Differential and shared genetic effects on kidney function between diabetic and non-diabetic individuals

Reduced glomerular filtration rate (GFR) can progress to kidney failure. Risk factors include genetics and diabetes mellitus (DM), but little is known about their interaction. We conducted genome-wide association meta-analyses for estimated GFR based on serum creatinine (eGFR), separately for individuals with or without DM (nDM = 178,691, nnoDM = 1,296,113). Our genome-wide searches identified (i) seven eGFR loci with significant DM/noDM-difference, (ii) four additional novel loci with suggestive difference and (iii) 28 further novel loci (including CUBN) by allowing for potential difference. GWAS on eGFR among DM individuals identified 2 known and 27 potentially responsible loci for diabetic kidney disease. Gene prioritization highlighted 18 genes that may inform reno-protective drug development. We highlight the existence of DM-only and noDM-only effects, which can inform about the target group, if respective genes are advanced as drug targets. Largely shared effects suggest that most drug interventions to alter eGFR should be effective in DM and noDM.

Six-Year Incidence and Risk Factors of Primary Glaucoma in the Singapore Indian Eye Study

PURPOSE

To determine the 6-year incidence of primary glaucoma and its risk factors in an Indian population in Singapore.

DESIGN

Cohort population-based study.

PARTICIPANTS

Indian adults between 40 and 80 years of age living in Singapore. A total of 3400 participants underwent the baseline examination between 2007 and 2009. Of them, 2200 (response rate, 75.5% of those eligible) participated in the 6-year follow-up visit between 2013 and 2015.

METHODS

Standardized examination and investigations were performed, including indentation gonioscopy, intraocular pressure (IOP) measurement, optic disc examination, and static automated perimetry. Glaucoma was defined according to the International Society Geographical and Epidemiological Ophthalmology criteria.

MAIN OUTCOME MEASURES

Incidences of primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG).

RESULTS

The age-standardized incidences of primary glaucoma, POAG, and PACG were 1.68% (95% confidence interval [CI], 1.21%-2.32%), 1.37% (95% CI, 0.94%-1.96%), and 0.32% (95% CI, 0.15%-0.66%), respectively. For eyes with ocular hypertension (n = 45) at baseline, the incidence of POAG was 4.83% (95% CI, 1.24%-17.21%) and for eyes with primary angle closure (n = 14) or suspected primary angle closure (n = 101), the incidence of PACG developing was 1.82% (95% CI, 0.37%-9.68%). Baseline factors associated significantly with risk of primary glaucoma developing included older age (per decade; odds ratio [OR], 1.84; 95% CI, 1.44-2.36; P < 0.001), larger vertical cup-to-disc ratio (per 0.1 unit; OR, 2.78; 95% CI, 2.12-3.64; P < 0.001), and higher IOP (per millimeter of mercury; OR, 1.25; 95% CI, 1.13-1.38; P < 0.001). However, 71 of 85 eyes (84.5%) diagnosed with incident glaucoma had IOP of less than 21 mmHg at the time of examination.

CONCLUSIONS

Our study showed that the overall age-standardized incidence of primary glaucoma was 1.68% in an Indian population in Singapore. In our population, the incidence of POAG was only half and the incidence of PACG was similar to the incidence reported by the Chennai Eye Disease Study.

Association of Cataract Surgery With Risk of Diabetic Retinopathy Among Asian Participants in the Singapore Epidemiology of Eye Diseases Study

IMPORTANCE

Cataracts and diabetic retinopathy (DR) are the leading causes of acquired blindness worldwide. Although extraction is the standard treatment option for cataracts, it is also reported to increase the risk of developing DR among individuals with diabetes. Nevertheless, the association between cataract surgery and risk of DR is still not well understood, and there have been no prior population-based reports in this area.

OBJECTIVE

To assess the risk of developing DR after cataract surgery among individuals with type 2 diabetes.

DESIGN, SETTING, AND PARTICIPANTS

A population-based prospective cohort study was conducted among participants recruited from the Singapore Epidemiology of Eye Diseases Study. The baseline visit was conducted between June 1, 2004, and March 31, 2009, and the 6-year follow-up visit was conducted between June 1, 2011, and July 31, 2016. Statistical analysis was performed from October 1 to 31, 2019.

EXPOSURES

Cataract surgery performed before a follow-up visit, determined based on slitlamp evaluation of lens status at baseline and follow-up visits.

MAIN OUTCOMES AND MEASURES

Eyes with incidence of DR were defined as those with the presence of any DR (level ≥15 based on the modified Airlie House classification system, graded from retinal photographs) at 6-year follow-up with no DR at baseline. The association between cataract surgery and incidence of DR was evaluated using a multivariable Poisson regression model with a generalized estimating equation to account for correlation between both eyes.

RESULTS

A total of 1734 eyes from 972 participants with diabetes (392 Malay individuals and 580 Indian individuals; 495 men; mean [SD] age, 58.7 [9.1] years) were included in the analysis. A total of 163 study eyes had already undergone cataract surgery at baseline, and a total of 187 eyes (originally phakic at baseline) underwent cataract surgery any time during the follow-up period. Of these 350 eyes, 77 (22.0%) developed DR. Among the 1384 eyes that never underwent cataract surgery, 195 (14.1%) developed DR. After adjustments for age, sex, race/ethnicity, baseline hemoglobin A1c level, duration of diabetes, random blood glucose level, antidiabetic medication use, hypertension, body mass index, and smoking status, multivariable regression analysis showed that any prior cataract surgery was associated with incidence of DR (relative risk, 1.70; 95% CI, 1.26-2.30; P = .001). Subgroup analyses by race/ethnicity showed similar associations in both Malay individuals (relative risk, 1.73; 95% CI, 1.13-2.69; P = .02) and Indian individuals (relative risk, 1.93; 95% CI, 1.33-2.80; P < .001).

CONCLUSIONS AND RELEVANCE

The findings of this population-based cohort study suggest that prior cataract surgery was associated with a higher risk of developing DR among individuals with diabetes. Further validation is warranted to confirm this association.

The associations of objectively measured sleep duration and sleep disturbances with diabetic retinopathy

AIMS

To assess the associations between objectively measured sleep duration, sleep disturbances and diabetic retinopathy (DR).

METHODS

This cross-sectional study recruited 92 patients with diabetes from retinal clinics. Objective measurements of sleep duration, apnea-hypopnea index (AHI) and minimum oxygen saturations (SaO2) were obtained through polysomnography. The Epworth Sleepiness Scale and Insomnia Severity Index were administered. Retinal photographs were taken and graded according to the modified Airlie House Classification System. Regression analysis used to determine associations with outcomes including moderate DR, vision-threatening DR (VTDR) and diabetic macular edema (DME).

RESULTS

Mean age of participants was 57.6 ± 8.3 years. 29 (32%) of them had moderate DR, and 17 (18.5%) had VTDR. Higher AHI (Odds Ratio [OR] 1.04; 95% confidence interval [CI] 1.00, 1.07) and short sleep duration (OR 3.22; 95%CI 1.18, 8.79) were associated with moderate DR. VTDR was associated with moderate obstructive sleep apnea (OSA) (OR 4.73; 95%CI 1.46, 15.31), higher AHI (OR 1.06; 95%CI 1.02, 1.10) and lower minimum SaO2 (OR 0.89; 95%CI 0.83, 0.96). High risk for insomnia was associated with DME (OR 4.01; 95%CI 1.09, 14.73).

CONCLUSIONS

Short sleep duration was associated with moderate DR while OSA-related parameters and a high risk for insomnia were associated with moderate DR, VTDR and DME.

Is Myopia Associated with the Incidence and Progression of Diabetic Retinopathy?

PURPOSE

We sought to determine the association of refractive error and its associated determinants (axial length [AL], anterior chamber depth, and corneal curvature) with the incidence and progression of diabetic retinopathy (DR).

DESIGN

Population-based cohort study.

METHODS

A total of 1562 eyes of 840 individuals with diabetes and gradable retinal photographs (mean age [SD], 57.0 [8.3] years, 48.2% female) from the Singapore Malay and Indian Eye Studies at baseline (2004-2009) and follow-up (2011-2015) examinations were included in the analyses. Refractive error was calculated as sphere plus half negative cylinder, while AL, anterior chamber depth, and corneal curvature were assessed using optical biometry. Incident DR was defined as having no baseline DR and any DR at follow-up; incident vision-threatening DR as no baseline vision-threatening DR but present at follow-up; and DR progression as an increase in severity at follow-up from at least minimal baseline DR. Eye-specific data and generalized estimating equation models were used to account for between-eye correlation to determine the relationships between the exposures and outcomes, adjusted for traditional DR risk factors.

RESULTS

At follow-up, 164 of 1273 (12.9%) eyes had incident DR, 17 of 1542 (1.1%) eyes had incident vision-threatening DR, and 75 of 269 (27.9%) eyes with baseline DR experienced progression. A longer AL (per millimeter increase) (risk ratio 0.58 [95% confidence interval 0.38-0.88) was associated with a lower risk of incident DR. No other associations were found.

CONCLUSION

Our findings show that a longer AL is protective of incident DR.

Genome-wide association meta-analyses and fine-mapping elucidate pathways influencing albuminuria

Increased levels of the urinary albumin-to-creatinine ratio (UACR) are associated with higher risk of kidney disease progression and cardiovascular events, but underlying mechanisms are incompletely understood. Here, we conduct trans-ethnic (n = 564,257) and European-ancestry specific meta-analyses of genome-wide association studies of UACR, including ancestry- and diabetes-specific analyses, and identify 68 UACR-associated loci. Genetic correlation analyses and risk score associations in an independent electronic medical records database (n = 192,868) reveal connections with proteinuria, hyperlipidemia, gout, and hypertension. Fine-mapping and trans-Omics analyses with gene expression in 47 tissues and plasma protein levels implicate genes potentially operating through differential expression in kidney (including TGFB1, MUC1, PRKCI, and OAF), and allow coupling of UACR associations to altered plasma OAF concentrations. Knockdown of OAF and PRKCI orthologs in Drosophila nephrocytes reduces albumin endocytosis. Silencing fly PRKCI further impairs slit diaphragm formation. These results generate a priority list of genes and pathways for translational research to reduce albuminuria.

A catalog of genetic loci associated with kidney function from analyses of a million individuals

Chronic kidney disease (CKD) is responsible for a public health burden with multi-systemic complications. Through trans-ancestry meta-analysis of genome-wide association studies of estimated glomerular filtration rate (eGFR) and independent replication (n = 1,046,070), we identified 264 associated loci (166 new). Of these, 147 were likely to be relevant for kidney function on the basis of associations with the alternative kidney function marker blood urea nitrogen (n = 416,178). Pathway and enrichment analyses, including mouse models with renal phenotypes, support the kidney as the main target organ. A genetic risk score for lower eGFR was associated with clinically diagnosed CKD in 452,264 independent individuals. Colocalization analyses of associations with eGFR among 783,978 European-ancestry individuals and gene expression across 46 human tissues, including tubulo-interstitial and glomerular kidney compartments, identified 17 genes differentially expressed in kidney. Fine-mapping highlighted missense driver variants in 11 genes and kidney-specific regulatory variants. These results provide a comprehensive priority list of molecular targets for translational research.

Glaucoma in myopia: diagnostic dilemmas

Myopic eyes have an increased risk of glaucoma. However, glaucomatous changes in a myopic eye are often difficult to detect. Classic structural and functional investigations to diagnose glaucoma may be confounded by myopia. Here, we identify some of the common pitfalls in interpreting these structural parameters, and the possible solutions that could be taken to overcome them. For instance, in myopic eyes, we discuss the limitations and potential sources of error when using neuroretinal rim parameters, and retinal nerve fibre layer and ganglion cell-inner plexiform layer thickness measurements. In addition, we also review new developments and potential adjuncts in structural imaging such as the assessment of the retinal nerve fibre layer texture, and the examination of the microcirculation of the optic nerve head using optical coherence tomography angiography. For the functional assessment of glaucoma, we discuss perimetric strategies that may aid in detecting characteristic visual field defects in myopic glaucoma. Ultimately, the evaluation of glaucoma in myopia requires a multimodal approach, to allow correlation between structural and functional assessments. This review provides overview on how to navigate this diagnostic dilemma.

Changes in the Anterior Lamina Cribrosa Morphology with Glaucoma Severity

This study was designed to evaluate if primary open angle glaucoma (POAG) and its severity are associated with the shape of the lamina cribrosa (LC) as measured by a global shape index (LC-GSI), or other indices of LC curvature or depth. Optical coherence tomography (OCT) scans of the optic nerve head (OHN) were obtained from subjects with POAG (n = 99) and non-glaucomatous controls (n = 76). ONH structures were delineated, the anterior LC morphology reconstructed in 3D, and the LC-GSI calculated (more negative values denote greater posterior concavity). Anterior LC depth and 2D-curvature were also measured. Severity of glaucoma was defined by the extent of visual field loss, based on the Hodapp-Parrish-Anderson grading. Linear regression analyses compared LC characteristics between controls, mild-moderate, and advanced POAG groups. After adjusting for age, gender, ethnicity, intraocular pressure, axial length and corneal curvature, the LC-GSI was most negative in the advanced POAG group (mean [standard error] = −0.34 [0.05]), followed by the mild-moderate POAG group (−0.31 [0.02]) and then controls (−0.23 [0.02], P_Trend = 0.01). There was also a significant trend of increasing LC depth and greater LC horizontal curvature with increasing severity of glaucoma (P_Trend = 0.04 and 0.02, respectively). Therefore, with more severe glaucoma, the LC-GSI was increasingly more negative, and the anterior LC depth and curvature greater. These observations collectively correspond to greater cupping of the ONH at the level of the LC. As the LC-GSI describes the 3D anterior LC morphology, its potential usage may be complementary to existing ONH parameters measured on OCT.

Multi-ancestry genome-wide gene-smoking interaction study of 387,272 individuals identifies new loci associated with serum lipids

The concentrations of high- and low-density-lipoprotein cholesterol and triglycerides are influenced by smoking, but it is unknown whether genetic associations with lipids may be modified by smoking. We conducted a multi-ancestry genome-wide gene-smoking interaction study in 133,805 individuals with follow-up in an additional 253,467 individuals. Combined meta-analyses identified 13 new loci associated with lipids, some of which were detected only because association differed by smoking status. Additionally, we demonstrate the importance of including diverse populations, particularly in studies of interactions with lifestyle factors, where genomic and lifestyle differences by ancestry may contribute to novel findings.

The Effect of Gender on Visual Field Sensitivity: The Singapore Chinese Eye Study

PURPOSE

Visual field (VF) sensitivity is known to be age-dependent, but there is a paucity of evidence on whether it is gender-dependent. We therefore investigated the effect of gender on VF sensitivity.

METHODS

An observational study involving 491 adults from the population-based Singapore Chinese Eye Study (SCES). Study participants underwent a comprehensive and standardised ocular examination and VF assessment on the Humphrey Field Analyzer II (Carl Zeiss Meditec, Inc., Dublin, CA, USA). The effect of gender on the mean deviation (MD) and pattern standard deviation (PSD) was analysed with linear regression models.

RESULTS

The mean age was 52.9 ± 5.9 years, and 229 (46.6%) participants were women. A total of 800 reliable VFs from 655 healthy eyes without visual impairment, glaucoma and significant cataract were included. The mean (± standard deviation) MD was -0.45 ± 1.01 dB in men, and -0.84 ± 1.20 dB in women. The MD [95% confidence interval] was 0.28 [-0.44 to -0.12] dB lower in females compared to males (P = 0.001) after adjusting for reliability indices, degree of lens opacity, and other potential confounders. The PSD was not significantly different between the genders.

CONCLUSIONS

In the SCES, the population-average of the central VF sensitivity was significantly lower in women compared to men by a small amount (0.28 dB). This effect was observed in healthy eyes, and was not explained by multiple potential confounders. Hence, this likely represents a physiological gender-based difference that is unaccounted for in standard automated perimetry. Further studies in other populations would be needed to corroborate our findings.

Direct and Indirect Associations Between Diabetes and Intraocular Pressure: The Singapore Epidemiology of Eye Diseases Study

Purpose

The association between diabetes and IOP is controversial; diabetes is associated with thicker central corneal thickness (CCT), and thicker CCT is associated with higher IOP. We therefore aimed to clarify the diabetes-IOP association, considering CCT as a potential mediator.

Methods

We included 8636 participants from the Singapore Epidemiology of Eye Diseases (SEED) Study. Associations of diabetes, serum glucose, or HbA1c with IOP were assessed using regressions models, with adjustments for potential confounding factors. Regression-based mediation (path) analyses were further performed to evaluate the indirect effects of diabetes on IOP through the mediator (CCT), in addition to the direct effect of diabetes on IOP.

Results

Of the 8636 participants, 2524 (29.23%) had diabetes. Diabetes, higher serum glucose, or HbA1c levels were all associated with higher IOP (all P < 0.01). The effect of diabetes on IOP was partially and minimally mediated through CCT; the proportion of mediating effect of CCT was 11.09% of the total effect of diabetes on IOP. Axial length and spherical equivalent were not mediating variables in the diabetes-IOP association. Findings were consistent across three ethnicity groups.

Conclusions

Diabetes or higher long-term hyperglycemia was associated with higher IOP. CCT contributed a small proportion of mediating effect to the total effect of diabetes on IOP. We conclude that high IOP observed in diabetes is mainly due to the direct association of diabetes and IOP, and this finding may have pathophysiologic significance with respect to the risk of glaucoma among persons with diabetes.

Normative pattern and determinants of outer retinal thickness in an Asian population: the Singapore Epidemiology of Eye Diseases Study

BACKGROUND/AIMS

To evaluate the distribution and determinants of outer retinal thickness in eyes without retinal diseases, using spectral-domain optical coherence tomography (SD-OCT).

METHODS

Participants were recruited from the Singapore Epidemiology of Eye Diseases Study, a population-based study among Chinese, Malays and Indians in Singapore. A total of 5333 participants underwent SD-OCT imaging in which a 6×6 mm² measurement area centred at the fovea. Outer retinal thickness was defined as the distance from the outer plexiform layer to the retinal pigment epithelium layer boundary.

RESULTS

7444 eyes from 4454 participants were included in final analysis. Of them, mean age was 58.4 years (SD 8.3), and 2294 (51.5%) were women. Women (121.0±8.1 µm) had thinner average outer retinal thickness than men (125.6±8.2 µm) (p<0.001). Malays (121.4±8.7 µm) had thinner average outer retinal thickness than Indians (124.3±8.6 µm) and Chinese (123.7±7.9 µm) (both p<0.001). In multivariable models, thinner average outer retinal thickness was associated with older age (per decade, β=-1.02, p<0.001), hypertension (β=-0.59, p=0.029), diabetes (β=-0.73, p=0.013), chronic kidney disease (β=-1.25, p=0.017), longer axial length (per mm, β=-0.76, p<0.001), flatter corneal curvature (per mm, β=-2.00, p<0.001) and higher signal strength (β=-1.46, p<0.001).

CONCLUSION

In this large sample of Asian population, we provided normative SD-OCT data on outer retinal thickness in eyes without retinal diseases. Women had thinner outer retina than men. For the first time, these findings provide fundamental knowledge on normative profile of outer retinal thickness in Asians.

Association of Diabetes With Central Corneal Thickness Among a Multiethnic Asian Population

IMPORTANCE

Thicker or thinner central corneas may lead to either overestimation or underestimation of intraocular pressure, which is the most important causal and treatable risk factor for glaucoma. However, the findings on the associations between diabetes, random glucose, and glycated hemoglobin A1c (HbA1c) with central corneal thickness (CCT) are conflicting.

OBJECTIVE

To evaluate the associations between diabetes, random glucose, and HbA1c with CCT in a multiethnic Asian population.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional analysis of the Singapore Epidemiology of Eye Diseases (SEED) Study conducted from 2004 to 2011. A total of 10 033 Chinese, Malay, and Indian individuals 40 years or older residing in Singapore were recruited. Participants with incomplete information on diabetes status (448 participants), prior refractive or cataract surgery (1940 eyes), and corneal edema or dystrophy (29 eyes) were excluded. A meta-analysis was conducted to estimate the overall association of diabetes with CCT.

EXPOSURES

Standardized clinical examinations and interviewer-administered questionnaire to collect information about demographic, systemic, and ocular factors.

MAIN OUTCOMES AND MEASURES

Measurement of CCT using ultrasound pachymetry.

RESULTS

A total of 8846 adults (mean [SD] age, 57.9 [9.9] years; 4447 women [50.3%]) (17 201 eyes) were included in the final analyses. The CCT profile was similar among participants with and without diabetes (mean [SD] CCT, 545.3 [33.7] μm vs 544.8 [33.9] μm; P = .39). Following adjustments of age, sex, ethnicity, corneal curvature, axial length, and body mass index, CCT was a mean (SD) of 4.9 (0.8) μm (95% CI, 3.3-6.5 μm) thicker in patients with diabetes than those without diabetes. Multivariable analyses also showed that thicker CCT was associated with higher random glucose (per 10 mg/dL [to convert to mmol/L, multiply by 0.0555], β = 0.3; 95% CI, 0.2-0.4) and higher HbA1c (per percentage, β = 1.5; 95% CI, 1.0-2.1) (all P < .001). These associations were significant in the subgroup with diabetes but not in the subgroup without diabetes. A meta-analysis including 12 previous population- and clinical-based studies showed that CCT was 12.8 μm (95% CI, 8.2-17.5 μm) thicker in eyes of patients with diabetes.

CONCLUSIONS AND RELEVANCE

These findings suggest that diabetes and hyperglycemia were associated with thicker CCT. This study provides useful information on the interpretation of intraocular pressure in patients with diabetes.

Retinal Nerve Fiber Layer Thickness in a Multiethnic Normal Asian Population: The Singapore Epidemiology of Eye Diseases Study

PURPOSE

To describe variations in retinal nerve fiber layer (RNFL) thickness based on spectral-domain (SD) OCT in a multiethnic Asian population.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Ethnic Chinese, Malay, and Indian adults older than 48 years without glaucoma who were recruited from the Singapore Epidemiology of Eye Diseases Study.

METHODS

All participants underwent standardized systemic and ocular examinations. Retinal nerve fiber layer thickness was measured using SD OCT. Participants with poor-quality scans were excluded. Linear regression models were used to investigate the associations of ocular and systemic factors with average RNFL thickness. Generalized estimating equation models were used to account for correlation between both eyes.

MAIN OUTCOME MEASURE

Average RNFL thickness.

RESULTS

Four thousand four hundred seventy-five participants (8178 eyes) consisting of 1371 Chinese, 1303 Malay, and 1801 Indian adults contributed to this analysis. Average RNFL thickness measured was 95.7±9.6 μm in Chinese participants, 94.9±10.6 μm in Malay participants, and 87.3±10.6 μm in Indian participants (P < 0.001). Multivariate analysis adjusted for age, gender, and ethnicity revealed a reduction in RNFL thickness with increased intraocular pressure and axial length (P < 0.001 for both), as well as a diagnosis of diabetes (P = 0.04); greater RNFL thickness was associated with increased disc area (P < 0.001), signal strength (P < 0.001), and low-density lipoprotein cholesterol (P = 0.02). When these significant variables were taken into account, the average RNFL thickness of Indian participants was significantly thinner compared with Chinese participants (7.45 μm thinner on average [95% confidence interval, 6.75-8.15 μm; P < 0.001]), whereas there was no significant difference in average RNFL thickness between Malay and Chinese participants (P = 0.15).

CONCLUSIONS

Average and regional RNFL thicknesses were significantly thinner in Indian eyes compared with Chinese and Malay eyes. Results of the study highlight the need to acquire more refined normative data for the comparison of individual patients with others of similar ethnic background while accounting for ocular factors that could influence RNFL thickness. This in turn may improve the sensitivity and specificity of glaucoma detection.

Racial differences and determinants of macular thickness profiles in multiethnic Asian population: the Singapore Epidemiology of Eye Diseases Study

Aim

To evaluate racial differences, and ocular and systemic determinants of macular thickness (MT), measured by spectral-domain optical coherence tomography (SD-OCT) in a normal multiethnic Asian population.

Method

MT was measured from a 6×6 mm2 central macular area using the Cirrus high-definition OCT (HD-OCT) (Carl Zeiss Meditec, Dublin, CA). The associations between ocular and systemic factors with MT were evaluated using linear regression analyses with generalised estimating equation models to account for intereye correlation.

Results

7447 healthy eyes (2577 Chinese, 2072 Malays and 2798 Indians) of 4510 subjects were included. Multivariable analysis showed that older age (per decade, β=−4.39), female gender (β=−5.74), diabetes (β=−1.10), chronic kidney disease (CKD) (β=−3.21), longer axial length (per mm, β=−2.34), flatter corneal curvature (per mm, β=−1.79) and presence of cataract (β=−0.94) were associated with thinner overall average MT (OMT) (all p≤0.026); higher total cholesterol (β=0.44; p=0.010) was associated with thicker OMT. All these factors were also associated with thinner central subfield MT (CSMT) (all p≤0.001), except for cataract, total cholesterol and CKD. Meanwhile, longer axial length (β=2.51; p<0.001) was associated with thicker CSMT. OMT (mean±SD) was thickest in Chinese (279.9±12.5 µm), followed by Malays (276.5±13.7 µm) and Indians (272.4±13.1 µm), with p≤0.003 for all interethnic comparisons. Similar trend was observed for CSMT.

Conclusion

There are interethnic differences in MT profile among Asians, particularly between Chinese and Indians. Ocular and systemic factors affect MT measurements as well. This Asian-specific information may be incorporated into existing clinical interpretation of macular OCT scans to aid in improving the diagnostic and monitoring accuracy of macular diseases among Asians.

Time trends, disease patterns and gender imbalance in the top 100 most cited articles in ophthalmology

We analysed the 100 top cited articles in ophthalmology to identify and characterise the most influential articles of the past four decades. Two independent investigators searched the Scopus database to determine the 100 most frequently cited articles in ophthalmology (T100-Eye) and general non-ophthalmology journals (T100-Gen) published from 1975 to December 2017. The T100-Eye list consisted of 83 original articles and 17 reviews, and the number of citations ranged from 582 to 2833. Seventy-eight of these articles were published in three journals alone (impact factor (IF): 5.05-8.2), led by the Archives of Ophthalmology The T100-Gen list consisted of 84 original articles and 16 reviews and the number of citations ranged from 358 to 3272. Forty-five of these articles were published in four journals alone (IF: 9.66-72.41). In both lists, majority of the first authors were from the USA (T100-Eye, n=80; T100-Gen, n=66), and were men (n=76 in T100-Eye; n=72 in T100-Gen). With regard to the article type, in the T100-Eye, among the 83 original research articles, most were randomised controlled trials (n=26) or clinical observational studies related to description of a new condition or new management (n=26). In the T100-Gen, of the 84 original research articles, many were clinical observational studies (n=27) or basic science research (n=26). In both lists, the most frequently examined diseases were age-related macular degeneration, diabetic retinopathy and glaucoma. Our analysis reveals landmark articles, trends and medical advancements in ophthalmology over the past four decades. It also highlights gender disparity and influence of the USA in seminal ophthalmic research.

Novel genetic associations for blood pressure identified via gene-alcohol interaction in up to 570K individuals across multiple ancestries

Heavy alcohol consumption is an established risk factor for hypertension; the mechanism by which alcohol consumption impact blood pressure (BP) regulation remains unknown. We hypothesized that a genome-wide association study accounting for gene-alcohol consumption interaction for BP might identify additional BP loci and contribute to the understanding of alcohol-related BP regulation. We conducted a large two-stage investigation incorporating joint testing of main genetic effects and single nucleotide variant (SNV)-alcohol consumption interactions. In Stage 1, genome-wide discovery meta-analyses in ≈131K individuals across several ancestry groups yielded 3,514 SNVs (245 loci) with suggestive evidence of association (P < 1.0 x 10-5). In Stage 2, these SNVs were tested for independent external replication in ≈440K individuals across multiple ancestries. We identified and replicated (at Bonferroni correction threshold) five novel BP loci (380 SNVs in 21 genes) and 49 previously reported BP loci (2,159 SNVs in 109 genes) in European ancestry, and in multi-ancestry meta-analyses (P < 5.0 x 10-8). For African ancestry samples, we detected 18 potentially novel BP loci (P < 5.0 x 10-8) in Stage 1 that warrant further replication. Additionally, correlated meta-analysis identified eight novel BP loci (11 genes). Several genes in these loci (e.g., PINX1, GATA4, BLK, FTO and GABBR2) have been previously reported to be associated with alcohol consumption. These findings provide insights into the role of alcohol consumption in the genetic architecture of hypertension.

Associations between sleep duration, sleep quality and diabetic retinopathy

Background

Abnormal durations of sleep have been associated with risk of diabetes. However, it is not clear if sleep duration is associated with diabetic retinopathy (DR).

Methods

In a cross-sectional study, we included 1,231 (Malay, n = 395; Indian, n = 836) adults (mean age 64.4 ± 9.0 years, 50.4% female) with diabetes from the second visit of two independent population-based cohort studies (2011–15) in Singapore. Self-reported habitual sleep duration was categorized as short (<6 h), normal (6≤ h <8), and long (≥8 h). Questionnaires were administered to detect risk of obstructive sleep apnea (OSA), excessive daytime sleepiness, and insomnia, all of which may indicate poor quality of sleep. The associations between sleep-related characteristics with moderate DR and vision-threatening DR (VTDR) were analysed using logistic regression models adjusted for potential confounders.

Results

Prevalence of moderate DR and VTDR in the study population were 10.5% and 6.3% respectively. The mean duration of sleep was 6.4 ± 1.5 h. Compared to normal sleep duration, both short and long sleep durations were associated with moderate DR with multivariable odds ratio (95% confidence interval) of 1.73 (1.03–2.89) and 2.17 (1.28–3.66) respectively. Long sleep duration (2.37 [1.16–4.89]), high risk of OSA (2.24 [1.09–4.75]), and excessive daytime sleepiness (3.27 [1.02–10.30]) were separately associated with VTDR.

Conclusion

Sleep duration had a U-shaped association with moderate DR; long sleep duration, excessive daytime sleepiness and high risk of OSA were positively associated with VTDR.

Falls and Recurrent Falls among Adults in A Multi-ethnic Asian Population: The Singapore Epidemiology of Eye Diseases Study

We evaluated the rate and risk factors associated with falls and recurrent falls in a multi-ethnic Asian population. 10,009 participants aged ≥40 years (mean[SD] age = 58.9[10.4] years) underwent clinical examinations and completed interviewer-administered questionnaires. Participants who self-reported at least one fall or ≥2 falls in past 12 months were defined as fallers and recurrent fallers, respectively. Age-standardized rates for falls and recurrent falls were 13.8% (95%CI, 13.1–14.6%) and 4.6% (95%CI, 4.2–5.1%), respectively. Multivariable analyses showed older age (OR = 1.20; 95%CI, 1.11–1.30), female gender (OR = 1.79; 95%CI, 1.54–2.07), diabetes (OR = 1.22; 95%CI, 1.07–1.40), cardiovascular disease (CVD, OR = 1.37; 95%CI, 1.14–1.65), ≥3 systemic comorbidities (OR = 1.35; 95%CI, 1.09–1.67), lower European Quality of Life-5 Dimensions (EQ-5D) score (OR = 1.36; 95%CI, 1.29–1.44), alcohol consumption (OR = 1.41, 95%CI, 1.11–1.78) and presenting visual impairment (VI, OR = 1.23; 95%CI, 1.02–1.47) were associated with falls. For recurrent falls, female gender (OR = 2.27; 95%CI, 1.75–2.94), diabetes (OR = 1.28; 95%CI, 1.03–1.61), CVD (OR = 2.00; 95%CI, 1.53–2.62), ≥3 systemic comorbidities (OR = 1.69; 95%CI, 1.19–2.39), lower EQ-5D score (OR = 1.47; 95%CI, 1.35–1.59), living in 1–2 room public flat (OR = 1.57; 95%CI, 1.05–2.33), monthly income <2000 Singapore Dollar (OR = 1.62; 95%CI, 1.13–2.31), alcohol consumption (OR = 1.81, 95%CI, 1.23–2.66) and presenting VI (OR = 1.34; 95%CI, 1.01–1.79) were significant risk factors. These findings will be useful for the formulation of fall prevention programs.

Sleep Duration and Diabetic Kidney Disease

Aims: Abnormally short or long durations of sleep have been proposed as a risk factors for diabetes and its micro- and macro-vascular complications. However, the relationship between sleep duration and diabetic kidney disease (DKD) has not been well-characterized. Thus, we aimed to examine the association of sleep duration with DKD in two Asian populations. Methods: We included 1,258 persons (Malay, n = 403; Indian, n = 855) aged 40-80 years with diabetes from a population-based cross-sectional sample from Singapore. DKD was defined by low estimated glomerular filtration rate (eGFR <60 mL/min/1.73 m²) and albuminuria (urinary albumin-to-creatinine ratio ≥30 mg/g, only measured in Indian participants). Self-reported habitual sleep duration was categorized into 4 categories: very short (<5 h), short (5-6.9 h), normal (7-8 h) and long (>8 h). The associations of sleep duration with low eGFR and albuminuria were analyzed using multivariable logistic regression models adjusted for multiple potential confounders (including classic risk factors such as HbA1c and hypertension). Results: In total, 268 (21.3%) participants had low eGFR, and 271 (34.7% in Indians) had albuminuria. The number (%) of individuals with very short, short, normal, and long durations of sleep were 117 (9.3%), 629 (50.0%), 429 (34.1%), and 83 (6.6%), respectively. Long sleep duration was associated with a higher odds of renal insufficiency compared to normal sleep duration (OR [95% CI]: 2.31 [1.27-4.19]) on multivariable analysis. Similarly, both long and very short durations of sleep were associated with higher odds of albuminuria (OR [95%]: 2.44 [1.36, 4.38] and 2.37 [1.25, 4.50], respectively) in Indian participants (where data on albuminuria were available). Conclusions: Our study suggests that abnormally short or long durations of sleep were associated with DKD, manifesting as either a reduced eGFR or increased albuminuria. However, further longitudinal data would be required for confirmation.

Macular thickness profile and diabetic retinopathy: the Singapore Epidemiology of Eye Diseases Study

BACKGROUND

To evaluate retinal thickness profiles in eyes with and without diabetic retinopathy (DR) using spectral-domain optical coherence tomography (SD-OCT) among individuals with diabetes.

METHODS

Participants were recruited from the Singapore Epidemiology of Eye Diseases Study, a population-based study among Chinese, Malays and Indians aged 40 years or older residing in Singapore. All participants underwent standardised systemic and ophthalmic examinations. Average thickness of the macula, ganglion cell-inner plexiform layer and outer retina layer (from the outer plexiform layer to the retinal pigment epithelium layer) were measured using SD-OCT. DR status and severity were graded based on fundus photographs using the modified Airlie House classification system. Participants with macular oedema were excluded.

RESULTS

2240 eyes from 1280 participants were included. Of these, 1764 (78.7%) eyes had no DR, 351 (15.7%) eyes had minimal or mild DR and 125 (5.6%) eyes had moderate or worse DR. After adjusting for age, gender, ethnicity, axial length, hypertension, glycated haemoglobin, body mass index, total cholesterol and diabetes duration, eyes with DR had thicker macula (245.44 µm vs 243.04 µm, P=0.03) and outer retina (124.26 µm vs 123.08 µm, P=0.01) than eyes without DR. When stratified by DR severity, thicker macula (250.24 µm vs 242.88 µm, P=0.011) and outer retina (126.4 µm vs 123.0 μm, P=0.006) were observed in eyes with moderate or worse, but not minimal or mild DR, compared with eyes without DR.

CONCLUSIONS

Even in the absence of macular oedema, eyes with DR, particularly those with more severe DR, had thicker macular and outer retinal layers than eyes without DR.

Prevalence and Associations of Retinal Emboli With Ethnicity, Stroke, and Renal Disease in a Multiethnic Asian Population: The Singapore Epidemiology of Eye Disease Study

Importance

To our knowledge, population-based data on retinal emboli are limited in Asia. Besides its associations with traditional cardiovascular risk factors and stroke, associations between retinal emboli and renal disease and function remain unclear.

Objective

To examine the prevalence of and risk factors for retinal emboli in a large, contemporary, multiethnic Asian population.

Design, Setting, and Participants

This population-based cross-sectional study was conducted from 2004 to 2011 and included a total of 10 033 Chinese, Malay, and Indian persons aged 40 to 80 years residing in the general communities of Singapore. Analyses were performed from November 2016 to February 2017.

Interventions or Exposures

Retinal emboli were ascertained from retinal photographs obtained from both eyes of all participants according to a standardized protocol. Age-standardized prevalence of retinal emboli was calculated using the 2010 Singapore adult population. Risk factors were assessed from comprehensive systemic and ophthalmic examinations, interviews, and laboratory investigations.

Main Outcomes and Measures

Retinal emboli.

Results

Of the 10 033 participants, 9978 (99.5%) had gradable retinal photographs. Of these, 5057 (50.7%) were female, and 3375 (33.8%) were Indian. We identified 88 individuals (0.9%) with retinal emboli; the overall person-specific, age-standardized prevalence of retinal emboli was 0.75% (95% CI, 0.60-0.95), with the highest prevalence seen in the Indian cohort (0.98%), followed by the Chinese (0.73%) and Malay (0.44%) cohorts (P = .03). In multivariable-adjusted analysis, factors associated with prevalent retinal emboli included older age (per 5-year increase; odds ratio [OR], 1.22; 95% CI, 1.05-1.41), Indian ethnicity (compared with Malay ethnicity; OR, 3.58; 95% CI, 1.95-6.60), hypertension (OR, 1.95; 95% CI, 1.03-3.70), chronic kidney disease (OR, 2.05; 95% CI, 1.15-3.64), creatinine level (per SD increase; OR, 1.13; 95% CI, 1.05-1.21), glomerular filtration rate (per SD increase; OR, 0.67; 95% CI, 0.51-0.86), and history of stroke (OR, 3.45; 95% CI, 1.70-6.99).

Conclusions and Relevance

Based on 88 individuals among 9978 participants of 3 major Asian ethnic populations, retinal emboli were most commonly seen in Indian persons and associated with conventional cardiovascular risk factors, stroke, and chronic kidney disease. Therefore, its presence may signal vascular embolic event and damage not only in the brain but also in the kidneys. If these data are confirmed in longitudinal studies, they would suggest that persons with retinal emboli may require both general cardiovascular and renal assessment.