Fetal and life course origins of serum lipids in mid-adulthood: results from a prospective cohort study

DNA Methylation Mediates the Association Between Individual and Neighborhood Social Disadvantage and Cardiovascular Risk Factors

Low socioeconomic status (SES) and living in a disadvantaged neighborhood are associated with poor cardiovascular health. Multiple lines of evidence have linked DNA methylation to both cardiovascular risk factors and social disadvantage indicators. However, limited research has investigated the role of DNA methylation in mediating the associations of individual- and neighborhood-level disadvantage with multiple cardiovascular risk factors in large, multi-ethnic, population-based cohorts. We examined whether disadvantage at the individual level (childhood and adult SES) and neighborhood level (summary neighborhood SES as assessed by Census data and social environment as assessed by perceptions of aesthetic quality, safety, and social cohesion) were associated with 11 cardiovascular risk factors including measures of obesity, diabetes, lipids, and hypertension in 1,154 participants from the Multi-Ethnic Study of Atherosclerosis (MESA). For significant associations, we conducted epigenome-wide mediation analysis to identify methylation sites mediating the relationship between individual/neighborhood disadvantage and cardiovascular risk factors using the JT-Comp method that assesses sparse mediation effects under a composite null hypothesis. In models adjusting for age, sex, race/ethnicity, smoking, medication use, and genetic principal components of ancestry, epigenetic mediation was detected for the associations of adult SES with body mass index (BMI), insulin, and high-density lipoprotein cholesterol (HDL-C), as well as for the association between neighborhood socioeconomic disadvantage and HDL-C at FDR q < 0.05. The 410 CpG mediators identified for the SES-BMI association were enriched for CpGs associated with gene expression (expression quantitative trait methylation loci, or eQTMs), and corresponding genes were enriched in antigen processing and presentation pathways. For cardiovascular risk factors other than BMI, most of the epigenetic mediators lost significance after controlling for BMI. However, 43 methylation sites showed evidence of mediating the neighborhood socioeconomic disadvantage and HDL-C association after BMI adjustment. The identified mediators were enriched for eQTMs, and corresponding genes were enriched in inflammatory and apoptotic pathways. Our findings support the hypothesis that DNA methylation acts as a mediator between individual- and neighborhood-level disadvantage and cardiovascular risk factors, and shed light on the potential underlying epigenetic pathways. Future studies are needed to fully elucidate the biological mechanisms that link social disadvantage to poor cardiovascular health.

Birth size is not associated with depressive symptoms from adolescence to middle-age: results from the Northern Swedish Cohort study

Low birth weight has been shown to be related to increased risk of depression later in life - but the evidence is not conclusive. We examined the association of size at birth with repeatedly measured depressive symptoms in 947 individuals from the Northern Swedish Cohort, a community-based age-homogeneous cohort born in 1965, and followed with questionnaires between ages 16 and 43 (participation rate above 90% in all the surveys). Information on birth size was retrieved from archived birth records. Length of gestation was known for a subsample of 512 individuals (54%). We studied the association of birth weight and ponderal index with self-reported depressive symptoms at ages 16, 21, 30 and 43; with the life-course average of depressive symptoms score and with longitudinal trajectories of depressive symptoms retrieved by latent class growth analysis. Socioeconomic background, mental illness or alcohol problems of a parent, exposure to social adversities in adolescence and prematurity were accounted for in the analyses. We did not find any relationship between weight or ponderal index at birth and our measure of depressive symptoms between ages 16 and 43 in a series of different analyses. Adjustment for length of gestation did not alter the results. We conclude that size at birth is not associated with later-life depressive symptoms score in this cohort born in the mid-1960s in Sweden. The time and context need to be taken into consideration in future studies.

Model Selection of the Effect of Binary Exposures over the Life Course

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Epidemiologists are often interested in examining the effect on a later-life outcome of an exposure measured repeatedly over the life course. When different hypotheses for this effect are proposed by competing theories, it is important to identify those most supported by observed data as a first step toward estimating causal associations. One method is to compare goodness-of-fit of hypothesized models with a saturated model, but it is unclear how to judge the “best” out of two hypothesized models that both pass criteria for a good fit. We developed a new method using the least absolute shrinkage and selection operator to identify which of a small set of hypothesized models explains most of the observed outcome variation. We analyzed a cohort study with repeated measures of socioeconomic position (exposure) through childhood, early- and mid-adulthood, and body mass index (outcome) measured in mid-adulthood. We confirmed previous findings regarding support or lack of support for the following hypotheses: accumulation (number of times exposed), three critical periods (only exposure in childhood, early- or mid-adulthood), and social mobility (transition from low to high socioeconomic position). Simulations showed that our least absolute shrinkage and selection operator approach identified the most suitable hypothesized model with high probability in moderately sized samples, but with lower probability for hypotheses involving change in exposure or highly correlated exposures. Identifying a single, simple hypothesis that represents the specified knowledge of the life course association allows more precise definition of the causal effect of interest.

Relation between birth weight, growth, and subclinical atherosclerosis in adulthood

Background and Objectives. Adverse conditions in the prenatal environment and in the first years of life are independently associated with increased risk for cardiovascular disease. This paper aims to study the relation between birthweight, growth in the first year of life, and subclinical atherosclerosis in adults. Methods. 88 adults aged between 20 and 31 were submitted to sociodemographic qualities, anthropometric data, blood pressure measurements, metabolic profile, and evaluation of subclinical atherosclerosis. Results. Birthweight <2,500 grams (g) was negatively correlated with (a) increased waist-to-hip ratio (WHR), according to regression coefficient (RC) equal to −0.323, 95% CI [−0.571, −0.075] P < 0.05; (b) diastolic blood pressure (RC = −4.744, 95% CI [−9.017, −0.470] P < 0.05); (c) low HDL-cholesterol (RC = −0.272, 95% CI [−0.516, −0.029] P < 0.05); (d) frequency of intima-media thickness (IMT) of left carotid >75th percentile (RC = −0.242, 95% CI [−0.476, −0.008] P < 0.05). Birthweight >3,500 g was associated with (a) BMI >25.0 kg/m², (RC = 0.317, 95% CI [0.782, 0.557] P < 0.05); (b) increased waist circumference (RC = 0.284, 95% CI [0.054, 0.513] P < 0.05); (c) elevated WHR (RC = 0.280, 95% CI [0.054, 0.505] P < 0.05); (d) minimum subcutaneous adipose tissue (SAT) (RC = 4.354, 95% CI [0.821, 7.888] P < 0.05); (e) maximum SAT (RC = 7.095, 95% CI [0.608, 13.583] P < 0.05); (f) right lobe of the liver side (RC = 6.896, 95% CI [1.946, 11.847] P < 0.001); (g) frequency's right lobe of the liver >75th percentile (RC = 0.361, 95% CI [0.169, 0.552] P < 0.001). Weight gain in the first year of life was inversely correlated with (a) mean IMT of left carotid (RC = −0.046, 95% CI [−0.086, −0.006] P < 0.05; (b) frequency IMT of left carotid >75th percentile (RC = −0.253, 95% CI [−0.487, −0.018] P < 0.05); (c) mean IMT (RC = −0.038, 95% CI [0.073, −0.002] P < 0.05); (d) the frequency of the mean IMT >75th percentile (RC = −0.241, 95% CI [−0.442, −0.041] P < 0.05). Conclusions. Adults birthweight <2,500 g and >3,500 g and with insufficient weight gain in the first year of life have showed different metabolic phenotypes, but all of them were related to subclinical atherosclerosis.

Adult lipids associated with early life growth in traditional Melanesian societies undergoing rapid modernization: a longitudinal study of the mid-20th century

Both poor fetal development and accelerated post-natal growth have been linked to adult dyslipidemias in many studies conducted in developed societies. It is not known, however, whether these relationships only characterize populations with typical Western diets or if they also may develop in groups at the early stages of a dietary transition. Our longitudinal study of traditional rural populations in the Southwest Pacific during a period of extremely rapid modernization in diet and life-styles shows a nascent association between child growth retardation, subsequent growth acceleration, and adult lipid values in spite of a continuing prevalence of very low lipid levels. However, our results do not entirely conform to results from populations with "modern" diets. Outcome (i.e., young adult) cholesterol and triglyceride levels are more consistently related to initial measures of body fat and growth in body fat measures than with stature, while outcome apo A-1 is more consistently related to initial stature or stature growth than to measures of body fat. We suggest this may reflect a pattern characteristic of the initial stages of "modernization" associated with dietary change, with stronger and more pervasive relationships emerging only later as populations complete the dietary transition.

Life course models of socioeconomic position and cardiovascular risk factors: 1946 birth cohort

PURPOSE

To identify the life course model that best describes the association between life course socioeconomic position (SEP) and cardiovascular (CVD) risk factors (ie, body mass index [BMI], systolic and diastolic blood pressure, total cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, and glycated hemoglobin) and explore BMI across the life course as mediators of the relationship.

METHODS

The Medical Research Council National Survey of Health and Development was used to compare partial F-tests of simpler nested life course SEP models corresponding to critical period, accumulation, and social mobility models with a saturated model. Then, the chosen life course model for each CVD risk factor was adjusted for BMI at age 53 and lifetime BMI (ages 4, 26, 43, and 53 years).

RESULTS

Among women, SEP was generally associated with CVD risk factors in a cumulative manner, whereas childhood critical period was the prominent model for men. When the best-fitting SEP models were used, we found that adjustment for BMI at age 53 reduced associations for all outcomes in both genders. Further adjustment for lifetime BMI (4, 26, 43, and 53 years) did not substantially alter most associations (except for triglycerides).

CONCLUSIONS

SEP at different points across life influences CVD risk factors differently in men and women.