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.

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.

No relationship between birth season and age at menarche in Indonesia.

In utero conditions and menarche are two important themes in human development, so the influence of birth season on menarche is of great interest. We investigated the relationship between birth season and age at menarche in the tropics by analysing a nationally representative sample of an Islamic population with a large sample size. We extracted 10,190 ever-married women, mostly aged 15-49, from the Indonesian Family Life Survey (IFLS) and IFLS East. We regressed age at menarche on birth month and subsequently birth season, while controlling for province fixed effects, current age fixed effects, and education. When we controlled only for province fixed effects, only women born in August exhibited a statistically significant difference in age at menarche (0.16 years later) relative to those born in January. Controlling for more covariates made the difference statistically nonsignificant. Birth season was not statistically significantly related to age at menarche, regardless of the set of covariates. The same was true when we focused on rural, poor women, presumably most affected by seasonality. Given inconsistent results in the literature and our null relationship between birth month or season and age at menarche, we doubt that there is any relationship between birth season and age at menarche.

Relationship of Smoking to Hypertension in a Developing Country.

BACKGROUND: Smoking and hypertension are 2 leading causes of death worldwide, and it has been claimed that smoking is a cause of hypertension despite inconsistent results in the literature. In addition, the literature focuses mostly on developed countries, although more people in developing countries are adversely affected by smoking and hypertension. OBJECTIVES: This study attempted to address critical limitations of the literature by analyzing a nationally representative survey of Indonesians with a large sample size and a long follow-up period. METHODS: This study drew on the Indonesian Family Life Survey and followed men aged ≥15 years from 1993 to 2014. The sample size was 14,722 in the unbalanced panel data, 7,876 in the balanced data, and 12,715 in the cross-sectional data. Fixed-effects models were used to remove time-invariant individual characteristics for the panel data. These results were compared to those derived from the cross-sectional data in linear probability models, and the importance of controlling for time-invariant individual characteristics was assessed. RESULTS: The results derived from fixed-effects models indicated no relation of smoking to hypertension. The relation remained null whether the unbalanced or balanced panel data, hypertension status or blood pressure, or smoking status or smoking intensity in linear or nonlinear form were analyzed. In contrast, the results derived from linear probability models exaggerated the relation. CONCLUSIONS: Given the null relation, smoking was not associated with hypertension in this population.

Prevalence of context effects: testing with a straightforward question of yesterday happiness.

PURPOSE: Although contexts effects were found in responding to general happiness, it is little known how prevalent the effects can be in other measures of subjective wellbeing. If context effects are still found for a measure of subjective wellbeing that exhibits a host of features minimizing the effects, one can conclude that the effects can be quite prevalent. We aimed to assess this possibility. METHODS: We analyzed the Indonesian Family Life Survey by exploiting the random assignment of four versions of a list of 12 yesterday affects. The random assignment established causality on firmer ground. We applied ordered probit models by sex (10,162 men and 11,531 women): the dependent variable of interest was a measure of happiness, and the independent variables of interest were four affects that immediately preceded happiness. RESULTS: We found that when sadness immediately preceded happiness, men were 2.4% points more likely to say not at all happy and 2.5% points less likely to say very happy. The corresponding figures for women were 1.5 and 1.8% points. We, however, found no discernible context effects when boredom and anger immediately preceded happiness. CONCLUSIONS: Context effects were still found for a measure of subjective wellbeing even when the effects were thought to be minimal. That said, the different influence of sadness versus boredom and anger suggests that there are ways to alleviate context effects.

Birthweight as a measure of holiday stress.

Young wives in South Korea often dread New Year's Day and Thanksgiving Day because they assume the burden of cooking, cleaning, and other household chores. We used their offspring's birthweight as an indicator of their stress levels. We included all Korean singletons born in hospitals during 1997-2014 (N = 8,589,426) and regressed birthweight on in utero holiday experience by trimester, along with covariates. Babies who experienced New Year's Day in the first trimester were 9.4 grams lighter than those who did not; the amount is equivalent to 120% of the reduced birthweight associated with experiencing landmine explosions during the first trimester in Colombia. Higher birthweight was related to being in the first trimester during Thanksgiving Day versus not. However, experiencing this holiday during the third trimester was associated with less increase in birthweight than during the other trimesters. These results suggest that the New Year's holiday may reflect stress for Korean women in their first trimester of pregnancy, resulting in reduced birthweight, but similar stress was not associated with the Thanksgiving Day holiday. Clinicians and policymakers should be aware of this potential high stress level among Korean women during New Year's Day and seek ways to prevent and alleviate it.

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.

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 Association between Height and Hypertension in Indonesia.

There is growing interest in the influence of early-life conditions on the development of disease. Among diseases in adulthood, hypertension is particularly important for the developing world because considerably more people there are and will be afflicted with the disease than in the developed world and hypertensives there are often unaware of their disease status. We employed height as a proxy for the influence of early-life conditions and estimated the relation between height and hypertension status in Indonesia. We analysed 9,597 men and 10,143 women, aged 25-70. We employed a linear probability model to relate height to hypertension status by sex and age. When we controlled for an array of covariates, a 10cm increase in height was related to an approximately 7% point reduction in the likelihood of being hypertensive for both men and women. This is about a quarter of the prevalence of hypertension in Indonesia. This relation was linear and stronger among older individuals. In addition, the pre- and post-pubertal environments (measured by leg and trunk lengths, respectively) contributed similarly to hypertension. Further evidence suggests that women are more likely to be hypertensive at older ages because they are on average shorter than men.

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.

Biological standards of living: age at menarche vs height.

Background Researchers typically use height to understand the growth environment, but recent evidence suggests that height does not reflect it well; height can even be misleading. Aim This study compared age at menarche and height to assess which better reflected the growth environment. Subjects and methods This study employed the Indonesian Family Life Survey to extract information on age at menarche from 7831 women and height from 7946 men, both aged 15-49 and born in 1944-1983. It drew on GDP per capita in childhood to represent the growth environment. The means of the two anthropometrics by birth decade were calculated. The trends in the two were then compared and each was regressed on the growth environment and a time trend. Results Between 1944-1953 and 1974-1983, the mean age at menarche decreased from 14.5 to 13.9, while height increased from 160.9 cm to 162.6 cm. Despite the expected broad trends, age at menarche was more closely related to the growth environment than height in graphs, correlation coefficients and regression results. Conclusion The results recommend using more than one anthropometric to investigate changes in the biological standards of living.

Improvement in the biological standard of living in 20th century Korea: Evidence from age at menarche.

OBJECTIVES: We used age at menarche to understand improvement in the biological standard of living in South Korea during the 20th century. METHODS: The main dataset, the Korean National Health and Nutrition Examination Survey, provided a consistent source of nationally representative data with a large number of observations over a long period of time. We calculated mean ages at menarche by birth year and estimated the rate of decrease in age at menarche, while avoiding survival bias. RESULTS: The mean age at menarche decreased from 16.64 for the birth year 1941 to 12.68 for the birth year 1992, decreasing 0.78 (or 0.81 in a regression) years per decade for the period. Comparisons with other populations demonstrate that this is the fastest rate of decline ever known. In contrast to other developed countries, the decreasing rate in Korea does not appear to slow. We also compared the trend in age at menarche to that of height and found that the rate of increase in height is also the fastest in history. CONCLUSIONS: Age at menarche is an appropriate index of change in the general standard of living in South Korea over the 20th century. Am. J. Hum. Biol. 29:e22882, 2017. © 2016 Wiley Periodicals, Inc.

The trend in suicide methods in South Korea in 1997-2015.

South Korea exhibited the highest crude suicide rate in the world. To better understand this phenomenon, the author analyzed all suicides in South Korea from 1997 to 2015 and charted the trend in suicide methods by gender. Over time, both genders rapidly chose hanging for suicide at the expense of drug/pesticide poisoning. Gassing was hardly used in the beginning, but its recent gain in use is noteworthy. Including undetermined deaths did not change the main results. The author regressed hanging on demographics and found that hanging was particularly chosen by ever-married men of prime working age with a respectable level of education.

Motor vehicle-related deaths around two major holidays in South Korea.

South Korea has consistently exhibited high rates of motor vehicle-related deaths (MVDs) since the late 1980s. This study investigated the number of MVDs around two major public holidays in South Korea-Lunar New Year's Day and Thanksgiving Day. MVDs from records of all individual deaths in 1997-2014 were extracted; then, MVDs per day from 14 days before and after each holiday (ie, 29 days in total) were summed across the years. Eventually, the 3-day mean values of MVDs before and after the holiday were compared, when holiday-related traffic peaks. The 3-day mean before Lunar New Year's Day was 385 fatalities, but dropped to 324 after the holiday; the corresponding figures for Thanksgiving Day were 494 and 413. These results are contrary to those of other countries. It appears that the severe congestion of highway traffic around the holidays resulted in a decrease in MVDs.

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.

Suicides around Major Public Holidays in South Korea.

A dip and peak pattern of suicide around major public holidays has been found in developed countries and explained by the broken promise effect. Focusing on two major holidays in South Korea (New Year's Day and Thanksgiving Day, both on the lunar calendar), replication of the dip and peak pattern was done by analyzing individual information on all suicides from 1997 to 2014. The replicated pattern revealed the most vulnerable group to be married men aged 50+ in nonmetropolitan areas in 2006-2014. Families, friends, and policy makers can use these findings to save the vulnerable.

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

Samples representative of South Korea, Indonesia, and Peninsular Malaysia were analyzed and the influence of climate on age at menarche was investigated. The sample size was 24,651 for Korea (birth years 1941-1992), for Indonesia 8331 (birth years 1944-1988) plus 20,519 (birth years 1978-1997), and 2842 for Peninsular Malaysia (birth years 1927-1968). Respondents recalled their age at menarche. The mean age at menarche was calculated for each birth year by country, and for Malaysia, additionally by ancestry. It has been found that mean ages at menarche for the early birth years were much younger in Indonesia than in Korea despite similar levels of socioeconomic conditions (proxied by GDP per capita). For example, for the birth year 1944, the mean age at menarche was 14.45 years for Indonesia and 16.19 years for Korea-a difference of 1.74 years. It was necessary to double the Korean GDP per capita to make the Korean mean age at menarche the same as the Indonesian one. Chinese and Malay women in Peninsular Malaysia were further analyzed, and the results provided indirect evidence that the difference between Korea and Indonesia was not due to ancestry differences. Results in multivariate settings provided consistent results. It has been concluded that climate exerts a significant influence on age at menarche because the relatively easy availability of food in the tropics increases energy intake while the absence of cold weather decreases energy expenditure on maintenance and activity.

Disappearing seasonality in birthweight.

OBJECTIVES: We estimated seasonality in birthweight over time and assessed how seasonality changed. METHODS: We analyzed all full-term singletons (N = 8,268,693) born in South Korea in 1997-2014. We first pooled all years and regressed birthweight on birth season while flexibly controlling for a large set of covariates. We then repeated the analysis by birth year and charted the trends in seasonality in birthweight. RESULTS: When we pooled all years, babies born in winter were the heaviest, while those born in summer the lightest; the difference in birthweight was about 11 g. When we analyzed the data by birth year, however, seasonality almost disappeared by the end of the period. CONCLUSIONS: Whatever causes the seasonality has lost its influence in Korea. Replication studies can determine whether other countries exhibit the same patterns. Am. J. Hum. Biol. 28:767-773, 2016. © 2016Wiley Periodicals, Inc.

The influence of birth season on mortality in the United States.

OBJECTIVES: Birth season is related to a variety of later outcomes. Among them, mortality is of great interest because it represents lifetime health outcomes. We examined the relationship between birth season and mortality in the US. METHODS: We merged the US National Health Interview Survey (NHIS) and NHIS public-use linked mortality files and analyzed 17,082 men and 19,075 women who were followed for 20 years from 1986 to 2006. We used the Cox proportional hazards model to relate birth quarter to mortality, controlling for birth year fixed effects. RESULTS: After controlling for years of schooling and birth year fixed effects, we found that, relative to men born in the first quarter, men born in the fourth quarter were 11% less likely to die. For women, the benefit was the largest for women born in the third quarter who were 14% less likely to die than women born in the first quarter. In the relationship between birth season and mortality, cardiovascular diseases played a noticeable role for men and malignant neoplasms for women. CONCLUSIONS: These results were consistent with those for some developed countries, but not entirely with those for contemporary developing countries and developed countries of the past. Simple mechanisms based on the perinatal environment cannot account for the inconsistent results. We suggest that family background may play some, but not an exhaustive, role in the relationship between birth season and mortality. Am. J. Hum. Biol. 28:662-670, 2016. © 2016 Wiley Periodicals, Inc.

Sexual stature dimorphism as an indicator of living standards?

BACKGROUND: A group of researchers has argued that sexual stature dimorphism (SSD) can serve as an indicator of living standards. This argument is based on evidence that boys' physical growth is more sensitive to environmental conditions than girls' physical growth. Because Korea's economic growth in the second half of the 20th century was unprecedentedly rapid, according to their logic, it is likely to see an increasing trend in SSD. AIM: We aimed to determine whether SSD can serve as an accurate indicator of living standards for a population that would exhibit a pronounced trend in SSD, providing that the logic for use of SSD is correct. SUBJECTS AND METHODS: We employed nationally representative Korean men born in 1941-1990 (n = 17 268) and women born in 1941-1991 (n = 22 543) and estimated mean heights by sex and birth years. We then calculated SSD values and charted the trend. RESULTS: Although male height increased faster than female height, the SSD trend was flat for the pooled observations and for sub-groups by socioeconomic status. CONCLUSION: These results cast doubt on the argument for using SSD as an indicator of living standards.