Many factors have contributed to the decline in China’s fertility level. Using China’s population census data from 1990, 2000 and 2010, the present study investigates the factors causing the decline in China’s fertility rate by decomposing changes in two fertility indices: the total fertility rate (TFR) and the net reproduction rate (NRR). The change in the TFR is decomposed into the change in the marital fertility rate (MFR) and the change in the proportion of married women (PMW). Four factors contribute to the change in the NRR. The following are the main findings. A drop in the MFR caused a decrease in the TFR and the NRR between 1989 and 2000. However, the change in MFR increased TFR and NRR between 2000 and 2010. Marriage postponement caused a decline in the fertility level between 1989 and 2000 as well as between 2000 and 2010. The effect of the MFR and marriage postponement varied with age and region and also between urban and rural areas.

Prior research has established associations between neighbourhood poverty and cumulative biological risk (CBR). CBR is conceptualized as indicative of the effects of stress on biological functioning, and is linked with increased morbidity and mortality. Studies suggest that supportive social relationships may be health protective, and may erode under conditions of poverty. This study examines whether social relationships are inversely associated with CBR and whether associations between neighbourhood poverty and CBR are mediated through social relationships. Data were from a stratified probability sample community survey (n=919) of residents of Detroit, Michigan, USA (2002–2003) and from the 2000 US Census. The outcome variable, CBR, included anthropometric and clinical measures. Independent variables included four indicators of social relationships: social support, neighbourhood satisfaction, social cohesion and neighbourhood participation. Multilevel models were used to test both research questions, with neighbourhood poverty and social relationships included at the block group level, and social relationships also included at the individual level, to disentangle individual from neighbourhood effects. Findings suggest some associations between social relationships and CBR after accounting for neighbourhood poverty and individual characteristics. In models that accounted for all indicators of social relationships, individual-level social support was associated with greater CBR (β=0.12, p=0.04), while neighbourhood-level social support was marginally significantly protective of CBR (within-neighbourhood: β=−0.36, p=0.06; between-neighbourhood: β=−0.24, p=0.06). In contrast, individual-level neighbourhood satisfaction was protective of CBR (β=−0.10, p=0.02), with no within-neighbourhood (β=0.06, p=0.54) or between-neighbourhood association (β=−0.04, p=0.38). Results indicate no significant association between either social cohesion or neighbourhood participation and CBR. Associations between neighbourhood poverty and CBR were not mediated by social relationships. These findings suggest that neighbourhood-level social support and individual-level neighbourhood satisfaction may be health protective and that neighbourhood poverty, social support and neighbourhood satisfaction are associated with CBR through independent pathways.

Schistosomiasis is a neglected tropical parasitic disease caused by different species of genus Schistosoma. Schistosoma mansoni causes a severe intestinal parasitic infection of high public and medical importance in Ethiopia. This study aimed to determine the prevalence of, and risk factors for, S. mansoni infection among the fishermen of Lake Hawassa, southern Ethiopia, using a cross-sectional study design. A total of 243 fishermen were selected from the Hawassa Town Fishermen Association’s list in 2013. Data on socio-demographic characteristics and risk factors were collected from the fishermen using semi-structured questionnaires. Stool samples were collected and processed using the Kato–Katz thick smear technique. The overall prevalence of S. mansoni among the fishermen was 29.21% and the mean intensity of infection was 158.88 eggs per gram (EPG). The overall prevalence of intestinal helminths, including S. mansoni, was 69.54%. Similar prevalences of S. mansoni were recorded in age groups 15–19, 20–24 and 25–29 years: 31.82%, 31.75% and 31.94%, respectively. Fishermen who swam a minimum of once a week in Lake Hawassa were 2.92 times (95% CI: 1.554, 5.502) more likely to have acquired S. mansoni infection than those who swam in the lake less than once a week. The results indicate moderate endemicity of S. mansoni infection among the fishermen of Lake Hawassa. These fishermen could be a potentially high-risk group for S. mansoni infection and might be responsible for the transmission of infection to other segments of the community visiting the lake for recreation. Moreover, a high prevalence of soil-transmitted helminths (STHs) was recorded among the fishermen. Integrated prevention and control strategies for schistosomiasis and STHs by different sectors are needed to tackle this problem.

Hypertension prevalence is on the rise in low- and middle-income countries (LMICs) like South Africa, and migration and its concomitant urbanization are often considered to be associated with this rise. However, relatively little is known about the relationship between blood pressure (BP) and internal migration – a highly prevalent population process in LMICs. This study employed data for a group of 194 adult men and women from an original pilot dataset drawn from the Agincourt Health and Demographic Surveillance System in north-east South Africa conducted in 2012. Migrants in the sample were identified, tracked and interviewed. The relationship between BP and migration distance and the number of months an individual spent away from his/her home village was estimated using robust OLS regression, controlling for a series of socioeconomic, health and behavioural characteristics. It was found that migrants who moved a longer distance and for longer durations had significantly higher systolic and diastolic blood pressures compared with shorter-term migrants and those who remained nearby or in their home village. These associations remained robust and statistically significant when adjusting for measures of socioeconomic conditions, as well as body mass index and the number of meals consumed per day. Migration, both in terms of distance and time away, explained significant variation in the blood pressure of migrants in this typical South African context. The findings suggest the need for further studies of the nutritional and psycho-social factors associated with geographic mobility that may be important to understand rising hypertension levels in LMICs.

The aim of this study was to examine the gender differential effects of eating habits and physical activity on overweight and obesity among school-aged adolescents in Bangladesh. Nationally representative data extracted from the 2014 Global School-based Student Health Survey (GSHS) were utilized. The survey collected information related to physical and mental health from 2989 school-aged adolescents in Bangladesh. An exploratory data analysis and multivariate logistic regression model were employed in this study. Female adolescents were at a lower risk of being overweight or obese (AOR=0.573) than males, with a prevalence of 7.4% (males: 9.9%). The results showed that high consumption of vegetables (both: AOR=0.454; males: AOR=0.504; females: AOR=0.432), high soft drink consumption (both: AOR=2.357; males: AOR=2.929; females: AOR=1.677), high fast food consumption (both: AOR=2.777; males: AOR=6.064; females: AOR=1.695), sleep disturbance (both: AOR=0.675; males: AOR=0.590; females: AOR=0.555) and regular walking or cycling to school (both: AOR=0.472; males: AOR=0.430; females: AOR=0.557) were vital influencing factors for being overweight or obese among adolescents for both sexes. Sedentary activities during leisure time were also identified as significant predictors of being overweight or obese for males. Regular fruit and vegetable consumption, the avoidance of soft drinks and fast food, an increase in vigorous physical activity, regular attendance at physical education classes and fewer sedentary leisure time activities could all help reduce the risk of being overweight or obese for both sexes.

Research on twinning in developed countries is well documented, but little is known about twinning in less-developed countries due to a lack of data or data limitations. This study examined the level of, trends in and determinants of twin births and their survival under age five in Jordan, using the 2012 Jordan Population and Family Health Survey (JPFHS) data. The birth history of 11,352 women included in the JPFHS provided information on 9859 live births that occurred within five years of the survey date, and these constituted the study subjects. Descriptive statistics, and bivariate and multivariate multilevel logistic regression models were used for data analysis. About 3.5% of the total live births were twins, which is one of the highest rates in developing countries. The twinning rate showed an increasing trend in Jordan, increasing by 45% from 2.4% in 1990 to 3.5% in 2012. Higher maternal age at child birth, higher parity, poor and richer economic status, contraceptive use status, secondary and above level of education of mothers and non-consanguinity were found to be associated with a higher rate of twin births in Jordan. Twins were observed to have a higher risk of low birth weight, being smaller in physical size at birth and at more than four times higher risk of neonatal death compared with singletons. To reduce the risk adverse outcomes of twin pregnancies and further improve maternal and child health, antenatal, delivery and postnatal care should be tailored towards the special needs of twin pregnancies and twin births in Jordan Twin pregnancies should be detected at the early stage of pregnancy so that perinatal outcomes can be improved by frequent prenatal visits, health education, counselling and proper management of peripartum complications.

Spearman’s hypothesis tested at the subtest level of an IQ battery states that differences between races on the subtests of an IQ battery are a function of the g loadings of these subtests, such that there are small differences between races on subtests with low g loadings and large differences between races on subtests with high g loadings. Jensen (1998) stated that Spearman’s hypothesis is a law-like phenomenon. It has also been confirmed many times at the level of items of the Raven’s Progressive Matrices. This study hypothesizes that with concern to Spearman’s hypothesis, subtests and items function in fundamentally the same way, and tested whether Spearman’s hypothesis is confirmed at the item level for White–East Asian comparisons. A group of Korean young adults (N=205) was compared with other groups of young adults from Canada, the US, Russia, Peru and South Africa (total N=4770) who took the Advanced Progressive Matrices. Spearman’s hypothesis was strongly confirmed with a sample-size-weighted r with a value of 0.63. Computing the g loadings of the items of the Raven with either the Raven-g or the Wechsler-g led to the same conclusions. Tests of Spearman’s hypothesis yielded less-strong outcomes when the 36-item Advanced Progressive Matrices were used than when the 60-item Standard Progressive Matrices were used. There is a substantial correlation between sample size and the outcome of Spearman’s hypothesis. So, all four hypotheses were confirmed, showing that a part of the subtest-level nomological net replicates at the item level, strengthening the position that, with concern to Spearman’s hypothesis, subtests and items function fundamentally the same. It is concluded that Spearman’s hypothesis is still a law-like phenomenon. Detailed suggestions for follow-up research are made.

Te Nijenhuis et al. (2019) cite studies that show that training on cognitive tasks produces the largest standardized gains on the easiest items and the smallest standardized gains on the most difficult items. They note that this creates an anti-Jensen effect, and use this as a trump that is supposed to show that my basketball examples are irrelevant. I use a new basketball example that is compatible with those studies. It assumes that at some point improvement on the easy skills ‘stalls’ – and all that is left is some improvement on the hard skills. Therefore, further environmental enhancement means the higher level skill gap is increased, which gives a classic Jensen effect, which shows that the presence of such does not entail genetic causality. The difference is that we really can produce virtually optimum basketball skills while for cognition, we are still well short. I also address the problem of why IQ gains over time do not show an anti-g pattern. After all, they are environmentally caused, and ‘should’ do so if an anti-g pattern and environmental causes go together.

A test of Jensen effects is of nil value as a diagnostic instrument when various good-sized meta-analyses show Jensen effects appear for both genetic effects and environmental effects. Using thought experiments, Flynn (2019) claims that some schooling gains yield Jensen effects, which should not be the case for an environmental effect. However, a meta-analysis (K = 12, total N = 60,993, mean r = 0.13) of schooling gains shows no Jensen effect. Real data trump thought experiments, so it is concluded there is no empirical proof of anomalous Jensen effects for schooling gains.

The effects of educational training are only one case of producing two groups (before and after) separated by IQ test performance on easier and harder items. The crux of the issue is whether we know that the causes between groups are genetic if they are differentiated by a Jensen effect and that the causes are environmental if they are differentiated by an anti-Jensen effect. A Jensen effect occurs when the two groups differ more as cognitive tasks become more complex. It is shown that genes vs environment must be diagnosed on a case-by-case basis, not in terms of whether a Jensen effect is present.