Educational attainment of same-sex and opposite-sex dizygotic twins: An individual-level pooled study of 19 twin cohorts.

Comparing twins from same- and opposite-sex pairs can provide information on potential sex differences in a variety of outcomes, including socioeconomic-related outcomes such as educational attainment. It has been suggested that this design can be applied to examine the putative role of intrauterine exposure to testosterone for educational attainment, but the evidence is still disputed. Thus, we established an international database of twin data from 11 countries with 88,290 individual dizygotic twins born over 100 years and tested for differences between twins from same- and opposite-sex dizygotic pairs in educational attainment. Effect sizes with 95% confidence intervals (CI) were estimated by linear regression models after adjusting for birth year and twin study cohort. In contrast to the hypothesis, no difference was found in women (ß = -0.05 educational years, 95% CI -0.11, 0.02). However, men with a same-sex co-twin were slightly more educated than men having an opposite-sex co-twin (ß = 0.14 educational years, 95% CI 0.07, 0.21). No consistent differences in effect sizes were found between individual twin study cohorts representing Europe, the USA, and Australia or over the cohorts born during the 20th century, during which period the sex differences in education reversed favoring women in the latest birth cohorts. Further, no interaction was found with maternal or paternal education. Our results contradict the hypothesis that there would be differences in the intrauterine testosterone levels between same-sex and opposite-sex female twins affecting education. Our findings in men may point to social dynamics within same-sex twin pairs that may benefit men in their educational careers.

Education in Twins and Their Parents Across Birth Cohorts Over 100 years: An Individual-Level Pooled Analysis of 42-Twin Cohorts.

Whether monozygotic (MZ) and dizygotic (DZ) twins differ from each other in a variety of phenotypes is important for genetic twin modeling and for inferences made from twin studies in general. We analyzed whether there were differences in individual, maternal and paternal education between MZ and DZ twins in a large pooled dataset. Information was gathered on individual education for 218,362 adult twins from 27 twin cohorts (53% females; 39% MZ twins), and on maternal and paternal education for 147,315 and 143,056 twins respectively, from 28 twin cohorts (52% females; 38% MZ twins). Together, we had information on individual or parental education from 42 twin cohorts representing 19 countries. The original education classifications were transformed to education years and analyzed using linear regression models. Overall, MZ males had 0.26 (95% CI [0.21, 0.31]) years and MZ females 0.17 (95% CI [0.12, 0.21]) years longer education than DZ twins. The zygosity difference became smaller in more recent birth cohorts for both males and females. Parental education was somewhat longer for fathers of DZ twins in cohorts born in 1990-1999 (0.16 years, 95% CI [0.08, 0.25]) and 2000 or later (0.11 years, 95% CI [0.00, 0.22]), compared with fathers of MZ twins. The results show that the years of both individual and parental education are largely similar in MZ and DZ twins. We suggest that the socio-economic differences between MZ and DZ twins are so small that inferences based upon genetic modeling of twin data are not affected.

The CODATwins Project: The Cohort Description of Collaborative Project of Development of Anthropometrical Measures in Twins to Study Macro-Environmental Variation in Genetic and Environmental Effects on Anthropometric Traits.

For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.

Zygosity Differences in Height and Body Mass Index of Twins From Infancy to Old Age: A Study of the CODATwins Project.

A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.

Genetic and environmental etiology of nicotine use in Sri Lankan male twins.

Little is known about the prevalence and etiology of tobacco use in Asian populations. This study aims to test whether the finding of substantial heritability for tobacco-related phenotypes in Western populations is generalizable to developing countries. The twin method was used to estimate the relative contribution of genetic and environmental influences on nicotine-related phenotypes. Participants were selected from the population based Sri Lankan Twin Registry. The Composite International Diagnostic Interview was administered to 1,804 male individuals to assess five phenotypes: nicotine use; desire and unsuccessful attempts to quit smoking; subjective feeling of being tobacco dependent; and two DSM-IV diagnoses; nicotine dependence and nicotine withdrawal. Almost one-third of the male twins were life-time smokers. The genetic results were consistent with the previously reported findings from Western and Chinese populations, in that the nicotine use traits were significantly heritable, with environmental influences being of the non-shared nature. The results derived from the Causal Contingent Common pathway model (CCC) supported previous findings that show that liabilities to regular smoking and subsequent problem smoking have both shared and specific genetic influences.

The aetiological relationship between depressive symptoms and health-related quality of life: A population-based twin study in Sri Lanka.

OBJECTIVE: Depression often co-occurs with poor health-related quality of life (HRQL). Twin studies report genetic and individual-level environmental underpinnings in the aetiology of both depression and HRQL, but there is limited twin research exploring this association further. There is also little evidence on sex differences and non-Western populations are underrepresented. In this paper we explored the phenotypic and aetiological relationship between depressive symptoms and HRQL and possible sex differences in a low-middle-income Sri Lankan population. METHOD: Data for 3,948 participants came from the Colombo Twin and Singleton Follow-up Study (CoTaSS-2). Using self-report measures of depressive symptoms and HRQL, we conducted univariate and bivariate sex-limitation twin analyses. RESULTS: Depressive symptoms showed moderate genetic (33%) and strong nonshared environmental influences (67%). Nonshared environment accounted for the majority of variance in all the subscales of HRQL (ranging from 68 to 93%), alongside small genetic influences (ranging from 0 to 23%) and shared environmental influences (ranging from 0 to 28%). Genetic influences were significant for emotional wellbeing (23%). Shared environmental influences were significant for four out of the eight HRQL variables (ranging from 22-28%), and they were more prominent in females than males. Depressive symptoms were significantly associated with lower HRQL scores. These correlations were mostly explained by overlapping nonshared environmental effects. For traits related to emotional functioning, we also detected substantial overlapping genetic influences with depressive symptoms. CONCLUSIONS: Our study confirmed previous findings of a negative association between depressive symptoms and HRQL. However, some of the aetiological factors of HRQL differed from Western studies, particularly regarding the effects of shared environment. Our findings highlight the importance of cross-cultural research in understanding associations between psychological wellbeing and HRQL.

Genetic and environmental contributions to the overlap between psychological, fatigue and somatic symptoms: a twin study in Sri Lanka.

BACKGROUND: Somatic symptoms often co-occur with psychological symptoms but this overlap is poorly understood. Some aspects of this overlap differ in the South Asian context, but it is not clear whether this is a reporting effect or an underlying difference in experienced illness. METHODS: Home interviews were administered to 4,024 twins randomly selected from a population-based twin register in the Colombo district of Sri Lanka (the CoTASS study). These included assessments of psychological, somatic and fatigue symptoms. The data were analyzed using factor analytic and quantitative genetic approaches. RESULTS: Confirmatory factor analysis showed that the symptoms from the three scales represented three separate dimensions, rather than all tapping into a single dimension. However, familial correlations among the data were most consistent with a common pathway model. This implies that a portion of the underlying vulnerability is common across psychological, fatigue and somatic symptoms. There were sex differences in the etiology of this model, with shared environmental and genetic influences playing different roles in men and women. CONCLUSIONS: There is a complex etiological relationship between psychological, fatigue and somatic symptoms. This is similar in Sri Lanka to Western countries, but there may be a greater influence from the family environment, suggesting that care needs to be taken when generalizing research findings between countries. People who complain of certain fatigue or somatic symptoms may well also have psychological symptoms, or may have genetic or environmental vulnerabilities to such problems.

Aetiology of fatigue in Sri Lanka and its overlap with depression.

BACKGROUND: Fatigue is a common symptom in Western high-income countries but is often medically unexplained and little is known about its presentation in other populations. AIMS: To explore the epidemiology and aetiology of fatigue in Sri Lanka, and of its overlap with depression. METHOD: A total of 4024 randomly selected twins from a population-based register in Sri Lanka (Colombo district) completed home interviews including the Chalder Fatigue Questionnaire. RESULTS: The prevalence of fatigue was similar to that in other countries, although prolonged fatigue may be less common. There was substantial comorbidity with a screen for lifetime depression. Non-shared environmental factors made the largest contributions, although genetic/family factors also contributed. The aetiology appeared consistent across the spectrum of severity. CONCLUSIONS: The aetiology of fatigue is broadly similar in Sri Lanka and Western high-income countries. Abnormal experiences of fatigue appear to be the extreme form of more common fatigue, rather than representing independent entities with different genetic or environmental risk factors.

Environmental exposures and their genetic or environmental contribution to depression and fatigue: a twin study in Sri Lanka.

BACKGROUND: There is very little genetically informative research identifying true environmental risks for psychiatric conditions. These may be best explored in regions with diverse environmental exposures. The current study aimed to explore similarities and differences in such risks contributing to depression and fatigue. METHODS: Home interviews assessed depression (lifetime-ever), fatigue and environmental exposures in 4,024 randomly selected twins from a population-based register in the Colombo district of Sri Lanka. RESULTS: Early school leaving and standard of living showed environmentally-mediated effects on depression, in men. In women, life events were associated with depression partly through genetic pathways (however, the temporal order is consistent with life events being an outcome of depression, as well as the other way around). For fatigue, there were environmentally mediated effects (through early school leaving and life events) and strong suggestions of family-environmental influences. CONCLUSIONS: Compared to previous studies from higher-income countries, novel environmentally-mediated risk factors for depression and fatigue were identified in Sri Lanka. But as seen elsewhere, the association between life events and depression was partially genetically mediated in women. These results have implications for understanding environmental mechanisms around the world.

Hemoglobin variants in patients with type 2 diabetes mellitus.

Measurement of HbA1c levels in diabetic patients is an established procedure for evaluating long-term control of diabetes. Despite its usefulness, conditions that effect hemoglobin concentration, such as hemoglobinopathies give rise to inappropriate HbA1c values. Since information about hemoglobinopathies in the diabetic population in Sri Lanka is limited, a prospective cross-sectional study was carried out among 2,695 diabetic subjects attending the diabetic clinic at Nawaloka Hospital, Sri Lanka. Hemoglobin type and HbA1c were measured by the HPLC method. The results reveal among 2,695 diabetic subjects, 53 (2%) had abnormal hemoglobin types (HbF and HbS). HbA1c concentrations in diabetic patients without Hb abnormalities show a higher correlation with fasting blood glucose than those with hemoglobin abnormalities. This study emphasizes that patients with inappropriate HbA1c values should be investigated for hemoglobinopathies.

Genetic and environmental variation in educational attainment: an individual-based analysis of 28 twin cohorts.

We investigated the heritability of educational attainment and how it differed between birth cohorts and cultural-geographic regions. A classical twin design was applied to pooled data from 28 cohorts representing 16 countries and including 193,518 twins with information on educational attainment at 25 years of age or older. Genetic factors explained the major part of individual differences in educational attainment (heritability: a2 = 0.43; 0.41-0.44), but also environmental variation shared by co-twins was substantial (c2 = 0.31; 0.30-0.33). The proportions of educational variation explained by genetic and shared environmental factors did not differ between Europe, North America and Australia, and East Asia. When restricted to twins 30 years or older to confirm finalized education, the heritability was higher in the older cohorts born in 1900-1949 (a2 = 0.44; 0.41-0.46) than in the later cohorts born in 1950-1989 (a2 = 0.38; 0.36-0.40), with a corresponding lower influence of common environmental factors (c2 = 0.31; 0.29-0.33 and c2 = 0.34; 0.32-0.36, respectively). In conclusion, both genetic and environmental factors shared by co-twins have an important influence on individual differences in educational attainment. The effect of genetic factors on educational attainment has decreased from the cohorts born before to those born after the 1950s.

Genetic and environmental contributions to depression in Sri Lanka.

BACKGROUND: Susceptibility to depression results from genetic and non-familially shared environmental influences in high-income, Western countries. Environments may play a different role for populations in different contexts. AIMS: To examine heritability of depression in the first large, population-based twin study in a low-income country. METHOD: Lifetime depression and a broader measure of depression susceptibility (D-probe) were assessed in 3908 adult twins in Sri Lanka (the CoTASS study). RESULTS: There were gender differences for the broad definition (D-probe), with a higher genetic contribution in females (61%) than males (4%). Results were similar for depression, but the prevalence was too low to estimate heritability for males. CONCLUSIONS: Genetic influences on depression in women appear to be at least as strong in this Sri Lankan sample as in higher-income countries. Conclusions are less clear for men but suggest a larger role for environments rather than genes. The nature as well as the magnitude of environmental influences may also differ across populations.

Colombo Twin and Singleton Study (CoTASS): a description of a population based twin study of mental disorders in Sri Lanka.

BACKGROUND: The Sri Lankan twin registry is one of the first to be established in a developing country, and its design has ensured sampling from a wide range of environmental conditions. It thus has great potential to examine environmental and genetic influences on diverse phenotypes, including psychiatric disorders, in the context of a diversity of environmental exposures, which may not have been fully explored in previous twin studies in developed countries. This paper presents the rationale for the study, describes its context, and the methods for twin ascertainment and data collection. METHODS: A population-based twin register was established in the Colombo district of Sri Lanka using infrastructure designed to periodically update the electoral register. We invited a subsample from this register to participate in the project on common mental disorders, using random ascertainment. A separate non-twin sample was randomly selected from the geographical areas where twins were found. Home interviewers collected diagnostic information on common mental disorders, as well as environmental exposures including life events, socio-economic conditions, and the impact of the civil war and the Tsunami of 2004. RESULTS: We identified 19,302 individuals in the creation of the population based twin register. We randomly selected a subsample, of whom 4,387 were eligible to participate and 4,024 agreed to be interviewed (including data on 1,954 complete pairs of twins and 5 sets of triplets). Those who refused consent had a similar mean age and sex ratio to those who were interviewed. We invited 2,485 singletons to participate and 2,019 were interviewed. CONCLUSION: Initial exploration of the data suggests the samples are very representative of the Colombo district of Sri Lanka, so we have created a unique resource for understanding the influences on mental disorders in developing countries, and to compare to the influences found in developed countries.

Agreement between subjective and objective measures of sleep duration in a low-middle income country setting.

OBJECTIVES: Describe sleep duration in adult Sri Lankans and determine the bias and agreement of self-report and actigraphic assessments. DESIGN: Validation sub-study nested within the Colombo Twin and Singleton Study (2012-2015). SETTING: Colombo, Sri Lanka. PARTICIPANTS: 175 adults with actigraphy, randomly selected from 3497 participants with self-reported sleep assessed in a population-based cohort. MEASUREMENTS: Self-reported sleep duration, ascertained by the Pittsburgh Sleep Quality Index (PSQI), was compared to a minimum of four days of actigraphy. Bias and agreement were assessed using the Bland-Altman method and a novel application of criterion cut-point analysis. Objective measurements of wake after sleep onset (WASO) and sleep efficiency were evaluated. RESULTS: Sri Lankans have short sleep duration; averaging 6.4h (SD 1.5) self-reported and 6.0h (SD 0.9) actigraphically. Poor sleep quality was prevalent with an average WASO of 49 min., and sleep efficiency <85%. Bias was observed, with self-report consistently over-reporting sleep on average by 27.6 min (95% CI: -0.68, -0.24) compared to objective measures, but wide individual variation in disagreement, ranging from over-reporting by 3.34h to under-reporting by 2.42h. A criterion cut-point method also failed to define agreed definitions of short and long sleep duration. CONCLUSIONS: Sleep in Sri Lankan adults, whether measured subjectively or objectively, is of short duration and suboptimal objective quality by High Income Country consensus standards. Given the high cardiometabolic morbidity in Sri Lanka and poor measurement agreement observed, this warrants further investigation and supports the need for culturally appropriate, reliable, and valid assessment for analytic epidemiology in non-Western settings.

Differences in genetic and environmental variation in adult BMI by sex, age, time period, and region: an individual-based pooled analysis of 40 twin cohorts.

Background: Genes and the environment contribute to variation in adult body mass index [BMI (in kg/m2)], but factors modifying these variance components are poorly understood.Objective: We analyzed genetic and environmental variation in BMI between men and women from young adulthood to old age from the 1940s to the 2000s and between cultural-geographic regions representing high (North America and Australia), moderate (Europe), and low (East Asia) prevalence of obesity.Design: We used genetic structural equation modeling to analyze BMI in twins ≥20 y of age from 40 cohorts representing 20 countries (140,379 complete twin pairs).Results: The heritability of BMI decreased from 0.77 (95% CI: 0.77, 0.78) and 0.75 (95% CI: 0.74, 0.75) in men and women 20-29 y of age to 0.57 (95% CI: 0.54, 0.60) and 0.59 (95% CI: 0.53, 0.65) in men 70-79 y of age and women 80 y of age, respectively. The relative influence of unique environmental factors correspondingly increased. Differences in the sets of genes affecting BMI in men and women increased from 20-29 to 60-69 y of age. Mean BMI and variances in BMI increased from the 1940s to the 2000s and were greatest in North America and Australia, followed by Europe and East Asia. However, heritability estimates were largely similar over measurement years and between regions. There was no evidence of environmental factors shared by co-twins affecting BMI.Conclusions: The heritability of BMI decreased and differences in the sets of genes affecting BMI in men and women increased from young adulthood to old age. The heritability of BMI was largely similar between cultural-geographic regions and measurement years, despite large differences in mean BMI and variances in BMI. Our results show a strong influence of genetic factors on BMI, especially in early adulthood, regardless of the obesity level in the population.

Exertional heat stroke in a young military trainee: is it preventable?

BACKGROUND: Heat stroke is a life-threatening condition with exertional heat stroke occurring frequently among soldiers and athletes. Because of its common occurrence, many military trainees practice preventive measures prior to any activity requiring severe exertion. Although it is said to be common in practice, different presentations of heat stroke are scarcely described in literature. CASE PRESENTATION: We describe a case of an exertional heat stroke in a 23-year-old male Sinhalese soldier who developed early changes of renal failure, liver failure and rhabdomyolysis. The patient initially presented with convulsions, delirium and loss of consciousness to an outside health care facility before being transferred to our institution. CONCLUSION: It is clear that heat stroke does occur in military trainees while preventive strategies are being practiced. It is important for those who provide healthcare to soldiers to provide proper advice on how to identify impending heat stroke prior to any exercises resulting in severe physical exertion. Further, treating physicians should educate all military trainees about preventive strategies.

Urinary Biomarkers KIM-1 and NGAL for Detection of Chronic Kidney Disease of Uncertain Etiology (CKDu) among Agricultural Communities in Sri Lanka.

Chronic Kidney Disease of uncertain etiology (CKDu) is an emerging epidemic among farming communities in rural Sri Lanka. Victims do not exhibit common causative factors, however, histopathological studies revealed that CKDu is a tubulointerstitial disease. Urine albumin or albumin-creatinine ratio is still being used as a traditional diagnostic tool to identify CKDu, but accuracy and prevalence data generated are questionable. Urinary biomarkers have been used in similar nephropathy and are widely recognised for their sensitivity, specificity and accuracy in determining CKDu and early renal injury. However, these biomarkers have never been used in diagnosing CKDu in Sri Lanka. Male farmers (n = 1734) were recruited from 4 regions in Sri Lanka i.e. Matara and Nuwara Eliya (farming locations with no CKDu prevalence) and two CKDu emerging locations from Hambantota District in Southern Sri Lanka; Angunakolapelessa (EL1) and Bandagiriya (EL2). Albuminuria (ACR ≥ 30mg/g); serum creatinine based estimation of glomerular filtration rate (eGFR); creatinine normalized urinary kidney injury molecule (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) were measured. Fourteen new CKDu cases (18%) from EL1 and nine CKDu cases (9%) from EL2 were recognized for the first time from EL1, EL2 locations, which were previously considered as non-endemic of the disease and associated with persistent albuminuria (ACR ≥ 30mg/g Cr). No CKDu cases were identified in non-endemic study locations in Matara (CM) and Nuwara Eliya (CN). Analysis of urinary biomarkers showed urinary KIM-1 and NGAL were significantly higher in new CKDu cases in EL1 and EL2. However, we also reported significantly higher KIM-1 and NGAL in apparently healthy farmers in EL 1 and EL 2 with comparison to both control groups. These observations may indicate possible early renal damage in absence of persistent albuminuria and potential capabilities of urinary KIM-1 and NGAL in early detection of renal injury among farming communities in Southern Sri Lanka.

Genetic and environmental influences on adult human height across birth cohorts from 1886 to 1994.

Human height variation is determined by genetic and environmental factors, but it remains unclear whether their influences differ across birth-year cohorts. We conducted an individual-based pooled analysis of 40 twin cohorts including 143,390 complete twin pairs born 1886-1994. Although genetic variance showed a generally increasing trend across the birth-year cohorts, heritability estimates (0.69-0.84 in men and 0.53-0.78 in women) did not present any clear pattern of secular changes. Comparing geographic-cultural regions (Europe, North America and Australia, and East Asia), total height variance was greatest in North America and Australia and lowest in East Asia, but no clear pattern in the heritability estimates across the birth-year cohorts emerged. Our findings do not support the hypothesis that heritability of height is lower in populations with low living standards than in affluent populations, nor that heritability of height will increase within a population as living standards improve.

Epidemiology and symptomatology of depression in Sri Lanka: a cross-sectional population-based survey in Colombo District.

BACKGROUND: It is important to understand the nature of depression in non-Western and lower-income countries, but little such research exists. This study aimed to examine the characteristic features of depression in Sri Lanka, and to identify environmental risk factors. METHODS: Depression diagnoses, symptoms and impairment were measured using the Composite International Diagnostic Interview, in a population-based sample of 6014 twins and non-twins in the Colombo region of Sri Lanka (the CoTASS sample). Socio-demographic factors and environments were assessed via questionnaires. RESULTS: Lifetime-ever depression was reported in 6.6% of participants, rising to 11.2% if the functional impairment criterion was excluded. The symptom profile of depression and its socio-demographic associations were very comparable to those in Western and more economically developed countries, whether functional impairment was included in the definition or not. Standard of living was independently associated with depression, especially among men at the more deprived end of the distribution. Specific associations were found with both financial wellbeing and material characteristics of the home environment. LIMITATIONS: The observational associations identified are cross-sectional, so do not necessarily imply causal links. CONCLUSIONS: Aside from a lower prevalence, depression is very similar in this predominantly urban Sri Lankan sample to higher-income, Western countries, and may be under-identified due to a relatively low cultural appropriateness of the assessment of impairment. Under Sri Lanka's cultural and environmental context, certain aspects of the material environment are associated with depression among certain segments of society, perhaps because of their particular link to social status and social networks.

Challenges in recruiting older twins for the Sri Lankan twin registry.

The National Twin Registry of Sri Lanka was established in 1997 as a volunteer register. To extend it to a population-based register, we examined the effectiveness of tracing older twins by inspecting birth records and recruiting them by postal invitation and in-person contact. Birth records at a divisional secretariat reported from 2 maternity hospitals between the years of 1954-1970 were scrutinised to identify a random sample of twins. These hospitals had the highest twin delivery rates for the whole country. We identified 620 twins and a questionnaire was mailed to them. Research assistants visited a cohort of non-respondents (71) in the postal survey. These 620 twins were identified after perusing 20700 birth records. The twinning rate was estimated at 29.95 ([620/20700] x 1000) twins per 1000 registered births (CI 27.63-32.27). In the postal survey, 37 (12%) responded and 62 letters were returned (20%). Both twins were still alive in 20 pairs, one was still alive in 15 pairs, and both twins were dead in 2 pairs. During field visits, 42 (59.2%) addresses were located. Information was available on 16 twin pairs. Both twins were alive in 8 pairs, one each in 4 pairs, and both were dead in 4 pairs and at least one twin was traced in 10 pairs (14%). Both the postal and the field survey gave a low yield. This finding is different from tracing younger twins born between 1985-1997 by using the same methods. Migration, urbanization and development in the country might have affected tracing older twins from the birth record addresses, which were decades old.