On the sources of the height-intelligence correlation: new insights from a bivariate ACE model with assortative mating.

A robust positive correlation between height and intelligence, as measured by IQ tests, has been established in the literature. This paper makes several contributions toward establishing the causes of this association. First, we extend the standard bivariate ACE model to account for assortative mating. The more general theoretical framework provides several key insights, including formulas to decompose a cross-trait genetic correlation into components attributable to assortative mating and pleiotropy and to decompose a cross-trait within-family correlation. Second, we use a large dataset of male twins drawn from Swedish conscription records and examine how well genetic and environmental factors explain the association between (i) height and intelligence and (ii) height and military aptitude, a professional psychologist's assessment of a conscript's ability to deal with wartime stress. For both traits, we find suggestive evidence of a shared genetic architecture with height, but we demonstrate that point estimates are very sensitive to assumed degrees of assortative mating. Third, we report a significant within-family correlation between height and intelligence (p^ = 0.10), suggesting that pleiotropy might be at play.

Association Between Lottery Prize Size and Self-reported Health Habits in Swedish Lottery Players.

Importance: Poor health and unhealthy lifestyles are substantially more prevalent among individuals with low income than among individuals with high income, but the underlying mechanisms are not well understood. Objective: To evaluate whether changes to unearned wealth from lotteries are associated with long-term health behaviors and overall health. Design, Setting, and Participants: In this quasi-experimental cohort study, 4820 participants (aged 18-70 years at the time of winning) in 3 Swedish lotteries were surveyed from September 1, 2016, to November 11, 2016, between 5 and 22 years after a lottery event. Outcomes of participants in the same lottery who were randomly assigned prizes of different magnitudes by the lotteries but were ex ante identical in terms of their probability of winning different prizes were compared. Data were analyzed from December 22, 2016, to November 21, 2019. Exposures: Lottery prizes ranged from $0 for nonwinning players to $1.6 million. Main Outcomes and Measures: Four lifestyle factors (smoking, alcohol consumption, physical activity, and a healthy diet index) and 2 measures of overall health (subjective health and an index of total health derived from responses to questions about 35 health conditions). Results: The survey was returned by 3344 of 4820 individuals (69%; 1722 [51.5%] male), which corresponded to 3362 observations. The mean (SD) age was 48 (11.8) years in the year of the lottery win and 60 (11.0) years at the time of the survey. There were no statistically significant associations between prize amount won and any of the 6 long-term health outcomes. Estimated associations expressed in SD units per $100 000 won were as follows: smoking (-0.006, 95% CI, -0.038 to 0.026); alcohol consumption (0.003, 95% CI, -0.027 to 0.033); physical activity (0.001, 95% CI, -0.029 to 0.032); dietary quality (-0.007, 95% CI, -0.040 to 0.026); subjective health (0.013, 95% CI, -0.017 to 0.043); and index of total health (-0.003, 95% CI, -0.033 to 0.027). Conclusions and Relevance: In this study of Swedish lottery players, unearned wealth from random lottery prize winnings was not associated with subsequent healthy lifestyle factors or overall health. The findings suggest that large, random transfers of unearned wealth are unlikely to be associated with large, long-term changes in health habits or overall health.

Is there an adverse effect of sons on maternal longevity?

Recent years have witnessed the emergence of a literature examining the effects of giving birth to sons on postmenopausal longevity in pre-industrial mothers. The original paper in this lineage used a sample (n=375) of Sami mothers from northern Finland and found that, relative to daughters, giving birth to sons substantially reduced maternal longevity. We examine this hypothesis using a similar and a much larger sample (n=930) of pre-industrial Sami women from northern Sweden, who in terms of their demographic, sociocultural and biological conditions, closely resemble the original study population. In contrast to the previously reported results for the Sami, we find no evidence of a negative effect of sons on maternal longevity. Thus, we provide the most compelling evidence to date that the leading result in the literature must be approached with scepticism.

Maternal longevity and the sex of offspring in pre-industrial Sweden.

BACKGROUND: Helle et al. (2000. Sons reduced maternal longevity in preindustrial humans. Science, 296, 1085) argued that giving birth to sons reduced maternal longevity in pre-industrial societies due to higher physiological costs of bearing sons and the elevated testosterone levels observed in mothers carrying male foetuses. AIM: The present study examined this hypothesis using a more comprehensive dataset and evaluated the merits of the statistical approach used in previous studies to identify the cost of giving birth to sons in terms of maternal old-age longevity. SUBJECTS AND METHODS: The analysis in Helle et al. (2002. Sons reduced maternal longevity in preindustrial humans. Science 296, 1085) was extended by using a considerably larger dataset of pre-industrial Swedish women, and with careful consideration paid to methodological problems of sample selection and omitted variable bias. We argue that the previous literature has underestimated the difficulties in quantifying the trade-off between parity and longevity due to unobserved heterogeneity in health. However, under less restrictive assumptions, one can estimate the marginal impact of a son for a fixed family size. RESULTS: No evidence was found of a negative relative impact of sons. Neither was any evidence found in favour of the male-biased intra-household resource competition hypothesis proposed elsewhere in the literature, despite the poverty of the study population. These results are robust to a wide range of specifications tested. CONCLUSION: The failure to reproduce earlier findings and the fact that studies in this area of research seem to continue to yield conflicting results warrant much caution in discussing and evaluating results. It is likely that the negative effect of sons, if it existed, only manifested itself under conditions that are not yet fully understood. We also argue that the previous literature on this topic has not fully acknowledged the inference problems associated with omitted variable bias and sample selection.