A cross-national comparison of the relative influence of male and female age on the frequency of marital intercourse

Predictors of Sexual Intercourse Frequency Among Couples Trying to Conceive

BACKGROUND

Little is known about the predictors of sexual intercourse frequency (SIF) among couples trying to conceive despite the well-established link between SIF and fecundity.

AIM

To evaluate men's and women's demographic, occupational, and lifestyle predictors of SIF among couples.

METHODS

469 Couples without a history of infertility participating in the Longitudinal Investigation of Fertility and the Environment Study (2005-2009) were followed up for ≤1 year while trying to conceive. At enrollment, both partners were interviewed about demographic, occupational, lifestyle, and psychological characteristics using standardized questionnaires. Multivariable generalized linear mixed models with Poisson distribution were used to estimate the adjusted percent difference in SIF across exposure categories.

OUTCOMES

SIF was recorded in daily journals and summarized as average SIF/mo.

RESULTS

The median (interquartile range) SIF during follow-up was 6 (4-9) acts/mo. For every year increase in age for women and men, SIF decreased by -0.8% (95% CI -2.5 to 1.0%) and -1.7% (95% CI -3.1 to -0.3%). Women with high school education or less and those of non-white race had 34.4% and 16.0% higher SIF, respectively. A similar trend was seen for men's education and race. Only couples where both partners (but not just 1 partner) worked rotating shifts had -39.1% (95% CI -61.0 to -5.0%) lower SIF compared to couples where neither partner worked rotating shifts. Men's (but not women's) exercise was associated with 13.2% (95% CI 1.7-26.0%) higher SIF. Diagnosis of a mood or anxiety disorder in men (but not women) was associated with a 26.0% (95% CI -42.7 to -4.4%) lower SIF. Household income, smoking status, body mass index, night work, alcohol intake, and psychosocial stress were not associated with SIF.

CLINICAL TRANSLATION

Even among couples trying to conceive, there was substantial variation in SIF. Both partners' age, education, race, and rotating shift work as well as men's exercise and mental health play an important role in determining SIF.

CONCLUSIONS

As this was a secondary analysis of an existing study, we lacked information on many pertinent psychological and relationship quality variables and the hormonal status of participants, which could have affected SIF. The unique population-based couple design, however, captured both partners' demographics, occupational characteristics, and lifestyle behaviors in advance of their daily, prospective reporting of SIF, which was a major strength. Important predictors of SIF among couples attempting to conceive include men's exercise and mental health and both partners' age, education, race, and rotating shift work. Gaskins AJ, Sundaram R, Buck Louis GM, et al. Predictors of Sexual Intercourse Frequency Among Couples Trying to Conceive. J Sex Med 2018;15:519-528.

Effects of relationship duration, cohabitation, and marriage on the frequency of intercourse in couples: Findings from German panel data

Research into the changes in the frequency of sexual intercourse is (with few exceptions) limited to cross-sectional analyses of marital duration. We investigate the frequency of intercourse while taking into account relationship duration as well as the duration of cohabitation and marriage, effects of parenthood, and relationship quality. For the analysis we apply fixed effects regression models using data from the German Family Panel (pairfam), a nationwide randomly sampled German panel survey. Our findings imply that the drop in sex frequency occurs early in the relationship, whereas neither cohabitation nor marriage affects the frequency of intercourse to a significant extent. Sex frequency is reduced during pregnancy and as long as the couple has small children, but becomes revived later on. Relationship quality is found to play a role as well. These results are contrary to the honeymoon effect found in earlier research, but indicate that in times of postponed marriage an analogous effect may be at work in the initial period of the relationship.

Fifty fertile years: anthropologists' studies of reproduction in high altitude natives

Early European colonists of the Andes had difficulties in reproducing, a fact that underpins the hypothesis that reproduction is impaired amongst all humans at high altitudes. Yet a 16th century missionary wrote, "… the Indians are healthiest and where they multiply the most prolifically is in these same cold air-tempers, … [yet most children of the Spaniards] when born in such regions do not survive." These observations suggest that humans at high altitudes are subjected to strong natural selection from hypoxia, cold and limited food sources and, furthermore, that human populations can and have adapted, and continue to adapt, to these conditions. Informed by multiple approaches and theoretical frameworks, anthropologists have investigated to what extent and precisely how high altitude environments impact human reproductive functioning and fertility. Analyses of the proximate determinants of natural fertility suggest that behaviors (breast/infant feeding practices in the Andes, and marriage practices and religious celibacy in the Himalaya) are major determinants of fertility in high altitude populations. Furthermore, data from Project REPA (Reproduction and Ecology in Provincía Aroma), a longitudinal study in rural Bolivia, demonstrate that fecundity is not impaired in this indigenous altiplano population, and that the risk for early pregnancy loss (EPL) is not elevated by environmental hypoxia but does vary seasonally with the agricultural cycle (contra to the assumption that EPLs are due almost entirely to genetically flawed concepti). This review discusses these and other findings that reveal the complex and dynamic adaptations of human reproductive functioning in high altitude environments.

Frequency of marital intercourse among patients with psychiatric and psychosomatic disorders in Japan

This study investigated the frequency of marital intercourse in 951 patients with psychiatric and psychosomatic disorders and compared it to that in a normative sample. Only fourteen percent of the patient group had sexual intercourse more than once per week; thirty-nine percent were sexually inactive. The groups of patients with eating disorders, mood disorders, or any mental or behavioral disorders complicated by organic diseases such as cancer, ischemic heart disease, and other physical disorders had fewer mean coital frequencies than the controls, whereas the coital frequency of patients with anxiety disorders, somatoform disorders, sleep disorders, or psychosomatic disorders did not differ significantly from that of controls.

The proximate determinants of fertility in populations exposed to chronic hypoxia

It has been hypothesized that hypoxia reduces fertility, but comparative studies of high and low altitude populations have been unable to verify or refute this proposal because it is difficult to control for the behavioral and sociocultural factors that may also either underlie fertility differentials or compensate for physiological changes caused by varying partial pressure of oxygen. Taken collectively, estimates of fertility in populations exposed to chronic hypoxia range widely and do not suggest any reproductive patterns specific to high altitude. Here we review the available data from the Andes and the Himalaya on the proximate determinants of fertility, that set of factors through which any and all environmental, behavioral, and sociocultural factors must act to influence fertility levels. Although hypoxia could potentially affect some of these factors, there is no unequivocal evidence that this occurs in human populations indigenous to high altitude. At this time, it appears that local variations in infant feeding beliefs and practices, often coupled with prolonged breast-feeding, play a major role in determining fertility variation in Andean populations. In the Himalaya, large numbers of adults are not in sanctioned sexual unions as a consequence of polyandrous marriage practices and religious celibacy. The absence of a clear negative effect of hypoxia on fertility in populations indigenous to high altitude, even though migrants report reproductive difficulties, argues that these populations have adapted to the conditions at high altitude. The experimental and clinical evidence presented in this issue suggests proximate mechanisms by which such adaptation, shaped by natural selection and developmental processes, is possible.

The home team advantage: reproduction in women indigenous to high altitude

Although there is substantial evidence that environmental conditions disrupt reproductive function among newcomers to hypoxic settings, it is not certain that low oxygen pressure reduces fertility among those indigenous to high altitude. Even when fertility does appear to be relatively lower, numerous behavioral and sociocultural factors may be responsible. These are best examined within demographic frameworks that delineate a finite list of the proximate determinants of fertility. The findings presented here are based on several studies of indigenous Andean populations (Peruvian Quechua at 4000m, Bolivian Quechua at 3100m, Bolivian Aymara at 4000m). Data on ovarian function suggest that neither progesterone levels nor menstrual cycle length or regularity are significantly different from those of women at lower altitudes. Data on two behavioral factors that determine fertility levels, coital frequency and infant feeding practices, suggest that the former is not likely to be of significance in co-habitating couples, but that variation in breastfeeding patterns has probably made a substantial contribution to differences in fertility among at least some populations at high altitude.

Does hypoxia impair ovarian function in Bolivian women indigenous to high altitude?

Fertility appears to be reduced in at least some high altitude populations relative to their counterparts at lower elevations. Inferring from the difficulties with reproduction of newcomers to high altitude and from animal experiments, it has been hypothesized that this apparent reduction is the result of hypoxia acting to reduce fecundity and/or increase fetal loss. In humans, however, several behavioral as well as biological factors may affect fertility levels. These many factors have been organized by demographers into a framework of seven proximate determinants that includes fecundability (the monthly probability of conception) of which successful ovulation is one component. To test whether ovarian function is impaired in women indigenous to high altitude, we measured salivary progesterone (P) in a sample (n = 20) of Quechua women (aged 19-42 years) residing at 3,100 m. It was found that mean luteal P = 179 pmol/L and mean midluteal P = 243 pmol/L, levels that fall about midway in the range of known values for several populations and are higher than some lower altitude populations. These findings suggest that hypoxia does not appear to significantly impair ovarian function in those with lifelong residence at high altitude. There are, however, several factors common to many high altitude populations that may act to reduce fecundability and fertility including intercourse patterns (affected by marriage and migration practices), prolonged lactation, dietary insufficiency, and hard labor.

Coital frequency among married and cohabiting couples in the United States

Coital frequency is studied among couples as a function of marital or cohabiting status, relationship duration, number of children, religious affiliation, income, education, fertility intentions, age, race, self-assessed health, time spent in work, and perceived relationship quality. Data are from the 1987-88 National Survey of Families and Households. Predictors of coital frequency that were stable across several analyses were male's and female's ages, the duration of the relationship, and the male partner's self-assessed health. When the discrepancy in partners' reports was adjusted, cohabitation status, number of children, future fertility intentions, religious affiliation, and relationship quality as assessed by the female partner were significant. The results suggest a substantial idiosyncratic component to the determination of coital frequency in relationships.

Implications of hormonal influences on sexual behavior for demographic models of reproduction

In exploring the implications of hormonal influences on sexual behavior for reproduction, we have focused on androgens because of the convincing evidence for androgenic effects on female sexual motivation. We have been guided by the simple idea, based on clinical findings among hyperandrogenic women, that higher testosterone levels will increase female sexual motivation which in turn will result in increased coital frequency. However, careful consideration of the evidence fails to confirm such a role for testosterone in sexual behavior among normal women at any point in the reproductive span. While some amount of testosterone appears to be important in maintaining female sexual motivation, there is little evidence that variation in testosterone within the normal range is associated with variation in sexual motivation. Reported associations between testosterone and sexual behavior among married women cannot be interpreted as resulting from androgenic effects on sexual motivation. Thus we are left with the task of explaining why testosterone does not appear to play the same role in libido among hyperandrogenic and normal women. As mentioned earlier, some of the difference may attributable to the much higher levels of testosterone among hyperandrogenic women. Sherwin points out that the levels of sexual motivation decline with declining testosterone levels even while testosterone is well above normally occurring levels. It is possible that the brain is simply not sensitive to the variation in testosterone levels found in normal women. Other evidence suggests that the presence of intact ovaries may be equally important. A recent study of androgen replacement in naturally post-menopausal women failed to find a dramatic effect of testosterone on sexual motivation and behavior, despite levels similar to those in studies on surgically menopausal women, pointing to the importance of other factors associated with the presence of ovaries. A similar point can be made with regard to hyperandrogenism related to endogenous sources of testosterone, as in the case of PCOS. High levels of testosterone effectively disrupt ovarian function and interfere with other ovarian processes. Among hyperandrogenic women sexual behavior appears to be related to the direct effects of androgens on motivation, while the indirect effects of estrogen and progesterone are essentially eliminated. Among normal women, on the other hand, there is little evidence for such a dominating role of a direct androgenic effect on sexual behavior. Instead, other ovarian hormones, including estrogen and progesterone may also play a demonstrable role, despite the lack of strong evidence at this point.(ABSTRACT TRUNCATED AT 400 WORDS)

Sexual activity of women in Taiwan

In this paper, we calculate a base line of statistical data on the frequency of sexual activity at various ages of Taiwanese women. A cross-sectional study using questionnaires administered during personal interviews was conducted on more than seventeen thousand women who attended family planning clinics in the Taipei metropolitan area in 1991 and 1992. Of the women surveyed, 2.8 per cent were sexually inactive in the previous month, 83.67 per cent had intercourse one to nine times in the previous month, and 13.56 per cent had intercourse ten times or more. The mean frequency of sexual activity was 6.8 times a month. Age-specific mean coital frequencies for the age groups of less than 25 years, of 25-34 years, and of 35-44 years were 10.3, 7.3, and 6.6 times per month, respectively. Increased sexual frequency was associated with the following factors: young age, unmarried, lower educational level, fewer years of marriage and being on the pill. When logistic regression was used to control for confounding variables, we found that a woman's age is the most significant factor in predicting her sexual frequency.

Determinants of coitus after childbirth

Using a sample of 3080 women from Cebu, Philippines, interviewed immediately after childbirth and every 2 months thereafter for 2 years, the determinants of return to coitus are analysed. Eighty per cent of the women returned to coitus before the return of menses, and 90% did so before stopping breast-feeding. In hazards models, variables associated with traditional life styles retarded return to coitus. Situational variables (husband resident, crowding, children aged 6 and under), especially husband residence, and biological variables (mother's age, return to menses, and lactation) were significant predictors of return to coitus. The implications of the analysis for the construction of models of birth interval dynamics are discussed.

Impact of tubal sterilization and vasectomy on female marital sexuality: results of a controlled longitudinal study

To determine if female or male sterilization affects long-term female marital sexuality, we prospectively compared baseline data and 5 consecutive years of follow-up data from 152 tubal sterilization women, 106 vasectomy wives, and 83 women not planning sterilization. By follow-up year 5, no group of women expressed any change in satisfaction with their own sexual response; however, all groups showed a significant decrease across time in satisfaction with their sexual relationship, in coital desire, and in coital frequency. There were no group differences in overall net changes or in rates of change over the 5-year period. However, two short-term group differences were noted: a decrease in coital desire among women not planning sterilization between baseline and follow-up year 4, compared with increases for both sterilization groups, and an increase in coital frequency at the first follow-up year only in the tubal sterilization group. These data indicate that there are no detrimental effects and some short-term benefits of both sterilization procedures on female marital sexuality.

Decline in coital rates with spouses' ages and duration of marriage

Cross-sectional and longitudinal study of a large sample confirms that mean marital coital rates decline very rapidly over the first year of marriage. They seem to halve over the first year of marriage, and then they take perhaps another 20 years to halve again. This pattern of decline is interpreted as evidence against the suggestion that coital rates are closely related to female hormone levels.

The higher correlation of marital coital rates with wife's age than with husband's age, it is argued here, is because wife's age is more closely associated than husband's age with duration of marriage (here seen as the most important of these three variables in the determination of coital rates). This is because of the substantially smaller variance of wife's age at marriage than husband's age at marriage.