The influence of climate on age at menarche: Augmented with the influence of ancestry

Secular trend in age at menarche among Indian women

Age at menarche is not only a parameter that signifies biological characteristics for women but is also considered as an indicator to measure the quality of life of a population. Moreover, menarche has significant implications on women's health and information about menarcheal age is crucial for health policymakers. However, little is known about the trends in menarcheal age in India. Thus, in order to fill this research gap, the present study aimed to explore the age at menarche, its trend and regional heterogeneity among Indian women. A birth cohort approach was used by polling data from the 1st (1992-93), 4th (2015-16) and 5th (2019-21) rounds of NFHS. Descriptive statistics and bivariate analyses were performed to present the distribution of age at menarche and mean age at menarche across birth cohorts and each category of covariates. A multiple linear regression model was fitted to examine the trend in age at menarche and further to investigate the association of covariates with menarcheal age among Indian women. The analysis demonstrated that a majority of women (66.2%) attained menarche between the ages of 13-14 years. Moreover, about 17.2% of women experienced an early age at menarche, whereas 16.7% of women had a late age at menarche. The mean age at menarche for the sampled women was 13.49 years. The analysis also observed a secular declining trend in menarcheal age among Indian women and a significant variation in the mean age at menarche across birth cohorts. It also highlighted significant socio-economic patterning in menarcheal age among women.

A Systematic Literature Review of Factors Affecting the Timing of Menarche: The Potential for Climate Change to Impact Women's Health

Menarche is the first occurrence of a woman’s menstruation, an event that symbolizes reproductive capacity and the transition from childhood into womanhood. The global average age for menarche is 12 years and this has been declining in recent years. Many factors that affect the timing menarche in girls could be affected by climate change. A systematic literature review was performed regarding the timing of menarche and four publication databases were interrogated: EMBASE, SCOPUS, PubMed, and Cochrane Reviews. Themes were identified from 112 articles and related to environmental causes of perturbations in menarche (either early or late), disease causes and consequences of perturbations, and social causes and consequences. Research from climatology was incorporated to describe how climate change events, including increased hurricanes, avalanches/mudslides/landslides, and extreme weather events could alter the age of menarche by disrupting food availability or via increased toxin/pollutant release. Overall, our review revealed that these perturbations in the timing of menarche are likely to increase the disease burden for women in four key areas: mental health, fertility-related conditions, cardiovascular disease, and bone health. In summary, the climate does have the potential to impact women’s health through perturbation in the timing of menarche and this, in turn, will affect women’s risk of disease in future.

The biological standard of living in Indonesia during the 20th century: Evidence from the age at menarche

This article analyses long-term changes in the mean age at menarche (MAM) as a biological indicator of changes in the standard of living in Indonesia. It finds that MAM was about 15.5 for birth cohorts in the late-19th century, decreasing to 14.5 by the 1930s, at which level it stagnated until the gradual decrease resumed since the early 1960s to around 12.5 in the mid-2000s. The article considers that long-term improvements in nutrition, educational attainment and health care explain these trends. An international comparison of long-term changes finds that MAM in Indonesia was much lower than in Korea and China until respectively 1970 and 1990, but comparable to Japan until 1950 and to Malaysia until 1930. The article presents reasons why these differences are unlikely to be related to dissimilarities in climate and ethnicity, and concludes that they are indicative of relative standards of living.

Determinants of demographic characteristics of the Lamkang tribe, Manipur

The present study provides the demographic account of the Lamkang tribe of Manipur who suffered the bottleneck effect in 1840s and 1992. The objectives are: (i) to determine the age-sex composition of the Lamkang, (ii) to see the sex disparity among the Lamkang (iii) to examine the various biological and social factors that govern the fertility pattern among the Lamkang tribe of Manipur. The present study reveals that the Lamkang population is showing tendency towards fertility transition as evident from the population pyramid. This has shown the beginning of positive effects of education and employment on the reduction of fertility. Overall, males have a higher literacy and better occupation than their female counterparts. One-way analysis of variance reveals that the mean number of conceptions and mean number of live births show statistically significant differences with respect to women's education and family type, which is also reaffirmed by correlation analysis indicating that factors such as family type and women's education along with the other factors such as age at marriage, age at first conception, age at menarche show significant association with fertility.

Having more siblings delays menarche in Indonesia

OBJECTIVES

Tanner (1968, Scientific American, 218(1), 21-27) concluded that having more siblings delayed menarche, but many subsequent studies have reported diverging results. We thus aimed to investigate whether the initial conclusion remains valid by controlling for sibship size and birth order together, analyzing a large number of observations, drawing on a nationally representative sample, adjusting for childhood socioeconomic status, and considering a developing country. We additionally aimed to assess the importance of sibling sex for age at menarche.

METHODS

We analyzed 10 212 ever-married women aged 20+ in the last wave of the Indonesian Family Life Survey. We regressed age at menarche on sibship size, birth spacing, and childhood socioeconomic status. We subsequently divided sibship size into the numbers of brothers and sisters.

RESULTS

Having more siblings was related to later menarche, and the relationship was strengthened when the birth order was controlled for. In addition, those born earlier experienced menarche later. Sibling sex was irrelevant to age at menarche, boosting the importance of sibship size itself.

CONCLUSIONS

Our results support the earlier conclusion that having more siblings delays menarche.

The Role of Vitamin D in the Pathogenesis of Adolescent Idiopathic Scoliosis

Several theories have been proposed to explain the etiology of adolescent idiopathic scoliosis (AIS) until present. However, limited data are available regarding the impact of vitamin D insufficiency or deficiency on scoliosis. Previous studies have shown that vitamin D deficiency and insufficiency are prevalent in adolescents, including AIS patients. A series of studies conducted in Hong Kong have shown that as many as 30% of these patients have osteopenia. The 25-hydroxyvitamin D3 level has been found to positively correlate with bone mineral density (BMD) in healthy adolescents and negatively with Cobb angle in AIS patients; therefore, vitamin D deficiency is believed to play a role in AIS pathogenesis. This study attempts to review the relevant literature on AIS etiology to examine the association of vitamin D and various current theories. Our review suggested that vitamin D deficiency is associated with several current etiological theories of AIS. We postulate that vitamin D deficiency and/or insufficiency affects AIS development by its effect on the regulation of fibrosis, postural control, and BMD. Subclinical deficiency of vitamin K2, a fat-soluble vitamin, is also prevalent in adolescents; therefore, it is possible that the high prevalence of vitamin D deficiency is related to decreased fat intake. Further studies are required to elucidate the possible role of vitamin D in the pathogenesis and clinical management of AIS.

The Null Relation between Father Absence and Earlier Menarche

Researchers have claimed that the absence of a biological father accelerates the daughter's menarche. This claim was assessed by employing a large and nationally representative sample of Indonesian women. We analyzed 11,138 ever-married women aged 15+ in the Indonesian Family Life Survey 2015. We regressed age at menarche on the interaction of father absence (vs. presence) and mother absence (vs. presence) at age 12 with or without childhood covariates. For robustness checks, we performed a power analysis, re-ran the same specification for various subgroups, and varied the independent variable of interest. All results produced a null relation between father absence and age at menarche. The power analysis suggests that a false negative was unlikely. Our review of the literature indicates that the claim of the relation between father absence and earlier menarche was based on weak statistical foundations. Other studies with higher-quality datasets tended to find no relation, and our results replicated this tendency. Therefore, the influence of father absence does not appear to be universal.

The trend in the relationship of advanced maternal age to preterm birth and low birthweight

PURPOSE

As women in developed countries tend to delay childbearing, it becomes more important to understand the relationship of advanced maternal age to birth outcomes. We aimed to estimate the trend in the relationship of advanced maternal age to preterm birth and low birthweight.

MATERIALS AND METHODS

We analysed 4,264,417 ethnically homogeneous, singleton firstborns, born in hospitals to married couples in South Korea in 1997-2014. We regressed an indicator for preterm birth or low birthweight on advanced maternal age, the baby's sex, advanced paternal age, and a set of socioeconomic status (SES) variables by year. We then collected the coefficient on advanced maternal age and charted its trend. We repeated the same procedure for 4,153,313 second- and third births.

RESULTS

When we controlled for only the baby's sex, the relationship between advanced maternal age and preterm birth dramatically weakened in the 2000s and slightly more thereafter: being an older mother was related to a 3.5% point increase in preterm birth in the late 1990s, but this figure decreased to less than 2% points by the early 2010s. Controlling for advanced paternal age slightly decreased the relationship and controlling for SES hardly affected the relationship. We obtained almost the same results for low birthweight. Second- and third-borns exhibited a declining, much weaker influence of advanced maternal age on the birth outcomes.

CONCLUSIONS

In relative terms, mothers of advanced age were more likely to deliver preterm and low birthweight babies than younger mothers. In absolute terms, however, the risk was small in the 1990s and much smaller in the early 2010s.

Parents are rapidly getting older in South Korea

While scholars and policymakers have investigated the causes and consequences of low fertility, they have neglected a related issue: advanced parental age. This is an important issue because advanced parental age adversely affects babies in the short and long run. South Korea recently topped the list of low-fertility countries, and so this study examined the trends in parental age in this country. We analysed all births between 1997 and 2014, the census for 2000 and 2010, and aggregate marriage data to report the trends in age at first marriage, interval from marriage to first birth, and parental age at first birth and at all births. At every stage, age increased rapidly for both parents. As a result, of babies born to fathers aged 20-54, 20.2% were born to fathers aged 35-54 in 2000 with the proportion increasing to 38.7% in 2010 - almost double in a single decade. The corresponding figures for mothers increased from 6.7% to 17.2% - more than double. Potential parents and policymakers can use this information to time births more appropriately, thereby reducing risks to babies and mothers.

The fatter are happier in Indonesia

PURPOSE

Although obesity and happiness are known to be negatively related in the developed world, little attention has been paid to this relationship in the developing world. We thus investigated the relationship in Indonesia and attempted to explain the underlying rationale.

METHODS

We considered about 12,000 respondents aged 15+ for each gender obtained from the Indonesian Family Life Survey 2007 by relating a measure of happiness to weight-related measures in ordered probit models.

RESULTS

The relationship between obesity and happiness was positive in Indonesia, and this relationship was robust. Our evidence suggests that the contrasting results for the two worlds result from affordability of obesity. That is, while even low socioeconomic status (SES) individuals in the developed world can afford to be obese, only high SES individuals in the developing world can do.

CONCLUSIONS

Our findings imply that obesity prevention in the developing world requires different measures than those used in the developed world.