The EHU12/24 cohort: survey design, instruments and participants.

The EHU12/24 (code of a survey from the University of the Basque Country/Euskal Herriko Unibertsitatea, UPV/EHU) study was designed to investigate the risk factors of overweight/obesity-related lifestyles, particularly those associated with diet, their psychosocial influences and the interactions among these factors. This observational cohort study was carried out according to a standardised protocol and involved a representative sample of the UPV/EHU student population. Anthropometric measurements, direct behavioural determinants, such as physical activity and diet, and indirect determinants, such as social/psychological factors, are considered. In this paper, we present the survey design, instruments, measurements and related quality management. We describe the study sample in terms of its socio-economic and demographic factors and knowledge area and summarise the methodology used to collect the data and obtain the anthropometric measurements. The participants were 603 students (59·5 % female) aged 18-28 years. The crude participation proportion was 53·5 %. Regarding the knowledge area, the lowest response proportions were obtained from the Health Sciences (38·6 %) compared with the Non-Health Sciences (48·3 %) (P = 0·003). The mean age was 20·9 years, and 83·1 % of the sample were from Basque Country. Regarding the socio-economic characteristics, there were significant differences by sex and knowledge area in most studied variables. Moreover, the Health Sciences students were more likely younger, from outside Basque Country, to have parents with university degrees and to have a higher social status. In conclusion, the EHU12/24 cohort provides valuable data for analysing the complexity and multidimensionality of obesity in university students.

Heritability of the somatotype components in Biscay families.

The anthropometric somatotype is a quantitative description of body shape and composition. Familial studies indicate the existence of a familial resemblance for this phenotype and they suggest a substantial action by genetic factors on this aggregation. The aim of this study is to examine the degree of familial resemblance of the somatotype components and of a factor of shape, in a sample of Biscay nuclear families (Basque Country, Spain). One thousand three hundred and thirty nuclear families were analysed. The anthropometric somatotype components [Carter, J.E.L., Heath, B.H., 1990. Somatotyping. Development and applications. Cambridge University Press, Cambridge, p. 503] were computed. Each component was fitted for the other two through a stepwise multiple regression, and also fitted through the LMS method [Cole, T., 1988. Fitting smoothed centile curves to reference data. J. Roy. Stat. Soc. 151, 385-418] in order to eliminate the age, sex and generation effects. The three raw components were introduced in a PCA from which a shape factor (PC1) was extracted for each generation. The correlations analysis was performed with the SEGPATH package [Province, M.A., Rao, D.C., 1995. General purpose model and computer programme for combined segregation and path analysis (SEGPATH): automatically creating computer from symbolic language model specifications. Genet. Epidemiol. 12, 203-219]. A general model of transmission and nine reduced models were tested. Maximal heritability was estimated with the formula of [Rice, T., Warwick, D.E., Gagnon, J., Bouchard, C., Leon, A.S., Skinner, J.S., Wilmore, J.H., Rao, D.C., 1997. Familial resemblance for body composition measures: the HERITAGE family study. Obes. Res. 5, 557-562]. The correlations were higher between offspring than in parents and offspring and a significant resemblance between mating partners existed. Maximum heritabilities were 55%, 52% and 46% for endomorphy, mesomorphy and ectomorphy, respectively, and 52% for PC1. In conclusion, the somatotype presents a moderate degree of familial aggregation. For the somatotype components, as well as for PC1, the degree of familial resemblance depends on age. The sex only has a significant effect on ectomorphy.

Genetic and environmental sources on familial transmission in Biscayan families. III. The dynamometric strength.

The present research analyses a cross-sectional sample of 284 individuals (86 fathers, 86 mothers, 54 sons and 58 daughters) in 86 nuclear families living in the province of Biscay (Basque Country, Spain), with the aim of estimating both transmissible and non-transmissible components acting on familial resemblance for the maximum dynamometric strength of both hands, by means of a path analysis. Standardised data of each generation and sex were adjusted to a BETA model of path analysis independent of sex effects, allowing nevertheless the possibility to differentiate between transmissible (genetic and cultural) and non-transmissible (environmental) components acting on the observed phenotypic variance in Biscayan offspring. The results supported the full model of familial transmission for the two variables, in addition to other reduced models that gave rise to transmission effects regardless of any influence from the siblings' shared environment on the environmental transmitted component from their parents (b = 0), and without social homogamy between mates (u = 0). The most parsimonious model created, based on the previous ones, was accepted for both traits. The total transmissible variance (t2) explained between 21% (right hand) and 44% (left hand) of the observed phenotypic variation. These values are close to those from the literature (t2 = 37%). However, we should take into account that these kinds of estimations are specific for each group or population.

Family resemblance for anthropometric traits. II. Assessment of maternal occupational and age effects.

The present study was based on a cross-sectional sample of 1326 subjects (197 fathers, 466 mothers, 307 sons and 356 daughters) belonging to 488 nuclear families from the province of Biscay (Basque Country, Spain), with the purpose of estimating the degree of familial resemblance, for several anthropometric traits, by analysing the correlation coefficients between parent-offspring pairs. Height, weight, biacromial and bicrystal breadths, humerus and femur biepicondylar breadths, arm, waist and hip circumferences, biceps, triceps, subscapular, suprailiac, abdominal, thigh and calf skinfolds were taken from each individual. BMI, WHR and the sum of the seven skinfolds was computed. The mother's occupation and the age of offspring were taken into account, since the combination of all these factors might have an effect on familial resemblance. The mothers were classified into housewife (HM) and working mothers (WM). The offspring were divided into prepuberal, puberal and postpuberal subgroups. Standardised residuals were used to compute father-offspring (FO) and mother-offspring (MO) relations through correlation coefficients computed by maximum likelihood. The results confirm the influence of age on the correlations, since FO correlations revealed an increasing trend in HM's children for weight and another six variables as they grew older. On the other hand, the weight change tends to decrease with age in FO correlations within the WM group. Depending on mother's occupation and children's age, the global trend in the sample results in higher correlations in the second group (WM) than in the first one (HM) for the whole age range, but specially in FO correlations before puberty, where four variables (weight, bicrystal breadth, triceps and subscapular skinfolds) yield statistically significant differences.

Heritability variations of body linearity and obesity indicators during growth.

Longitudinal as well as cross-sectional studies have shown variations with age in heritability estimates for body dimensions from infancy to adulthood, even though the patterns of variation are not completely clear. Further study on this subject is of great interest and may help obesity interventions for preventing or treating obesity in children. Therefore, the aim of the present study is to analyse the changes in the genetic and environmental architecture of 8 body linearity and obesity-related phenotypes during the growth process in a cross-sectional sample of 1018 nuclear families from the province of Biscay (Basque Country, Spain). The contribution of additive genetic effects to the variation of the analysed traits was estimated by a variance component analysis using the SOLAR program. Moderate to high heritability estimates were obtained for all 8 anthropometric phenotypes (38.23-65.98%). The heritability values show an increasing trend with age and in the course of the entire ontogenetic development two age periods were remarkable. At 7(+)-8(+) years of age a strong increase in heritability estimates was found for all the anthropometric phenotypes, except for the sum of skinfolds (SF6), reflecting the biological significance of genes during mid-childhood. During puberty, most of the obesity related phenotypes showed their highest heritability values while linear measurements and weight presented a decrease in the genetic contributions. In conclusion, this study confirms that additive genetic influences have a considerable effect on body linearity and obesity-related traits throughout the growth period and that mid-childhood and puberty are very sensitive periods in human life cycle.

Multifactorial analysis of a mixed-longitudinal sample of Indian siblings: Age and sex effects on heritability.

The aim of the present study was to examine the heritability of 11 traits in a mixed-longitudinal sample of Indian siblings, and to determine whether heritability estimates vary during the growth period and whether they are influenced by sex. The sample consisted of 245 brothers and 213 sisters from 138 nuclear families living in a semi-urban area in Kolkata, India. The age ranged between 5 and 19 years. The traits were standardised for age and sex using standard deviation scores (SDS) produced by the LMS method (Cole, T.J., 1988. Fitting smoothed centile curves to reference data. J. R. Stat. Soc. A 151, 385-418). The standard deviation scores were analysed by PCA. The two factors with eigenvalues above 1 explained 77.3% of the variance; they showed a high level of pleiotropism present among the studied traits and represented body lengths (PC1) and body weight and breadths (PC2). The heritability between all types of siblings (irrespective of sex) for the PC1 and PC2 was estimated. The heritability between various pairs of siblings showed variations along the whole ontogenetic period studied. During the childhood and pre-pubertal period, heritability between brothers, brother-sister pairs and any sibling pairs was mostly constant, with small and non-significant variations. All the pairs showed the lowest degree of heritability during puberty for PC1 but not for PC2, with significant changes of heritability estimates between adolescence and adulthood, in most of the analysed sibling pairs and in both PC factors. The highest heritability was generally observed at the end of the examined growth period in all pairs. A significant effect of sex on heritability was only detected for PC2 at 11 years of age.

Heritability variations of morphometric traits in West Bengal (India) children aged 4-19 years: a mixed-longitudinal growth study.

BACKGROUND: Longitudinal and semi-longitudinal growth studies on siblings reflecting heritability changes during growth are very scarce. Moreover, studies of variables other than height, weight and BMI are virtually non-existent. AIM: The study compared changes in the heritability of six body lengths, four body breadths, and three indices between ages 4 and 19 years on the basis of a mixed-longitudinal sample of siblings, and examined whether heritability estimates change during the growth period. The data consisted of 238 brothers and 214 sisters from 134 middle-class nuclear families living in Kolkata (India). The analysis of sibling correlation was performed by maximum likelihood. The age-related patterns of heritabilities of the various traits were described by a cubic spline. RESULTS: The heritability was very high and significant in most traits, and at all considered ages. Mean heritability in the 10 morphometric traits was 69.3%, which was higher than the heritability values for the three indices. CONCLUSIONS: These results confirmed the existence of age-related trends in heritability of the considered morphometric traits. The sharp decline of the heritabilities at adolescence in most of the morphometric traits, and the acromio-iliac index in particular, may be due to the large inter-individual variation in the age at which the adolescent growth spurt is reached in both sexes.

Age trends of sibling resemblance for height, weight and BMI during growth in a mixed longitudinal sample from Sarsuna-Barisha, India.

BACKGROUND: Even though some studies have considered that sibling resemblance remains constant throughout the life cycle, several investigations emphasize the importance of age and its interactions with genetic and environmental factors in determining sibling similarity in several bodily traits. In fact, the study of age changes in familial resemblance is of great importance for the analysis of certain sources of variation observed in growth processes. AIM: The study examined sibling resemblance for height, weight and body mass index (BMI) in a mixed longitudinal sample from West Bengal, ages 2-19 years, in order to analyse the variations with age of the sibling resemblance for these phenotypes during growth. SAMPLE AND METHODS: Two hundred and forty-five brothers and 213 sisters from 138 middle-class nuclear families living in a semi-urban area of South Kolkata, India were analysed. The analysis of sibling resemblance was performed through correlations estimated by the maximum-likelihood method. The patterns of different trends of sibling resemblance with age were examined by fitting a cubic non-linear regression to the observed correlations. RESULTS: The results show clear variations with age in the sibling resemblance for the traits height and weight, though to a lesser extent for BMI. In general, we found the highest correlation values during the period of infancy, a remarkable decrease during puberty, and a trend of increase towards the end of the growth cycle. CONCLUSION: The study confirms the effect of age on the degree of similarity among siblings for height, weight and BMI in the sample. The sharp decline of correlation at adolescence can be interpreted in terms of the individual variation in age of reaching the adolescent growth spurt.

Skin colour in the Basque population.

Skin colour has been analysed in 352 males and 393 females of the Basques. Measurements of upper-arm reflectance were taken using 9 filters of an EEL reflectance spectrophotometer. Regional differences are not found. Sexual dimorphism is not equally revealed in all filters in the same manner, but females are, on average, lighter skinned than males. By means of Penrose's size ans shape distance comparisons were made with several European populations.

Incidence of red-green color blindness in the Basque population.

The incidence of red-green colour vision defects was studied in a sample of 392 Basque students (174 males and 218 females), using the Ishihara test cards (1987). The frequency of red-green colour blindness was 4.02 percent in the males and 0.46 percent in the females. The colour blindness frequencies found among males are within the range of other Spanish samples. Nevertheless they are lower than the values reported in other European populations.

Evidence of phenotypic and social assortative mating for anthropometric and physiological traits in couples from the Basque country (Spain).

This study examined 28 anthropometrical and physiological traits in 107 married couples living in the province of Biscay (Basque Country, Spain). The aim was to verify the existence of a phenotypic and/or social preference when choosing a mate. For this, correlations between pairs of spouses were estimated by maximum likelihood, and a model of familial transmission (path analysis) was applied in order to test if social homogamy between mates existed. The results provide significant evidence of phenotypic as well as social homogamy in several of the studied traits. Even if an assortment existed when choosing a mate for bony traits such as height, the effect of cohabitation cannot be discounted as the main causal factor for the high phenotypic resemblance observed between spouses for body composition traits. In addition, with the social homogeneity of the studied sample, significant evidence of the existence of social homogamy between mates was only found for 20% of the studied variables.

Age at menarche from a Biscayan coastal population (Basque Country).

Data on menarcheal age were collected by the status quo method on a sample of 894 schoolgirls (9-19 years of age), from the Biscay province coast (Basque Country, Spain). Logit analysis provided a mean age at menarche of 12.75 +/- 0.04 years with a standard deviation of 0.93. The result was compared with data from another previous Basque study.

ABH antigen secretion in Basques and the spatial variation pattern of the secretor locus in Spain.

Secretion of the ABH blood group antigen was analyzed in 305 saliva samples of students in the Basque Country University. The frequency of ABH non-secretor was 26.23%, a result very close to that obtained in autoctonous Basques (22-23%) and in other populations from the West (Galicia) and Centre (Castille) of Spain. With certain exceptions, the frequencies of non-secretor se allele present a fairly homogeneous variability pattern and no significant spatial orientation or tendencies of se gene distribution are observed in the Iberian Peninsula.

Menarcheal age in a sample of Basque schoolgirls: a comparative study with other Spanish populations.

Reported data on age at menarche in a sample of Biscayan schoolgirls are compared with data from several Spanish populations. Though the mean age falls in the range of variation of the Spanish means, the analysis of variance shows significant differences among the series. With regard to the possible secular trend of this event in the Biscay province, both a stability of menarcheal age and a diminution of the process of variability are observed.

Skin colour variability in Basque boys aged 8-19 years.

Skin colour variation with increasing age was analysed using a cross-sectional sample of 796 Basque boys aged from 8 to 19 years. Measurements were taken at the upper inner arm and forehead by means of an EEL DS29 Digital Unigalvo reflectance spectrophotometer with a nine-filter head. Ontogenic changes of skin pigmentation were found to be statistically significant. The influence of the month in which measurements were taken on reflectance values has been studied. Comparisons with another similar study (Pembrokeshire, Wales population) were carried out.

Somatotypes of 14 to 19 years old urban boys and girls from Bilbao (Basque Country).

Following the anthropometric method of Heath-Carter (1967) individual somatotypes of a sample of 1260 school children (605 boys and 655 girls) living in Bilbao and aged between 14-19 years have been investigated. Age differences of the somatotype components and sexual dimorphism of the physique were also analyzed. In both sexes, somatotype varies with age. The main factor for these variations of the somatotype is in the boys the endomorphy, and in the girls the mesomorphy. The mean somatotypes of the total sample are in boys central (3.9-3.9-2.7) and in girls mesomorphic-endomorphic (5.3-3.1-2.3).

A somatotypical study of the geographic variations between two Spanish populations.

Morphological differences between university students from Bilbao (Basque Country) and Madrid (Spanish Meseta) have been studied. The sample sizes are 99 and 119, respectively, and the age ranges from 18 to 22 years. The main differences between the two groups under study were observed concerning the skinfold thicknesses. Body weight, stature and limb girths do not show remarkable differences. The physiques, as judged from anthropometric somatotypes, differ in the first component (endomorphy): Basques have higher values.

Analysis of sibling resemblance in anthropometric somatotype components.

We analysed the Heath-Carter somatotype familial resemblance degree in a sample of 1350 siblings (685 males and 665 females) from 634 nuclear families in the province of Biscay (Basque Country, Spain). Sibling correlations were estimated according to maximum likelihood procedures for endomorphy, mesomorphy, ectomorphy and somatotypical attitudinal distance (SADi), after having adjusted for age, sex and the two other components (Model I), and after taking into account several environmental variables shared by all members of each sibship (Model II). All sibling correlations of the somatotype components were significant, tending to be higher in the case of mesomorphy than in the case of endomorphy. Same-sex siblings (BB and SS) displayed significant mesomorphic and ectomorphic resemblances, but in the case of endomorphy, sisters (SS) revealed relatively low correlation compared with brothers (BB). The sex of sibs had a significant influence on correlations of mesomorphy, but not on the other two components. Further control of socio-familial variables such as the father's occupation and education, and the sibship size, resulted in lower mesomorphy correlation coefficients, but had no effect whatsoever on the other two components. SADi correlations were very low and not significant, indicating high degrees of dispersion in the individual somatotypes of the sample.

Sibling correlations of skin pigmentation during growth.

The present study is focused on the analysis of skin color correlations in a sample of 1039 siblings aged 4 to 20 years from the province of Biscay (Basque Country, Spain). Measurements were taken at the upper inner arm and forehead by means of an EEL DS29 Digital Unigalvo reflectance spectrophotometer fitted with filters 601, 605, and 609. The reflectance data were internally standardized according to sex and age of the individuals, and the analysis of the degree of similarity between siblings was based on the calculation of intraclass correlation coefficients. All 3 filters gave fairly high and statistically significant correlations regarding forehead skin color (between 0.28 and 0.45) for all types of siblings under consideration. However, with respect to filter 609 the arm reflectance values did not reveal correlation either between brothers (0.01) or between siblings (0.02), even though it did reveal correlation between sisters (0.29). When other filters or type of sibling were considered (also for arm), all coefficients happened to be statistically significant and relatively high (0.35-0.43). This study confirms that the degree of sibling resemblance with regard to skin pigmentation is influenced by growth factors and that the upper inner arm and the forehead skin patterns change with age in the sense that, during and especially after puberty, the coefficients of correlation are higher for arm reflectance than for forehead reflectance; the forehead is a site that is more influenced by environment.