Twins, smoking and mortality: a 12-year prospective study of smoking-discordant twin pairs

Despite the increasing scientific evidence for a causal role of tobacco smoking in lung cancer and coronary heart disease, critics, several decades ago, put forward an alternative hypothesis. The constitutional hypothesis has stated that there are genetic or other common factors, which predispose both to smoking and disease, but that the two are not causally related. A critical test of this hypothesis is the study of disease in monozygotic (MZ) twin pairs in which one smokes and the other never has. Earlier twin studies found only small differences in the mortality of smoking and nonsmoking twins of discordant pairs. In the Finnish Twin Cohort, a population-based panel of adult like-sexed twin pairs, a questionnaire study carried in 1975 permitted identification of twin pairs discordant for cigarette smoking. The nonsmoking cotwins had never been regular smokers. The smoking twins were divided into 1278 current smokers [CS; 143 MZ and 598 dizygotic (DZ) males and 171 MZ and 585 DZ females] and 1210 former smokers (FS; 129 MZ and 408 DZ males and 113 MZ and 341 DZ females). Exposure to tobacco was much higher among males; over 25% of men smoked 20 or more cigarettes daily compared to less than 10% of women. Follow-up of mortality yielded data on time and cause of death. Analyzing on first deaths from concordant pairs, there were 13 deaths in the smokers of male CS MZ pairs and 1 death in the nonsmoking cotwins (relative risk = 13.0, P less than 0.01). Excess mortality was also found for male CS DZ smokers (RR = 2.43, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Smoking and mortality: a 21-year follow-up based on the Swedish Twin Registry

Data on smoking and mortality from the Swedish Twin Registry were analysed as a prospective cohort study and as a co-twin control study. The twin method involves control of genetic and early environmental factors and thereby a general control of the nested factors that may act as confounders, adjustments not obtainable in ordinary study designs. In the cohort analyses the following relative risks for cigarette smokers were found for men and women, respectively: death all causes 1.4 (90% Cl 1.3; 1.5), 1.4 (1.3; 1.5), CHD death 1.4 (1.3; 1.7), 1.6 (1.3; 2.0), lung cancer 19.7 (9.1; 42.7), 5.1 (3.0; 8.7), and other cancers 1.2 (1.0; 1.4), 1.2 (1.0-1.4). The comparison of deaths in cigarette-smoking twins and their non-smoking co-twins gave the following risk estimates for monozygotic (MZ) men: death all causes 1.6 (35 versus 22 first deaths), CHD death 2.8 (11 versus 4). The results for dizygotic (DZ) males and for females were in agreement. Four lung-cancer deaths occurred in MZ and 17 in DZ smoker twins while the non-smoker co-twins showed two such cases (DZ women). Other cancer deaths did not occur more often in the smoker than in the non-smoker twin. The impact of smoking on mortality, CHD death and lung cancer is also valid among smoking discordant twins.     

Lifestyle factors in monozygotic and dizygotic twins

In examining genetic influences on biological variables using twins, it may be important to examine the distribution between and within twin pairs of demographic and lifestyle factors that may themselves affect the biological variable being studied. We explored the distribution of demographic and lifestyle factors that may affect blood lipid levels or ischaemic heart disease (IHD) risk among a sample of 106 monozygotic (MZ) and 94 like-sex dizygotic (DZ) twin pairs. In our sample, MZ twins were statistically significantly different from DZ twins only in marital status, cigarette smoking habits, and the ratio of polyunsaturated to saturated fat (P:S ratio) in their dietary intake. The latter variable was among many dietary variables examined (using 4-day weighed food diaries), and the size of the difference in intake was small. When comparisons were made of the similarities within twin pairs, we found members of MZ twin pairs to be statistically significantly closer than DZ twins in educational achievement, occupation, cigarette smoking, and exercise habits, and the number of days a week on which alcohol was consumed. These last three variables were consistently closer among twins with closer contact than among those with a smaller degree of current shared environment. For 12 of the 13 nutrients examined, the within-pair correlations were higher for MZ than for DZ twins, although our test for significant genetic variance showed statistical significance only for intake of complex carbohydrates. We conclude that MZ twins share demographic and lifestyle factors that might influence the risk of IHD and blood lipid levels to a greater degree than do DZ twins, although it is difficult to say if these similarities in lifestyle result from genetic influences or not. Nevertheless, ascribing differences between correlations in MZ and DZ twin pairs for lipid levels as being purely "genetic"--as implicit in conventional measures of heritability--is likely to overestimate the influence of genetic factors.     

中国成年双生子饮茶行为分布特征

目的 描述中国双生子登记系统（CNTR）成年双生子饮茶行为的分布特征,探索饮茶行为在双生子人群中的分布规律,为探究遗传和环境因素对饮茶行为的影响提供线索。方法 样本选自2010-2018年在CNTR进行登记的双生子,纳入≥18岁且具有饮茶信息的双生子共25 264对进行分析,描述双生子中饮茶行为的人群、地区分布特征,以及不同卵型双生子饮茶行为一致率和对内饮茶量差异分布情况。结果 研究对象年龄（35.38±12.45）岁,每周饮茶者占比17.0%,饮茶量（3.36±2.44）杯/d。男性、50~59岁、南方、城镇、文化程度高、双生子中先出生的个体中每周饮茶者比例较高（P<0.05）,未婚者中比例较低（P<0.001）。双生子对内分析发现同卵饮茶行为一致率均大于异卵,饮茶遗传度为13.45%（11.38%~15.51%）,除女性亚组外,不同性别、年龄、地区间饮茶一致率差异有统计学意义（均P<0.05）;根据性别、年龄、地区分层后仅男性同卵一致率始终呈大于异卵趋势。同性别双生子对内饮茶量差异在男性中呈现同卵小于异卵的特征（P<0.05）,而女性中差异不明显。结论 本研究双生子人群饮茶行为的分布存在人群和地区差异,饮茶行为主要受环境因素影响,遗传因素影响较弱,且遗传效应大小在不同性别、年龄、地区间不尽相同,性别可修饰这一遗传作用。     

Likelihood-based concordance tests for analysis of ascertained twin pair multinomial data

The classic twin model design has a wide application in human genetics. Under the assumption that nongenetic effects are shared to the same degree by monozygotic (MZ) and dizygotic (DZ) twin pairs, a test of the equality of casewise concordances between MZ and DZ twins provides a clue to the influence of genetic and environmental factors on a disease. The casewise concordance is the conditional probability that given that one member of a twin pair is affected, the other is also affected. When disease prevalence is low or cost-effectiveness is considered, collection of twin pairs by ascertainment for performing casewise concordance analysis is required. In this article, by defining an overall casewise concordance parameter, several likelihood-based tests, such as likelihood ratio test LR, score test Score, the usual Wald test Wald and an alternative Wald test WaldA are investigated for a test of the equality of concordances between ascertained MZ and DZ twin pairs under multinomial models. Simulation studies were conducted for data with small sample sizes. The results show that the type I error rates and power of LR and Score are stable only when the overall casewise concordances are not extremely small or large. The Wald has higher power performance in most cases but would slightly inflate type I error rates; the WaldA is the most robust and recommended approach.     

The epidemiology of anencephaly and spina bifida in Izmir, Turkey, in the light of recent aetiological theories

The data from this study suggest that, in western Turkey, potato consumption and water hardness do not play a significant role in the aetiology of anencephaly and spina bifida (ASB). Several of the predictions of the fetus-fetus interaction theory are not supported. Other predictions could not be tested because of lack of information on the dizygotic (DZ) twinning rate. Twin data from this study, together with previous material containing explicit information on zygosity, suggest that true concordance of a particular neural tube anomaly occurs only in monozygotic (MZ) twins. It also seems that even ASB concordance occurs in DZ twins only at a rate comparable with recurrence in siblings. This confirms the earlier refutation (Field and Kerr, 1974) of the supposition of Nance (1971) that MZ twin pairs are strikingly discordant for ASB compared with DZ pairs. However, the evidence seems to go further than Field's assertion that MZ and DZ pairs are affected about equally. Concordance in DZ twins is in comparison with sibling data, but MZ pairs show a significantly higher rate of concordance in both categories. Finally, the incidence of ASB in Izmir compared with the areas of ethnic origin of the Turks, and the high representation of families from Balkan areas where the incidence more closely resembles that of Izmir, suggest that the genetic factor is important in this area.     

The heritability of cause-specific mortality: a correlated gamma-frailty model applied to mortality due to respiratory diseases in Danish twins born 1870-1930

The genetic influence on susceptibility to diseases of the respiratory system and all-cause mortality was studied using data for identical (MZ) and fraternal (DZ) twins. Data from the Danish Twin Register include 1344 MZ and 2411 DZ male twin pairs and 1470 MZ and 2730 DZ female twin pairs born between 1870 and 1930, where both individuals were alive on 1 011943. We used the correlated gamma-frailty model. Proportions of variance in frailty attributable to genetic and environmental factors were assessed using the structural equation model approach. For all-cause mortality the correlation coefficients of frailty for MZ twins tend to be higher than for DZ twins. For mortality with respect to respiratory diseases this effect was only seen in females, whereas males showed the opposite effect. Five standard biometric models are fitted to the data to evaluate the magnitude and nature of genetic and environmental factors on mortality. Using the best fitting biometric model heritability for cause of death was found to be 0.58 (0.07) for all-cause mortality (AE-model) and zero for diseases of the respiratory system for males. Heritability was 0.63 (0.11) for all-cause mortality (DE-model) and 0.18 (0.09) for diseases of the respiratory system (DE-model) for females. The analysis confirms the presence of a strong genetic influence on individual frailty associated with all-cause mortality. For respiratory diseases, no genetic influence was found in males and only weak genetic influence in females. The nature of genetic influences on frailty with respect to all-cause mortality is probably additive in males and dominant in females, whereas for frailty with respect to deaths caused by respiratory diseases in females, there are genetic factors present which are caused by dominance. Environmental influences are non-shared with exception of frailty with respect to respiratory diseases in males, where the shared environment plays an important role.     

Concordance of ischemic heart disease in the NHLBI twin study after 14-18 years of follow-up

Morbidity and mortality were assessed in the NHLBI twin study at the end of 1987. Deaths were greater in DZ twins (58/520, 11.2%) than MZ twins (38/508, 7.5%). Ischemic heart disease concordances were 2.3 times higher in MZ pairs and 2.8 times higher in DZ pairs than expected based on the prevalence of ischemic heart disease in the cohort. Family history scores for heart disease, calculated 14-18 years earlier at entry to the study, were significantly higher in DZ pairs where one or both members later developed ischemic heart disease and in corcordant MZ pairs than in twin-pairs without any subsequent heart disease. Concordance rates were not significantly different between MZ and DZ pairs. The results agree with previous suggestions that selection at enlistment into the armed services over 40 years ago, as well as later volunteering for the NHLBI twin study, resulted in a decline in the number of concordant MZ pairs.     

中国成年双生子体质指数的分布特征

目的 描述中国双生子登记系统（CNTR）成年双生子BMI的分布特征,探索BMI在双生子人群中的特殊分布规律,为超重及肥胖高危因素分析和制定防制策略提供线索和基础资料。方法 选自CNTR中2010-2018年完成问卷调查的双生子对,纳入≥ 18岁具有完整双生子对登记信息,且身高、体重等关键变量无缺失或异常者进行分析,共计32 725对成年双生子。描述CNTR项目成年双生子BMI的人群、地区分布特征及双生子对内成员BMI差异的分布现况。结果 研究对象年龄（34.6±12.4）岁,同性别双生子对79.7%。研究对象平均BMI为22.5 kg/m²,超重率为23.7%,肥胖率为4.9%。男性、50~59岁组、北方地区、低文化程度者、在婚者的双生子超重率和肥胖率相对更高（P<0.001）。同卵和异卵间差异无统计学意义,但先出生的双生子超重和肥胖率略高于后出生者（P<0.05）。同性别双生子对内分析发现,对内BMI差异与年龄呈正相关（趋势性检验P<0.001）,异卵差异高于同卵,且卵型间差异随年龄增长发生变化。BMI一致率存在卵型差异（P<0.05）,同卵高于异卵。结论 本研究的双生子人群BMI的分布存在人群和地区差异;BMI为可遗传的性状,且遗传作用可能随年龄而变化。     

Male factor infertility: a twin study

There is a considerable body of literature on the causes of female infertility, but far less is known about male factor infertility. We conducted a classical twin study to estimate the genetic influence on 12-month male factor infertility. The study used the Vietnam Era Twin (VET) Registry, which includes male twin pairs born between 1939 and 1957, and who served in the US military between 1965 and 1975. In 1987, a health survey was mailed to all twins and obtained a 74% response rate. The current analyses comprised 1795 complete pairs in which both twins were married only once. Proband-wise concordance rates, tetrachoric correlations, and a bivariate probit model were used to calculate estimates of familial clustering and heritability for male factor infertility. The proband concordance rate for male factor infertility was 38% [95% CI 32.8, 42.4] in monozygotic (MZ) pairs and 33% [95% CI 28.0, 38.6] in dizygotic (DZ) pairs. The tetrachoric correlations for male infertility were 0.15 in MZ and 0.04 in DZ pairs. This pattern provides evidence of familial clustering, although genetic influence was not evident (P = 0.21). The current study identified that 12-month male factor infertility clustered within families. However, results suggest that factors unique to individual twins may play a more prominent role in male infertility than additive genetic effects or the common environment.     

Ten-year follow-up for male twins divided into high- or low-risk groups for ischemic heart disease based on risk factors measured 25 years previously

PURPOSE: To undertake medical follow-up in white males in the National Heart, Lung, and Blood Institute (NHLBI) twin study, previously divided on the basis of cardiovascular disease risk factors. METHODS: Tree structured survival analysis (TSSA) used at a mean age of 63 years to classify twins into high and low risk subgroups for ischemic heart disease (IHD) found that subjects at a mean age of 48 years were at highest risk with high systolic blood pressures and low high density lipoprotein cholesterol levels. Low risk subjects had lower blood pressures, better pulmonary function tests, and a negative family history for IHD or low post load plasma glucose levels. Medical record review was performed ten years later at the 4th Examination of the NHLBI twin cohort conducted in 1995-1997. RESULTS: The percentage of men in the NHLBI twin study who died nearly tripled (from 9.3% to 25.8%) in the ten-year period between the ages of 63 and 73 years. Deaths have tended to remain higher in DZ than MZ twins (27.8% versus 23.7%). At Exam 4, the relative risk of IHD (fatal or non-fatal) was 5.24 times higher for those in the high risk group than those in the low risk class (95% confidence limit 2.72-10.07, p < 0.0001 and 5.86 for any cardiovascular disease (95% confidence limit 3.03-11.33). The proportion of deaths from IHD in subjects with a high risk profile at entry was 51.7%, and 70.0% had died from all cardiovascular related disease. CONCLUSION: The present results indicate TSSA remained effective in classifying subjects into subgroups with greater risk of morbidity and mortality related to cardiovascular disease after ten additional years.     

Lifestyle and blood pressure levels in male twins in Utah

Healthy male monozygotic (MZ) and dizygotic (DZ) twin pairs (MZ pairs = 77; DZ pairs = 88) were studied to assess the effect of dietary intake, physical activity, physical fitness, body mass index (BMI), sum of the triceps and subscapular skinfold measurements, alcohol and caffeine consumption, and smoking patterns on blood pressure. Data on physical activity, detailed dietary intake, medical history, and demographics were obtained from a questionnaire. A bicycle ergometer was used to estimate level of fitness; other medical information was ascertained from physical examination. After normalizing the study variables, intraclass correlations for BMI and the sum of the triceps and subscapular skinfold measurements were higher in MZ than in DZ twin pairs (BMI: MZ r = 0.76, DZ r = 0.48; skinfolds: MZ r = 0.73, DZ r = 0.28), as were VO2max(MZ r = 0.63, DZ r = 0.25) and post-bike heart rate (MZ r = 0.69, DZ r = 0.19). Both systolic (SBP) and diastolic blood pressure (DBP) had high heritability estimates (SBP = 0.60, and DBP = 0.66). Using factor analysis, four major lifestyle factors were identified and categorized as: 1) dietary intake; 2) a factor heavily weighted by cigarette smoking, alcohol and caffeine consumption; 3) fatness; 4) physical activity and physical fitness. Adjustment for these factors did not alter heritability estimates for either SBP or DBP.     

Heritability estimate for refractive errors--a population-based sample of adult twins

The population-based Finnish Twin Cohort study was used to establish a heritability estimate for refractive errors especially for myopia. The twin cohort was derived from adult same-sexed twins in Finland. The total number of twins with both members alive in 1984 was 23,570. Of these, 3,676 twin pairs were monozygotic, and 8,109 pairs dizygotic. The sample for the present study was linked from the Finnish Police Force data base in 1984, where information of a person's possession of a driver's license and the obligation to wear glasses for far correction when driving a motor vehicle is recorded. Correlations in liability were estimated according to a multifactorial method of Smith. Falconer's heritability was 0.62 among males and 0.98 among females in the age group 28-29 years. When compared to previous twin studies of myopia, the proband concordance rates were higher for both MZ and DZ twin pairs.     

Genetic susceptibility to burnout in a Swedish twin cohort

Most previous studies of burnout have focused on work environmental stressors, while familial factors so far mainly have been overlooked. The aim of the study was to estimate the relative importance of genetic influences on burnout (measured with Pines Burnout Measure) in a sample of monozygotic (MZ) and dizygotic (DZ) Swedish twins. The study sample consisted of 20,286 individuals, born 1959–1986 from the Swedish twin registry who participated in the cross-sectional study of twin adults: genes and environment. Probandwise concordance rates (the risk for one twin to be affected given that his/her twin partner is affected by burnout) and within pair correlations were calculated for MZ and DZ same—and opposite sexed twin pairs. Heritability coefficients i.e. the proportion of the total variance attributable to genetic factors were calculated using standard biometrical model fitting procedures. The results showed that genetic factors explained 33% of the individual differences in burnout symptoms in women and men. Environmental factors explained a substantial part of the variation as well and are thus important to address in rehabilitation and prevention efforts to combat burnout.     

The association between body height and coronary heart disease among Finnish twins and singletons

OBJECTIVE: An inverse association between body height and the incidence of coronary heart disease (CHD) has been observed. However, the mechanisms behind this association are still largely unknown. We will examine the role of genetic and familial factors behind the association in a large twin data set. DESIGN AND SETTING: The data were derived from the Finnish Twin cohort including 2438 singletons, 4073 monozygotic (MZ) twins, and 9202 dizygotic (DZ) twins aged 25-69 years at baseline in 1976. Incident CHD cases were derived from hospital discharge data and cause of death data between 1977 and 1995. Cox regression analysis and conditional logistic regression analysis were used. RESULTS: In population-level analyses no differences in the general risk of CHD between zygosity groups were found. The association between body height and CHD was similar between sexes and zygosity groups. When men and women in all zygosity groups were studied together an increased risk of CHD was found only among the shortest quartile (hazard ratio [HR] = 1.34, 95% CI: 1.14-1.57). Among the twin pairs discordant for CHD a suggestive increased risk for the shorter twin was seen among DZ twins (odds ratio [OR] = 1.19, 95% CI: 0.95-1.48) when men and women were studied together. CONCLUSION: An inverse association between body height and CHD was broadly similar between sexes and twin zygosity groups and was associated with short stature. Among discordant twin pairs we found a weak association among DZ twins but not MZ twins. This may suggest the role of genetic liability behind the association between body height and CHD.     

Early-life environment influencing susceptibility to cytomegalovirus infection: evidence from the Leiden Longevity Study and the Longitudinal Study of Aging Danish Twins

Human cytomegalovirus (CMV) is a common herpesvirus establishing lifelong persisting infection, which has been implicated in immunosenescence and mortality in the elderly. Little is known about how and when susceptibility to CMV infection is determined. We measured CMV seroprevalence in two genetically informative cohorts. From the Leiden Longevity Study (LLS) we selected long-lived sib-pairs (n=844) and their middle-aged offspring and the offspring's partners (n=1452). From the Longitudinal Study of Aging Danish Twins (LSADT) 604 (302 pairs) same-sex monozygotic (MZ) and dizygotic (DZ) twins aged 73-94 years were included (n=302 pairs). Offspring of the long-lived LLS participants had significantly lower seroprevalence of CMV compared to their partners (offspring: 42% vs. partners: 51%, P=0·003). Of 372 offspring living with a CMV-positive partner, only 58% were infected. The corresponding number for partners was 71% (P<0·001). In the LSADT, MZ and DZ twins had high and similar CMV-positive concordance rates (MZ: 90% vs. DZ: 88%, P=0·51) suggesting that shared family environment accounts for the similarity within twin pairs. Our findings suggest that susceptibility to CMV infection--even under continuous within-partnership exposure--appears to be more strongly influenced by early-life environment than by genetic factors and adult environment.     

Socioeconomic position and twins' health: a life-course analysis of 1266 pairs of middle-aged Danish twins

BACKGROUND: The association between socioeconomic circumstances and health in adulthood could come about through processes that may be divided into factors experienced early in life and those experienced in later adulthood. In order to disentangle the influences on health of the early genetic, prenatal and rearing environmental factors from environmental factor later in life, we compared the health status among male and female twin pairs who lived together during childhood and were discordant or concordant on adult socioeconomic position. METHODS: A cross-sectional survey among a random sample of middle-aged Danish twins was conducted in 1998-99. The study population included 1266 like-sex twin pairs [52.5% monozygotic (MZ) and 47.6% dizygotic (DZ)]. Data were obtained on childhood and adult social class and on height, BMI, grip strength, depression symptoms, self-rated health, cognitive function, physical activity, smoking, alcohol and food intake. RESULTS: The expected associations between the individual twins' adult social class and health measures were observed. Among DZ male twins discordant on adult social class, the higher social class twin was on average significantly taller and had higher cognitive test scores. Among DZ female twins discordant on adult social class, the higher social class female twin was more physically active and had a higher cognitive test score. There were no significant health disparities or behavioural differences between the members of MZ twin pairs discordant on adult social class. For most health outcomes, the variability within twin pairs was related to zygosity (higher for DZ than for MZ) but not to social class. CONCLUSION: This study suggests that the relationship between adult social class and health outcomes in Denmark is due mainly to selection effects rather than a causal effect of social class exposures on health and behaviour.     

Trends in mortality due to cardiovascular diseases in Andalusia, Spain (1975-2004)

BACKGROUND: Cardiovascular diseases are ranked among the leading causes of death in the industrialized countries. This study is aimed at ascertaining the mortality trends by ischemic heart disease (IHD) and cerebrovascular diseases (CVD) in Andalusia within the 1975-2004 period. METHOD: Based on the official IHD and CVD death statistics and the related populations, the gross rates (GR) and age-adjusted rates (TS) and the Potential Years of Life Lost (PYLL) were calculated. To quantify the trends and their change points, a joinpoint regression analysis was made. RESULTS: The number of IHD deaths for females rose from 2,086 deaths in 1975 to 3,336 in 2004, the TS having dropped from 74.29 to 50.94 deaths/100,000 females, the PYLL having dropped from 173.65 years to 90.56 years/100,000 females. The number of deaths for males rose from 2,854 deaths in 1975 to 4,085 in 2004, the TS having dropped from 147, 67 to 104.96 deaths /100,000 males. The PYLL showed a like behaviour from the first to the last year of the series, showing values of 716.46 and 460.04 years / 100,000 males. For the IHD in females, the number of deaths in absolute numbers dropped from 4,712 to 4,221, the TS having dropped from 166.00 to 62.08 deaths in females, and the PYLL from 338.08 to 87.63 years / 100,000 females. For males, the number of deaths dropped from 3,714 to 2,951, the TS from 206.88 deaths /100,000 males in 1975 to 76.12 /100,000 males in 2004, and the PYLL dropping from 533.12 to 182.38 years / 100,000 males. CONCLUSIONS: The trend in mortality due to IHD was not constant either among females or males, although it has always been a downward trend, the drop being statistically significant. The drop in the CVD has been such a major one that both the absolute numbers and the gross rates are lower for the most recent years that the first years in the series studied despite the aging of Andalusias population.     

Stress-Relaxation of Stretched Callus Strips

Among 706 male, dizygotic, smoking discordant twin pairs born in 1901 to 1925, 13 deaths occurred among nonsmokers or less exposed partners against 34 among smokers or more exposed. In 246 corresponding monozygotic pairs the figures were 14 against 9. The excess mortality among male dizygotic smokers was not associated with any specific cause of death. Four cases of lung cancer among males occurred only in smokers. Accidents and suicides seemed to be associated with smoking, supporting the hypotheses regarding differences in personality typebetween smokers and nonsmokers. Only time will show whether trends found are stable. The data suggest, however, that part of the greater mortality in smokers is not due to smoking per se but to factors associated with smoking.     

双生子儿童贫血状况分析

目的通过分析双生子儿童贫血状况和贫血同病率,探讨其遗传和环境效应.方法选取5～19岁双生子228对,其中MZ(单卵双生子)142对,DZ(二卵双生子)86对,在DNA卵性鉴定基础上,以成对法计算同病一致率、调整BMI前后组内相关系数及遗传度.结果双生子儿童贫血检出率与一般人群无明显差异,贫血同病一致率分别为MZ 0.28,DZ 0.15,Hb(血红蛋白)遗传度为0.23.调整BMI前后MZ与DZ组内相关系数和遗传度无显著变化.结论儿童贫血状态受遗传及环境因素共同影响,环境效应更明显.