Is early natural menopause a biologic marker of health and aging?

Cross-sectional and case-controlled analyses of the association between smoking and early menopause

To examine potential confounders and dose-response data for the association between smoking and menopause, we used both a cross-sectional and case-controlled approach. In total, 10,606 middle-aged women residing in eastern Massachusetts were surveyed about their age at menopause and smoking history; 344 women (cases) with natural menopause prior to age 47 and 344 age-matched women (controls) who were still menstruating or who had a menopause after age 46 were selected for further study. Risk for menopause was assessed by Kaplan-Meier, Cox proportional hazards, or logistic regression models. From cross-sectional data on 8657 women aged 45-54, the hazards odds ratio for a natural menopause among women who ever smoked compared to non-smokers was 1.31 (95% C.L. 1.21-1.42) and among women who had accumulated 30 or more pack-years was 1.87 (95% C.L. 1.67-2.04) after adjustment for parity and weight. An additional potential confounder from the case-controlled study was lower educational attainment, and after adjustment for this variable, significant trends persisted for risk of early menopause associated with age began smoking (P = 0.03), years of smoking (P = 0.01) and pack-years of smoking (P = 0.03). This study demonstrates an association between smoking and early menopause in both cross-sectional and case-controlled data that is not confounded by parity, weight, socio-economic status, or nutritional variables.

Evolutionary origin of expandable G-C-rich triplet repeat DNA sequences

A model explaining properties exhibited by fragile-X DNA systems arises from observations that time-dependent base substitutions are expressed at G-C sites but not at A-T sites (Biochem. Genet. 32:383, 1994). [CGG]n sequences are classified as most sensitive to evolutionary base substitution processes involving time-dependent populating of G-C sites with enol-imine states having enhanced stability. Increased density of these states in oocyte DNA would introduce a ground-state collapse double-helix of reduced energy that would inhibit strand separation by the replicase. Evolutionarily altered G' in CG'G triplets allows CG'G to be transcribed as CTG, an initiation codon. And this will cause reinitiation of DNA synthesis, thereby adding additional CGG units to the collapsed double helix. This situation would not occur in slower-evolving male haploid DNA that replicates frequently.

Does "incessant" ovulation increase risk for early menopause?

OBJECTIVE

We attempted to determine whether gynecologic histories differ in women who have and have not experienced an early menopause.

STUDY DESIGN

A group of 344 "case" women whose average age at menopause was 42.2 years and an age-matched group of 344 "control" women still menstruating or menopausal after age 46 were selected from a survey of 10,606 women aged 45 to 54 years for interviews about their reproductive history.

RESULTS

Case women were more likely to have had menarche at or before age 11, had shorter cycle lengths, had fewer pregnancies with live births, and had more frequent pelvic operations including unilateral oophorectomy and multiple cesarean sections. Case women had a greater number of presumed ovulatory cycles, as estimated from age at menarche, average cycle length, and years of anovulation associated with pregnancies or oral contraceptive use. In a multivariate model including smoking status and body mass index, ovulatory cycles were a significant predictor of early menopause, especially after an estimated 300 ovulations.

CONCLUSION

The reproductive histories of women who experienced an early menopause suggest a pattern of more rapid oocyte loss ("incessant" ovulation).

Premature menopause and low back pain. A population-based study

The association between premature menopause and low back pain was examined among 5325 women surveyed in the second National Health and Nutrition Examination survey. Nearly 49% of the women were postmenopausal. In a multiple logistic regression model that included age, postmenopausal women were approximately twice as likely to report low back pain compared to premenopausal women (odds ratio = 2.1; 95% confidence interval: 1.4-3.0). Among postmenopausal women, significant positive trends in low back pain were observed with decreasing age at menopause (P = 0.005) and increasing years since menopause (P = 0.004). The prevalence odds ratio for women who had their menopause before the age of 30 was 3.2 (1.8-5.4); and for women who had their menopause for 15 or more years the odds ratio was 3.0 (1.7-5.3). These findings suggest that premature menopause is associated with low back pain. Further studies appear warranted to confirm these findings, assess possible explanations, and examine the circumstances in which premature menopause occurs.

Environment, human reproduction, menopause, and andropause

As the hypothalamic gonadotropin-releasing hormone (GnRH) pulse generator is an integrator of hormonal, metabolic, and neural signals, it is not surprising that the function of the hypothalamogonadal axis is subject to the influence of a large array of environmental factors. Before puberty, the central nervous system (CNS) restrains the GnRH pulse generator. Undernutrition, low socioeconomic status, stress, and emotional deprivation, all delay puberty. During reproductive life, among peripheral factors that effect the reproductive system, stress plays an important role. Stress, via the release of corticotropin-releasing factor (CRF), eventually triggered by interleukin 1, inhibits GnRH release, resulting in hypogonadism. Effects of CRF are probably mediated by the opioid system. Food restriction and underweight (anorexia nervosa), obesity, smoking, and alcohol all have negative effects on the GnRH pulse generator and gonadal function. Age and diet are important determinants of fertility in both men and women. The age-associated decrease in fertility in women has as a major determinant chromosomal abnormalities of the oocyte, with uterine factors playing a subsidiary role. Age at menopause, determined by ovarian oocyte depletion, is influenced by occupation, age at menarche, parity, age at last pregnancy, altitude, smoking, and use of oral contraceptives. Smoking, however, appears to be the major determinant. Premature menopause is most frequently attributable to mosaicism for Turner Syndrome, mumps ovaritis, and, above all, total hysterectomy, which has a prevalence of about 12-15% in women 50 years old. Premature ovarian failure with presence of immature follicles is most frequently caused by autoimmune diseases or is the consequence of irradiation or chemotherapy with alkylating cytostatics. Plasma estrogens have a physiological role in the prevention of osteoporosis. Obese women have osteoporosis less frequently than women who are not overweight. Early menopause, suppression of adrenal function (corticoids), and thyroid hormone treatment all increase the frequency of osteoporosis. Aging in men is accompanied by decreased Leydig cell and Sertoli cell function, which has a predominantly primary testicular origin, although changes also occur at the hypothalamopituitary level. Plasma testosterone levels, sperm production, and sperm quality decrease, but fertility, although declining, is preserved until senescence. Stress and disease states accelerate the decline on Leydig cell function. Many occupational noxious agents have a negative effect on fertility.(ABSTRACT TRUNCATED AT 400 WORDS)

The biological basis of the menopause

Age-related changes occur throughout the reproductive lifespan of normal healthy women. From the age of 20, the menstrual interval gradually shortens and becomes increasingly regular until the perimenopause. This is related to a shortening of the follicular rather than the luteal phase of the cycle. Serum FSH concentration is elevated during the follicular phase in older women who are still menstruating regularly, while serum inhibin levels are decreased in both the follicular and luteal phases. The relationship between FSH secretion, ageing and feedback inhibition by oestradiol, inhibin, or other presently unmeasured factors in women with regular menses, remains to be elucidated. The primary factor influencing the transition from regular menses to the perimenopause and subsequent menopause appears to be the size of the residual primordial follicle pool. Fecundability begins to decline by the age of 29 years. There is considerable evidence from the experience gained in assisted fertilization procedures that this is related to the effect of age on the quality of the oocyte rather than on the endometrium. At the time of the last menses, few follicles remain. There are no endocrine markers to signal the last cycle. Hence, menopause can only be identified retrospectively when there is no further menses. The probability of being menopausal increases with the duration of amenorrhea and age. Considerable evidence suggests that both serum FSH and serum inhibin are biomarkers of the number and/or quality of follicles remaining in the ovary. There is also evidence that the age of menopause, itself, is a potent biomarker of the general ageing state of the individual.

An application of longitudinal methods to the analysis of menstrual diary data

Despite the considerable morbidity associated with menstrual dysfunction and mounting evidence that women's endogenous endocrine environment influences their long term health, epidemiologic investigation of menstruation is limited. A major obstacle has been the difficulty in analyzing menstrual diary data. This paper describes the variability in menstrual cycle length in college women using a longitudinal perspective. We first characterize the distribution of cycle length and show that it can be approximated by a mixture of a nearly symmetric distribution centered at 28 days and a stochastically larger component which produces a long right tail. After assessing the degree of heterogeneity in cycling patterns, we propose an analytical approach that examines cycle lengths within the symmetric portion of the distribution and cycle lengths within the tail of the distribution separately using random effects models.

Relationship of endogenous sex steroid hormones to lipids and apoproteins in postmenopausal women

The relationships between blood levels of estrogen and lipoprotein lipids and apoproteins were evaluated in 120 women early in the climacteric. Among women who were 1-year amenorrheic, not taking hormone replacement therapy, and with follicle-stimulating hormone levels greater than 720 ng/ml, serum estradiol levels were positively related to concentrations of the high density lipoprotein 2 cholesterol (HDL2c) subfraction. There was a substantial decrease in HDL2c and apoprotein (apo) A-I in women whose estradiol levels decreased to less than or equal to 2.5 pg/ml from the first to the second postmenopausal examination. In a sample of women evaluated during the perimenopause (3-months' amenorrheic), those with the highest concentrations of estradiol or estrone showed a (nonsignificantly) higher level of HDL2c and a lower level of low density lipoprotein cholesterol (LDLc) than did those with the lowest concentration of estradiol or estrone. Estradiol levels declined dramatically between the perimenopausal and the postmenopausal examinations, and this was accompanied by a decrease in HDL2c and a nonsignificant increase in LDLc. HDL2c levels fell substantially in those women whose estradiol decreased below the sensitivity of the assay. The change, however, was not statistically significant. Estrone is the primary postmenopausal estrogen, and levels are directly related to obesity, as are levels of insulin. The interrelationship among obesity, conversion of estrone to estradiol at the tissue level, and insulin (or insulin sensitivity) is probably the primary determinant of HDLc concentration among postmenopausal women.

Early natural menopause and the duration of postmenopausal life. Findings from a mathematical model of life expectancy

Menopause marks the beginning of a stage of life characterized by an increased susceptibility to diseases such as coronary heart disease and osteoporosis. It was therefore hypothesized that early age at natural menopause would lengthen the duration of the postmenopausal stage of life and thereby result in an earlier age at death. This study investigated the relations between age at natural menopause, duration of postmenopausal life (ie, life expectancy at menopause), and age at death (ie, age at menopause plus life expectancy at menopause). Data were derived from a study of 5,287 naturally postmenopausal Seventh-day Adventists observed during 1976-1982. Life expectancy was estimated by a mathematical model that used mortality ratios from the study and mortality rates from the US general population. For natural menopause before the age of 47 years, each one-year decrease in age at menopause was associated with a 0.53-year increase in postmenopausal life (P = .04) and a 0.47-year decrease in the age at death (P = .04). For natural menopause at the age of 47 years and older, however, each one-year decrease in age at menopause was associated with a 0.99-year increase in postmenopausal life (P = .03) and only a 0.01-year decrease in the age at death (P = .85). Overall, these findings argue against the possibility that the association between age at menopause and age at death in this study was due to the relation of age at menopause to the duration of postmenopausal life.