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Quaternionic bertrand curves in euclidean 4-space
(Int Center Scientific Research & Studies, 2013) Kecilioğlu, Osman; İlarslan, Kazım
In this paper, by using the similar idea of Matsuda and Yorozu [12], we prove that if bitorsion of a quatenionic curve alpha is no vanish, then there is no quaternionic curve in E-4 is a Bertrand curve. Then we define (1, 3) type Bertrand curves for quatenionic curve in Euclidean 4-space. We give some characterizations for a (1, 3) type quaternionic Bertrand curves in Euclidean 4-space by means of the curvature functions of the curve.
An Algebraic Approach to Clustering and Classification with Support Vector Machines
(Mdpi, 2022) Arslan, Güvenç; Madran, Uğur; Soyoğlu, Duygu
In this note, we propose a novel classification approach by introducing a new clustering method, which is used as an intermediate step to discover the structure of a data set. The proposed clustering algorithm uses similarities and the concept of a clique to obtain clusters, which can be used with different strategies for classification. This approach also reduces the size of the training data set. In this study, we apply support vector machines (SVMs) after obtaining clusters with the proposed clustering algorithm. The proposed clustering algorithm is applied with different strategies for applying SVMs. The results for several real data sets show that the performance is comparable with the standard SVM while reducing the size of the training data set and also the number of support vectors.
An almost unbiased Liu-type estimator in the linear regression model
(Taylor & Francis Inc, 2024) Erdugan, Funda
A biased estimator, compared to least squares estimators, is one of the most used statistical procedures to overcome the problem of multicollinearity. Liu-type estimators, which are biased estimators, are preferred in a wide range of fields. In this article, we propose an almost unbiased Liu-type (AUNL) estimator and discuss its performance under the mean square error matrix criterion among existing estimators. The proposed AUNL estimator is a general estimator and is based on the function of a single biasing parameter. It includes an ordinary least squares estimator, an almost unbiased ridge estimator, an almost unbiased Liu estimator, and an almost unbiased two-parameter estimator. Finally, real data examples and a Monte Carlo simulation are provided to illustrate the theoretical results.
A geometric process with Hjorth marginal: Estimation, discrimination, and reliability data modeling
(Wiley, 2022) Demirci Biçer, Hayrinisa; Biçer, Cenker; Bakouch, Hassan Salah Hassan
The geometric process is one of the important simple monotonic processes with a positive ratio parameter in the theory of stochastic processes. Simply, it can be thought of as a generalization of the renewal process (RP). In the current paper, we mainly study the geometric process with the Hjorth marginal distribution, with parameters theta and lambda, for being able to model the successive inter-arrival times with a trend. We first examine inference problem for the mentioned process from different perspectives and obtain the different estimators of its parameters by employing different estimation methods such as maximum likelihood, modified moments, modified maximum spacing, and modified least-squares. The efficiencies of these estimators are compared via a series of extensive simulation studies in the paper. Further, we give also a discrimination statistic for discriminating among geometric processes with the Hjorth distribution and its alternatives. This is quite important to select the optimal geometric process model for data. Finally, a modeling study by using the geometric process with the Hjorth distribution is provided in detail to display its effectiveness to model the reliability data sets.
Validity and reliability of the full cup test in patients with chronic low back pain
(Kare Publ, 2022) Ağır, Hatice; Aras, Müyesser; Keskin, Esra Dilek; Özer, Hafsa Feyza; Karaca, Gülten; Ergün, Ufuk; Yörübulut, Serap
Objectives:This study aims to determine the validity and reliability of the full cup test (FCT), evaluating the pain severity in patients with chronic low back pain. Methods: A total of 100 patients (70 women and 30 men) aged over 18 years with mechanical low back pain were enrolled in the study. Demographic and clinical characteristics were recorded. Pain severity was evaluated using the visual analog scale (VAS) and FCT, the functional state was assessed by the Oswestry Disability Index (ODI), and the quality of life was assessed using the Nottingham Health Profile (NHP). FCT was performed on the 1st day by two independent observers (G1 and G2) and 3 days after the first application, patients were readministered the FCT by G1. Results:The mean age of participants was 56.04 +/- 12.33 years and mean body mass index was 27.7 +/- 4.3 kg/m(2). The reliability of the FCT and intraclass correlation coefficient (ICC) was found to be 0.989 for intrarater compliance, ICC was found to be 0.984 for inter-rater compliance, and Cronbach's alpha reliability coefficient was alpha=0.994. External construct validity of the scale was confirmed with expected correlations with all subgroups of NHP except for social isolation, VAS and ODI (p<0.01). Conclusion:This study concludes that the FCT provides a reliable and valid instrument for measuring pain severity and loss of the function in patients with chronic mechanical back pain. We consider that FCT is a simple and easy test in patients with low education and advanced age.
Sıralı Küme Örneklemesi ile Kumaraswamy Dağılımı Parametrelerinin Tahmin Edilmesinde Genetik Algoritma Kullanılması
(2019) Kılıç, Adil; Arslan, Güvenç
Bu çalışmada, Kumaraswamy dağılımının parametrelerinin en çok olabilirlik yöntemi ile tahmin edilmesi genetik algoritma yaklaşımı kullanılarak araştırılmıştır. Ayrıca basit rasgele örneklemeye göre daha iyi sonuç verebileceği düşünülerek parametrelerin tahmin edilmesinde sıralı küme örneklemesi de incelenmiştir. Genetik algoritma yaklaşımı, Kumaraswamy dağılımı parametrelerinin pozitif olma koşulunun hesaba katılması nedeniyle tercih edilmiştir. Ek olarak genetik algoritma yaklaşımında en çok olabilirlik fonksiyonunun türev bilgisine ihtiyaç duyulmaması da hesaplamalarda kolaylık sağlamaktadır. Genetik algoritma kullanılarak elde edilen her iki örnekleme yöntemine ait olabilirlik tahmin edicilerinin performanslarının karşılaştırılması için yan, hata kareler ortalaması ve etkinlikleri hesaplanmıştır. Simülasyon çalışmasındaki hesaplamalar için R yazılımı ve ilgili paketler kullanılmıştır.
Risk factors for smoking behavior among university students
(2011) Öncel, Yurt Sevgi; Gebizlioğlu, Ömer Lütfi; Alioğlu, Aliev Fazil
Amaç: Sigara içme, Türkiye’de yaygın bir alışkanlık ve dünyada önemli bir halk sağlığı sorunudur. Bu çalışmada, anket formu kullanarak Kırıkkale Üniversitesi öğrencilerinin sigara içme riskinin artışı ile bağlı olan faktörlerin belirlenmesi için istatistiksel analizler yapılmıştır. Yöntem ve gereç: Yaş, cinsiyet, öğrencinin sigara içme durumu, velilerin sigara içme durumu ve eğitim düzeyi, gelir, günlük spor aktiviteleri, sigara içme öyküsü (sigaraya başlama/bırakma yaşı, günlük içtiği ortalama sigara sayısı, sigara bırakma girişimi, sigaraya başlama nedenleri), alkol kullanımı ve davranış problemlerini kapsayan anket 1734 (toplam 15.000 öğrencinin % 11,6’sı) Kırıkkale Üniversitesi öğrencilerine (869 erkek ve 866 kız, sigara kullanan ve kullanmayan) uygulanmıştır. Bireysel puanlara dayalı olarak nikotin bağımlılık puanları Fagerström Test for Nicotine Dependence (FTND) ve kategorik nikotin bağımlılığı değişkenleri hesaplandı. Aynı zamanda iki düzeyli gelir (income2) ve sigara içme durumu değişkenlerini oluşturulmuştur. Analizler için betimsel istatistikler, t-testi, ki-kare testi, tek ve çok değişkenli lojistik regresyon kullanılmıştır. Bulgular: Çalışmaya katılan öğrecilerden bir ay veya daha uzun süre içerisinde her gün sigara içmiş olan 548 (% 31,6)’i sigara kullanan olarak tespit edildi. Veriler sigara içen 548 öğrencinin % 66,1’inin erkek, % 33,9’unun bayan olduğunu göstermektedir. Günlük içilen sigara sayısının, sigaraya başlama yaşının ve FTND puanlarının ortalaması ve standart sapması (SS) erkekler için, uygun olarak, 15,9 (SS = 7,7), 16,6 (SS = 3,0) ve 4,4 (SS = 2,3), kızlar için, uygun olarak, 13,1 (SS = 6,5), 17,4 (SS = 2,4) ve 3,9 (SS = 2,4) olarak bulunmuştur. FTND puanları ve günlük içilen sigara sayısı arasında pozitif korelasyon (r = 0,612, P < 0,05); FTND puanları ve sigaraya başlama yaşı arasında negarif korelasyon (r = –0,232, P < 0,05) saptandı. Erkeklerin sigara içme riskleri kızlara göre 2,968 kez çok çıkmıştır. Öğrencinin sigara içme riskini sigara içen kardeşinin olması 2,368 kez, annenin sigara içmesi 1,564 kez, babanın sigara içmesi 1,488 kez artırmaktadır. Yüksek aile geliri de riski 1,579 kez artırıyor. Sonuç: Çalışmamız, üniversite öğrencilerinin sigara içme davranışında cinsiyet, ailede sigara içen kimselerin bulunması, annenin eğitim düzeyi, ailenin gelir durumu anlamlı rol oynamaktadır. Ebeveynlerin günlük içtikleri sigara sayısı artıkça gençlerin de sigara içme düzeyinde ve sigaraya olan bağımlılık durumunda artış gözlenmiştir. Gençlerle beraber aile büyüklerinin de sigaranın zararları ve sigarayı bırakma konusunda bilgilendirilmesi önerilmektedir. Sigara alışkanlığının hem çevresel hem de genetik boyutlarının ortak değerlendirilmesinin büyük önem arzettiği görülmektedir.
Trpv2 Polymorphisms Change The Risk Of Type 2 Diabetes - Hashimoto Thyroiditis Comorbidity
(EDITURA ACAD ROMANE, 2020) Arikan, F. Bulut; Ozdemir, F. A.; Sen, D.; Erdem, S.; Yorubulut, S.; Dogan, H.; Keskin, L.
Context. Thyroid disorders are common in diabetics and related to severe diabetic complications. TRPV2 ion channels have crucial functions in insulin secretion and glucose metabolism which have an important role in the pathophysiology of diabetes. Also, they have a significant effect on various immunological events that are involved in the HT pathophysiology. Objective. This study aimed to investigate rs14039 and rs4792742 polymorphisms of the TRPV2 ion channels in type 2 diabetes mellitus (T2DM, n=100) Hashimoto thyroiditis (HT, n=70) and comorbid T2DM and HT (T2DM+HT, n=100) patients and control (n=100). Design. Case-control study Subject and Methods. RT-PCR genotyping was used to determine rs14039 and rs4792742 polymorphisms with DNA samples of subjects and appropriate primer and probes. Besides, required biochemical analyses were performed. Results. It was determined that the frequencies of the rs14039 GG homozygote polymorphic genotype and the G allele were significantly higher in T2DM+HT patients compared to the control (p=0.03 and p=0.01, respectively) and that especially the GG genotype increases the risk of T2DM+HT 3.046-fold (p=0.01, OR=3.046). It was detected that the GG genotype increased the risk of HT 2.54-fold (p=0.05, OR=2.541). TRPV2 rs4792742 polymorphisms reduce the risk of HT and T2DM+HT comorbidity almost by half and have a protective effect against HT and T2DM+HT. Conclusion. The rs14039 GG genotype of the TRPV2 gene significantly increases the risks of development of T2DM+HT and HT disorders, may have a significant role in the pathophysiology of these diseases, also leading to predisposition for their development. Conversely, rs4792742 polymorphic genotypes have a strong protective effect against the HT and T2DM+HT comorbidity.
Spatial Patterns of Infant Mortality in Turkey between 2011 and 2016
(INT COMMUNITY SPATIAL PLANNING & SUSTAINABLE DEVELOPMENT, 2020) Turkan, Ayca Hatice; Erdugan, Funda; Aldemir, Suleyman
Health studies are important for the evaluation of health services and the improvement of poor conditions as well as for the determination of the development levels of countries. The purpose of this study was to demonstrate the spatial patterns of infant mortality, which is considered an indicator of health conditions, in Turkey between 2011 and 2016. The existence of global autocorrelation was first studied using the infant mortality rate, the standardised mortality ratio, and the infant mortality rate which was corrected by Bayes smoothers. Local spatial autocorrelation analysis was performed to determine statistically significant hot spots or clusters in infant mortality. It was determined that the spatial distribution between 2011 and 2016 was not coincidental, and aggregation tendency and spatial dependence were observed in the data. According to local spatial statistics, spatial differences of Southeastern Anatolia and Eastern Anatolia regions appeared in Turkey in terms of infant mortality. Furthermore, the factors related to the infant mortality rate were considered. It was found that the age of marriage for women, the net schooling rates of females in secondary education, the number of midwives, and the gross domestic product (GDP) were related to infant mortality rates. It is important to determine different associated factors in the provinces with high infant mortality rates found in this study and to develop an understanding of what can be done to prevent infant mortality in the future. In the South-eastern Anatolia and Eastern Anatolia regions, it is necessary to produce and implement policies with the scope of reducing the infant mortality rate.
The Effect of Extractum Cepae, Heparin Sodium, and Allantoin in Experimental Peritoneal Adhesion
(SPRINGER INDIA, 2020) Ozmen, Ismail; Gunal, Yasemin Dere; Atasoy, Pinar; Kisa, Ucler; Yorubulut, Serap; Aslan, Mustafa Kemal; Boybeyi-Turer, Ozlem
The purpose of the study is to investigate the effects of extractum cepae (EC), heparin sodium (HS), and allantoin (AA) on postoperative peritoneal adhesion (PPA) prevention. Forty-eight rats were allocated into six groups (n = 8). PPA was performed by Harris method. In group 1, no additional procedure was done. Abdominal cavity was washed with normal saline in group 2, EC in group 3, HS in group 4, AA in group 5, and EC-HS-AA mixture (EHA-m) in group 6. On the 21st postoperative day, PPA was scored with Nair adhesion score and examined for fibrosis histopathologically and hydroxy-proline levels (OHP) biochemically. Macroscopically, PPA was decreased in groups 2, 4, and 6 compared to groups 1, 3, and 5 (p < 0.05) and decreased in group 2 compared to other groups (p < 0.05). Histopathologically, fibrosis was decreased in groups 2, 4, and 6 compared to other groups and decreased in group 2 compared to other groups (p < 0.05). Tissue OHP level was decreased in groups 2, 3, 4, and 5 compared to groups 1 and 6 (p < 0.05). Tissue OHP level was decreased in group 6 compared to group 1, but the difference was not statistically significant. PPA formation decreases with normal saline, HS and EHA-m, whereas increases with EC and AA both macroscopically and microscopically. Although HS and EHA-m seem to have adhesion prevention effect, washing the intestines with saline seems to be more effective.
Genetic and environmental influences on human height from infancy through adulthood at different levels of parental education
(NATURE RESEARCH, 2020) Jelenkovic, Aline; Sund, Reijo; Yokoyama, Yoshie; Latvala, Antti; Sugawara, Masumi; Tanaka, Mami; Matsumoto, Satoko
Genetic factors explain a major proportion of human height variation, but differences in mean stature have also been found between socio-economic categories suggesting a possible effect of environment. By utilizing a classical twin design which allows decomposing the variation of height into genetic and environmental components, we tested the hypothesis that environmental variation in height is greater in offspring of lower educated parents. Twin data from 29 cohorts including 65,978 complete twin pairs with information on height at ages 1 to 69 years and on parental education were pooled allowing the analyses at different ages and in three geographic-cultural regions (Europe, North America and Australia, and East Asia). Parental education mostly showed a positive association with offspring height, with significant associations in mid-childhood and from adolescence onwards. In variance decomposition modeling, the genetic and environmental variance components of height did not show a consistent relation to parental education. A random-effects meta-regression analysis of the aggregate-level data showed a trend towards greater shared environmental variation of height in low parental education families. In conclusion, in our very large dataset from twin cohorts around the globe, these results provide only weak evidence for the study hypothesis.
On Using Structural Patterns In Data For Classification
(PUSHPA PUBLISHING HOUSE, 2020) Arslan, G.; Karabulut, B.; Unver, H. M.
There are some interesting approaches for classification such as semi-supervised algorithms, algorithms that learn distance functions, and various extensions and generalizations of support vector machines. In this study, we propose a new clustering algorithm that uses similarities only and is used as an intermediate step for classification. The motivation for this combined approach is to obtain information from the data set that can be used for classification. After obtaining a clustering of the data set with the proposed clustering algorithm, we apply different strategies for classification. The results on some data sets show that this approach can have some advantages. For example, when using support vector machines, the size of the training set is reduced, while at the same time, comparable performance results are obtained with a smaller number of support vectors.
Statistical inference for geometric process with the Two-Parameter Lindley Distribution
(TAYLOR & FRANCIS INC, 2020) Demirci Bicer, Hayrinisa
The geometric process is a popular method for the modeling of arrival times with trend. In this study, the statistical inference problem for geometric process is considered when the distribution of first arrival time is two-parameter Lindley. The parameters a, lambda and beta are estimated using the maximum likelihood, modified least-squares, modified moments and modified L-moments methods. The estimation performances of the obtained estimators are compared by comprehensive simulations. The simulation results show that maximum likelihood estimators outperform the other estimators. Finally, on three real-life datasets, we present data analyses showing the modeling performance of geometric process against renewal process.
Age estimation by measuring maxillary canine pulp/tooth volume ratio on cone beam CT images with two different voxel sizes
(Taylor & Francis Ltd, 2020) Adışen, Mehmet Zahit; Keleş, Aydan; Yörübulut, Serap; Nalcaci, Rana
The aim of this study is to estimate age by measuring maxillary canine pulp/tooth volume ratio using CBCT images with a voxel resolution of 0.2 mm and 0.4 mm. This study was performed on CBCT images of 131 individuals between 17 and 75 years of age with fully erupted maxillary canine teeth. DICOM data were transferred to 3D-Doctor software, and pulp and tooth surfaces at each 0.2 mm or 0.4 mm axial section were manually drawn. Measurements in CBCT panoramic sections were also performed using Kvaal's method. Pearson's correlation coefficient was used to determine the relationship between pulp/tooth measurements and age. Results show that all measurements, except pulp/tooth length volume (R), are associated with age and that pulp/tooth volume (PV/TV) has the highest correlation with age (r = -0.486). Explanatory coefficient (R-2) of the regression model based on PV/TV is 0.236. There is no statistically significant difference between estimated and chronological ages across different gender and voxel groups (p>0.05). Regression models based on different voxel sizes are statistically significant for age estimation for both voxel groups. The present results should be tested on a wider patient population with evenly distributed samples to determine optimum voxel resolution for age estimation.
Parental Education and Genetics of BMI from Infancy to Old Age: A Pooled Analysis of 29 Twin Cohorts
(Wiley, 2019) Silventoinen, Karri; Jelenkovic, Aline; Latvala, Antti; Yokoyama, Yoshie; Sund, Reijo; Sugawara, Masumi; Kaprio, Jaakko
Objective The objective of this study was to analyze how parental education modifies the genetic and environmental variances of BMI from infancy to old age in three geographic-cultural regions. Methods A pooled sample of 29 cohorts including 143,499 twin individuals with information on parental education and BMI from age 1 to 79 years (299,201 BMI measures) was analyzed by genetic twin modeling. Results Until 4 years of age, parental education was not consistently associated with BMI. Thereafter, higher parental education level was associated with lower BMI in males and females. Total and additive genetic variances of BMI were smaller in the offspring of highly educated parents than in those whose parents had low education levels. Especially in North American and Australian children, environmental factors shared by co-twins also contributed to the higher BMI variation in the low education level category. In Europe and East Asia, the associations of parental education with mean BMI and BMI variance were weaker than in North America and Australia. Conclusions Lower parental education level is associated with higher mean BMI and larger genetic variance of BMI after early childhood, especially in the obesogenic macro-environment. The interplay among genetic predisposition, childhood social environment, and macro-social context is important for socioeconomic differences in BMI.
Statistical Inference for Alpha-Series Process with the Generalized Rayleigh Distribution
(Mdpi, 2019) Bicer, Hayrinisa Demirci
In the modeling of successive arrival times with a monotone trend, the alpha-series process provides quite successful results. Both selecting the distribution of the first arrival time and making an optimal statistical inference play a crucial role in the modeling performance of the alpha-series process. In this study, when the distribution of the first arrival time is the generalized Rayleigh, the problem of statistical inference for the alpha, beta, and gamma parameters of the alpha-series process is considered. Further, in order to obtain optimal modeling performance from the mentioned alpha-series process, various estimators for the model parameters are obtained by employing different estimation methodologies such as maximum likelihood, modified maximum spacing, modified least-squares, modified moments, and modified L-moments. By a series of Monte Carlo simulations, the estimation efficiencies of the obtained estimators are evaluated through the different sample sizes. Finally, two real datasets are analyzed to illustrate the importance of modeling with the alpha-series process.
Agreement and repeatability of central corneal thickness measurements by four different optical devices and an ultrasound pachymeter
(Springer, 2019) Gokcinar, Nesrin Buyuktortop; Yumusak, Erhan; Ornek, Nurgul; Yorubulut, Serap; Onaran, Zafer
Purpose To compare the repeatability and agreement of central corneal thickness (CCT) measurements by spectral-domain optical coherence tomography (OCT), corneal topography (CT) with a combined Scheimpflug-Placido system, optical biometry (OB), specular microscopy (SM), and ultrasound pachymetry (UP). Methods A single observer measured CCT twice in 150 eyes of 150 subjects with each of five devices: Nidek RS-3000 Advance OCT, CSO Sirius combined Scheimpflug-Placido disc system CT, Nidek AL-Scan partial coherence interferometry-based OB, Tomey EM-3000 SM, and Reichert iPac ultrasonic pachymeter. Pachymetry values corrected by the SM device software were also recorded. Levels of agreement between devices were evaluated by Bland-Altman plots with 95% limits of agreement, and repeatability for each device was analysed with intraclass correlation coefficients. Results The mean CCTs measured by OCT, CT, OB, SM, corrected SM, and UP were 544.60 +/- 29.56, 536.19 +/- 32.14, 528.29 +/- 29.45, 524.88 +/- 32.38, 537.88 +/- 32.38, and 545.29 +/- 30.75 mu m, respectively. Mean CCT differed significantly between the devices (p<0.05) apart from between OCT and UP, and between CT and corrected SM. Mean paired differences between devices ranged between 0.68 and 20.41 mu m. Repeatability with all devices was excellent (>0.99). The range of limits of agreement was the least between OCT and UP. Conclusions Different CCT measurement techniques produce quite different results, so CCT evaluation and follow-up should be performed using the same device or devices with close compatibility.
Properties and Inference for a New Class of Generalized Rayleigh Distributions with an Application
(Sciendo, 2019) Bicer, Hayrinisa Demirci
In the present paper, we introduce a new form of generalized Rayleigh distribution called the Alpha Power generalized Rayleigh (APGR) distribution by following the idea of extension of the distribution families with the Alpha Power transformation. The introduced distribution has the more general form than both the Rayleigh and generalized Rayleigh distributions and provides a better fit than the Rayleigh and generalized Rayleigh distributions for more various forms of the data sets. In the paper, we also obtain explicit forms of some important statistical characteristics of the APGR distribution such as hazard function, survival function, mode, moments, characteristic function, Shannon and Renyi entropies, stress-strength probability, Lorenz and Bonferroni curves and order statistics. The statistical inference problem for the APGR distribution is investigated by using the maximum likelihood and least-square methods. The estimation performances of the obtained estimators are compared based on the bias and mean square error criteria by a conducted Monte-Carlo simulation on small, moderate and large sample sizes. Finally, a real data analysis is given to show how the proposed model works in practice.
Properties and inference for a new class of XGamma distributions with an application
(Springer Heidelberg, 2019) Bicer, Hayrinisa Demirci
The current paper introduces a new flexible probability distribution model called transmuted XGamma distribution which pullulates from the XGamma distribution and possesses the characteristics of XGamma distribution in special cases. In the paper, we obtain the explicit expressions for some important statistical properties of the introduced distribution such as hazard rate and survival functions, mean residual life, moment-generating function, moments, skewness, kurtosis, distribution of its order statistics, Lorenz and Bonferroni curves. Besides obtaining the various effective estimators for the parameters of the distribution, estimation performances of these estimators are comparatively examined with a series of Monte Carlo simulations. Furthermore, to demonstrate the modeling ability of the proposed distribution on real-world phenomena, an illustrative example is performed by using an actual data set in connection with the field of the lifetime.
The CODATwins Project: The Current Status and Recent Findings of COllaborative Project of Development of Anthropometrical Measures in Twins
(Cambridge Univ Press, 2019) Silventoinen, K.; Jelenkovic, A.; Yokoyama, Y.; Sund, R.; Sugawara, M.; Tanaka, M.; Kaprio, J.
The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) project is a large international collaborative effort to analyze individual-level phenotype data from twins in multiple cohorts from different environments. The main objective is to study factors that modify genetic and environmental variation of height, body mass index (BMI, kg/m(2)) and size at birth, and additionally to address other research questions such as long-term consequences of birth size. The project started in 2013 and is open to all twin projects in the world having height and weight measures on twins with information on zygosity. Thus far, 54 twin projects from 24 countries have provided individual-level data. The CODATwins database includes 489,981 twin individuals (228,635 complete twin pairs). Since many twin cohorts have collected longitudinal data, there is a total of 1,049,785 height and weight observations. For many cohorts, we also have information on birth weight and length, own smoking behavior and own or parental education. We found that the heritability estimates of height and BMI systematically changed from infancy to old age. Remarkably, only minor differences in the heritability estimates were found across cultural-geographic regions, measurement time and birth cohort for height and BMI. In addition to genetic epidemiological studies, we looked at associations of height and BMI with education, birth weight and smoking status. Within-family analyses examined differences within same-sex and opposite-sex dizygotic twins in birth size and later development. The CODATwins project demonstrates the feasibility and value of international collaboration to address gene-by-exposure interactions that require large sample sizes and address the effects of different exposures across time, geographical regions and socioeconomic status.

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