Differential fertility in the United States, 1980: continuity or change?

This paper considers how changes in women's sociocultural characteristics have influenced recent patterns of differential fertility in the US and whether the convergence of fertility differentials observed up to 1970 has continued. The data are drawn from the June 1980 US Current Population Survey, which is a probability sample survey selected to represent the civilian non-institutionalized population living in households. The study population consists of 20,621 ever-married White and Black women aged 25-44, a group for various reasons considered to have a high impact from the point of view of fertility behavior. Fertility to date and ever expected fertility are the dependent variables. The respondents were separated into age cohorts, and differentiated by race. The data suggest that there has been no change in differential fertility in recent years: the 2 youngest cohorts (25-29 and 30-34 years) have similar expected fertilities that are lower than those of the older cohorts. Age at 1st birth, length of 1st birth interval, income, and education were negatively associated with fertility, among both older and younger women, of both races. Differentials by race have narrowed slightly. When fertility expectations were examined, the association of the independent variables with expected completed fertility was weaker among younger women, indicating that there has been some convergence in expected fertility. Further narrowing of differentials in actual fertility depends on how successful the younger women are in preventing future unplanned births. If the present tendency towards surgical sterilization (among both races and groups above and below the poverty level) persists, it will make it possible for more women to stay within their expected total fertility levels.     

Population based study of rates of multiple pregnancies in Denmark, 1980-94.

OBJECTIVE: To study trends in multiple pregnancies not explained by changes in maternal age and parity patterns. DESIGN: Trends in population based figures for multiple pregnancies in Denmark studied from complete national records on parity history and vital status. POPULATION: 497,979 Danish women and 803,019 pregnancies, 1980-94. MAIN OUTCOME MEASURES: National rates of multiple pregnancies, infant mortality, and stillbirths controlled for maternal age and parity. Special emphasis on primiparous women > or = 30 years of age, who are most likely to undergo fertility treatment. RESULTS: The national incidence of multiple pregnancies increased 1.7-fold during 1980-94, the increase primarily in 1989-94 and almost exclusively in primiparous women aged > or = 30 years, for whom the adjusted population based twinning rate increased 2.7-fold and the triplet rate 9.1-fold. During 1989-94, the adjusted yearly increase in multiple pregnancies for these women was 19% (95% confidence interval 16% to 21%) and in dizygotic twin pregnancies 25% (21% to 28%). The proportion of multiple births among infant deaths in primiparous women > or = 30 years increased from 11.5% to 26.9% during the study period. The total infant mortality, however, did not increase for these women because of a simultaneous significant decrease in infant mortality among singletons. CONCLUSIONS: A relatively small group of women has drastically changed the overall national rates of multiple pregnancies. The introduction of new treatments to enhance fertility has probably caused these changes and has also affected the otherwise decreasing trend in infant mortality. Consequently, the resources, both economical and otherwise, associated with these treatments go well beyond those invested in specific fertility enhancing treatments.     

Continuing fertility transitions in a plural society: ethnic trends and differentials in Peninsular Malaysia

Fertility in Peninsular Malaysia has declined continuously from the late 1950s, reaching a total fertility rate of 3735 in 1983. All ethnic groups in Malaysia have contributed to this modern demographic transition but the rate of change has been most rapid for Chinese and Indians, Malay fertility having reached a plateau in the early 1980s. The effect of age structure, marital patterns and marital fertility (by parity) on the fertility declines for each ethnic community are analyzed. There has been a tendency, in each ethnic group, for the age distribution within the group of reproductive-age women to grow younger, reflecting the entry into the younger reproductive ages of the large birth cohorts of the 1950s and early 1960s. The effect of this on crude birth rates is hard to determine, because rising age at marriage and increasing use of contraception meant that fertility was increasingly concentrated in the more central reproductive ages. By the 1990s, the earlier declines in fertility will bring about a decline in the proportion of the total population made up of females in the main reproductive ages. After that point, further declines in fertility will be reflected in a sharper decline in the crude birth rate and hence the rate of population increase. Between 1947 and 1980, the age at marriage changed dramatically for females of all ethnic groups. The transition to higher age at marriage for Chinese was completed earlier, and since 1970 has risen by only a year. For Malays and Indians, the rise began later, proceeded faster and continued right up to 1980 when the medium ages at 1st marriage were Malays 22, Indians 23, Chinese 24 years. In 1980, Malay women on average were marrying 5 years later, and Indian women 6 years later than had their mothers' generation in 1947. The proportion never-married among Malay and Indian women aged 20-24 rose from 1/10 to 1/2 over this period; relatively greater changes are evident at ages 25-29. Other factors are the almost complete shift from parent-arranged to self-arranged marriages. Family size desired has decreased for all groups and the decline in breastfeeding has been offset by the sharp increase in the practice of contraception. Continuation of these trends would lead to replacement-level fertility for Malaysian Chinese and Indians by the year 2000. Malay fertility is likely to continue to decline but at a more moderate pace.     

Stable aggregate fertility in a time of family change: a decomposition of trends in American fertility, 1970-1999

Population-level birth rates in the United States were largely stable between 1970 and 1999. This stability contrasts with rapid change in marriage rates and fertility timing during the same period. In this article, I use decomposition techniques to analyze this seeming paradox. I decompose the general fertility rate into four components: age distribution, marital status, age-specific nonmarital fertility, and age-specific marital fertility. Absent other changes, declining time spent married would have led to substantial decline in fertility. Several factors combined to counterbalance these changes in marital behavior. Among white women in the 1970s and 1980s, marital fertility rates increased at older ages, consistent with a scenario in which women postponed both marriage and childbearing; increased nonmarital birth rates during this period were not a driving factor in overall fertility trends. Increased nonmarital fertility was more important in compensating for declining time spent married among African American women and among white women in the 1990s.     

Changes in maternal age distribution and their possible impact on demand for prenatal diagnostic services

Between 1977 and 1985 there was a 65% increase in births to women aged 35 or more in England and Wales, but only a 15% increase in all births. Two factors of roughly equal importance were responsible for this differential increase. Firstly, the proportion of older women (35-44) among all women of reproductive age (15-44) increased from 28% in 1977 to 31% in 1985; and, secondly, in the same period the fertility rate for women aged 35-39 increased from 18·2 to 24·1 per 1000 and for women aged 40-44 from 4·1 to 4·6 per 1000.The increased fertility rate among older women is not due to an extension of the reproductive period but to a delay in childbearing. This delay was seen in women married only once and also in those who had remarried.As prenatal diagnosis for the exclusion of chromosome abnormalities is customarily offered to older mothers the increased numbers of women aged 35 or more and their increased fertility rate have important implications for the provision of obstetric and laboratory services. There were 51 859 live births to women aged 35 and over in 1985; the projected figure for 2001 is 85 000. If the use of prenatal diagnosis continues to increase facilities for about 70 000 prenatal cytogenetic analyses will be needed in 2001.     

Fertility levels, trends and differentials in Kuwait

Data used in this study come from the published reports of the censuses and vital registration systems. The crude birth rate in Kuwait is very high, although an apparent decline seems to have started in the period 1975-80. There are considerable differences between the Kuwaiti and non-Kuwaiti populations. The former had a relatively stable high rate around 50 until 1975 and then fell to 47 in 1980. The total fertility rate was 6.8 per woman. The rate for the non-Kuwaitis rose in 1965-70 and then fell sharply throughout 1970-1980, from 44 to 30. Non-Kuwaiti fertility is consistently lower than Kuwaiti fertility at all ages, the differences being relatively greater after age 35. The peak ages of fertility are 25-29 years for Kuwaitis and 20-29 years for non-Kuwaitis. For Kuwaitis, there is clear evidence of declining fertility in the younger age groups but not in the older, largely reflecting the trend towards later marriage among the younger Kuwaitis. As expected, there is a diminishing trend in completed family size from the least to the most educated women in both Kuwaiti and non-Kuwaiti women in all age groups. The illiterate women at marriage are younger than the university educated women by about 5 years. Results further show that women who are economically active have lower fertility than those who are not, both in Kuwaiti and non-Kuwaiti groups. The differences in each group are significant, as are differences in the fertility level by husband's occupation. High fertility in Kuwait, as well as in other oil-exporting Arab countries, is a result of a variety of factors including the generally pronatalist sentiment of the Arab population, improved health facilities, rising wealth, the youthful age structure, the young age at marriage and the substantial incentives in the different governmental schemes to promote native high fertility and keep a balance between the native and immigrant populations.     

Genetic and environmental influences on expression of recurrent headache as a function of the reporting age in twins.

To explore age-related mechanisms in the expression of recurrent headache, we evaluated whether genetic and environmental influences are a function of the reporting age using questionnaire information that was gathered in 1973 for 15- to 47-year-old Swedish twins (n = 12,606 twin pairs). Liability to mixed headache (mild migraine and tension-type headache) was explained by non-additive genetic influences (49%) in men aged from 15 to 30 years and additive genetic plus shared environmental influences (28%) in men aged from 31 to 47 years. In women, the explained proportion of variance, which was mainly due to additive genetic effects, ranged from 61% in adolescent twins to 12% in twins aged from 41 to 47 years, whereas individual specific environmental variance was significantly lower in twins aged from 15 to 20 years than in twins aged from 21 to 30 years. Liability to migrainous headache (more severe migraine) was explained by non-additive genetic influences in men, 32% in young men and 45% in old men, while total phenotypic variance was significantly lower in young men than in old men. In women, the explained proportion of variance ranged from 91% in the youngest age group to 37% in the oldest age group, with major contributions from non-additive effects in young and old women (15-20 years and 41-47 years, respectively) and additive genetic effects in intermediate age groups (21-40 years). While total variance showed a positive age trend, genetic variance tended to be stable across age groups, whereas individual specific environmental variance was significantly lower in adolescent women as compared to older women.     

Down syndrome: interaction between culture, demography, and biology in determining the prevalence of a genetic trait

The incidence of Down syndrome (DS) at conception is highly dependent upon the maternal age distribution and age-specific pregnancy rates. Live-birth prevalence of DS reflects these factors and fetal deaths. Since the introduction of prenatal diagnosis in the early 1970s, the role of fetal deaths in the equation has increased. Between 1920 and the early 1980s, DS live-birth prevalence decreased in many populations due to declining fertility rates, particularly among older women. In the late-1970s the trend reversed, as the median age of populations and birth rates among older women steadily increased. This paper illustrates these interactions using data we have analyzed for New York State (NYS) and comparative data obtained from the literature. Between 1983 and 1997 DS live-birth prevalence in NYS remained stable at about 9.9 per 10,000 live births. The number of prenatal tests performed increased by 158%, and the number of DS fetuses detected prenatally more than quadrupled. Fertility rates of women aged 35-49 continued to increase. The proportion of DS cases born to these older mothers increased from 23% in 1985 to 43% in 1997. We estimated that without prenatal diagnosis, DS live-birth prevalence would have been 17.0 per 10,000 live births by 1995. Cultural factors influence demographic trends, birthing technologies, physician practices, and women's decision-making regarding prenatal screening and diagnosis for DS.     

Maternal age at last birth in Egypt

To assess the effects of women's education, residence, and marital experience on their age at the birth of their last child, a proportional hazards regression model was applied to 1980 Egyptian Fertility Survey (EFS) data. The detailed data include the date of birth of each child for every women interviewed, and the woman's date of birth and age at interview. Age at last birth was examined by regression analysis on birth history and socioeconomic information. 4 hypotheses were tested: women who are well educated have a greater probability of ending childbearing earlier than women with less education; women in rural areas have a higher probability of having their last child at older ages than urban women; marital disruption without remarriage lowers the probability of older maternal age at last birth; and marital disruption with remarriage increases the probability that a woman stops reproducing at an older age. The overall chi-square indicates a significant regression. All coefficients were significant, except the coefficient for women with intact 1st marriages. Women with more education had a greater probability of ending childbearing earlier than women with less education. Rural women tended to have their last children at ages significantly older than overall age at last birth. Current residence in urban areas had the opposite effect. The coefficient for those with intact 1st marriages was insignificant, meaning that the mean age at last birth for this group of women was not much different from the overall mean. Remarried women tended to end childbearing at ages significantly older than the overall average age at last birth, suggesting that these women tended to have children by their new husbands. Those with dissolved 1st marriages who had not remarried had a higher probability of ending childbearing earlier than did older women. Marriage age and final parity had highly significant negative coefficients; as marriage age and number of children born increased, so did the "survival" time or the age at last birth. Results from the hazards model indicate that the effects were as anticipated. The median age at last birth for the total sample of women aged 45-49 was 45-49 years. The median age at last birth was about 2 years older for rural compared to urban women. Illiterate women had the oldest median age at last birth of the education groups. There was little differences between median ages at last birth for women with intact 1st marriages and those whose 1st unions were dissolved and who had remarried. The median age at last birth increased with final parity.     

Fertility and suicide rates: a time series analysis in the United States.

In a time series study of the USA from 1933 to 1984, fertility rates were associated with the suicide rates of those aged 15-44. The higher the fertility rate the lower the suicide rate for these age groups, for both whites and non-whites, and for both men and women. The results were seen as supporting Durkheim's theory of suicide.     

Melanoma in people aged 65 and over in Scotland, 1979-89.

OBJECTIVE--Detailed analysis of primary cutaneous melanoma first diagnosed in Scotland in patients aged 65 and over. DESIGN--Comparison of changing incidence, sex distribution, site, histogenetic type, tumour thickness, and prognosis of all primary cutaneous melanomas in patients aged 65 and over diagnosed in Scotland in the 11 years 1979-89 with similar data for patients aged under 65. SETTING--Data were obtained from the Scottish Melanoma Group''s database, established in 1979, which aims to record detailed clinical, pathological, and surgical follow up details of all primary cutaneous melanomas registered in Scotland. PATIENTS--1430 patients (954 women, 476 men) aged 65 and over; comprising over a third of the 3903 patients with primary melanoma recorded for all age groups in Scotland during this period. RESULTS--The overall incidence of melanoma in patients aged 65 and over increased from 12.2/100,000 in 1979 to 20.7/100,000 in 1989, with the greatest increase seen in older men, from 7.8/100,000 in 1979 to 18.0/100,000 in 1989. The site most commonly affected was the face in both men and women (33% of all tumours). The most common histogenetic type was superficial spreading melanoma. 526 patients (37%) had melanomas with a tumour thickness of 3.5 mm or greater in the older age group, compared with 453 patients (18%) in those aged under 65. The highest proportion of thick tumours was seen in older men. Five year survival figures for 616 patients diagnosed between 1979 and 1984 were 88%, 66%, and 47% for thin, intermediate, and thick tumours respectively. Overall five year survival for the older age group was 64% compared with 78% for the younger age group. CONCLUSION--The increase in melanoma in the elderly and the high proportion of thick tumours, especially in men, require a specific educational programme for both primary and secondary prevention directed towards the older population.     

Time trends and demography of mortality after fractured neck of femur in an English population, 1968-98: database study

Objectives To investigate time trends in mortality after admission to hospital for fractured neck of femur from 1968 to 1998, and to report on the effects of demographic factors on mortality.Design Analysis of hospital inpatient statistics for fractured neck of femur, incorporating linkage to death certificates.Setting Four counties in southern England.Subjects 32 590 people aged 65 years or over admitted to hospital with fractured neck of femur between 1968 and 1998.Main outcome measures Case fatality rates at 30, 90, and 365 days after admission, and standardised mortality ratios at monthly intervals up to one year after admission.Results Case fatality rates declined between the 1960s and the early 1980s, but there was no appreciable fall thereafter. They increased sharply with increasing age: for example, fatality rates at 30 days in 1984-98 increased from 4% in men aged 64-69 years to 31% in those aged ≥ 90. They were higher in men than women, and in social classes IV and V than in classes I and II. In the first month after fracture, standardised mortality ratios in women were 16 times higher, and those in men 12 times higher, than mortality in the same age group in the general population.Conclusions The high mortality rates, and the fact that they have not fallen over the past 20 years, reinforce the need for measures to prevent osteoporosis and falls and their consequences in elderly people. Whether post-fracture mortality has fallen to an irreducible minimum, or whether further decline is possible, is unclear.     

Cessation of childbearing in the absence of contraception in Sri Lanka

In data from the Sri Lanka Fertility Survey, 1975, the cessation of childbearing is examined among women who have never used contraception. The sample consisted of 6810 currently or previously married women, 57% of whom reported that they had never used contraception. Cessation of childbearing is studied according to age and marriage duration. The variables analyzed are age at last birth, proportions infertile during the last 5 or 7 years, and the infertile open interval. The duration of breastfeeding is taken into account where necessary, and the contraceptive users and nonusers are compared where appropriate. Non-users tend to cease childbearing early, and therefore are infertile for longer periods during their marriages. It is probably age of the 1st child that influences decisions on future fertility. Among women aged 45-49 who married before age 20 and continued in their 1st marriage, mean age at last live birth in non-users, was 34.5 years, about 2 years earlier than in those who had used contraception. Non-users who married at any age below 30 years cease childbearing well below age 40. The proportion not currently pregnant and infertile over the past 5 years increases with marriage duration among the fertile non-users in each age group. When age at last birth and the duration of breastfeeding in the open interval are taken into account and the reference period is increased to 7 years, the period of infertility increases with marriage duration among nonpregnant non-users below age 45. The proportion of women who were currently not pregnant and had remained infertile over the past 7 years is higher among the older non-users whose 1st child was born more than 10 years ago.     

Variations de l'incidence des fractures de l'extrémité supérieure du fémur chez les personnes agées de la région de Québec.

To estimate the incidence of fracture of the proximal end of the femur in people aged 50 years or older living in the Quebec area in 1971, 1976 and 1981 we determined the number of admissions for such fractures to the 15 acute care hospitals in the region. From 1971 to 1981 the number of fractures increased by 71%; the increases for those aged 75 to 84 years and 85 years or over were 98% and 118% respectively. The variation is only partly explained by changes in sex and age distribution of the population; the incidence rates also increased. Among men aged 75 to 84 years the incidence rate per 1000 person-years rose from 2.63 in 1971 to 5.22 in 1981, an increase of 98%; the corresponding figures for men aged 85 years or more were 9.76 and 16.91, an increase of 73%. Among women aged 75 to 84 years the rate rose from 7.28 to 8.81, an increase of 21%; the corresponding figures for women aged 85 years or more were 20.40 and 24.27, an increase of 21% and 19% respectively.     

Mortality and age differences in marriage.

Data from the 1971 census population were used to evaluate the effects of age differences of married partners on mortality rates. Different age groups were isolated to highlight the association between mortality and age of spouse for specific ages of married men and women. Men married to much younger or to older women exhibited a higher mortality rate than men married to women who were only a few years younger than themselves. A similar trend was observed among women married to much younger or much older men compared with those whose spouses were a few years older or of similar ages as themselves. Trends for other age groups (women aged 60-69 years, men below 40, and women below 30) did not exhibit a clear pattern. Although statistical biases within age groups may in part account for the differences in the findings, the trend which emerged from the analysis suggests that lower morbidity is associated with the most common age combinations (husbands same age or slightly older than wives). Other factors could also account for the differences (e.g., selection of healthy partners in 1st marriages, differences in lifestyles between married and single).     

Metabolic Syndrome,Sarcopenia and Role of Sex and Age: Cross-Sectional Analysis of Kashiwa Cohort Study

Recent epidemiological evidence suggests that effects of cardiovascular risk factors may vary depending on sex and age. In this study, we assessed the associations of metabolic syndrome (MetS) with sarcopenia and its components in older adults, and examined whether the associations vary by sex and age. We also tested if any one of the MetS components could explain the associations. We conducted a cross-sectional analysis of the baseline data from the cohort study conducted in Kashiwa city, Chiba, Japan in 2012 which included 1971 functionally-independent, community-dwelling Japanese adults aged 65 years or older (977 men, 994 women). Sarcopenia was defined based on appendicular skeletal muscle mass, grip strength and usual gait speed. MetS was defined based on the National Cholesterol Education Program’s Adult Treatment Panel-III criteria. The prevalence of sarcopenia was 14.2% in men and 22.1% in women, while the prevalence of MetS was 43.6% in men and 28.9% in women. After adjustment for potential confounders, MetS was positively associated with sarcopenia in men aged 65 to 74 years (odds ratio 5.5; 95% confidence interval 1.9–15.9) but not in older men or women. Among the sarcopenia components, MetS was associated with lower muscle mass and grip strength, particularly in men aged 65 to 74 years. The associations of MetS with sarcopenia and its components were mainly driven by abdominal obesity regardless of sex or age. In conclusion, MetS is positively associated with sarcopenia in older men. The association is modified by sex and age, but abdominal obesity is the main contributor to the association across sex and age.     

Epidemiological trends in multiple births in the United States, 1971-1998.

The astounding rise in multiple births in the United States continues. We analyzed live birth files from the U.S. National Center for Health Statistics. Twin, triplet, quadruplet, and quintuplet+ rates were calculated for the period 1971-1977 and for each year between 1990 and 1998. Triplet rates were also computed within categories of mother's education and age. The twin rate increased from 1.8% in 1971-77 to 2.8% in 1998. The rate of triplets increased 5.9-fold, quadruplets 11.9-fold, and quintuplets+ 5.3-fold between 1971-77 and 1998. Increases in triplet rates were much more marked among births to university-educated women and women 30 years and older. Among women 45 years and older, the triplet rate was approximately fifty times higher in 1998 than in 1971-77. This group of older women (> or = 45 years) had the highest multiple birth rate in 1998.     

An analysis of paternal age and 47,+21 in 35,000 new prenatal cytogenetic diagnosis data from the New York State Chromosome Registry: no significant effect

Summary In 35,680 fetuses of women who had prenatal cytogenetic diagnosis done upon amniotic fluid specimens obtained during 2nd trimester amniocentesis and in whom there was no increased cytogenetic risk except for age, there was no statistically significant evidence for an increase of 47,+21 at any paternal age after adjustment for maternal age. The ratio of observed-to-expected numbers in fathers less than 30 years old was 1.0 and in fathers 40 years or older was 0.9 when compared with numbers derived from maternal-age-specific rates in men 30–39 years old. The ratio was 1.1 for those younger than 34 years when compared with rates in fathers aged 34–39 years old. Only for men 55 years or older was there any, even suggestive, increase. The ratio was roughly 1.5 (9 observed to about 6 expected). This was not statistically significant, and moreover, the increase such as it was, was in men married to women 37–42 years old. Regression analyses using several additive parental age models introducing a parabolic function for paternal age, failed to reveal any paternal age contribution.     

Initiation of hypertension in utero and its amplification throughout life.

OBJECTIVE--To determine whether the relation between high blood pressure and low birth weight is initiated in utero or during infancy, and whether it changes with age. DESIGN--A longitudinal study of children and three follow up studies of adults. SETTING--Farnborough, Preston, and Hertfordshire, England, and a national sample in Britain. SUBJECTS--1895 children aged 0-10 years, 3240 men and women aged 36 years, 459 men and women aged 46-54 years, and 1231 men and women aged 59-71 years. The birth weight of all subjects had been recorded. MAIN OUTCOME MEASURE--Systolic blood pressure. RESULTS--At all ages beyond infancy people who had lower birth weight had higher systolic blood pressure. Systolic blood pressure was not related to growth during infancy independently of birth weight. The relation between systolic pressure and birth weight became larger with increasing age so that, after current body mass was allowed for, systolic pressure at ages 64-71 years decreased by 5.2 mm Hg (95% confidence interval 1.8 to 8.6) for every kg increase in birth weight. CONCLUSIONS--Essential hypertension is initiated in fetal life. A raised blood pressure is then amplified from infancy to old age, perhaps by a positive feedback mechanism.