Cataract Hospitalizations in 96 Grade (cid:0) A Hospitals in China

Background: To examine the demographic, medical care and nancial characteristics of cataract inpatients in China, based on analysis of a large national database. Design: A multicenter, cross-sectional, 6-year period retrospective study. Subjects: This study included 185147 inpatients with a principal or secondary diagnosis of cataract, between 2009 and 2014, in China. Methods: All types of cataract-related hospitalization information from 96 grade (cid:0) A hospitals, over a 6-year period (from 2009 to 2014), were identied and the data from 230250 eyes (185147 inpatients) were retrospectively analyzed statistically. Main Outcome Measures: hospitalization


Background
Cataract, de ned as any opacity of the crystalline lens in the eye that affects clear vision, is a major public health issue and is also the leading cause of blindness worldwide, affecting about 111.74 million individuals in China in 2015. (1,2) Since 90% of cataracts globally are reported in developing countries, its social, physical, and economic burden cannot be ignored. (3,4) There is a signi cantly higher prevalence of cataracts in China, especially in the rural areas, than in developed countries. It has been estimated that the number of individuals affected by any type of cataract in China will reach 240.83 million by 2050. (1) Untreated cataract can gradually progress to severe visual impairment and eventually blindness, thereby reducing the vision-related life quality of those patients and accordingly increasing social and family burdens. (5)(6)(7)(8) Cataract surgery, an effective technique in resolving crystalline lens opacity, is currently the only available method for restoring vision for those patients. As cataract surgery techniques have advanced and have become more universal, elderly patients suffering from cataract, even those in outlying poverty-stricken areas, have the opportunity to bene t from appropriate intervention.
Nevertheless, cataract still remains one of the major socioeconomic and public health burdens in China and poor individuals have limited access to cataract surgery services. (9,10) In addition, China has a low cataract surgical rate (cataract operations per million population per year) and cataract surgical coverage as compared with other countries in Asia. (11)(12)(13)(14)(15)(16)(17) In this study, we evaluated the epidemiologic and clinical characteristics of cataract and cataract surgery and examined the economic costs for treatments of cataract in China, by performing a multicenter review of cataract inpatients in grade A hospitals in China over a 6-year period.  Data Collection Data of inpatients diagnosed with "cataract", according to the International Classi cation of Diseases (ICD-9 and ICD-10), (19,20) were collected for statistical analysis; this including information such as age, sex, consultative hospital, arrival time, diagnosis, operation style, preoperative and postoperative length of hospital stay, nancial cost, and therapeutic outcomes.

De nitions
The

Statistical Analysis
All data were collected in an electronic database. Continuous variables were evaluated for normality and homogeneity with ANOVA. One-sample t-tests were performed to assess the signi cance of differences between groups. SPSS (version 19) software (IBM SPSS Inc., Chicago, IL, USA) was used for statistical analysis. A P < 0.05 was considered to be statistically signi cant for all tests.
For the purpose of estimating a rough relative "hospitalization rate (HR)" to evaluate the geographical distribution of cataract and investigate the risk factors, we used the following formula: where I is the number of inpatients, P is the population, M is the number of grade A hospitals IS, and L is the number of grade A hospitals OS. . When considering the vast differences in regional populations and numbers of local hospitals, the estimated "HR" remained highest in northwest China (0.23%) and lowest in northeast China (0.07%) (Fig. 2B).

Results
The age of inpatients with cataract ranged from 1 to 109 years (mean age 64.50 ± 16.72 years). More male than female inpatients in the 0-49-years and 80-109-years age groups visited hospitals, in contrast to the 50-79-year age group (Fig. 2C). No signi cant difference of morbidity on either eye was found in any age group (p value > 0.01; Fig. 2C).  (Fig. 3B).
Intracapsular cataract extraction (ICCE), extracapsular cataract extraction (ECCE), and phacoemulsi cation (Phaco) have been the most common cataract surgeries in China over the past decades. During the study period, 125179 cataract surgeries were performed on 105136 inpatients with any type of cataract, of which Phaco accounted for 97.15% (Fig. 4). The number of Phaco procedures increased markedly, from 12120 to 26596, over the 6-year period. A few ECCE and ICCE procedures were also performed. Intraocular lens (IOL) implantation was subsequently performed on most, but not all, inpatients who underwent cataract surgery.
Among the 185147 inpatients with any type of cataract, 96731 inpatients (52.25%) were covered by social medical insurance (SMI), while another 70966 inpatients (38.33%) without SMI were either covered by their private health-care insurance or paid for their procedures out of pocket, which we termed private medical treatment (PMT). The remaining 17232 (9.42%) inpatients received free medical service (FMS) provided by the state. MC, which was signi cantly lower than that in any other region (Fig. 5D). The proportion of the total AMEC accounted for by the OC and MC showed a similar tendency (Fig. 5C, D).

Discussion
This study provided a comprehensive description of the epidemiological and clinical characteristics of cataract and cataract surgery in 96 grade A hospitals in China, based on a nationally representative database of 185147 participants, over a 6-year study period. Since the 96 grade A hospitals inside of the information system shared similar medical services, technology, and circumstances with the grade A hospitals outside of information system, the data reported here should be representative of the status quo of cataract and cataract surgery over the past 6 years in China, in general. However, as the study was conducted in hospitals, we were only able to describe the distribution and clinical characteristics of cataract and cataract surgery based on inpatients with any type of cataract, and could not calculate the actual occurrence and incidence rates. Therefore, we introduced a formula to estimate a rough relative "HR", which should be helpful in investigating the risk factors for cataract. (21) Cataract can develop due to various reasons, such as ageing, trauma, or other diseases, resulting in visual impairments. As revealed in our study and other previous studies, the number of cataract inpatients increases markedly with advances in age, indicating the prominent role of ageing as a constant risk factor in cataract development. (22) Age-related cataract inpatients thus occupy the majority of total cataract inpatients. With rapidly ageing populations in China, the number of people with cataract in China will double and redouble in the near future, and the social-economic and medical care issues related to older individuals is an ever-present concern.(23, 24) Congenital cataract continued to have a fairly low prevalence, but is also the primary cause of treatable childhood blindness. (25) We consider that the number of individuals with congenital cataract will gradually decrease in China, due to the national prenatal and postnatal care policy.
In the present study, women were affected slightly more than men, especially in those aged > 50 years and < 80 years; cataracts in these groups were primarily age-related. This result was in accordance with numerous previous population-based studies, which demonstrated a higher prevalence of age-related cataract in women than in men. (1,(26)(27)(28) This is not caused by lifestyle-related factors, since men generally have more exposure to ultraviolet B (UVB) and smoking, which are risk factors for cataract, than women. Although the mechanism underlying the sex disparity in cataract formation still remains unclear, a number of previous studies suggested that the estrogens may play a protective role in cataract development. Several studies have indicated that hormone therapy may decrease the risk of cataract and thus hypothesized that the decrease in estrogen at menopause women increased the risk of cataract. more experimental evidence is needed to elucidate the exact mechanism by which estrogens may protect against cataract (29). Additionally, more young men than women are exposed to environments involving physical work, and thus have a higher risk of sustaining eye injuries leading to traumatic cataract.
There were more cataract inpatients who were treated in summer than in other seasons, mainly because of the higher UVB exposure, which is generally considered to be a strong risk factor for age-related cataract. (30) Interestingly, there were also markedly more cataract inpatients in winter than in spring and autumn. Given that China is a largely agricultural country and that most of the population are involved in agriculture, older farmers may prefer to receive treatment after the busy farming seasons, since age-related cataract is not a medical emergency and does not require immediate care.(31) However, these were opposite to those found in Canada. (32) Due to the high elevation and UVB exposure, low economic income, educational, and medical care levels, and poor lifestyle, people living in the western region (including northwest and southwest China) were more likely to develop cataract. In contrast, given the higher economic income, educational, and medical care levels, the incidence of cataract in the central and eastern regions, including northeast, east, north, and south-central China, was markedly lower than that in the western region.
Since traumatic, complicated, and drug-induced and toxic cataract are usually associated with injuries or lesions in other ocular parts, inpatients with these types of cataract have a more complex condition than those with age-related and congenital cataract, which require much simpler treatment. These inpatients therefore have a longer AHS and relatively worse prognosis. As disclosed in the present study and previous studies, ICCE and ECCE are now very infrequently used surgical techniques in cataract treatment and have gradually been replaced by Phaco with IOL implantation. A number of previous studies have suggested that ICCE surgeries often have poor visual outcomes and that the visual acuity of patients treated with Phaco was signi cantly better than that of patients treated with ECCE or ICCE. (17,33,34) Nearly all cases in this study received IOL implantation. Previous studies have shown that the use of IOL implantation after cataract extraction increased with economic development. (8,35,36) Previous studies also suggested that more precise preoperative IOL power estimation and better postoperative care with correct optometry and spectacle provision helps to maximize surgical bene ts. (37) With the rapid economic development and improvement in the quality of medical services and technology, the mean total cost for cataract surgery has increased year by year. Medical costs were higher in FMS inpatients, who can enjoy better medical conditions without personal costs, than in SMI and PMT inpatients. Interestingly, along with improvements in the standard of living, increasing numbers of inpatients have tended to choose better medical care at their own expense. As the most economically developed region, north China had the highest medical resource consumption in cataract treatment, regardless of the type (FMS, SMI, or PMT) of inpatients. OC accounted for a markedly higher proportion of the total medical cost than did MC, which is reasonable, given that cataract is mainly treated through surgery. It is noteworthy that both OC and MC decreased from 2012. This might be associated with the national New Medical Reform policy that seeks to reduce the medical economic burden for patients through establishing and improving the basic medical and health system covering both urban and rural residents, and providing safe, effective, convenient, and cheap medical and health services for the people. Therefore, cataract patients in areas with relatively poor economic conditions have an equal chance of undergoing cataract surgeries, without being hampered by the expensive cost. (38)(39)(40) There still are several potential limitations in our study. First, the prevalence of cataract could only be estimated based on cataract hospitalization situation. This is far from enough as a small but signi cant number of cataract patients refuse to receive treatment in hospitals, which might lead to an underestimation in morbidity rate. Second, potential risk factors for cataract, such as smoking and diabetes, could not be analyzed for the absence of relevant personal information. Considering the above limitations, several analytic results in the present study should be interpreted with considerable caution.

Conclusion
In conclusion, our study provided a comprehensive and up-to-date description and analysis of the epidemiological and clinical characteristics and the economic cost of cataract-related hospitalizations in China, at both the national and regional levels, taking the effects of both demographic and geographic features into account. Cataract and cataract blindness have emerged as a leading public-health issue in China and the cost burden of cataract surgery has increased with the aging population.

Availability of data and materials
All data generated or analysed during this study are included in this published article.

Competing interests
The authors declare that they have no competing interests.

Funding
Chinese PLA General Hospital medical big data project (2017MBD-020). Figure 1 Geographical distribution of 96 grade A hospitals in China. There were 96 grade A hospitals inside the system (IS) and 677 grade A hospitals outside the system (OS) in the study period. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.'