Distributions of coital rates and of fecundability

Abstract

Attempts have been made to fit distributions of conception waits on the assumption that fecundability is distributed as a Pearson Type I beta distribution. Since the fits were unsatisfactory (Majumdar and Sheps, 1970), the question arises whether fecundability is distributed as a Type III. If it were, then the probability of coitus should also be distributed as a Type III, and distributions of coital rates should be better fitted by the negative binomial than by Skellam's distribution. The data available for such fits have been briefly reviewed here and fits attempted. There is some slight evidence in favor of the hypothesis, but more data are needed before the question can be decisively answered.     

Effect of marriage on duration of chest pain associated with acute myocardial infarction before seeking care

Background:

Coronary artery disease is the most common cause of death in the Western world, and being married decreases the risk of death from cardiovascular causes. We aimed to determine whether marital status was a predictor of the duration of chest pain endured by patients with acute myocardial infarction before they sought care and whether the patient’s sex modified the effect.

Methods:

We conducted a retrospective, population-based cohort analysis of patients with acute myocardial infarction admitted to 96 acute care hospitals in Ontario, Canada, from April 2004 to March 2005. We excluded patients who did not experience chest pain. Using multivariable regression analyses, we assessed marital status in relation to delayed presentation to hospital (more than six hours from onset of pain), both overall and stratified by sex. In patients who reported the exact duration of chest pain, we assessed the effect of marital status on the delay in seeking care.

Results:

Among 4403 eligible patients with acute myocardial infarction, the mean age was 67.3 (standard deviation 13.6) years, and 1486 (33.7%) were women. Almost half (2037 or 46.3%) presented to a hospital within two hours, and 3240 (73.6%) presented within six hours. Overall, 75.3% (2317/3079) of married patients, 67.9% (188/277) of single patients, 68.5% (189/276) of divorced patients and 70.8% (546/771) of widowed patients presented within six hours of the onset of chest pain. Being married was associated with lower odds of delayed presentation (odds ratio [OR] 0.46, 95% confidence interval [CI] 0.30–0.71, p < 0.001) relative to being single. Among men, the OR was 0.35 (95% CI 0.21–0.59, p < 0.001), whereas among women the effect of marital status was not significant (OR 1.36, 95% CI 0.49–3.73, p = 0.55).

Interpretation:

Among men experiencing acute myocardial infarction with chest pain, being married was associated with significantly earlier presentation for care, a benefit that was not observed for married women. Earlier presentation for medical care appears to be one reason for the observed lower risk of cardiovascular death among married men, relative to their single counterparts.Marriage has long been known to offer health benefits^1,2 and is associated with a lower risk of death^3,4 relative to people who are not married. The effect is more pronounced among men than among women.^5,6 However, the specific mechanisms responsible for the lower rate of cardiovascular deaths in married persons⁷ are not known.Effective, time-sensitive therapy for acute myocardial infarction is available,^8,9 and delays in the emergency department and for in-hospital components of care have been substantially reduced over the past few decades.^10,11 In contrast, patients’ delay in seeking care for acute myocardial infarction has shown little improvement over time,^12,13 despite intensive campaigns to raise public awareness.^14,15 Patients’ delay remains by far the largest component of the overall delay between onset of symptoms and receipt of therapy.¹⁶ No study has examined the effect of marital status on patients’ delay, and only a few small studies have examined predictors of this component of delay by sex.^17,18We examined the effect of marital status, a social factor, on the time from onset of chest pain to arrival in an emergency department or hospital, in a population-based cohort of patients with acute myocardial infarction. We hypothesized that being married or in a common-law relationship would be associated with less delay, because we surmised that a spouse would encourage earlier pursuit of medical care, either directly or indirectly (i.e., even if the spouse was not physically present during the symptoms, his or her existence might spur the patient to seek care earlier). We hypothesized that wives would be more likely than husbands to assume the caregiver role and that the beneficial effect of marriage would therefore be stronger among men than among women.     

Down syndrome rates and relaxed selection at older maternal ages.

Preferential survival in older mothers of fetuses with Down syndrome has been proposed as contributing to the maternal-age effect of this condition. If correct, this provocative hypothesis, which may be termed "relaxed selection," has major implications for approaches to prevention of Down syndrome live births in older women. Several predictions of this hypothesis are examined here by comparisons of parental ages among various populations. These revealed that: (1) mean maternal age of Down syndrome live births is slightly lower than that of Down syndrome spontaneous fetal deaths; (2) mean maternal age of those with mutant D/21 translocation Down syndrome is about the same as that of controls; (3) the ages of Down syndrome mothers who have Down syndrome live births is slightly lower than ages of Down syndrome mothers who have unaffected live births; and (4) in recent data on 47, +21 cases in which the extra chromosome 21 is of paternal origin, the mean maternal ages are 4-5 years lower than the maternal ages of cases of maternal origin (in contrast to earlier reports). All of these observations are contrary to the hypothesis that relaxed selection contributes significantly to the maternal-age association of Down syndrome. If there is any effect of relaxed selection, it is likely to be very weak and/or act primarily upon abortions that occur before recognition of pregnancy.     

Socioeconomic factors affecting first marriage and birth rates by sex and age in the total Japanese population.

The effects of a wide variety of social, economic and demographic factors on age-specific first marriage and live birth rates in 46 Japanese prefectures were analyzed using stepwise regression analysis for 1970 and again for 1975 after classification of those twenty-two factors by factor analysis. The principal results were as follows: (1) high employment (high income) and social mobility caused by industrialization had a strongly positive influence on the first marriage and birth rates for young females, (2) rural and urban residence factors had positive effects on the marriage and birth rates for young males and females, respectively, (3) old age factor had an inverse effect on the marriage rates for both males and females over a wide range of ages, and (4) young age factor promoted the birth rate for young and middle-aged females. The characteristics of the first marriage and live birth rates in Japan were discussed in the light of these findings.     

The variations of human sex ratio at birth with time of conception within the cycle, coital rate around the time of conception, duration of time taken to achieve conception, and duration of gestation: a synthesis

There is a large research literature on the variation of human sex ratio (proportion of males at birth) with (1) time of insemination within the mother's fruitful cycle (TWC), (2) duration of gestation (DOG), (3) coital frequency, here called ‘coital rate’ (CR) and (4) duration of time taken to achieve conception in a period of risk (viz. in the absence of birth limitation methods) (TTC). The variation of sex ratio with each of these four variables has usually been treated as a discrete topic. Consider the four propositions that each of these sorts of variation exists. Here it is argued that these propositions entail one another to varying degrees, and that, for that reason, empirical failures to detect (at conventional levels of significance) one such form of variation (as e.g. with time to conception) should not justify rejecting the hypothesis that such variation exists until the whole network of propositions has been considered. Evidence that offspring sex ratio varies with time of conception within the cycle is strong. It is argued here that, as a consequence, the available data constitute evidence that sex ratio varies with CR and with time to achieve conception, although this variation is small, difficult to detect and of no clinical significance. Lastly, sex ratio varies substantially with DOG, though the explanation for this is not established: it is suggested that the present treatment provides a testable framework for such an explanation.     

Decline in male mouse pheromone with age

An age-related decline in urinary-borne pheromone was found in male C57BL/6J mice aged from 2 to 30 months. Pheromone activity, estimated by bioassay, declined sharply after about 10 months of age. Two other strains of mice tested (DBA/2J and CBA/HT6J) also appeared to show an age-related decline in pheromone activity. Within each strain, however, pheromone activity was consistently similar to or higher than that of the C57BL/6J male mice. The DBA/2J and BALB/cWt strains appeared to be high pheromone producers, and the C57BL/6J and CBA/HT6J strains, low producers. This report is the first demonstration of a decline with age in male mouse pheromone activity. This decline appears to be synchronized with the well-defined loss of reproductive function in female mice.     

Consanguineous marriage and differentials in age at marriage, contraceptive use and fertility in Pakistan

Fertility rates in Pakistan have remained consistently high over the past three decades. While numerous studies have examined sociodemographic determinants, the role of biological factors, and particularly consanguinity, has received little attention, even though marriage between close biological relatives continues to be the norm in Pakistan. Reproductive behaviour among women in consanguineous (first cousin) and non-consanguineous unions was compared, using data from a 1995 study of multi-ethnic communities in Karachi and the 1990-91 Pakistan Demographic & Health Survey (PDHS). The results show that, although female age at first marriage has been gradually rising in both study samples, women in consanguineous unions married at younger ages and were less likely to use modern contraceptive methods. In the Karachi sample, women in first cousin unions experienced a higher mean number of pregnancies and also reported a higher mean number of children ever born (CEB). However, their mean number of surviving children did not differ from those born to women in non-consanguineous unions, implying higher prenatal and/or postnatal losses in couples related as first cousins. On the other hand, the PDHS showed both lower CEB values for women in consanguineous marriages and a lower number of surviving children. Given the continuing popularity of consanguineous marriage, these findings have important implications for future fertility reduction in Pakistan.     

Regular Decline in Physical Working Capacity with Age

Analysis of the results of two cross country races, one on foot and one on skis, in which nearly 10,000 men competed showed that performance is very closely matched with age. There is a decrease of 5-10% in the performance every 10 years from optimum age for the event. This optimum varies for different types of physical activity. Studies in a small group of women showed similar variations.     

Social and family characteristics of marriage in England and Wales: information derived from marriage registration records

Information on social and family aspects of marriage was obtained from a sample of over a thousand marriages solemnised in England and Wales in 1979. The data include the standard demographic variables concerning the couple and their marriage and also: the day of the week the marriage was celebrated; whether the fathers or relatives of similar surname to the spouses acted as witnesses; the patterns of name usage by brides; the numbers of forenames of the marriage partners and their fathers; and the frequency of bridegrooms having one or more forenames in common with their fathers. The factors are analysed in terms of social class differences as well as in relation to the distance over which marriages range and other demographic characteristics of the partners and their marriage.