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PubMed1995

Immunization status and birth order.

OBJECTIVE: To determine whether an association exists between immunization status and birth order. DESIGN: Medical record review of immunization dates for matched siblings. SETTING: Pediatric clinic at a university medical center. SUBJECTS: A total of 892 children (446 sibling pairs of firstborn and secondborn children) born between 1983 and 1991 who received regular pediatric care at the clinic. OUTCOME MEASURES: Median ages at which firstborn children and their secondborn siblings had been immunized with the initial four doses of diphtheria and tetanus toxoids and pertussis vaccine (DTP1, DTP2, DTP3, and DPT4) and the initial dose of measles-mumps-rubella vaccine; point prevalences of firstborn and secondborn children up-to-date with all immunizations at each month of life to 2 years of age. RESULTS: Between 5 and 12 months of life, the percentage of secondborn children who were fully immunized was significantly lower than the percentage of fully immunized firstborn children (P values ranging from < .0001 to < .05). Firstborn children were much more likely than their secondborn siblings to have been immunized on time with DTP2 (z = 3.80, P = .0001) and DTP3 (z = 3.31, P = .0009). Overall, DTP2 immunizations were given at median ages 10 days later, and DTP3 immunizations, 20 days later to secondborn children than to their firstborn siblings. In addition, late immunization of a firstborn child was found to increase the risk that a secondborn sibling would also be immunized late. CONCLUSIONS: Secondborn children are likely to be immunized later than firstborn children. Secondborn children with an older sibling who was immunized late are at particular risk for delayed immunizations.

Age Factors↗
PubMed1998

Birth order and male homosexuality: extension of Slater's index.

Homosexual men tend to be later-born children. Slater's index, the ratio of older sibs to all sibs, is consistently higher for male homosexuals than for comparable heterosexuals. According to some explanations of this tendency, homosexual men are later born with respect to their brothers and later born with respect to their sisters only secondarily and less strongly. We show that if sisters have no direct bearing on a brother's sexual orientation and brothers do, then [formula: see text] On the other hand, if sisters have the same bearing on a brother's sexual orientation as male sibs do, then [formula: see text] These ratios are calculated and compared in nine samples of homosexual men and nine corresponding samples of control heterosexuals. The first equation holds for homosexual men, and the second equation holds for heterosexual men. The late birth order of homosexual men is sex specific. What matters is a boy's birth order relative to his brothers only. This effect may have its origins in an immune reaction or in behavioral contagion.

Analysis of Variance↗
PubMed2003

Correlation of age and birth order of parents with chromosomal anomalies in children.

One hundred children with suspected congenital and/or malformation and their parents who reported to SAT hospital, Medical College, Trivandrum, India formed the test group. Fifty children with no obvious anomalies or abnormalities and their parents formed the control group. The criteria for selection of the control was 1) the maternal age at delivery was below 30 years and 2) the parents belong to 1st or 2nd birth order. The chromosomal analysis was carried out in all the subjects using peripheral blood lymphocyte microculture to investigate for any constitutional chromosomal markers and quantitate the mutagen (bleomycin) sensitivity of the chromosomes. All the subjects were evaluated clinically and a complete family history was recorded. Chromosome anomalies were noted in 41 out of the one hundred children and in 4 out of the 200 parents of the test group. No constitutional aberrations were seen either in the parents or in the children of the control group. Bleomycin sensitivity study revealed a high b/c value in 35 children (24 hypersensitive and 11 sensitive) of the test group whereas in the control group the b/c values were low denoting hyposensitivity and very good DNA repair mechanism. This study reveals that the incidence of chromosome aberrations is higher when the age and birth order of parents are higher. A direct correlation was noted with parental order and b/c value. This was also true with the parental age and birth defects.

Abnormalities, Multiple↗
PubMed1976

Sex, birth order, and maternal age characteristics of infants with congenital heart defects.

The records of the New England Regional Infant Cardiac Program, a service program covering all of New England, provide a useful source of information about the characteristics of children born with congenital heart defects. Data were analyzed on more than 2000 children born in New England who were diagnosed with a congenital heart defect before the first birthday. Children with arterio-venous fistula, aortic stenosis, transposition of the great arteries or hypoplastic left ventricle were predominantly male; children with persistent ductus arteriosus and endocardial cushion defect were predominantly female. Positive trends in risk with increasing birth order were present for pulmonic stenosis and transposition of the great arteries, and a negative trend was seen for persistent ductus arteriosus. What evidence there was for associations with maternal age was greatly reduced after controlling for confounding by birth order.

Adult↗
PubMed1993

Relation of birth order and scores on measures of pathological narcissism.

To study the relationship between birth order and pathological narcissism, it was predicted that firstborn and only children would score significantly higher on standardized measures of pathological narcissism. Two such measures, the Millon Clinical Multiaxial Inventory and the Narcissistic Personality Inventory, were administered to 50 randomly selected subjects from a metropolitan mental health and family treatment agency. Subjects were asked to indicate their ordinal birth positions, e.g., first, middle, last, or only, and then were administered both instruments. Analysis supported the initial prediction by indicating that firstborn and only children had higher mean scores on the measures of pathological narcissism. It might be advisable for clinicians to identify patients' ordinal positions while appraising relevant diagnostic criteria and eventual treatment planning.

Adult↗
PubMed1975

Genetics of acheiropodia ("The handless and footless families of Brazil"): IV. Sex ratio, consanguinity and birth order.

The sex ratio among acheiropods is shown to be not significantly different from the sex ratio among their normal sibs, as well as among other segments of the family (parental sibships, cousin sibships and other sibships). The frequency of consanguineous marriages among the parents of acheiropods (82%) is one of the highest thus far reported among parents of individuals affected with rare autosomal recessive anomalies or diseases. No evidence was found of any overall positive or negative birth order effect on the incidence of acheiropodia. These results further strengthen the hypothesis of a simple genetic mechanism for acheiropodia, namely autosomal recessive inheritance, without any detectable complication as regards sex ratio, consanguinity and birth order. Although the family size from heterozygous parents (producing at least one acheiropod) was twice as large as family sizes in other segments of the families (8 against 4), we have at present no evidence to support either heterozygous advantage or reproductive compensation.

Birth Order↗
PubMed1975

Childhood mortality, family size and birth order in pre-industrial Europe.

Based on parish registers, demographic histories of Crulai (France), Tourouvre-au-Perche (France), and Geneva (Swizertland) established the childhood mortality experienced by complete sibships during periods of at least half a century before the Fench revolution. These observations may be presented as frequenceis in incomplete five-dimensional contingency tables. The five dimensions are: survival (living or dead), completed sibship size, birth order, type of family (according to completeness of information about family), and epoch (period in which the family lived). This paper reanalyzes these published data, using hierarchical log-linear models to discern which interations among the five variables can justifiably be inferred from the data. The neonatal and infant mortality rates of firstborn are probably higher than those of later sibs (in Crulai and Tourouvre). But mortality by age 20 (in Geneva) is associated strongly with the epoch, type of family, and family size, and not significantly with birth order. The increase in mortality with completed family size is insufficient to select, in an evolutionary sense, for limited family size.

Adolescent↗
PubMed1992

Age at first establishment of chronic hepatitis B virus infection and hepatocellular carcinoma risk. A birth order study.

It is frequently assumed that the risk of hepatocellular carcinoma related to hepatitis B virus is higher when chronic hepatitis B virus infection is acquired early in life. This hypothesis has never been directly evaluated. However, firstborn and secondborn children are exposed to common infections after their school enrollment, whereas laterborn children are exposed much earlier, through their older siblings. The authors analyzed sibship size and birth order data from a large case-control study of patients admitted to Athens, Greece, hospitals between April 1976 and October 1984. The analyses included 185 patients with hepatocellular carcinoma, 35 patients with metastatic liver cancer, and 432 other hospital controls. There was a tendency for cases of hepatocellular carcinoma to concentrate at higher birth orders. When the analysis was restricted to cases and controls who were positive for hepatitis B surface antigen, this tendency was even more notable. These results are compatible with the hypothesis that establishment of chronic hepatitis B virus infection at an early age increases the risk of hepatocellular carcinoma substantially more than does chronic infection with this virus established at a later age.

Age Factors↗
PubMed2000

Relationship of birth order and the marketing-related variable of materialism.

The relationship between the birth order and materialism scores was investigated using materialism conceptualized as a consumer value. Data were collected from 275 alumni of a major southwestern university. The analysis indicated that first-borns in this sample scored significantly lower on materialism than younger siblings.

Adult↗
PubMed1979

Obesity in nineteen-year-old men: family size and birth order associations.

The authors analyzed the prevalence of obesity by family size and birth order for a total population of over 280,000 19-year-old Dutch males, who were born between 1944 and 1947 and who were from one- to five-child families. Obesity was defined by a relative weight index, 120% or more of the standard of weight for height. Overall obesity prevalence was 1.83%; sons of manual workers were more prone to obesity than sons of non-manual workers. Individuals from one-child families (only children) were uniquely at risk for obesity, particularly in the non-manual social class. This result was similar to reported findings for childhood obesity.

Adult↗
PubMed1978

[Schizophrenia and birth order].

With the possible most powerful goodness-of-fit test available until now, the Halperin's chi-square, a statistically significant association between schizophrenia and birth order in 1016 brazilian patients is reported. This association is with early and last born males, favoring theories which put emphasis on stressful experiences over children who are in the extremes of their sibships. There is a sex factor: females show no association. Factors which could introduce bias, as family size, social class and incomplete sibships were tentatively controlled. Since in Brazil no population data are available, the Greenwood-Yule method seems useful and valid for the purpose, with the aid provided by Halperin's chi square modification. A brief comment on results and earlier studies is made, together with suggestions for future research.

Adolescent↗
PubMed1992

Sibship size, sibling sex ratio, birth order, and parental age in homosexual and nonhomosexual gender dysphorics.

This study investigated whether demographic variables previously reported to differentiate ordinary homosexuals from heterosexuals also differentiate gender-dysphoric homosexuals from gender-dysphoric persons with other sexual orientations. Subjects were outpatients aged 16 and older who were referred by physicians to a specialty clinic for the assessment of gender identity disorders. The subjects were divided into three groups: 204 homosexual women, 193 homosexual men, and 273 nonhomosexual men; the last category included men sexually attracted to females, to both sexes, and to neither sex. Demographic data on patients' families of origin were extracted from their clinical charts and from structured interview protocols. A multiple-range test at the .05 level showed that the homosexual men had significantly more siblings than the homosexual women, who, in turn, had significantly more siblings than the nonhomosexual men. The sibling sex ratio of the homosexual men, 131 brothers per 100 sisters, was significantly higher than the sex ratio of live births for the population as a whole (106 men per 100 women; p = .01); the sibling sex ratios of the other groups did not differ from the expected value. The homosexual men had a significantly later birth order than the nonhomosexual men (p = .004); the homosexual women, who fell in between, did not differ significantly from either male group. There were no between-groups differences in paternal or maternal age at the time of the subject's birth. The results concerning sibling sex ratio and birth order are consistent with previous findings for homosexual men.

Birth Order↗
PubMed1986

Birth order in Australian vital statistics.

The author examines factors contributing to the poor quality of Australian vital statistics on birth order. Among these are the lack of standardization of birth registration procedures, census respondents' reluctance to provide information concerning illegitimate births, and problems associated with differences in instructions to parents registering births. Instructions for Australian birth registration forms are suggested. The author stresses that "information needs to be gathered on previous issue in respect of all births registered, not just marital births; and it needs to be gathered in respect of all children born alive to the mother, not just those of the current marriage or relationship."

Australia↗
PubMed2005

The association between the fraternal birth order effect in male homosexuality and other markers of human sexual orientation.

Later fraternal birth order (FBO) is a well-established correlate of homosexuality in human males and may implicate a maternal immunization response in the feminization of male sexuality. This has led to the suggestion that FBO may relate to other markers of male sexual orientation which are robustly sexually dimorphic. If so, among homosexual males the number of older brothers should strongly correlate with traits such as spatial ability and psychological gender, indicative of greater behavioural feminization, compared to heterosexual males. The present study failed to find significant associations between number of older brothers and these traits.

Adolescent↗
PubMed1997

Birth order, sibship size and risk of Hodgkin's disease in children and young adults: a population-based study of 31 million person-years.

It has been proposed that Hodgkin's disease (HD) may have an infectious origin and that delayed exposure to infection may increase the risk of HD in young adults. This hypothesis is addressed by studying the family structure among children and young adults. The Civil Registration System was used to establish a population-based cohort consisting of all persons whose mothers were born in Denmark since 1935. Persons who developed HD were identified by linkage with the Danish Cancer Registry. HD incidence rate ratios were estimated based on a log-linear Poisson regression model. The cohort of 2.1 million persons (aged 0-42 years) was followed for 31.1 million person years, during which period 378 cases of HD occurred. Among children (< 15 years, n = 72), the relative risk (RR) of HD tended to increase with increasing sibship size, the relative increase in risk per increase in sibship size (the trend) being 1.28 [95% confidence interval (CI) 1.00-1.63]. The trend for birth order was 1.26 (95% CI 0.92-1.73). Among young adults (> or = 15 years, n = 306) the risk of HD, on the contrary, tended to decrease with increasing sibship size [trend = 0.91 (95% CI, 0.81-1.03)] and birth order (trend = 0.85 (95% CI, 0.71-1.01). These trends among young adults were significantly different from the corresponding trends among children (p < 0.05). Siblings of cases were at increased risk of HD (RR = 18; 95% CI, 2.2-65, n = 2). Our findings are compatible with the hypothesis that delayed exposure to infection may be a risk factor for HD in young adults, and that early exposure perhaps to another infectious agent may increase the risk of HD in children.

Adolescent↗