597 participants who had completed the PHQ-9 questionnaire, 228 had previous cataract surgery in both eyes and were excluded from analysis. Among the remaining 4369 study participants, age-related cataract of any subtypes in at least one eye was found in 2121 (48.5%) participants. For cataract subtypes, nuclear, cortical, and PSC cataract were found in 1349 (30.9%), 1776 (40.7%), and 414 (9.5%) subjects, respectively.
Table 1 summarizes the characteristics of the study participants based on the status of depressive symptoms as measured by PHQ-9. In this study, adults with any depressive symptoms were more likely to be older (p < 0.001), female (p < 0.001), and living alone (p < 0.001) compared with those without. They also had lower monthly income (p < 0.001), were less educated (p < 0.001), were less likely to smoke (p < 0.001), drink alcohol (p < 0.001) or tea (p < 0.001), spent less time outdoors (p = 0.03), and slept for more hours per day (p < 0.001).
Associations of depressive symptoms with cataract and other risk factors were further examined in a multiple logistic regression model, and the results are shown in Table 2. In multivariate analysis, the presence of depressive symptoms was significantly associated with older age, female gender, lower income, living alone, tea consumption, more sleeping hours per day, the presence of cataract, and poor presenting visual acuity. In the regression model, 14% of the variance in the depression symptoms was explained by cataract (R2 = 0.14).
In addition, we found that there were no significant differences in the odds of having depressive symptoms between those with bilateral cataract (cataract in both eyes) and with unilateral cataract (cataract only in one eye). For cataract subtypes, nuclear cataract was associated with a higher likelihood of having any depressive symptoms. The association between cortical cataract and the presence of depressive symptoms was only of marginal significance, and the magnitude of association was smaller as compared with that of nuclear cataract. PSC cataract was not related to the presence of depressive symptoms. Furthermore, we also assessed the association between self-reported cataract history and the presence of depressive symptoms. Participants who reported a cataract history were more likely to have depressive symptoms compared with those who did not (Table 3).
A significant joint effect of education level with age-related cataract on the presence of depressive symptoms was detected using a likelihood ratio test (p for interaction = 0.03). Further education-stratified analysis indicated the association of age-related cataract with depressive symptoms was stronger in adults with no formal education (OR = 1. 50) compared with those with formal education (OR = 1.29) in multivariate analysis. Those without formal education also had a poorer presenting visual acuity in this study.
In this community-based survey of Chinese adults aged 60 years or older, we reported that age-related cataract including both bilateral and unilateral cataracts was associated with the presence of depressive symptoms as measured by PHQ-9 after controlling for a wide range of potential confounders. This association was found to be independent of socioeconomic status, lifestyle-related exposures, and presenting visual acuity. The association of aged-related cataract with depressive symptoms was modified by people’s education level. These findings provided preliminary data on the possible relationship between cataract and depression. Ophthalmologists should be aware of the high likelihood of depression in their patients with cataract and screen for depression or refer for counseling in the clinics. The findings also emphasize the need for timely cataract surgery to reduce the risk of depression in older people.
To the best of our knowledge, this was the first population-based study of large sample size which directly assessed the association of cataract, the leading cause of visual impairment in older adults, with the likelihood of having depressive symptoms. In the present study, the presence of aged-related cataract was significantly associated with an increased likelihood of having depressive symptoms, and this association was even more pronounced in those who had not been formally educated. Quite a few studies have shown that visual impairment may be an independent risk factor for depression, but the findings among different studies was inconsistent.12–15 These inconsistent findings among different studies may be due to different study designs and characteristics of the study populations. For example, a major difference among studies is that different studies used different instruments for screening depressive symptoms. However, visual acuity is a balanced effect of different eye disorders and there was little evidence regarding the impact of a specific eye disorder on depression or depressive symptoms. Other evidence has supported a significant improvement in depressive symptoms scores after cataract surgery among older populations.16–20 However, there have been few population-based data examining the association between the presence of cataract and depression or depressive symptoms. In multivariate analysis controlling for the effect of presenting visual impairment, the association between age-related cataracts and the presence of depressive symptoms remained significant, though the magnitude of association seemed to be attenuated. Thus, one may speculate that the association of cataracts with depressive symptoms is not simply explained by poor visual acuity, but also perhaps of other vision-related factors such as halos, contrasts, light adaptation factors, etc. There may also be emotional factors such as fear of surgery and frustration with limitations in participation, which may have contributed to the effect on depressive symptoms in this study.
The biological mechanism underlying the observed associations between cataract and depressive symptoms remains unclear and warrants further clarification. It has been well established that age-related cataract is the leading cause of visual impairment in older people. Vision loss might weaken the ability to perform activities of daily living and isolate individuals from communicating with friends and family, potentially leading to tremendous negative psychological impact. However, our data indicated that the association was independent of vision loss caused by cataract. One explanation for this finding is that age-related cataract and depression may share risk factors, such as oxidative stress.28 Alternatively, depressive adults may be less likely to seek treatment for cataract than adults with normal mental health.
Another interesting finding was that the association of age-related cataract with depressive symptoms was stronger in people without formal education. Adults with different education level may need to cope with various psychosocial issues due to disparities in lifestyle, responsibility, or circumstances. On the other hand, perceived costs of attending an eye care clinic and lack of knowledge of the potential benefits from cataract extraction might also inhibit many poorly educated persons from seeking medical assistance. This interaction effect observed in this study suggests a complex interplay among eye disorders, socioeconomic status reflected by education, and mental health that merits further investigation.
Some important public health implications from our study should be noted. Mental health problems among the elderly are a major problem in China and other countries, and are sometimes under-detected and undertreated. Considering the fact that cataract can be treated easily and effectively with surgical approach, it may be recommended that efforts and resources be channeled towards the surgical treatment program of cataract in depressive older adults, especially in rural areas where people are poorly educated. In addition, further randomized control trials are warranted to examine the impact of cataract surgery on depression in these populations.
Although this study has several strengths, including a large and representative sample and the use of a well-validated instrument to measure depressive symptoms, there are still some limitations, which need to be acknowledged here. As cultures may have a great impact on people’s mental health, the findings from Chinese population may not be directly extrapolated to other ethnic groups considering the huge disparities in cultures among different ethnic groups. Furthermore, although we had adjusted a wide range of confounders in multivariate analysis, residual confounding may still exist. Finally, we cannot determine whether aged-related cataract predates depressive symptoms or to what extent self-reported depressive symptoms may affect cataract grading considering the cross-sectional design of the study. It also remains possible that factors associated with depression led to an environmental exposure that resulted in cataracts.
In conclusion, we found a significant association between age-related cataract and depressive symptoms among older Chinese adults, particularly in poorly educated ones. Despite the unclear direction of causality in this cross-sectional study, our study sheds further light on the complex relationship between aging, vision loss, cataract, and depression and suggests that there may be a role for cataract surgery in improving mental health in the elderly.
School of Public Health
Medical College of Soochow University
199 Ren Ai Road
This study was funded by National Natural Science Foundation of China (no. 81502824 and no. 81402761). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
H.W. and H.-P.S. contributed equally to the work presented here and therefore should be considered equivalent authors.
Received November 23, 2015; accepted April 20, 2016.
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