Epigenetic and integrative cross-omics analyses of cerebral white matter hyperintensities on MRI.

Cerebral white matter hyperintensities on MRI are markers of cerebral small vessel disease, a major risk factor for dementia and stroke. Despite the successful identification of multiple genetic variants associated with this highly heritable condition, its genetic architecture remains incompletely understood. More specifically, the role of DNA methylation has received little attention. We investigated the association between white matter hyperintensity burden and DNA methylation in blood at ∼450 000 cytosine-phosphate-guanine (CpG) sites in 9732 middle-aged to older adults from 14 community-based studies. Single CpG and region-based association analyses were carried out. Functional annotation and integrative cross-omics analyses were performed to identify novel genes underlying the relationship between DNA methylation and white matter hyperintensities. We identified 12 single CpG and 46 region-based DNA methylation associations with white matter hyperintensity burden. Our top discovery single CpG, cg24202936 (P = 7.6 × 10-8), was associated with F2 expression in blood (P = 6.4 × 10-5) and co-localized with FOLH1 expression in brain (posterior probability = 0.75). Our top differentially methylated regions were in PRMT1 and in CCDC144NL-AS1, which were also represented in single CpG associations (cg17417856 and cg06809326, respectively). Through Mendelian randomization analyses cg06809326 was putatively associated with white matter hyperintensity burden (P = 0.03) and expression of CCDC144NL-AS1 possibly mediated this association. Differentially methylated region analysis, joint epigenetic association analysis and multi-omics co-localization analysis consistently identified a role of DNA methylation near SH3PXD2A, a locus previously identified in genome-wide association studies of white matter hyperintensities. Gene set enrichment analyses revealed functions of the identified DNA methylation loci in the blood-brain barrier and in the immune response. Integrative cross-omics analysis identified 19 key regulatory genes in two networks related to extracellular matrix organization, and lipid and lipoprotein metabolism. A drug-repositioning analysis indicated antihyperlipidaemic agents, more specifically peroxisome proliferator-activated receptor-alpha, as possible target drugs for white matter hyperintensities. Our epigenome-wide association study and integrative cross-omics analyses implicate novel genes influencing white matter hyperintensity burden, which converged on pathways related to the immune response and to a compromised blood-brain barrier possibly due to disrupted cell-cell and cell-extracellular matrix interactions. The results also suggest that antihyperlipidaemic therapy may contribute to lowering risk for white matter hyperintensities possibly through protection against blood-brain barrier disruption.

Unusual Cerebral Aneurysm after Stereotactic Radiosurgery to Treat Trigeminal Neuralgia.

Stereotactic radiosurgery is a treatment option for trigeminal neuralgia. This procedure is minimally invasive, but tumor development and facial numbness have been reported. Here, we report an unusual presentation after stereotactic radiosurgery to treat trigeminal neuralgia. A 60-year-old man demonstrated typical signs for type 1 trigeminal nerve neuralgia and was treated with medication for 5 years. Owing to an intolerance to that medication, he received stereotactic radiosurgery with 66 Gy. During a 9-year follow-up exam, dizziness with a spinning sensation was reported and a right superior cerebellar thrombosed aneurysm was diagnosed. He received transarterial embolization with coiling of aneurysm and subsequently reported no complications on follow-up exams. Although stereotactic radiosurgery is a promising treatment for trigeminal neuralgia, aneurysm development may be considered a possible complication. Long-term follow-up care of these patients should be considered. To understand the relationship between radiosurgery and the potential development of a cerebral aneurysm, further research is needed.

Cerebral air embolism after percutaneous kyphoplasty: a rare case report.

Cerebral air embolism (CAE) is considered as a rare complication during the routine medical procedures in the literature review. We reported a very rare complication of CAE after the percutaneous kyphoplasty (PKP) for the treatment of acute vertebral compression fracture.

Psychiatric Disorders After Traumatic Brain Injury: A Nationwide Population-Based Cohort Study and the Effects of Rehabilitation Therapies.

OBJECTIVE: To investigate the risk of psychiatric disorders after traumatic brain injury (TBI), and to clarify whether the post-TBI rehabilitation was associated with a lower risk of developing psychiatric disorders. DESIGN: A register-based, retrospective cohort design. SETTING: Using data from the National Health Insurance Research Database of Taiwan, we established an exposed cohort with TBI and a nonexposed group without TBI matched by age and year of diagnosis between 2000 and 2015. PARTICIPANTS: This study included 231,894 patients with TBI and 695,682 patients without TBI (N=927,576). INTERVENTIONS: Rehabilitation therapies in TBI patients. MAIN OUTCOME MEASURES: A multivariable Cox proportional hazards regression model was used to compare the risk of developing psychiatric disorders. RESULTS: The incidence rate of psychiatric disorders was higher in the TBI group than the control group. Compared with the control group, the risk of psychiatric disorders in the TBI group was twofold (hazard ratio [HR]=2.072; 95% confidence interval [95% CI], 1.955-2.189; P<.001). Among the participants with TBI, 49,270 (21.25%) had received rehabilitation therapy and had a lower risk of psychiatric disorders (HR=0.691; 95% CI, 0.679-0.703; P<.001). In the subgroup analysis, the medium- to high-level intensity rehabilitation therapy was associated with lower risks of psychiatric disorder (HR=0.712 and 0.568, respectively), but there was no significant finding in the low-intensity group. CONCLUSIONS: We found that TBI was associated with a high risk for developing psychiatric disorders, and that the post-TBI rehabilitation significantly reduced the risk of psychiatric disorders in a dose-dependent manner.

Interaction analysis of ancestry-enriched variants with APOE-ɛ4 on MCI in the Study of Latinos-Investigation of Neurocognitive Aging.

APOE-ɛ4 risk on Mild Cognitive Impairment (MCI) and Alzheimer's Disease (AD) differs between race/ethnic groups, presumably due to ancestral genomic background surrounding the APOE locus. We studied whether African and Amerindian ancestry-enriched genetic variants in the APOE region modify the effect of the APOE-ɛ4 alleles on Mild Cognitive Impairment (MCI) in Hispanics/Latinos. We defined African and Amerindian ancestry-enriched variants as those common in one Hispanic/Latino parental ancestry and rare in the other two. We identified such variants in the APOE region with a predicted moderate impact based on the SnpEff tool. We tested their interaction with APOE-ɛ4 on MCI in the Study of Latinos-Investigation of Neurocognitive Aging (SOL-INCA) population and African Americans from the Atherosclerosis Risk In Communities (ARIC) study. We identified 5 Amerindian and 14 African enriched variants with an expected moderate effect. A suggestive significant interaction (p-value = 0.01) was found for one African-enriched variant, rs8112679, located in the ZNF222 gene fourth exon. Our results suggest there are no ancestry-enriched variants with large effect sizes of interaction effects with APOE-ɛ4 on MCI in the APOE region in the Hispanic/Latino population. Further studies are needed in larger datasets to identify potential interactions with smaller effect sizes.

Genetic loci of beta-aminoisobutyric acid are associated with aging-related mild cognitive impairment.

We studied the genetic associations of a previously developed Metabolomic Risk Score (MRS) for Mild Cognitive Impairment (MCI) and beta-aminoisobutyric acid metabolite (BAIBA)-the metabolite highlighted by results from a genome-wide association study (GWAS) of the MCI-MRS, and assessed their association with MCI in datasets of diverse race/ethnicities. We first performed a GWAS for the MCI-MRS and BAIBA, in Hispanic/Latino adults (n = 3890) from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). We identified ten independent genome-wide significant (p value <5 × 10-8) variants associated with MCI-MRS or BAIBA. Variants associated with the MCI-MRS are located in the Alanine-Glyoxylate Aminotransferase 2 (AGXT2 gene), which is known to be associated with BAIBA metabolism. Variants associated with BAIBA are located in the AGXT2 gene and in the SLC6A13 gene. Next, we tested the variants' association with MCI in independent datasets of n = 3178 HCHS/SOL older individuals, n = 3775 European Americans, and n = 1032 African Americans from the Atherosclerosis Risk In Communities (ARIC) study. Variants were considered associated with MCI if their p value <0.05 in the meta-analysis of the three datasets and their direction of association was consistent with expectation. Rs16899972 and rs37369 from the AGXT2 region were associated with MCI. Mediation analysis supported the mediation effect of BAIBA between the two genetic variants and MCI (p value = 0.004 for causal mediated effect). In summary, genetic variants in the AGXT2 region are associated with MCI in Hispanic/Latino, African, and European American populations in the USA, and their effect is likely mediated by changes in BAIBA levels.

Proteomics analysis of plasma from middle-aged adults identifies protein markers of dementia risk in later life.

A diverse set of biological processes have been implicated in the pathophysiology of Alzheimer's disease (AD) and related dementias. However, there is limited understanding of the peripheral biological mechanisms relevant in the earliest phases of the disease. Here, we used a large-scale proteomics platform to examine the association of 4877 plasma proteins with 25-year dementia risk in 10,981 middle-aged adults. We found 32 dementia-associated plasma proteins that were involved in proteostasis, immunity, synaptic function, and extracellular matrix organization. We then replicated the association between 15 of these proteins and clinically relevant neurocognitive outcomes in two independent cohorts. We demonstrated that 12 of these 32 dementia-associated proteins were associated with cerebrospinal fluid (CSF) biomarkers of AD, neurodegeneration, or neuroinflammation. We found that eight of these candidate protein markers were abnormally expressed in human postmortem brain tissue from patients with AD, although some of the proteins that were most strongly associated with dementia risk, such as GDF15, were not detected in these brain tissue samples. Using network analyses, we found a protein signature for dementia risk that was characterized by dysregulation of specific immune and proteostasis/autophagy pathways in adults in midlife ~20 years before dementia onset, as well as abnormal coagulation and complement signaling ~10 years before dementia onset. Bidirectional two-sample Mendelian randomization genetically validated nine of our candidate proteins as markers of AD in midlife and inferred causality of SERPINA3 in AD pathogenesis. Last, we prioritized a set of candidate markers for AD and dementia risk prediction in midlife.

Clinical Use of Lansoprazole and the Risk of Osteoporosis: A Nationwide Cohort Study.

BACKGROUND: Proton pump inhibitor (PPI) lansoprazole acts as a liver X receptor agonist, which plays a crucial role in the crosstalk of osteoblasts and osteoclasts in vitro and during bone turnover in vivo. However, epidemiological studies on the association between the use of lansoprazole and osteoporosis risk are limited. We aimed to determine the risk of developing osteoporosis in patients with lansoprazole use. METHODS: A retrospective cohort study was conducted using the National Health Insurance Research Database of Taiwan dated from 2000 to 2013. The study includes 655 patients with lansoprazole use (the exposed cohort) and 2620 patients with other PPI use (the comparison cohort). The main outcome was the primary diagnosis of osteoporosis. The hazard ratios (HRs) and 95% confidence intervals (CIs) were used to assess the association between the use of lansoprazole and risk of osteoporosis. RESULTS: Patients receiving lansoprazole treatment had a reduced risk of osteoporosis as compared with those undergoing other PPI therapy (adjusted HR, 0.56; 95% CI, 0.46-0.68). Moreover, this inverse association is evident in both sexes and in various age groups. CONCLUSIONS: This population-based cohort study demonstrated that lansoprazole use was associated with a reduced risk of osteoporosis. The clinical implications of the present study need further investigations.

Identification of Functional Genetic Determinants of Cardiac Troponin T and I in a Multiethnic Population and Causal Associations With Atrial Fibrillation.

BACKGROUND: Elevated cardiac troponin levels in blood are associated with increased risk of cardiovascular diseases and mortality. Cardiac troponin levels are heritable, but their genetic architecture remains elusive. METHODS: We conducted a transethnic genome-wide association analysis on high-sensitivity cTnT (cardiac troponin T; hs-cTnT) and high-sensitivity cTnI (cardiac troponin I; hs-cTnI) levels in 24 617 and 14 336 participants free of coronary heart disease and heart failure from 6 population-based cohorts, followed by a series of bioinformatic analyses to decipher the genetic architecture of hs-cTnT and hs-cTnI. RESULTS: We identified 4 genome-wide significant loci for hs-cTnT including a novel locus rs3737882 in PPFIA4 and 3 previously reported loci at NCOA2, TRAM1, and BCL2. One known locus at VCL was replicated for hs-cTnI. One copy of C allele for rs3737882 was associated with a 6% increase in hs-cTnT levels (minor allele frequency, 0.18; P=2.80×10-9). We observed pleiotropic loci located at BAG3 and ANO5. The proportions of variances explained by single-nucleotide polymorphisms were 10.15% and 7.74% for hs-cTnT and hs-cTnI, respectively. Single-nucleotide polymorphisms were colocalized with BCL2 expression in heart tissues and hs-cTnT and with ANO5 expression in artery, heart tissues, and whole blood and both troponins. Mendelian randomization analyses showed that genetically increased hs-cTnT and hs-cTnI levels were associated with higher odds of atrial fibrillation (odds ratio, 1.38 [95% CI, 1.25-1.54] for hs-cTnT and 1.21 [95% CI, 1.06-1.37] for hs-cTnI). CONCLUSIONS: We identified a novel genetic locus associated with hs-cTnT in a multiethnic population and found that genetically regulated troponin levels were associated with atrial fibrillation.

Large-scale plasma proteomic analysis identifies proteins and pathways associated with dementia risk.

The plasma proteomic changes that precede the onset of dementia could yield insights into disease biology and highlight new biomarkers and avenues for intervention. We quantified 4,877 plasma proteins in nondemented older adults in the Atherosclerosis Risk in Communities cohort and performed a proteome-wide association study of dementia risk over five years (n = 4,110; 428 incident cases). Thirty-eight proteins were associated with incident dementia after Bonferroni correction. Of these, 16 were also associated with late-life dementia risk when measured in plasma collected nearly 20 years earlier, during mid-life. Two-sample Mendelian randomization causally implicated two dementia-associated proteins (SVEP1 and angiostatin) in Alzheimer's disease. SVEP1, an immunologically relevant cellular adhesion protein, was found to be part of larger dementia-associated protein networks, and circulating levels were associated with atrophy in brain regions vulnerable to Alzheimer's pathology. Pathway analyses for the broader set of dementia-associated proteins implicated immune, lipid, metabolic signaling and hemostasis pathways in dementia pathogenesis.

Secondary Genome-Wide Association Study Using Novel Analytical Strategies Disentangle Genetic Components of Cleft Lip and/or Cleft Palate in 1q32.2.

Orofacial cleft (OFC) is one of the most prevalent birth defects, leading to substantial and long-term burdens in a newborn's quality of life. Although studies revealed several genetic variants associated with the birth defect, novel approaches may provide additional clues about its etiology. Using the Center for Craniofacial and Dental Genetics project data (n = 10,542), we performed linear mixed-model analyses to study the genetic compositions of OFC and investigated the dependence among identified loci using conditional analyses. To identify genes associated with OFC, we conducted a transcriptome-wide association study (TWAS) based on predicted expression levels. In addition to confirming the previous findings at four loci, 1q32.2, 8q24, 2p24.2 and 17p13.1, we untwined two independent loci at 1q32.2, TRAF3IP3 and IRF6. The sentinel SNP in TRAF3IP3 (rs2235370, p-value = 5.15 × 10-9) was independent of the sentinel SNP at IRF6 (rs2235373, r2 < 0.3). We found that the IRF6 effect became nonsignificant once the 8q24 effect was conditioned, while the TRAF3IP3 effect remained significant. Furthermore, we identified nine genes associated with OFC in TWAS, implicating a glutathione synthesis and drug detoxification pathway. We identified some meaningful additions to the OFC etiology using novel statistical methods in the existing data.

Association between traumatic spinal cord injury and affective and other psychiatric disorders-A nationwide cohort study and effects of rehabilitation therapies.

BACKGROUND: This study aimed to investigate the association between traumatic spinal cord injury (TSCI) and the risk of affective and other psychiatric disorders, and the role of the rehabilitation therapies. METHODS: In this population-based, retrospective cohort study, we used Taiwan's National Health Insurance Research Database to analyze the patients who were newly diagnosed with TSCI between 2000 and 2015 were included, with a 1:3 ratio by age, sex, and index year matched in the non-TSCI comparison group, for the risk of affective and other psychiatric disorders. RESULTS: In total, 5375 out of 16,151 patients with TSCI developed psychiatric disorders, and 1467 out of 48,543 patients in the non-TSCI group developed psychiatric disorders (2930.88 vs 2823.29 per 100,000 persons/year). The Kaplan-Meier analysis showed that the TSCI cohort had a significantly higher risk of psychiatric disorders (log-rank, p < 0.001). Fine and Gray's survival analysis revealed that the adjusted hazard ratio was 1.977 (95% CI: 1.914-2.042, p < 0.001). Rehabilitation therapies, including physical and occupational therapies, within 90 days after the injury, was associated with a lowered risk of psychiatric disorders, including anxiety, depression, and bipolar disorder, in the TSCI cohort (adjusted HR = 0.702 [95% CI: 0.661-0.746, p < 0.001]). In the subgroups with low, medium, and high intensity, rehabilitation therapies were associated with a lowered risk of psychiatric disorders. CONCLUSIONS: TSCI was associated with the risk of affective and other psychiatric disorders, and rehabilitation therapies were associated with a lowered risk of these in the TSCI cohort.

Dose Comparison Using Thermoluminescent Dosimeters During Multislice Computed Tomography With Different Parameters for Simulated Spine Tumor Examination.

This study aims to compare the effect of Philips' Brilliance 64-slice and 256-slice (multislice) computed tomography on effective doses when changing the operating parameters for simulated examinations of patients' spine tumors, including changes in pitch, tube voltage (kV), and effective tube current-time product (mA s). This study considers the possibility of using other probable operating conditions to reduce patients' effective doses. The absorbed doses to organs and skin are measured by taking data from thermoluminescent dosimeters (GR-200 and GR-200F) in relevant positions on the anthropomorphic Rando phantom. We also used an American College of Radiology computed tomography accreditation phantom to experiment with image spatial resolution under various scan conditions in order to achieve results over 5 line pairs per cm, the analytical capability required to meet diagnostic needs. The results show that, in general, when we change the pitch, effective tube current-time product, and tube voltage, the effective doses from 256-slice computed tomography exceed those from 64-slice computed tomography.

Risk of Erectile Dysfunction After Traumatic Brain Injury: A Nationwide Population-Based Cohort study in Taiwan.

INTRODUCTION: In our study, we aimed to investigate the association between a traumatic brain injury (TBI) and subsequent erectile dysfunction (ED). This is a population-based study using the claims dataset from The National Health Insurance Research Database. METHODS: We included 72,642 patients with TBI aged over 20 years, retrospectively, selected from the longitudinal health insurance database during 2000-2010, according to the ICD-9-CM. The control group consisted of 217,872 patients without TBI that were randomly chosen from the database at a ratio of 1:3, with age- and index year matched. Cox proportional hazards analysis was used to estimate the association between the TBI and subsequent ED. RESULTS: After a 10-year follow-up, the incidence rate of ED was higher in the TBI patients when compared with the non-TBI control group (24.66 and 19.07 per 100,000, respectively). Patients with TBI had a higher risk of developing ED than the non-TBI cohort after the adjustment of the confounding factors, such as age, comorbidity, residence of urbanization and locations, seasons, level of care, and insured premiums (adjusted hazard ratio (HR) = 2.569, 95% CI [1.890, 3.492], p < .001). CONCLUSION: This is the first study using a comprehensive nationwide database to analyze the association of ED and TBI in the Asian population. After adjusted the confounding factors, patients with TBI have a significantly higher risk of developing ED, especially organic ED, than the general population. This finding might remind clinicians that it's crucial in early identification and treatment of ED in post-TBI patients.

Analysis of volumetric response of pituitary adenomas receiving adjuvant CyberKnife stereotactic radiosurgery with the application of an exponential fitting model.

Tumor control rates of pituitary adenomas (PAs) receiving adjuvant CyberKnife stereotactic radiosurgery (CK SRS) are high. However, there is currently no uniform way to estimate the time course of the disease. The aim of this study was to analyze the volumetric responses of PAs after CK SRS and investigate the application of an exponential decay model in calculating an accurate time course and estimation of the eventual outcome.A retrospective review of 34 patients with PAs who received adjuvant CK SRS between 2006 and 2013 was performed. Tumor volume was calculated using the planimetric method. The percent change in tumor volume and tumor volume rate of change were compared at median 4-, 10-, 20-, and 36-month intervals. Tumor responses were classified as: progression for >15% volume increase, regression for ≤15% decrease, and stabilization for ±15% of the baseline volume at the time of last follow-up. For each patient, the volumetric change versus time was fitted with an exponential model.The overall tumor control rate was 94.1% in the 36-month (range 18-87 months) follow-up period (mean volume change of -43.3%). Volume regression (mean decrease of -50.5%) was demonstrated in 27 (79%) patients, tumor stabilization (mean change of -3.7%) in 5 (15%) patients, and tumor progression (mean increase of 28.1%) in 2 (6%) patients (P = 0.001). Tumors that eventually regressed or stabilized had a temporary volume increase of 1.07% and 41.5% at 4 months after CK SRS, respectively (P = 0.017). The tumor volume estimated using the exponential fitting equation demonstrated high positive correlation with the actual volume calculated by magnetic resonance imaging (MRI) as tested by Pearson correlation coefficient (0.9).Transient progression of PAs post-CK SRS was seen in 62.5% of the patients receiving CK SRS, and it was not predictive of eventual volume regression or progression. A three-point exponential model is of potential predictive value according to relative distribution. An exponential decay model can be used to calculate the time course of tumors that are ultimately controlled.

Overexpression of TELO2 decreases survival in human high-grade gliomas.

High-grade gliomas are characterized with poor prognosis. To improve the clinical outcome, biomarker is urgently needed for distinguishing oncotarget in high-grade gliomas. Telomere maintenance 2 (TELO2) regulates S-phase checkpoint in cell cycle, and is involved in DNA repair. However, the role of TELO2 in survival outcome of high-grade gliomas is still not yet clarified. This study aims to investigate the correlation between TELO2 mRNA expression and survival outcome of patients with high-grade gliomas. Based on bioinformatics study, we found that Kaplan-Meier analysis demonstrated shorter survival in patients with higher TELO2 mRNA levels than in those with lower TELO2 expression (median survival, 59 vs. 113 weeks, p=0.0017, by log-rank test, hazard ratio: 0.3505, 95% CI: 01824.-0.6735). TELO2 mRNA expression significantly higher in World Health Organization (WHO) grade IV than in non-tumor control (p=2.85 x 10-9). Moreover, TELO2 level was greater in WHO grade III than in non-tumor controls (p= 0.017) human gliomas. We further validated TELO2 mRNA expression and protein levels by using quantitative RT-PCR, Western blot, and immunohistochemical (IHC) stain of tissue microarray. Consistently, the TELO2 mRNA and protein expression were significantly elevated in human glioma cells in comparison with normal brain control. Additionally, IHC staining showed higher TELO2 immunostain score in high-grade gliomas than in low-grade gliomas, or normal brain control. Taken together, human high-grade gliomas increase TELO2 mRNA expression, and overexpression of TELO2 mRNA expression correlates with shorter survival outcome, supporting that TELO2 is an oncotarget in human gliomas.

Changes in eating behaviors and body weight in Koreans: the Healthy Twin Study.

OBJECTIVE: We examined the associations between eating behavior at baseline and changes in eating behaviors with weight change, and quantified the contribution of eating behavior and genetic effects on weight change. METHODS: A prospective study of male (n = 482) and female (n = 879) Korean twins and family members who were weighed and assessed twice (baseline visit from December 2005 to December 2008, follow-up visit 2.7 ± 0.9 y later) using eating behavior subscales (external, emotional, and restrained eating) as measured by the Dutch Eating Behavior Questionnaire. RESULTS: After adjusting for family variables, eating behavior subscales at baseline, changes in emotional and restrained eating, age, education, weight, and lifestyle at baseline, and menopausal status at baseline (for women), an increase in external eating was significantly associated with weight gain in men (1.08, 95% confidence interval 0.41-1.74) and in women (0.63, 95% confidence interval 0.13-1.12). None of the three eating behavior subscales at baseline or changes in emotional and restrained eating were associated with weight change. Eating behavior at baseline and changes in those eating behaviors accounted for 4% and 1% of the changes in weight in men and women, respectively. Additive genetic effects in women contributed to 18% of weight change, whereas in men there was no genetic contribution. CONCLUSIONS: These results suggest that an increase in external eating may predict adult weight gain in men and women. However, the relative contribution of eating behavior to weight change was very small, whereas the contribution of genetic effects on weight change was significant in women.

Genetic influences on macular thickness in Koreans: the healthy twin study.

PURPOSE: To estimate genetic influences accounting for macular thickness in the Korean population. METHODS: Study subjects were 830 healthy Korean adults (117 monozygotic twin pairs and 523 family members) from the Healthy Twin study. Macular thickness was measured with optical coherence tomography for nine subfields including the fovea, four inner quadrants (within 1 to 3 mm of the center), and four outer quadrants (within 3 to 6 mm of the center). Quantitative genetic analyses were performed to estimate the heritability of macular thickness with respect to familial correlations. RESULTS: Macular thickness varied by subfield and was thinnest at the fovea and thickest at the inner superior area. Heritability of macular thickness at each subfield was 0.76, 0.73, 0.70, 0.56, 0.67, 0.70, 0.73, 0.29, and 0.36 at the fovea, inner superior area, inner inferior area, inner nasal area, inner temporal area, outer superior area, outer inferior area, outer nasal area, and outer temporal area, respectively. CONCLUSIONS: Genetic factors play a significant role in determining macular thickness in the Korean population.