To assess the relationship between telomere length and adiposity, using dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI), in addition to conventional anthropometric proxies including body mass index (BMI) and cardiovascular disease risk factors.
A cross-sectional sample of 309 non-Hispanic white participants in the Fels Longitudinal Study aged 8 to 80 yr (52% female) was included. Average telomere length was measured by quantitative PCR.
Telomere length was negatively correlated with age (r = -0.32, P < 0.0001) and had numerous significant correlations with established cardiovascular disease risk factors including waist circumference (r = -0.33), apolipoprotein B (r = -0.26), systolic blood pressure (r = -0.28), and fasting serum glucose (r = -0.15); all P < 0.0025. In backward selection linear regression models of telomere length, adiposity measures were consistently retained in the best models; BMI, waist circumference, hip circumference, total body fat, and visceral adipose tissue volume were all inversely associated with telomere length at the nominal P < 0.05 level or lower, independent of age, sex, systolic blood pressure, and fasting serum lipid, lipoprotein, and glucose concentrations. The negative association of BMI with telomere length was stronger among younger than older participants (P for interaction, 0.03).
Individuals with higher total and abdominal adiposity have lower telomere length, a marker of cellular senescence, suggesting obesity may hasten the aging process. Longitudinal studies are required to establish the causal association of early life adiposity with biological aging.
Mean stature in a population has been observed to vary with living conditions. If, and how, this affects sexual dimorphism in stature is not fully understood. We analyzed stature data from Swedish populations from the 10th to the end of the 20th century to investigate if male stature is more plastic than female stature in response to environmental changes. Further, we examined if there, as a consequence of this, exists an allometric relationship between male and female stature that is not caused by genetic factors, coupling greater stature with greater dimorphism. We found no significant change in stature from the 10th century to the 17th century, but a clear increase in both male and female stature during the 20th century, most likely because of improved living conditions. Regression analyses revealed no consistent change in sexual stature dimorphism over time for any of the time periods, including the 20th century. Further, we found no significant allometric relationship between male and female stature, and could consequently not identify any significant relationship between stature and stature dimorphism. Thus, contrary to previous suggestions, the regressions did not provide support for the assertion that male stature is more sensitive to environmental changes than female stature, nor that stature dimorphism increases with increasing stature.
Project HeartBeat! is a four year mixed-longitudinal study of the development of cardiovascular risk factors in White and African American children who at baseline comprised three age cohorts 8, 11, and 14 years. This paper focuses on the anthropometric variables which were chosen to reflect body fat and fat-free mass. Selected anthropometric dimensions are compared with those of samples from the combined National Health and Nutrition Examination Surveys I and II to explore the similarities of the samples in terms of central tendencies and variances. The measurements were then explored in terms of their ability to estimate the two compartment model of body composition: fat-free mass (FFM) and body fat (BF) from bioelectrical impedance (BIA). Project HeartBeat! children are slightly larger than NHANES children and have variances that are generally comparable to the national surveys. Over seven percent (7.7%) of children were overweight (BMI) and 25% had 'mild obesity' by %BF. Three different factor analytic methods (incomplete principal components, alpha and maximum likelihood) produced two latent variables from 17 anthropometric dimensions which together accounted for 76-83% of the variation: (1) A body mass factor (F1) which was weighted highly on six circumferences, weight and six skinfolds, and (2) a linear growth factor (F2) which was strongly associated with height, arm length, and sitting height. Triceps, subscapular and midaxillary skinfolds were consistently highly loaded on the body mass factor and their sum was highly correlated to %BF and fat mass (0.90-0.99). This suggests that this sum could be used to estimate fatness in children in studies where the BIA or other body composition techniques are unavailable. FFM and %BF were predicted from the anthropometric factors. Both factors contributed to the estimate of FFM (R(2) = 0.81-0.93), although F2 contributed proportionately more. The 'body mass' factor (F1) was the main predictor of %BF (R(2) = 0.86-0.93), though at some ages the linear factor (F2) was significantly and negatively related to %BF. This set of anthropometric dimensions, taken for the purpose of estimating body composition and summarized as two latent vectors by factor analysis, strongly reflects body fat and FFM in children and adolescents. Am. J. Hum. Biol. 11:69-78, 1999. Copyright 1999 Wiley-Liss, Inc.
This study tested hypotheses that: (1) levels of adiposity, as assessed by triceps and subscapular skinfold thicknesses (SFTs), and blood pressure would be higher in British Pakistani children than in white British children; and (2) British Pakistani children of mothers born in the UK would have smaller SFTs and lower blood pressure than children of mothers born in Pakistan.
Participants aged 7 to 11 years were recruited from five primary schools in a deprived urban area. BMI, waist circumference, triceps and subscapular SFT, and blood pressure were measured.
Participants comprised 209 white British and 132 British Pakistani children, including 79 children born in the UK to migrant mothers and 49 children born to British-born mothers. In comparisons by ethnic group, triceps SFT was significantly higher in British Pakistani children only after controlling for BMI. Subscapular SFT was higher in British Pakistani children, a finding strengthened after controlling for BMI. Systolic blood pressure was significantly higher in British Pakistani children, but not after controlling for socioeconomic status (SES). There were no significant differences between British Pakistani children born to migrant or British-born mothers, except that systolic blood pressure was lower in children of British-born mothers after controlling for SES, a finding that was not significant after controlling for BMI.
This study confirms previous findings of larger SFTs and higher blood pressure in British children of Pakistani origin than in children of white European origin. Further work with larger sample sizes is needed to investigate differences between generations.
The age-related pattern of body density and body composition in Japanese males (n = 266) and females (n = 318), 11.00 to 18.99 years of age was studied. Body density (BD) as well as height, body weight, and seven skinfold thicknesses were measured. Percentage fat (%Fat) was calculated using the age- and sex-specific equation of Lohman. Fat mass (FM), fat-free mass (FFM), and the body mass index (BMI) were calculated. The trend for BD in males was lowest at 11 years (1.0530 g/ml) and increased to 1.0695 g/ml at 14 years, and then decreased slightly at 15 to 17 years. In female, BD decreased from 1.0530 g/ml at 13 years to 1.0424 g/ml at 17 years. Mean %Fat was highest in males at 11 years (15.8%), and lowest at 14 years (10.1%). The highest mean %Fat in females occurred at 16 years (22.8%), and the lowest at age 11 years (15.2%). Overall, only 6.8% of males and 3.1% of females were classified as obese. Between 11 and 18 years, FFM of males differed by 20.7 kg or 67.9%, whereas females showed a difference of only 10.8 kg or 34.7%. Consequently, age effects explained approximately 60% of the male variance of FFM but only 26% in females. Body density of each sex and age group in this study did not differ significantly from previous Japanese studies, and the pooled BD data for 1,457 Japanese including the present study are reported as a reference.
C-reactive protein, a marker of chronic, low-grade inflammation, is strongly associated with current central adiposity, and has been linked to elevated risk of cardiovascular disease. Less is known about the contribution of longitudinal change in waist circumference to current inflammation. We evaluated the extent to which current waist circumference and change over an 11-year interval contribute independently to low-grade systemic inflammation measured in a group of 1,294 women, 35-69 years, participating in the Cebu Longitudinal Nutrition and Health Survey in the Philippines. Waist circumference was measured at the time of blood draw for CRP analysis in 2005 and during an earlier survey in 1994. A waist circumference delta variable was constructed by subtracting current circumference from past circumference. We used logistic regression models to predict having an elevated plasma CRP concentration (3 mg L(-1) < CRP < 10 mg L(-1)). Waist circumference in 2005 was a strong predictor of elevated CRP (OR 1.10, 95% CI = 1.08, 1.12, P < 0.001). In combined models, increase in circumference over 11 years was a significant and independent predictor of elevated CRP risk (OR = 1.023, 95% CI = 1.00, 1.05, P < 0.05). Considering the average increase over time, the cumulative risk of elevated CRP due to increased central adiposity was 25.7%. However, women who reduced their waist circumference between 1994 and 2005 had greatly reduced risk (6.2%), suggesting that even long-term inflammatory burden can be reversed by weight loss. Although current waist circumference is an important contributor to risk of elevated systemic inflammation in this as in other populations, history of central adiposity may be an independent phenomenon.
Socioeconomic variation in the growth status of urban school children 6-13 years of age in 1972 and 2000 was compared. The children were resident in the city of Oaxaca and were students in the same primary school in each year. Socioeconomic status (SES) was based on parental occupation. Height, sitting height, estimated leg length, weight, and the body mass index in 218 boys and 191 girls in 1972 and 173 boys and 166 girls in 2000 were compared. Sex-specific MANCOVA was used to evaluate SES differences within each year, while sex- and SES-specific MANCOVA was used to evaluate differences between years. The prevalence of stunting, overweight and obesity was estimated. There were no SES differences among boys and girls in 1972 and boys in 2000; low-middle and middle SES girls were significantly taller and heavier with longer legs than low SES girls in 2000. Within each SES group, children in 2000 were significantly larger in body size and segment lengths except for sitting height in low SES children of both sexes. Estimated secular gains increased from low to low-middle to middle SES in both sexes. Inequitable gains by SES contributed to an increase in the magnitude of differences between SES groups, especially between low SES children on one hand and low-middle and middle SES children on the other hand. The prevalence of stunting declined while the prevalence of overweight and to a lesser extent in obesity increased from 1972 to 2000, more so in low-middle and middle SES than in low SES children.
We investigated the occurrence and intra-allelic variability of the T(-13910) variant located upstream of the lactase gene in 965 individuals from 20 different locations of Italy and Greece. The T(-13910) frequency ranges from 0.072 (Sardinia) to 0.237 (North-East Italy), with a statistically significant difference between North-East Italians and other Italian populations. The comparison of the lactose tolerance predicted by T(-13910) and that assessed by other studies using physiological tests shows a one-way statistically significant discrepancy that could be due to sampling differences. However, the possible role of other genetic factors underlying lactase persistence is worth exploring. The time of the most recent common ancestor and departures from neutrality of the T(-13910) allele were assessed using three microsatellite loci. Time estimates were found to be congruent with the appearance of dairy farming in Southern Europe and the occurrence of a single introgression event. Robust signals of selection can be observed in North-East Italy only. We discuss the possible role of cultural traits and genetic history in determining these observed micro-evolutionary patterns.
The present study is part of a research project on growth models of children in an area of central-southern Italy. It analyzes the phases of pubertal breast development (BD) in 397 girls, pubic hair development (PHD) in 399 girls, and menarche in 583 girls from 6-14 years old. The status quo method was used to evaluate the age at menarche. Probit analysis was used to analyze the data for all three variables. The onset of BD and PHD (Tanner stage 2) occurs at age 7 in 6.1% of girls. Passage to stage 3 of one or both secondary sexual characteristics occurs at age 10 in 8.5% of girls. Comparison with data from the United States shows higher percentages of American white girls in stage 2 (or greater) of both characteristics at any age. The mean (median) age of onset (Tanner stage 2) of BD or PHD or both of them is 9.96 years. The passage to stage 3 occurs at age 12.36 for BD (95% confidence interval: 1.36 years) and at age 12.10 for PHD (95% confidence interval: 0.51 years). The mean age at menarche is 12.55 years, in general agreement with other values found in Italy. Sexual maturation at any considered stage for both pubertal characteristics is generally in line with literature data concerning other Mediterranean and industrialized countries or countries in which the demographic transition is in an advanced phase. It does not show a significant earlier onset. The evidence emerging from the general project suggests that the secular trend is still in progress in this region of Italy.
Obesity has reached epidemic proportions in the U.S. and more developed countries, particularly so among adolescents. A substantial impact on public health could be achieved if other factors causing obesity besides the conventional ones of diet and physical activity could be identified and acted upon. The present study investigates whether there is a link between low sleep quality and obesity in a tri-ethnic, cross-sectional sample (n = 383) of male and female adolescents ages 11-16 years old (Heartfelt Study). Sleep quality was expressed as two variables, total sleep time and sleep disturbance time obtained by 24-hour wrist actigraphy. Percent body fat and body mass index (BMI) were used together to define obesity. The potential influence of demographic and behavioral confounders were considered in models that described the relation of sleep to obesity occurrence. Obese adolescents experienced less sleep than nonobese adolescents (P < 0.01). For each hour of lost sleep, the odds of obesity increased by 80%. Sleep disturbance was not directly related to obesity in the sample, but influenced physical activity level (P < 0.01). Daytime physical activity diminished by 3% for every hour increase in sleep disturbance. The above observations were independent of potential confounding variables. Inadequate and poor sleep quality in adolescents may be important factors to consider in the prevention of childhood obesity.
The purpose of the study reported here was to further investigate a new method of estimating inbreeding in large, relatively isolated populations over historic times, as reported by Pattison (1999, 2001). The method is based on modeling the genealogical "paradox" and produces values of Pearl's coefficients of inbreeding as a function of time for any given population curve. In particular, this study demonstrates that the new method of estimating inbreeding may be used to examine the effect of unusual features in population curves on levels of inbreeding in that population. As an example, the medieval population "bump" that spans the 13th and 14th centuries in the population of Britain, which terminated abruptly with the outbreak of bubonic plague in 1348 AD, is examined. It is first assumed that the whole population was the adult (breeding) population, corresponding to minimum inbreeding. For this case it is found that, for distant generations, about 90% of the whole population occurs in any present-day British pedigree. This value compares favorably with the values of 85% and 80% reported by Wachter (1980) and Derrida et al. (1999, 2000), respectively. The population bump causes the curves for Pearl's coefficient, for minimum inbreeding, to have a plateau of about 96% over the period from about 1220 AD to 1380 AD. The effect of introducing a single known estimate of inbreeding into the model is to produce a more realistic situation where the adult (breeding) population is considerably less than the whole population. It is found that the maximum number of different ancestors in any generation, in the average British pedigree, is about 22900 individuals and occurs about 1220 AD. More importantly, and possibly contrary to expectation, it is now found that the population bump had virtually no effect on the level of inbreeding.
The aim of this study was to assess the prevalence of overweight and obesity in Portuguese children age 7-9 years and to analyze trends in body mass index (BMI) from 1970-2002. Data were collected from October 2002 to June 2003 in a random sample of Portuguese children. Height and weight were measured and BMI (Kg/m(2)) was calculated. The International Obesity TaskForce (IOTF) cutoffs to define overweight and obesity were used. In the total sample we found 20.3% of overweight children and 11.3% of obese children. These results indicate a prevalence of overweight/obesity of 31.5%. Girls presented higher percentages of overweight than boys except at age 7.5. Girls also showed a higher percentages of obesity than boys except at age 9. From 1970 to 1992 and 1992 to 2002, height, weight, and BMI increased at different velocities: weight increased faster than height, and, consequently, BMI increased more in the last period than in the first one, leading to an increase in obesity values. Compared to published data by IOTF on other European countries, who applied the same methods to define overweight and obesity, Portuguese children showed the second-highest mean values in overweight/obesity. Italy showed the highest values (36%). The present study shows a very high prevalence of overweight/obesity (31.5%) in Portuguese children compared to other European countries. Portugal followed the trend of other Mediterranean countries like Spain (30%), Greece (31%), and Italy (36%). These high values require a national intervention program to control childhood obesity.
Little data are available on the growth and development of young female dancers. The objective of this study was to determine whether the body structure and adipose tissue distribution of dancers aged 8-16 years differ from that of non-dancer girls. Our cross-sectional study included a group of 1,482 female dancers, aged 8-16 years, and a control group of 226 female non-dancers of similar age cohorts. Fourteen anthropometric measurements were recorded and 15 indices calculated. In none of the linear anthropometric measures, were significant differences found between the two groups. The only significant difference relates to the extent and distribution of adipose tissue: At age 8, both groups show similar weight while at age 13 non-dancers are significantly heavier than dancers (48.4 +/- 9.8 kg for non-dancers and 40.6 +/- 8.7 kg for dancers). At age 15, weight differences between the two groups decrease to only 2 kg. The differences in weight are also expressed in skinfold thickness and chest circumference. Patterns of adipose tissue distribution differ between the two groups. Mean age at menarche was 13.1 years among dancers and 12.3 years in non-dancers. In conclusion, musculoskeletal development was found to be very similar in dancers and non-dancers. The specific body type reported for professional dancers is more likely acquired via "teacher's selection" and not training programs. Parents should not dread the possibility that dance training will delay the growth or reduce the height of their daughters.
Coefficients of relationship by isonymy, based on the frequency of common surnames, were used to estimate the biological affinity between (R(ib)) and within (R(iw)) 16 Sardinian villages in the periods 1825-1849, 1875-1899, and 1925-1949. The database for the surname analysis consisted of 13,515 marriages registered in the parishes of villages, all belonging to the Sardinian linguistic area. The values of R(ib) and R(iw) tend to decrease in time. In all three periods, the R(ib) values generally decrease as the geographical distance between villages increases. The negative values of the Bravais-Pearson coefficient of correlation between the matrix of R(ib) values and the matrices of geographical distances (calculated both in a straight line and from road distances) are significant for each period (modified Mantel test), with slightly higher correlation coefficients for road distances. Moreover, the plots of isonymic relationships obtained by nonmetric multidimensional scaling for 1825-1849 and 1925-1949 show that the biological relationships between neighboring villages increase in the latter period. The positive values of the Bravais-Pearson coefficients of correlation between R(iw) and altitude are significant in all three periods, while the correlation between R(iw) and population size is not significant, even when altitude is controlled for. Since altitude is considered an indicator of isolation, the results obtained with the coefficient of relationship by isonymy within villages also support the isolation-by-distance model. R(ib) values provided a reliable picture of the biological relationships between 16 Sardinian villages, while R(iw) values illustrated the biological affinity within the communities for a period of 100 years, from 1825-1849 to 1925-1949.
The purpose of the present study was to assess the age differences in growth characteristics and physical abilities of physically active adolescent girls and to compare them to corresponding data for girls nonactive in sport. The cross-sectional study was carried out on 643 Estonian girls, 10-17 years of age, who were regularly training track and field, and 902 nonactive girls. The organized physical activity of the studied girls consisted of lessons in the school curriculum (2 x 45 minutes per week) for both groups and special track and field training for the first group. Height, weight, and the body mass index (BMI) were used to characterize growth status. Physical ability was assessed with the 30-m dash, standing long jump, medicine ball throw (2 kg), standing quintuplet jump, isometric strength of back extensor muscles, and 1-minute ergocycling at the highest possible rate. Girls active in track and field were taller in all the age groups (P < 0.05-0.001) and lighter except at 17 years, when they were heavier (P > 0.05), but the differences at 12 and 13 years were not significant. BMI was also significantly lower in active girls (P < 0.05-0.001) in all age groups, except at 17 (P > 0.05). The actively training girls had higher physical abilities at all ages from 10-17. The annual differences in performance scores were significant (P < 0.05-0.001) up to 15 years except for the standing long jump. Differences in mean scores of most motor abilities were minimal or reduced significantly at 13-14 years in nonactive girls, but were significant in active girls.
Reference percentiles (5th, 10th, 50th, 85th, 90th, and 95th) of black and nonblack children ages 8-17 years from Project HeartBeat! (n = 678) are presented for body mass index (BMI), percent body fat (PBF), fat-free mass (FFM), and fat mass (FM) derived from bioelectrical impedance. Project HeartBeat! is a mixed longitudinal study in which three cohorts of children (seen initially at age 8, 11, or 14 years) were followed for 4 years and measured thrice-yearly from 1991 through 1995. Weight, height, and BMI of Project HeartBeat! children are similar in central tendency and variability to those of nationally representative samples for nonblack children but not black children, for whom there is an excess of children at or above the 95th percentile for weight and BMI. Values of PBF above which cardiovascular risk variables increase (as suggested in the literature) are located at the 85th percentile of the Project HeartBeat! distributions. This percentile of PBF may be tentatively considered as a cutoff point with epidemiological significance for children.
The purpose of the study was to develop ethnic-specific equations for fat-free mass (FFM) from selected anthropometric dimensions and bioelectrical impedance measures of resistance (R) and reactance (Xc) for use in the NHLBI Growth and Heath Study. Using dual-energy X-ray absorptiometry measures of body composition as the dependent variable and field measures of body composition by anthropometry and bioelectrical impedance as the explanatory variables, ethnic-specific prediction equations were developed on a sample of girls representing a wide range of ages and BMI. The equations were cross-validated using (1) the Prediction of Sum of Squares (PRESS) statistic and (2) an independent sample of 20 girls of each race from a study conducted at the National Institute of Child Health and Human Development (NICHD). Subjects were 65 White and 61 Black girls 6-17 years of age. The best race-specific equations for FFM each explained 99% and 97% of the variance in the White and Black girls, respectively. Root mean square errors (RMSE) ranged from 1.14 to 1.95 kg. The equation for Black girls used Stature2/Resistance (R), weight, and reactance (Xc) as predictor variables; the equation for White girls used Stature2/R, weight, and triceps skinfold thickness. The results indicate that (1) equations to predict FFM in girls should be ethnic-specific and that (2) accurate values for TBF and %BF can be calculated from the predicted FFM.
The observation that declines in the human secondary sex ratio (SSR) may be linked to stressful periconceptional periods has received considerable attention (Catalano  Hum Reprod 18:1972-1975; Catalano et al.  Int J Epidemiol 34:944-948,  Hum Reprod 20:1221-1227,  Paediatr Perinat Epidemiol 19:413-420). For the purpose of testing the external validity of this phenomenon, birth records from four German village genealogies (N = 1,048) were analyzed to study the impact of the French Revolutionary Wars (1787-1802) on the proportion of male births. All births were subdivided into three cohorts (prewar, 1787-1792; war, 1792-1797; and postwar, 1797-1802). Differences in SSR between cohorts achieved statistical significance (chi2= 7.695; df = 2; P = 0.021). In addition, changes in SSR before, during, and after the wars were monitored by risk analysis. Using the SSR of the prewar period as a control, the results of the war cohort failed to achieve statistical significance (regression coefficient, -0.257; ExpB= 0.773; P = 0.118), while the odds reduction of 32.3% in the postwar period proved to be statistically significant (regression coefficient, -0.390; ExpB= 0.677; P = 0.006). It is hypothesized that the experience of postwar economic hardship (attributable to lowered food availability paired with dietary changes) represents the most likely proximate cause. The study also finds evidence of a parental sex ratio manipulation strategy meant to offset the female-biased SSR after the wars. It is argued that from an evolutionary perspective both the decline in SSR in response to stress as well as parental manipulation of the tertiary sex ratio convey reproductive advantages.
Three national surveys on the physical status of 18-, 19-, and 20-year-old male candidates for military service were carried out in six geographic regions of China in 1955, 1974, and 2001. Data from these surveys for 72,000 individuals were compared by region, by time, and by age, and estimates of incremental changes by decade were made. Overall, at all time points, males in the north and northeast areas were larger and heavier than males in the southwest. Similarly, the proportion of males in the north and northeast who were overweight was greater than in the other areas. The proportion classified as "thin" was highest in the south, southwest, and northwest, reaching 42.6% in the northwest. When urban and rural areas were compared, the mean value of every measure in every region was higher for urban youth, with all but two comparisons reaching significance (P<0.05). Differences of chest circumference among age groups were significant, as were differences in height, weight, and body mass index for 18-year-olds compared to 20-year-olds. Overall, height increments per decade were greatest for males in the southwest (average of age groups 1.79 cm, 1974 to 2001) and least in the northeast (1.08), indicating some tendency toward convergence over time. Weight increments per decade over the same time were greatest in north China (1.37 kg) and least in the northwest region (0.58 kg).
The main objective of the work is to compare the growth and nutritional status of Australian Aboriginal term infants born with (n = 81) and without fetal growth restriction (n = 260). A prospective birth cohort study of 341 Aboriginal babies from the Top End of the Northern Territory of Australia was recruited at birth (1987-1990) and re-examined at a mean age of 18.3 years (2006-2008) for outcome measures of growth and nutrition status. Those with growth restriction at birth were 3 cm shorter (P = 0.0026) and 9 kg lighter (P = 0.0001) with head circumferences 0.95 cm smaller (P = 0.0008) than those without growth restriction. The proportions of growth restricted participants with body mass index <18.5 kg/m(2) were significantly greater (P = 0.028), and those with BMI > 25 kg/m(2) and with fat percentage >85th percentile were significantly smaller (P = 0.012 and 0.004, respectively). In this cohort, those Aboriginal babies born smaller and lighter have remained smaller and lighter at 18 years of age. However, the highest risk of later chronic noncommunicable disease has been reported in subjects who were born small and become relatively larger in later life. The continued study of this Aboriginal birth cohort will give us an opportunity to determine if and when in later life the effects of birth weight are modified by environmental nutritional factors.
Growth is a complex process, and only little is known on the genetic regulation of it. We analyzed the effect of genetic and environmental factors on growth in a longitudinal Swedish cohort of 231 monozygotic and 144 dizygotic twin pairs born 1973-1979 with length or height measured annually from birth to age 18. The data were analyzed by two different multivariate variance component models for twin data using the Mx statistical package. At birth and 1 year of age, a substantial part of the variation in length was because of common environment (50 and 57%, respectively) and the effect of genetic factors was minor. After 2 years of age, 91-97% of the variation of height could be explained by genetic differences whereas the rest was because of environmental variation not shared by twins. The genetic correlation between heights at ages 2 and 18 was 0.73 (95% confidence intervals 0.68-0.77) showing that 53% of the genes affecting height at these ages are the same or closely linked; with increasing age the correlation with genetic effects at age 18 become subsequently stronger. Especially in mid-childhood, growth was largely regulated by the same genetic factors. During puberty new genetic factors started to affect height, but also genetic variation affecting height at previous ages remained. These results suggest that genetic regulation of growth is rather uniform, which is encouraging for further efforts to identify genes affecting growth.