The relationship of fatty acids to ischaemic heart disease and lifespan in men and women using Mendelian randomization

BACKGROUND

Observationally, polyunsaturated fatty acids (PUFAs) have health benefits compared with saturated fatty acids (SFAs); randomized controlled trials suggest fewer benefits. We used uni- and multi-variable Mendelian randomization to assess the association of major fatty acids and their sub-species with ischaemic heart disease (IHD) overall and sex-specifically and with lifespan sex-specifically, given differing lifespan by sex.

METHODS

We obtained strong (P <5x10-8), independent (r2<0.001) genetic predictors of fatty acids from genome-wide association studies (GWAS) in a random subset of 114 999 UK Biobank participants. We applied these genetic predictors to the Cardiogram IHD GWAS (cases = 60 801, controls = 123 504) and to the Finngen consortium GWAS (cases = 31 640, controls = 187 152) for replication and to the UK Biobank for sex-specific IHD and for lifespan based on parental attained age (fathers = 415 311, mothers = 412 937). We used sensitivity analysis and assessed sex differences where applicable.

RESULTS

PUFAs were associated with IHD [odds ratio 1.23, 95% confidence interval (CI) 1.05 to 1.44] and lifespan in men (-0.76 years, 95% CI -1.34 to -0.17) but not women (0.20, 95% CI -0.32 to 0.70). Findings were similar for omega-6 fatty acids and linoleic acid. Independent associations of SFAs, mono-unsaturated fatty acids or omega-3 fatty acids with IHD overall or lifespan in men and women were limited.

CONCLUSIONS

PUFAs, via specific subspecies, may contribute to disparities in lifespan by sex. Sex-specific dietary advice might be a start towards personalized public health and addressing inequities.

Unraveling Potential Sex-Specific Effects of Cardiovascular Medications on Longevity Using Mendelian Randomization

BACKGROUND

Establishing the sex-specific efficacy of cardiovascular medications is pivotal to evidence-based clinical practice, potentially closing the gender gap in longevity. Trials large enough to establish sex differences are unavailable. This study evaluated sex-specific effects of commonly prescribed cardiovascular medications on lifespan.

METHODS AND RESULTS

In a two-sample Mendelian randomization study, established genetic variants mimicking effects of lipid-lowering drugs, antihypertensives, and diabetes drugs were applied to genetic associations with lifespan proxied by UK Biobank maternal (n=412 937) and paternal (n=415 311) attained age. Estimates were obtained using inverse variance weighting, with sensitivity analyses where possible. For lipid-lowering drugs, genetically mimicked PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors were associated with longer lifespan, particularly in men (2.39 years per SD low-density lipoprotein cholesterol reduction [95% CI, 0.42-4.36], P for interaction=0.14). Genetically mimicked treatments targeting APOC3, LPL, or possibly LDLR were associated with longer lifespan in both sexes. For antihypertensives, genetically mimicked β-blockers and calcium channel blockers were associated with longer lifespan, particularly in men (P for interaction=0.17 for β-blockers and 0.31 for calcium channel blockers). For diabetes drugs, genetically mimicked metformin was associated with longer lifespan in both sexes. No associations were found for genetically mimicked statins, ezetimibe, or angiotensin-converting enzyme inhibitors.

CONCLUSIONS

PCSK9 inhibitors, β-blockers, and calcium channel blockers may prolong lifespan in the general population, particularly men. Treatments targeting APOC3, LPL, or LDLR and metformin may be relevant to both sexes. Whether other null findings are attributable to lack of efficacy requires investigation. Further investigation of repurposing should be conducted.

Assessing the safety of lipid-modifying medications among Chinese adolescents: a drug-target Mendelian randomization study

BACKGROUND

With increasing hypercholesterolemia prevalence in East Asian adolescents, pharmacologic interventions (e.g., HMGCR inhibitors (statins) and PCSK9 inhibitors) may have to be considered although their longer-term safety in the general adolescent population is unclear. This study aims to investigate the longer-term safety of HMGCR inhibitors and PCSK9 inhibitors among East Asian adolescents using genetics.

METHODS

A drug-target Mendelian randomization study leveraging the Global Lipid Genetics Consortium (East Asian, n = 146,492) and individual-level data from Chinese participants in the Biobank clinical follow-up of Hong Kong's "Children of 1997" birth cohort (n = 3443, aged ~ 17.6 years). Safety outcomes (n = 100) included anthropometric and hematological traits, renal, liver, lung function, and other nuclear magnetic resonance metabolomics. Positive control outcomes were cholesterol markers from the "Children of 1997" birth cohort and coronary artery disease from Biobank Japan.

RESULTS

Genetic inhibition of HMGCR and PCSK9 were associated with reduction in cholesterol-related NMR metabolomics, e.g., apolipoprotein B (HMGCR: beta [95% CI], - 1.06 [- 1.52 to - 0.60]; PCSK9: - 0.93 [- 1.56 to - 0.31]) and had the expected effect on the positive control outcomes. After correcting for multiple comparisons (p-value < 0.006), genetic inhibition of HMGCR was associated with lower linoleic acid - 0.79 [- 1.25 to - 0.35]. Genetic inhibition of PCSK9 was not associated with the safety outcomes assessed.

CONCLUSIONS

Statins and PCSK9 inhibitors in East Asian adolescents appeared to be safe based on the outcomes concerned. Larger studies were warranted to verify these findings. This study serves as a proof of principle study to inform the medication safety among adolescents via genetics.

Breastfeeding and ApoB in late adolescence: a Hong Kong birth cohort study

Breastfeeding is widely promoted. Experimental evidence concerning long-term benefits is limited. Observational studies are open to bias from confounding by socio-economic position. We assessed the association of breastfeeding with late adolescent lipid sub-fractions, particularly apolipoprotein B (ApoB) and non-high-density lipoprotein cholesterol (non-HDL-c), overall and by sex. We took advantage of a setting where breastfeeding has little association with higher socio-economic position and where several results from randomized controlled trials of breastfeeding promotion have been replicated. We used the population-representative "Children of 1997" birth cohort comprising 88% of births in Hong Kong in April and May 1997. Associations of breastfeeding in the first 3 months of life (never, mixed, exclusive) with lipid sub-fractions were obtained using linear regression adjusted for potential confounders including parental socio-economic position, maternal place of birth, type of delivery, gestational age, and birth weight. Differences by sex were assessed. Multiple imputation and inverse probability weighting were used to recover the original sample. Of the 3462 participants included, mean age was 17.6 years and 48.8% were girls. Mean ApoB was 0.74 g/L (standard deviation 0.15). Exclusive versus never breastfeeding was associated with lower ApoB (-0.027 g/L, 95% confidence interval (CI)-0.046 to-0.007, p = 0.007) and lower non-HDL-c (-0.143 mmol/L, 95% CI-0.237 to-0.048) with similar estimates by sex.

CONCLUSION

Breastfeeding may provide some population-level lifelong protection against cardiovascular disease. This study supports policies promoting breastfeeding as a modifiable exposure that contributes to a healthy start in life as an investment for lifelong cardiovascular disease prevention.

WHAT IS KNOWN

• Apolipoprotein B (ApoB) is a recognized risk factor for cardiovascular disease, but whether breastfeeding affects ApoB in later life overall and by sex is unknown.

WHAT IS NEW

• Exclusive breastfeeding in the first 3 months of life was associated with lower ApoB in late adolescence, with similar estimates for both sexes. • The inverse association of breastfeeding with ApoB suggests that breastfeeding could reduce cardiovascular disease and overall mortality over the lifespan.

The influence of growth and sex hormones on risk of alzheimer's disease: a mendelian randomization study

Alzheimer's disease is more prevalent in women, possibly due to sex or growth hormones but existing evidence is inconclusive. We investigated whether genetically predicted sex and growth hormones are associated with risk of Alzheimer's disease. Genetic variants strongly and independently predicting insulin-like growth factor 1 (IGF-1), testosterone and sex hormone-binding globulin (SHBG) were obtained from large, published genome wide associations studies (GWAS) and applied to GWAS of Alzheimer's disease based on clinical diagnosis (cases = 21,982, control = 41,944) from the International Genomics of Alzheimer's Project and the UK Biobank parental (maternal cases = 27,696; paternal cases = 14,338) and siblings' diagnosis (cases = 2,171) as proxy cases. Published GWAS summary statistics were used in our analyses. Estimates were obtained from inverse variance weighting with sensitivity analysis (i.e., MR-Egger, weighted median and MR-PRESSO). Multivariable analyses adjusted for pleiotropic effects and possible sources of selection bias were also performed. Genetically predicted higher total testosterone may reduce the risk of paternal Alzheimer's disease (odds ratio (OR) 0.86, 95% confidence interval (CI) 0.76 to 0.97, per SD increase in testosterone) and in meta-analysis for women (OR 0.92, 95% CI 0.87, 0.98) with directionally similar results from other analyses. SHBG were not associated with Alzheimer's disease. IGF-1 in women was inversely associated with risk of clinical Alzheimer's disease in sensitivity analysis but not in the main analysis. These results suggest genetically predicted higher total testosterone may lower risk of Alzheimer's disease. The role of testosterone and the immune system in Alzheimer's disease could be further investigated.

Association of growth patterns during infancy and puberty with lung function, wheezing and asthma in adolescents aged 17.5 years: evidence from ‘Children of 1997’ Hong Kong Chinese Birth Cohort

Background

Rapid growth is related to adverse respiratory outcomes although possibly confounded or limited by growth modelling methods. We investigated the association of infant and pubertal growth with lung function, wheezing and asthma in a non-Western setting.

Methods

In Hong Kong’s ‘Children of 1997’ Chinese birth cohort (n = 8327), weight during infancy and weight, height and body mass index (BMI) during puberty were modelled using a super-imposition by translation and rotation model to identify (larger or smaller) size, (earlier or later) tempo and (slower or faster) velocity. Sex-specific associations with forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1/FVC (Global Lung function Initiative z-score) and self-reported wheezing and asthma at ∼17.5 years were assessed.

Results

For each fraction higher than average weight growth velocity during infancy, FVC was higher in boys (0.90 SD, 95% CI 0.35; 1.44) and girls (0.77 SD, 95% CI 0.24; 1.30), FEV1/FVC was lower (–0.74 SD, 95% CI –1.38; –0.10) and wheezing was higher (odds ratio 6.92, 95% CI 1.60; 29.99) in boys and an inverse association with FVC was observed for tempo but not for size. Associations for weight growth velocity in puberty were similar but weaker. Greater size and higher velocity of BMI growth was associated with higher FVC, lower FEV1/FVC and higher asthma and wheezing risk.

Conclusion

Accelerated infant and pubertal weight growth were associated with disproportionate lung size and airway growth, and higher risk of asthma; optimizing early-life growth patterns could be important.

Do deaths from competing risks influence COPD patterns in China and high socio-demographic index countries?: a cross-sectional analysis of summary statistics from the Global Burden of Disease Study 2017

OBJECTIVE

To explore possible reasons for the difference in chronic obstructive pulmonary disease (COPD) incidence/mortality rates between China and high socio-demographic index (SDI) countries.

DESIGN

A cross-sectional analysis of summary statistics from the Global Burden of Disease Study 2017.

PARTICIPANTS

Data were publicly available and de-identified, and individuals were not involved.

MEASUREMENT AND METHODS

We extracted the age-standardised and age-specific incidence/mortality rates, and risk factors attributed to COPD in China and high SDI countries from the Global Burden of Disease Study 2017. We first described differences in COPD patterns (ie, incidence and mortality rates) in China and high SDI countries briefly, and then explored possible reasons for driving such differences by comparing rankings for six well-established COPD risk factors and estimating change points in age-specific incidence and mortality rates for COPD and several commonly encountered competing risks using segmented regression models.

RESULTS

Differences in age-standardised incidence and mortality rates for COPD between China and high SDI countries converged during 1990-2017 but still differed, particularly for mortality rates. Smoking was the leading attributable risk factor followed by ambient air pollution, with higher rankings for occupational risks in China than in high SDI countries. The change point was ~80 years for age-specific COPD mortality rate in both China and high SDI countries. However, the change point for COPD incidence was 5-year later in China (~65 years) than in high SDI countries (~60 years). The change points for mortality rates due to competing risks (eg, ischaemic heart disease) also varied between settings.

CONCLUSION

Differences in risk factors largely shaped the differences in COPD patterns between China and high SDI countries. Varying patterns of mortality due to competing risks might also contribute to the discrepancy in COPD mortality rates, by affecting the survival of the underlying population.

Relative Deprivation, Income Inequality, and Cardiovascular Health: Observational and Mendelian Randomization Studies in Hong Kong Chinese

The associations between absolute vs. relative income at the household or neighborhood level and cardiovascular disease (CVD) risk remain understudied in the Chinese context. Further, it is unclear whether stress biomarkers, such as cortisol, are on the pathway from income to CVD risk. We examined the associations of absolute and relative income with CVD risk observationally, as well as the mediating role of cortisol, and validated the role of cortisol using Mendelian Randomization (MR) in Hong Kong Chinese. Within Hong Kong's FAMILY Cohort, associations of absolute and relative income at both the individual and neighborhood levels with CVD risk [body mass index (BMI), body fat percentage, systolic blood pressure, diastolic blood pressure, self-reported CVD and self-reported diabetes] were examined using multilevel logistic or linear models (n = 17,607), the mediating role of cortisol using the mediation analysis (n = 1,562), and associations of genetically predicted cortisol with CVD risk using the multiplicative generalized method of moments (MGMMs) or two-stage least squares regression (n = 1,562). In our cross-sectional observational analysis, relative household income deprivation (per 1 SD, equivalent to USD 128 difference in Yitzhaki index) was associated with higher systolic blood pressure (0.47 mmHg, 95% CI 0.30–0.64), but lower BMI (−0.07 kg/m², 95% CI −0.11 to −0.04), independent of absolute income. Neighborhood income inequality was generally unrelated to CVD and its risk factors, nor was absolute income at the household or neighborhood level. Cortisol did not clearly mediate the association of relative household income deprivation with systolic blood pressure. Using MR, cortisol was unrelated to CVD risk. Based on our findings, relative household income deprivation was not consistently associated with cardiovascular health in Hong Kong Chinese, nor were neighborhood income inequality and absolute income, highlighting the context-specific ways in which relative and absolute income are linked to CVD risk.

Development and validation of the EHS-COPD model to predict sex-specific risk of chronic obstructive pulmonary disease (COPD) in older Chinese adults: Hong Kong’s Elderly Health Service Cohort

Background

No screening program is recommended for chronic obstructive pulmonary disease (COPD) in adults based on current clinical practice guidelines. Risk prediction models for COPD developed in Western settings may not be directly applicable to older Chinese adults. To evaluate the performance of an existing risk prediction model for COPD developed in a Western setting in Chinese adults and investigate whether a new risk prediction model performs better in predicting 5-year risk of COPD (EHS-COPD).

Methods

This study is based on 135,822 participants aged 65+ years from Hong Kong’s Elderly Health Service (EHS) cohort. We assessed the performance of an existing risk prediction model in the entire cohort, and in a random sub-sample of 91,133 participants, we recalibrated the existing model and derived a new model using extended Cox proportional hazards regression. Candidate risk predictors from the literature and the EHS cohort were considered for inclusion. Risk prediction performance, discrimination, and calibration of the newly derived models were assessed in the remaining 44,689 participants.

Results

The existing risk prediction model overestimated the 5-year risk of COPD in older Chinese adults (65+ years); after recalibration, it still overestimated the 5-year risk of COPD for both men and women. The new EHS-COPD risk prediction model, including time-varying factors (i.e., age and smoking status) and time-invariant factors (i.e., education level, public assistance, alcohol use, body mass index, physical activity, existing hypertension, recent falls, cognitive function, and self-rated health status), had an improved performance. For men, EHS-COPD explained 19.5% of COPD risk, the D statistic was 23.1, and Harrell’s C statistic was 0.93. The corresponding values for women were 8.5%, 21.1, and 0.93.

Conclusions

The existing COPD risk prediction model overpredicted COPD risk in older Chinese and could not be recalibrated to predict well. A revised prediction model using time-invariant and time-varying factors provides a better tool for identifying older Chinese adults at high risk of developing COPD.

Timing of Pubertal Development and Midlife Blood Pressure in Men and Women: A Mendelian Randomization Study

INTRODUCTION

Observational studies suggest earlier puberty is associated with higher adulthood blood pressure (BP), but these findings have not been replicated using Mendelian randomization (MR). We examined this question sex-specifically using larger genome-wide association studies (GWAS) with more extensive measures of pubertal timing.

METHODS

We obtained genetic instruments proxying pubertal maturation (age at menarche [AAM] or voice breaking [AVB]) from the largest published GWAS. We applied them to summary sex-specific genetic associations with systolic and diastolic BP z-scores, and self-reported hypertension in women (n = 194 174) and men (n = 167 020) from the UK Biobank, using inverse-variance weighted meta-analysis. We conducted sensitivity analyses using other MR methods, including multivariable MR adjusted for childhood obesity proxied by body mass index (BMI). We used late pubertal growth as a validation outcome.

RESULTS

AAM (beta per 1-year later = -0.030 [95% confidence interval, -0.055 to -0.005] and AVB (beta -0.058 [95% CI, -0.100 to -0.015]) were inversely associated with systolic BP independent of childhood BMI, as were diastolic BP (-0.035 [95% CI, -0.060 to -0.009] for AAM and -0.046 [95% CI, -0.089 to -0.004] for AVB) and self-reported hypertension (odds ratio 0.89 [95% CI, 0.84-0.95] for AAM and 0.87 [95% CI, 0.79-0.96] for AVB). AAM and AVB were positively associated with late pubertal growth, as expected. The results were robust to sensitivity analysis using other MR methods.

CONCLUSION

Timing of pubertal maturation was associated with adulthood BP independent of childhood BMI, highlighting the role of pubertal maturation timing in midlife BP.

Maternal respiratory health and intrauterine exposure-driven birthweight: a two-sample Mendelian randomization study

BACKGROUND

Observationally, poorer maternal respiratory health is associated with poorer birth outcomes, possibly confounded by socioeconomic position and other maternal attributes. We used multivariable Mendelian randomization (MR) to obtain unconfounded estimates of effect of maternal lung function on birthweight, independent of maternal height.

METHODS

Single nucleotide polymorphisms (SNPs) for forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) in women were obtained from publicly available summary statistics from the UK Biobank. SNPs for asthma were obtained from the Trans-National Asthma Genetic consortium. SNPs for height in women were obtained from the Genetic Investigation of Anthropometric Traits consortium and the genetic estimates were obtained the UK Biobank. The genetic associations with maternally-driven birthweight were obtained from the Early Growth Genetics consortium. Multivariable MR estimates were obtained using inverse variance weighting with multivariable MR-Egger as sensitivity analysis.

RESULTS

Maternal lung capacity, as indicated by FVC, was positively associated with maternally-driven birthweight (0.08 per standard deviation, 95% confidence interval 0.01 to 0.15) independent of maternal height, whereas no clear such associations were shown for maternal airway function, indicated by FEV1 and peak expiratory flow, or for asthma, on maternally-driven birthweight. Similar findings were shown using MR-Egger.

CONCLUSIONS

These findings suggest that maternal lung function, especially lung capacity independent of maternal height, is directly associated with maternally-driven birthweight, and highlights the importance of maternal respiratory health in fetal growth.

Blood pressure and risk of cancer: a Mendelian randomization study

Background

Previous large observational cohort studies showed higher blood pressure (BP) positively associated with cancer. We used Mendelian randomization (MR) to obtain less confounded estimates of BP on total and site-specific cancers.

Methods

We applied replicated genetic instruments for systolic and diastolic BP to summary genetic associations with total cancer (37387 cases, 367856 non-cases) from the UK Biobank, and 17 site-specific cancers (663–17881 cases) from a meta-analysis of the UK Biobank and the Kaiser Permanente Genetic Epidemiology Research on Adult Health and Aging. We used inverse-variance weighting with multiplicative random effects as the main analysis, and sensitivity analyses including the weighted median, MR-Egger and multivariable MR adjusted for body mass index and for smoking. For validation, we included breast (Breast Cancer Association Consortium: 133384 cases, 113789 non-cases), prostate (Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome Consortium: 79194 cases, 61112 non-cases) and lung (International Lung and Cancer Consortium: 10246 cases, 38295 non-cases) cancer from large consortia. We used asthma as a negative control outcome.

Results

Systolic and diastolic BP were unrelated to total cancer (OR 0.98 per standard deviation higher [95% confidence interval (CI) 0.89, 1.07] and OR 1.00 [95% CI 0.92, 1.08]) and to site-specific cancers after accounting for multiple testing, with consistent findings from consortia. BP was nominally associated with melanoma and possibly kidney cancer, and as expected, not associated with asthma. Sensitivity analyses using other MR methods gave similar results.

Conclusions

In contrast to previous observational evidence, BP does not appear to be a risk factor for cancer, although an effect on melanoma and kidney cancer cannot be excluded. Other targets for cancer prevention might be more relevant.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-09067-x.

Credible Mendelian Randomization Studies in the Presence of Selection Bias Using Control Exposures

Selection bias is increasingly acknowledged as a limitation of Mendelian randomization (MR). However, few methods exist to assess this issue. We focus on two plausible causal structures relevant to MR studies and illustrate the data-generating process underlying selection bias via simulation studies. We conceptualize the use of control exposures to validate MR estimates derived from selected samples by detecting potential selection bias and reproducing the exposure-outcome association of primary interest based on subject matter knowledge. We discuss the criteria for choosing the control exposures. We apply the proposal in an MR study investigating the potential effect of higher transferrin with stroke (including ischemic and cardioembolic stroke) using transferrin saturation and iron status as control exposures. Theoretically, selection bias affects associations of genetic instruments with the outcome in selected samples, violating the exclusion-restriction assumption and distorting MR estimates. Our applied example showing inconsistent effects of genetically predicted higher transferrin and higher transferrin saturation on stroke suggests the potential selection bias. Furthermore, the expected associations of genetically predicted higher iron status on stroke and longevity indicate no systematic selection bias. The routine use of control exposures in MR studies provides a valuable tool to validate estimated causal effects. Like the applied example, an antagonist, decoy, or exposure with similar biological activity as the exposure of primary interest, which has the same potential selection bias sources as the exposure-outcome association, is suggested as the control exposure. An additional or a validated control exposure with a well-established association with the outcome is also recommended to explore possible systematic selection bias.

The total and direct effects of systolic and diastolic blood pressure on cardiovascular disease and longevity using Mendelian randomisation

The 2017 American College of Cardiology/American Heart Association (ACC/AHA) blood pressure (BP) guidelines lowered the hypertension threshold to ≥ 130/80 mmHg, but the role of diastolic BP remains contested. This two-sample mendelian randomisation study used replicated genetic variants predicting systolic and diastolic BP applied to the UK Biobank and large genetic consortia, including of cardiovascular diseases and parental lifespan, to obtain total and direct effects. Systolic and diastolic BP had positive total effects on CVD (odds ratio (OR) per standard deviation 2.15, 95% confidence interval (CI) 1.95, 2.37 and OR 1.91, 95% CI 1.73, 2.11, respectively). Direct effects were similar for systolic BP (OR 1.83, 95% CI 1.48, 2.25) but completely attenuated for diastolic BP (1.18, 95% CI 0.97, 1.44), although diastolic BP was associated with coronary artery disease (OR 1.24, 95% CI 1.03, 1.50). Systolic and diastolic BP had similarly negative total (- 0.20 parental attained age z-score, 95% CI - 0.22, - 0.17 and - 0.17, 95% CI - 0.20, - 0.15, respectively) and direct negative effects on longevity. Our findings suggest systolic BP has larger direct effects than diastolic BP on CVD, but both have negative effects (total and direct) on longevity, supporting the 2017 ACC/AHA guidelines lowering both BP targets.

Mendelian randomization study on atrial fibrillation and cardiovascular disease subtypes

Atrial fibrillation (AF) has been associated with numerous diseases. However, whether AF is a cause or consequence of these diseases is uncertain. To clarify, we assessed the causal role of AF on ischemic heart disease (IHD), stroke, other cardiovascular disease (CVD) subtypes, type 2 diabetes mellitus (T2DM), and late-onset AD using bi-directional two-sample Mendelian randomization (MR) among people primarily of European descent. Genetically predicted log odds of AF was associated with any stroke (odds ratio (OR) 1.22, 95% CI 1.18 to 1.27), particularly cardioembolic stroke and possibly subdural hemorrhage, with sensitivity analyses showing similar positive findings. Genetically predicted AF was also associated with arterial thromboembolism (1.32, 1.13 to 1.53), and heart failure (1.26, 1.21 to 1.30). No association of genetically predicted AF with IHD, T2DM, cognitive function, or late-onset AD was found. Conversely, genetically predicted IHD, heart failure and possibly ischemic stroke, particularly cardioembolic stroke, were positively associated with AF. Atrial fibrillation plays a role in any stroke, arterial thromboembolism, and heart failure, corroborating current clinical guidelines on the importance of preventing these complications by effective AF management. In addition, patients with IHD, heart failure or possibly ischemic stroke might be predisposed to developing AF, with implications for management.

Mendelian randomization study of interleukin (IL)-1 family and lung cancer

The role of interleukin (IL)-1 family members/receptors in lung cancer remains uncertain due to the susceptibility of observed associations to confounding. We appraised the association of IL-1 family members/receptors with lung cancer and its subtypes [lung adenocarcinoma (LUAD) and squamous cell lung cancer (LUSC)] using two-sample Mendelian randomization. This study found that no IL-1 family members/receptors were significantly associated with lung cancer and its subtypes risk after correction for multiple testing. However, suggestive total effects of increased risk were noted for genetically predicted IL-1Racp with lung cancer (P = 0.006), IL-1α with LUAD (P = 0.027), and IL-1Racp with LUSC (P = 0.008). Suggestive direct effects were also noted for IL-1β, IL-1Ra, IL-36γ with lung cancer, IL-1α/β, IL-1Ra with LUAD, and IL-1β, IL-18BP with LUSC, after adjusting for genetically predicted effects of other IL-1 family members/receptors. Taken together, our findings suggest that interventions decreasing IL-1Racp might protect against lung cancer, perhaps via IL-1α/β or IL-1Ra.

Genetic Evidence on the Association of Interleukin (IL)-1-Mediated Chronic Inflammation with Airflow Obstruction: A Mendelian Randomization Study

Preclinical studies suggest interleukin (IL)-1α/β is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, recent trials of anti-IL-1 therapies showed limited benefit for COPD. To clarify, we primarily examined total and direct effects of IL-1 and its receptors/coreceptors/receptor antagonists (IL-1/IL-1Rs) on airflow obstruction (AO) using Mendelian randomization (MR), and secondarily explored reverse causation using bidirectional MR. We selected independent cis protein quantitative trait loci (cis-pQTLs) as genetic instruments for IL-1/IL-1Rs from two proteomic genome-wide association studies (n = 11,594) of European ancestry (mean age ∼47 years). We applied those cis-pQTLs to the International COPD Genetics Consortium (n = 15,256 cases, 47,936 controls) of ∼81.9% European descent (∼57 years). No IL-1/IL-1Rs were significantly associated with AO after correction for multiple testing. However, a higher genetically predicted IL-1 receptor antagonist (IL-1Ra) was nominally associated with a 20% reduction in AO risk using univariable MR, with a larger direct effect (∼31%, i.e. not via IL-1α/β) using multivariable MR. Furthermore, higher total IL-18 binding protein (IL-18BP) was nominally associated with lower AO. Nominal total effects were also noted for higher IL-1α with lower AO and higher IL-1R1 with higher AO. Higher IL-1Ra and IL-18BP might have a role in preventing AO, but need to be contextualized.Supplemental data for this article is available online at https://doi.org/10.1080/15412555.2021.1955848 .

Blood Pressure and Risk of Cardiovascular Disease in UK Biobank: A Mendelian Randomization Study

This study aims to evaluate the causal association of blood pressure (BP) with cardiovascular diseases (CVDs). Two-sample Mendelian randomization was performed using a large genome-wide association study (n=299 024) and the UK Biobank cohort (n=375 256). We identified 327 and 364 single-nucleotide polymorphisms strongly and independently associated with systolic BP and diastolic BP, respectively, as genetic instruments to assess the causal association of BP with total CVD, CVD mortality, and 14 cardiovascular conditions. Nonlinearity was examined with nonlinear instrumental variable assumptions. Genetically predicted BP was significantly positively associated with total CVD (systolic BP, per 10 mm Hg: odds ratio [OR], 1.32 [95% CI, 1.25-1.40]; diastolic BP, per 5 mm Hg: OR, 1.20 [95% CI, 1.15-1.26]). Similar positive causal associations were observed for 14 cardiovascular conditions including ischemic heart disease (systolic BP, per 10 mm Hg: OR, 1.33 [95% CI, 1.24-1.41]; diastolic BP, per 5 mm Hg: OR, 1.20 [95% CI, 1.14-1.27]) and stroke (systolic BP, per 10 mm Hg: OR, 1.35 [95% CI, 1.24-1.48]; diastolic BP, per 5 mm Hg: OR, 1.20 [95% CI, 1.12-1.28]). Nonlinearity Mendelian randomization test demonstrated linear causal association of BP with these outcomes. Consistent estimates were observed in sensitivity analyses, suggesting robustness of the associations and minimal horizontal pleiotropy. The linear positive causal association of BP and CVD was consistent with previous findings that lower BP is better, thus consolidating clinical knowledge on hypertension management in CVD risk reduction.

The role of cortisol in ischemic heart disease, ischemic stroke, type 2 diabetes, and cardiovascular disease risk factors: a bi-directional Mendelian randomization study

BACKGROUND

Cortisol, a steroid hormone frequently used as a biomarker of stress, is associated with cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). To clarify whether cortisol causes these outcomes, we assessed the role of cortisol in ischemic heart disease (IHD), ischemic stroke, T2DM, and CVD risk factors using a bi-directional Mendelian randomization (MR) study.

METHODS

Single nucleotide polymorphisms (SNPs) strongly (P < 5 × 10-6) and independently (r2 < 0.001) predicting cortisol were obtained from the CORtisol NETwork (CORNET) consortium (n = 12,597) and two metabolomics genome-wide association studies (GWAS) (n = 7824 and n = 2049). They were applied to GWAS of the primary outcomes (IHD, ischemic stroke and T2DM) and secondary outcomes (adiposity, glycemic traits, blood pressure and lipids) to obtain estimates using inverse variance weighting, with weighted median, MR-Egger, and MR-PRESSO as sensitivity analyses. Conversely, SNPs predicting IHD, ischemic stroke, and T2DM were applied to the cortisol GWAS.

RESULTS

Genetically predicted cortisol (based on 6 SNPs from CORNET; F-statistic = 28.3) was not associated with IHD (odds ratio (OR) 0.98 per 1 unit increase in log-transformed cortisol, 95% confidence interval (CI) 0.93-1.03), ischemic stroke (0.99, 95% CI 0.91-1.08), T2DM (1.00, 95% CI 0.96-1.04), or CVD risk factors. Genetically predicted IHD, ischemic stroke, and T2DM were not associated with cortisol.

CONCLUSIONS

Contrary to observational studies, genetically predicted cortisol was unrelated to IHD, ischemic stroke, T2DM, or CVD risk factors, or vice versa. Our MR results find no evidence that cortisol plays a role in cardiovascular risk, casting doubts on the cortisol-related pathway, although replication is warranted.

Herpes simplex virus and Alzheimer's disease: a Mendelian randomization study

This study assessed if any herpes simplex virus (HSV) infection was a genetically valid target for late-onset Alzheimer's disease (AD) using 2-sample Mendelian randomization. We applied strong (p-value <5×10^-6) and independent (r² < 0.05) genetic variants for any HSV infection (n = 450,581) to genome wide association studies of cognitive function (n = 300,486), and late-onset AD (n = 455,258) to obtain estimates. Genetically predicted log odds of any HSV infection was not associated with cognitive function (mean difference 0.0004 per any HSV infection, 95% confidence interval (CI) -0.001 to 0.001), or late-onset AD (odds ratio (OR) 0.999, 95% CI 0.998-1.001). Different genetic variant selections produced similar results. Any HSV infection does not appear to be a genetically valid target of intervention in late-onset AD, suggesting a rethink of the relevance of any HSV infection to late-onset AD.

Associations of growth from birth to puberty with blood pressure and lipid profile at ~17.5 years: evidence from Hong Kong's "Children of 1997" birth cohort

The role of early growth in later health is controversial. We examined the associations of growth at different phases from birth to puberty with blood pressure and lipid profile at ~17.5 years. In the population-representative "Children of 1997" birth cohort, growth was measured as (i) weight-for-age z score (WAZ) at birth and WAZ gains from 0 to 2 and 2 to 8 years and (ii) body-mass-index-for-age z score (BAZ) and length/height-for-age z score (LAZ) at 3 months and BAZ and LAZ gains from 3 months to 3 years, 3 to 8 years and 8 to 14 years, based on the World Health Organization growth standards/references. Adjusted partial least squares regression was used to assess simultaneously the associations of growth with height-, age- and sex-specific systolic (SBPZ) and diastolic blood pressure z scores (DBPZ), low- (LDL) and high-density lipoprotein (HDL) and triglycerides (TG) at ~17.5 years. Among 3410 children, higher WAZ, BAZ and LAZ gains from initial size to 8 years were associated with higher SBPZ. Higher gains in WAZ and BAZ from 2 to 8 years were consistently associated with higher DBPZ, LDL and TG and lower HDL. Lower LAZ at 3 months and higher LAZ gain from 3 months to 3 years were associated with lower HDL and higher TG. Greater growth in weight, body mass index and length/height had negative associations with blood pressure and lipid profile at ~17.5 years, but the differences by growth measure, phase and outcome suggest a complex underlying process.

The effect of sleep duration on hemoglobin and hematocrit: observational and Mendelian randomization study

STUDY OBJECTIVE

Observationally sleep duration is positively associated with hemoglobin (Hgb), whether this association is causal and consistent by sex remains unclear. Here, we assessed the association of sleep duration with Hgb and hematocrit (Hct) observationally in late adolescence in a population-representative Chinese birth cohort "Children of 1997" with validation using Mendelian randomization (MR) in adults.

METHODS

In the "Children of 1997" birth cohort (recruited = 8327, included = 3144), we used multivariable linear regression to assess the adjusted associations of sleep duration (measured as time in bed) with Hgb and Hct at 17.5 years and any sex differences. Using two-sample MR, we assessed the effect of sleep duration on Hgb and Hct, based on 61 single nucleotide polymorphisms (SNPs) applied to genome-wide association studies of Hgb and Hct in adults (n = 361 194).

RESULTS

Observationally, self-reported sleep duration was positively associated with Hct (0.034 standard deviations [SDs] per hour, 95% confidence interval [CI] 0.019 to 0.049), but not with Hgb. Using MR longer sleep increased Hct (0.077 SD per hour, 95% CI 0.035 to 0.119) and Hgb (0.065 SD per hour, 95% CI 0.020 to 0.109) using Mendelian randomization pleiotropy residual sum and outlier (MR PRESSO), with more pronounced associations in men.

CONCLUSIONS

Our novel findings indicate sleep increases both Hgb and Hct, particularly in men, perhaps contributing to its restorative qualities. Potential difference by sex and the implications of these findings warrant investigation.

Association of Sugar-Sweetened Beverage Frequency with Adiposity: Evidence from the "Children of 1997" Birth Cohort

Background: Observationally, sugar-sweetened beverage (SSB) consumption is associated with adiposity in Western children but could be confounded. We examined the association of SSB frequency with adiposity in the non-Western setting of Hong Kong. Methods: We examined the associations of SSB consumption frequency at 11 and 13 years assessed by using a food frequency questionnaire with subsequent body mass index (BMI) z-score and overweight/obesity up to 18 years using generalized estimating equations, and with waist circumference, waist-to-hip ratio, and body fat percentage at 16–19 years using linear regression in a population-representative Chinese birth cohort “Children of 1997” (n = 3628). Results: At 11 and 13 years, 6.8% and 8.2% of children respectively consumed SSB daily. Neither SSB frequency at 11 nor at 13 years was associated with subsequent BMI z-score or overweight/obesity up to 18 years, or with waist circumference, waist-to-hip ratio, or body fat percentage at 16–19 years adjusted for age, sex, socioeconomic position, health status, physical activity and other food consumption, although bias to the null from under-reporting cannot be eliminated. Conclusion: Although we cannot definitively exclude a small association of SSB frequency with adiposity, lack of association of SSB frequency with adiposity in a non-Western setting with low SSB consumption suggests that the role of SSB in adiposity appears to be minor.

Age of puberty and Sleep duration: Observational and Mendelian randomization study

Earlier age of puberty has detrimental consequences for many aspects of health. Here, for the first time, we assessed the association of earlier puberty with sleep duration observationally and with validation using Mendelian Randomization. In the “Children of 1997” birth cohort (n = 8,327), we used adjusted multivariable logistic regression to assess the associations of each clinically assessed marker of earlier puberty with self-report sleep duration in adolescence. Using two-sample MR, we assessed the effect of earlier puberty timing based on 203 single nucleotide polymorphisms applied to genome wide association studies of sleep duration in adults (n = 335,410). In “Children of 1997”, cross-sectionally, older age of menarche was associated with longer (9+ hours) sleep duration [odds ratio (OR) 1.11, 95% confidence interval (CI) 1.01 to 1.21] at 13.5 years. The other earlier puberty markers were unrelated to sleep duration. Using inverse variance weighting, later of age at menarche increased adult sleep duration [0.020 per category, 95% CI 0.006 to 0.034]. This study demonstrated a causal effect of age at menarche on adult sleep duration, since age of menarche also affects obesity, our novel finding may be relevant to the observed relation of sleep duration with obesity and poor health.

The effect of liver enzymes on body composition: A Mendelian randomization study

Background

Higher alanine transaminase (ALT), indicating poor liver function, is positively associated with diabetes but inversely associated with body mass index (BMI) in Mendelian randomization (MR) studies, suggesting liver function affects muscle mass. To clarify, we assessed the associations of liver enzymes with muscle and fat mass observationally with two-sample MR as a validation.

Methods

In the population-representative “Children of 1997” birth cohort (n = 3,455), we used multivariable linear regression to assess the adjusted associations of ALT and alkaline phosphatase (ALP) at ~17.5 years with muscle mass and body fat percentage observationally. Genetic variants predicting ALT, ALP and gamma glutamyltransferase (GGT) were applied to fat-free and fat mass in the UK Biobank (n = ~331,000) to obtain unconfounded MR estimates.

Results

Observationally, ALT was positively associated with muscle mass (0.11 kg per IU/L, 95% confidence interval (CI) 0.10 to 0.12) and fat percentage (0.15% per IU/L, 95% CI 0.13 to 0.17). ALP was inversely associated with muscle mass (-0.03 kg per IU/L, 95% CI -0.04 to -0.02) and fat percentage (-0.02% per IU/L, 95% CI -0.03 to -0.01). Using MR, ALT was inversely associated with fat-free mass (-0.41 kg per 100% in concentration, 95% CI -0.64 to -0.19) and fat mass (-0.58 kg per 100% in concentration, 95% CI -0.85 to -0.30). ALP and GGT were unclearly associated with fat-free mass or fat mass.

Conclusion

ALT reducing fat-free mass provides a possible pathway for the positive association of ALT with diabetes and suggests a potential target of intervention.

Age-period-cohort projection of trends in blood pressure and body mass index in children and adolescents in Hong Kong

Background

Blood pressure (BP) and body mass index (BMI) trends during childhood and adolescence are complex, making context-specific projections necessary to inform prevention and presage changes.

Objective

This study aimed to project BP and BMI in Hong Kong Chinese children and adolescents from 2015 to 2024 based on trends in BP and BMI observed from 1996/99 to 2014.

Methods

We decomposed recent trends into sex-specific contributions of age, period and cohort using age-period-cohort linear regression with Bayesian inference and autoregressive priors based on BP in children and adolescents aged 9–18 years from 1999 to 2014 and BMI in those aged 6–18 years from 1996 to 2014. We then used the resultant models to project BP and BMI from 2015 to 2024.

Results

During the study period, systolic BP decreased from 1999 to 2004/5 before gradually increasing to 2014 during childhood (for boys: from 104.6 to 101.9 and then to 103.4 mmHg) and during adolescence. Similar patterns were observed for diastolic BP. BMI generally increased from 1996 to 2009 before falling to 2014 during childhood (e.g. for boys: from 17.2 to 18.0 and then to 17.1 kg/m²). From 2015 onwards, systolic BP was projected to increase in girls, but remain stable in boys. For both sexes, diastolic BP was projected to increase, whereas BMI was projected to decrease to 2024.

Conclusions

In this economically developed Chinese setting, future trends in BP and BMI in children and adolescents are predicted to be divergent, consistent with prior discordant trends in BP and BMI.

The effect of birth weight on body composition: Evidence from a birth cohort and a Mendelian randomization study

BACKGROUND

Lower birth weight is associated with diabetes although the underlying mechanisms are unclear. Muscle mass could be a modifiable link and hence a target of intervention. We assessed the associations of birth weight with muscle and fat mass observationally in a population with little socio-economic patterning of birth weight and using Mendelian randomization (MR) for validation.

METHODS

In the population-representative "Children of 1997" birth cohort (n = 8,327), we used multivariable linear regression to assess the adjusted associations of birth weight (kg) with muscle mass (kg) and body fat (%) at ~17.5 years. Genetically predicted birth weight (effect size) was applied to summary genetic associations with fat-free mass and fat mass (kg) from the UK Biobank (n = ~331,000) to obtain unconfounded estimates using inverse-variance weighting.

RESULTS

Observationally, birth weight was positively associated with muscle mass (3.29 kg per kg birth weight, 95% confidence interval (CI) 2.83 to 3.75) and body fat (1.09% per kg birth weight, 95% CI 0.54 to 1.65). Stronger associations with muscle mass were observed in boys than in girls (p for interaction 0.004). Using MR, birth weight was positively associated with fat-free mass (0.77 kg per birth weight z-score, 95% CI 0.22 to 1.33) and fat mass (0.58, 95% CI 0.01 to 1.15). No difference by sex was evident.

CONCLUSION

Higher birth weight increasing muscle mass may be relevant to lower birth weight increasing the risk of diabetes and suggests post-natal muscle mass as a potential target of intervention.

Indoleamine 2,3-dioxygenase and ischemic heart disease: a Mendelian Randomization study

Tryptophan is an essential amino acid. Indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme in the tryptophan-kynurenine pathway, is positively associated with cardiac events, and may be relevant to cancer. We used Mendelian Randomization to obtain unconfounded estimates of the association of IDO1 with ischemic heart disease (IHD), ischemic stroke and their risk factors, all-cancer, cancer of the prostate, lung and bronchus, and breast. We obtained genetic instruments independently and strongly (p-value < 5 × 10-8) predicting plasma IDO1 from a proteome genome-wide association study (GWAS), and applied them to consortia GWAS of the outcomes, including the UK Biobank SOFT CAD GWAS (cases < = 76 014, non-cases < = 264 785) for IHD. Estimates were obtained using inverse variance weighting; with MR-Egger, weighted median and MR-PRESSO as sensitivity analyses. IDO1 was inversely associated with IHD (odds ratio (OR) 0.96 per standard deviation, 95% confidence interval (CI) 0.93 to 1.00, p-value = 0.04), diabetes (OR 0.91, 95% CI 0.85 to 0.97) and prostate cancer (OR 0.96, 95% CI 0.93 to 0.99) with a directionally consistent estimate for stroke (OR 0.98, 95% CI 0.95 to 1.02) but not with blood pressure, or the other cancers considered. IDO1 might be a potential therapeutic target for IHD, diabetes and prostate cancer.

Associations of growth from birth to puberty with glycemic indicators at ~17.5 years: Evidence from Hong Kong's "Children of 1997" birth cohort

BACKGROUND

From an evolutionary biology perspective, where growth and reproduction trade-off against longevity, we assessed the associations of growth from birth to puberty by phase with later glycemic indicators and any differences by sex.

METHODS

In the population-representative Hong Kong Chinese "Children of 1997" birth cohort (n = 8327), the relation of initial size (weight-for-age z score (WAZ) at birth, length/height-for-age z score (LAZ) at 3 months or body-mass-index-for-age z score (BAZ) at 3 months based on the World Health Organization growth standards/references) and growth at different phases (WAZ gains from 0 to 2 and 2 to 8 years, LAZ or BAZ gains from 3 months to 3 years, 3 to 8 years and 8 to 14 years) with fasting plasma glucose (FPG) and glycated hemoglobin (HbA1c) at ~17.5 years, was assessed using adjusted partial least squares regression. Additional analyses further considered growth in late and early infancy.

RESULTS

This study included 3276 of the cohort participants. Higher WAZ gain from 2 to 8 years, LAZ and BAZ gains from 3 to 8 years were consistently associated with higher FPG, adjusted for maternal and infant characteristics, family history of diabetes and household income. Also, higher BAZ gain from 3 to 8 years was associated with higher HbA1c. These associations did not differ by sex.

CONCLUSIONS

Our findings suggest different mechanisms could underlie the pathogenesis of glucose intolerance. Factors that drive specific growth at different phases need to be evaluated to better inform child growth management for long-term health outcomes.

Breastfeeding in Infancy and Lipid Profile in Adolescence

OBJECTIVES

Breast milk has higher cholesterol than formula. Infants who are breastfed have different cholesterol synthesis and metabolism in infancy than infants who are formula fed. Little is known as to whether breastfeeding is associated with subsequent lipid profile, independent of adiposity. We assessed the association of breastfeeding in early infancy with lipid profile and adiposity at ∼17.5 years in a setting where exclusive breastfeeding is not associated with higher socioeconomic position.

METHODS

We used multivariable linear regression with multiple imputation and inverse probability weighting to examine the associations of contemporaneously reported feeding in the first 3 months of life (exclusive breastfeeding [7.5%], mixed feeding [40%], or always formula feeding [52%]) with lipids and adiposity at ∼17.5 years in 3261 participants in the Hong Kong Chinese birth cohort Children of 1997, adjusting for sex, birth weight, gestational weeks, parity, pregnancy characteristics, parents' highest education, mother's place of birth, and age at follow-up.

RESULTS

Exclusive breastfeeding, but not mixed feeding at 0 to 3 months, compared with formula feeding was associated with lower total cholesterol and low-density lipoprotein cholesterol but not with high-density lipoprotein cholesterol at ∼17.5 years. BMI and fat percentage measured by bioimpedance did not differ by type of infant feeding.

CONCLUSIONS

Exclusive breastfeeding in early infancy may promote a healthier lipid profile in late adolescence through mechanisms unrelated to adiposity, implicating its potential long-term benefits for cardiovascular health.

Effect of glutamate and aspartate on ischemic heart disease, blood pressure, and diabetes: a Mendelian randomization study

BACKGROUND

Evolutionary biology suggests reproduction trades off against longevity. Genetic selection in favor of fertility and ischemic heart disease (IHD) exists in humans. Observationally, soy protects against IHD. Soy amino acids, glutamate and aspartate, may lower androgens. No large randomized controlled trials testing their health effects exist.

OBJECTIVE

Using Mendelian randomization, we assessed how genetically predicted glutamate and aspartate affected IHD, blood pressure, and diabetes.

METHODS

A separate sample instrumental variable analysis with genetic instruments was used to obtain unconfounded estimates using genetic variants strongly (P < 5 × 10(-8)) and solely associated with glutamate or aspartate applied to an IHD case (n ≤76,014)-control (n ≤ 264,785) study (based on a meta-analysis of CARDIoGRAMplusC4D 1000 Genomes, UK Biobank CAD SOFT GWAS and Myocardial Infarction Genetics and CARDIoGRAM Exome), blood pressure from the UK Biobank (n ≤ 361,194), and the DIAbetes Genetics Replication And Meta-analysis diabetes case (n = 26,676)-control (n = 132,532) study. A weighted median and MR-Egger were used for a sensitivity analysis.

RESULTS

Glutamate was not associated with IHD, blood pressure, or diabetes after correction for multiple comparisons. Aspartate was inversely associated with IHD (odds ratio (OR) 0.92 per log-transformed standard deviation (SD); 95% confidence interval (CI) 0.88, 0.96) and diastolic blood pressure (-0.03; 95% CI -0.04, -0.02) using inverse variance weighting, but not diabetes (OR 1.00; 95% CI 0.91, 1.09). Associations were robust to the sensitivity analysis.

CONCLUSIONS

Our findings suggest aspartate may play a role in IHD and blood pressure, potentially underlying cardiovascular benefits of soy. Clarifying the mechanisms would be valuable for IHD prevention and for defining a healthy diet.

Sleep duration and risk of diabetes: Observational and Mendelian randomization studies

Inadequate sleep could contribute to type 2 diabetes, but observational studies are inconsistent and open to biases, particularly from confounding. We used Mendelian randomization (MR) to obtain an unconfounded estimate of the effect of sleep duration on diabetes, fasting glucose (FG) and hemoglobin A1c (HbA1c), and an observation study to assess differences by sex. Using MR, we assessed the effects of genetically instrumented sleep on diabetes, based on 68 single nucleotide polymorphisms (SNPs), applied to the DIAbetes Genetics Replication and meta-analysis case (n = 26,676)-control (n = 132,532) study and on FG and HbA1c, based on 55 SNPs, applied to the Meta-Analyses of Glucose and Insulin-related traits Consortium (MAGIC) study of FG (n = 122,743) and HbA1c (n = 123,665). In the population-representative Hong Kong Chinese "Children of 1997" birth cohort we assessed whether associations of sleep duration at ~17.5 years with FG and HbA1c differed by sex. Using inverse variance weighting with multiplicative random effects, sleep duration was not associated with diabetes (odds ratio (OR) 0.85 per hour of sleep, 95% confidence interval (CI) 0.64 to 1.13), FG (-0.032 mmol/l per hour of sleep, 95% CI -0.126 to 0.063) or HbA1c (-0.022% per hour of sleep, 95% CI -0.069 to 0.024). In "Children of 1997", the associations of sleep duration with FG differed by sex (p for interaction 0.05) but not with HbA1c. Overall sleep duration does not appear to be related to diabetes, FG or HbA1c, but the possibility of sex differences merits investigation.

The association of early-life exposure to air pollution with lung function at ~17.5 years in the "Children of 1997" Hong Kong Chinese Birth Cohort

BACKGROUND

Early-life air pollution exposure is associated with lung function in children and adolescents. However, whether the association of prenatal and early postnatal exposure to air pollution with lung function continues into adulthood remains unclear.

OBJECTIVE

To investigate the associations of early exposure to air pollution with lung function at ~17.5 years in a non-western developed setting with more concentrated air pollutants.

METHODS

We examined the associations of exposure to particular matter with an aerodynamic diameter of <10 μm (PM₁₀), nitrogen dioxides (NO₂), nitric oxide (NO), sulfur dioxide (SO₂) in standard deviations (SD)) at different early life stages with lung function (indicated by forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁) and forced expiratory flow at 25%-75% of the pulmonary volume (FEF_25%-75%)) in SD at ~17.5 years, personal history of wheezing and asthma in the population-representative Hong Kong Chinese birth cohort "Children of 1997"(n = 2942).

RESULTS

Higher in utero and infancy and toddlerhood NO₂ were associated with lower FEV₁ (-0.022, 95% confidence interval (CI) -0.029 to -0.015 and - 0.026, 95% CI -0.033 to -0.019), FEV₁/FVC (-0.035, 95% CI -0.050 to -0.021 and -0.052, 95% CI -0.066 to -0.038) and FEF_25%-75% (-0.031, 95% CI -0.040 to -0.022 and -0.043, 95% CI -0.051 to -0.035). A similar association was observed for NO. Weak associations of NO₂ and NO with FVC were observed (-0.011, 95% CI -0.018 to -0.003 and -0.010, 95% CI -0.020 to -0.001). NO_x was associated with higher risk of wheezing (1.08, 95% CI 1.03 to 1.14) but not asthma (1.02, 95% CI 0.94 to 1.11). SO₂ and PM₁₀ were not clearly associated with lung function, wheezing or asthma.

CONCLUSION

Our findings suggest that early exposure to air pollution from NO₂ may have long-term effects on lung function, which could affect respiratory health throughout life.

Glucose-6-phosphate dehydrogenase deficiency and metabolic profiling in adolescence from the Chinese birth cohort: "Children of 1997"

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency affects 6.0% of the global population. G6PD deficiency has been associated with lower risk of cardiovascular disease and higher risk of diabetes, which could be etiologically informative, but these relations are uncertain. To clarify, we assessed the associations of G6PD deficiency with serum metabolite profiles in late adolescence.

METHODS

In a nested case-control study of 50 G6PD-deficient late adolescents (~17.5 years) and 150 sex-matched non-G6PD-deficient controls from a Chinese birth cohort: "Children of 1997", we compared 80 serum metabolites analyzed by nuclear magnetic resonance spectrometry using adjusted linear regression with Bonferroni correction for testing 12 traits (p < 0.0042).

RESULTS

G6PD-deficiency was inversely associated with serum levels of total cholesterol (-0.27 mmol, 95% confidence interval (CI) -0.46, -0.09, p = 0.004), free cholesterol (-0.08 mmol, 95% CI -0.13, -0.03, p = 0.003) and creatinine (-0.004 mmol, 95% CI -0.007, -0.001, p = 0.003), adjusted for sex and parental education. G6PD deficiency was not associated with fatty acids, amino acids, glucose or related metabolites, ketone bodies or glycoprotein.

CONCLUSIONS

G6PD deficiency is associated with lower serum levels of cholesterol and creatinine, but not other serum metabolites. Whether such differences are transient or become more evident in adulthood warrant further investigations.

Re-thinking Alzheimer's disease therapeutic targets using gene-based tests

Background

Alzheimer's disease (AD) is a devastating condition with no known effective drug treatments. Existing drugs only alleviate symptoms. Given repeated expensive drug failures, we assessed systematically whether approved and investigational AD drugs are targeting products of genes strongly associated with AD and whether these genes are targeted by existing drugs for other indications which could be re-purposed.

Methods

We identified genes strongly associated with late-onset AD from the loci of genetic variants associated with AD at genome-wide-significance and from a gene-based test applied to the most extensively genotyped late-onset AD case (n = 17,008)-control (n = 37,154) study, the International Genomics of Alzheimer's Project. We used three gene-to-drug cross-references, Kyoto Encyclopedia of Genes and Genomes, Drugbank and Drug Repurposing Hub, to identify genetically validated targets of AD drugs and any existing drugs or nutraceuticals targeting products of the genes strongly associated with late-onset AD.

Findings

A total of 67 autosomal genes (forming 9 gene clusters) were identified as strongly associated with late-onset AD, 28 from the loci of single genetic variants, 51 from the gene-based test and 12 by both methods. Existing approved or investigational AD drugs did not target products of any of these 67 genes. Drugs for other indications targeted 11 of these genes, including immunosuppressive disease-modifying anti-rheumatic drugs targeting PTK2B gene products.

Interpretation

Approved and investigational AD drugs are not targeting products of genes strongly associated with late-onset AD. However, other drugs targeting products of these genes exist and could perhaps be re-purposing to combat late-onset AD after further scrutiny.

The Roles of 27 Genera of Human Gut Microbiota in Ischemic Heart Disease, Type 2 Diabetes Mellitus, and Their Risk Factors: A Mendelian Randomization Study

Manipulation of the gut microbiota presents a new opportunity to combat chronic diseases. Randomized controlled trials of probiotics suggest some associations with adiposity, lipids, and insulin resistance, but to our knowledge no trials with "hard" outcomes have been conducted. We used separate-sample Mendelian randomization to obtain estimates of the associations of 27 genera of gut microbiota with ischemic heart disease, type 2 diabetes mellitus, adiposity, lipid levels, and insulin resistance, based on summary data from CARDIoGRAAMplusC4D and other consortia. Among the 27 genera, a 1-allele increase in single nucleotide polymorphisms related to greater abundance of Bifidobacterium was associated with lower risk of ischemic heart disease (odds ratio = 0.985, 95% confidence interval (CI): 0.971, 1.000; P = 0.04), a 0.011-standard-deviation lower body mass index (95% CI: -0.017, -0.005), and a 0.026-standard-deviation higher low-density lipoprotein cholesterol level (95% CI: 0.019, 0.033), but the findings were not robust to exclusion of potential pleiotropy. We also identified Acidaminococcus, Aggregatibacter, Anaerostipes, Blautia, Desulfovibrio, Dorea, and Faecalibacterium as being nominally associated with type 2 diabetes mellitus or other risk factors. Results from our study indicate that these 8 genera of gut microbiota should be given priority in future research relating the gut microbiome to ischemic heart disease and its risk factors.

Birth weight, gestational age and late adolescent liver function using twin status as instrumental variable in a Hong Kong Chinese birth cohort: "Children of 1997"

Birth weight (BW) is inversely associated with diabetes and liver function in Mendelian Randomization studies. Observationally, lower BW is usually also associated with poorer liver function. However, these studies could be confounded by socioeconomic position. Here we assessed if BW is associated with liver function in a unique population with little socio-economic patterning of BW, using both instrumental variable and an observational analysis. We used instrumental variable analysis (IVA) to assess the association of BW with liver function (alanine transaminase (ALT), alkaline phosphatase (ALP), bilirubin, and albumin) at ~17 years with twin status as an instrumental variable in the prospective population-representative "Children of 1997" birth cohort (n = 8327). We also conducted an observational analysis adjusted for sex, maternal age, maternal migrant status, smoking and parental socio-economic position. A generalized linear model with gamma family was used for ALT, ALP, and bilirubin because they are not normally distributed. Using IVA, BW was not associated with ALT, ALP or bilirubin, but was possibly negatively associated with albumin (-1.12 g/L, 95% confidence interval (CI) -2.08 to -0.16). Observationally, BW was negatively associated with ALT (-1.23 IU/L, 95% CI -2.16 to -0.30), ALP (-1.72 IU/L, 95% CI -3.43 to -0.01) and higher albumin (-0.23 g/L, 95% CI -0.40 to -0.06). Poor liver function may be a pathway by which the risks of lower BW are actuated. This insight might help identify post-natal targets of intervention to mitigate the adverse health effects of lower birth weight.

The Associations of Breast Feeding with Infant Growth and Body Mass Index to 16 years: 'Children of 1997'

BACKGROUND

Controversial findings concerning associations of breast feeding with growth have been reported. This study examined whether the associations of breast feeding with early growth trajectories and body mass index to 16 years differed by sex or age.

METHODS

In Hong Kong's 'Children of 1997' population-representative birth cohort, contemporaneously reported breast-feeding status in the first 3 months was classified as exclusive breast feeding (BF) (n = 470), mixed feeding (MF) (n = 2693), and formula feeding (FF) (n = 4204). Adjusted sex- and age-specific associations of breast feeding with infant growth (gains in weight-for-age z scores (WAZ), length/height-for-age z scores (LAZ), and body-mass-index-for-age z score (BAZ) based on the World Health Organization standards/references from birth to 36 months) were assessed using linear regression and mixed modelling, respectively. Adjusted sex-specific associations of breast feeding with average BAZ from 3 months to 16 years were assessed using generalized estimating equation. Potential confounders were maternal and infant characteristics, and household income.

RESULTS

Among 7367 children, associations of breast feeding with infant growth did not vary by sex, but WAZ gains varied by age. Greater WAZ gains were observed in BF than FF infants from 0 to 3 months but in FF than BF infants from 3 to 9 months. Breast feeding was not associated with overall BAZ from 3 months to 16 years, with no differences by sex.

CONCLUSIONS

Our findings suggest that breast feeding may only have short-term effects on growth. Further studies of the role of breast feeding in other metabolic diseases may be needed.

Disconnect Between Genes Associated With Ischemic Heart Disease and Targets of Ischemic Heart Disease Treatments

Background

Development of pharmacological treatments to mitigate ischemic heart disease (IHD) has encompassed disappointing results and expensive failures, which has discouraged investment in new approaches to prevention and control. New treatments are most likely to be successful if they act on genetically validated targets. We assessed whether existing pharmacological treatments for IHD reduction are acting on genetically validated targets and whether all such targets for IHD are currently being exploited.

Methods

Genes associated with IHD were obtained from the loci of single nucleotide polymorphisms reported in either of two recent genome wide association studies supplemented by a gene-based analysis (accounting for linkage disequilibrium) of CARDIoGRAMplusC4D 1000 Genomes, a large IHD case (n = 60,801)-control (n = 123,504) study. Treatments targeting the products of these IHD genes and genes with products targeted by current IHD treatments were obtained from Kyoto Encyclopedia of Genes and Genomes and Drugbank. Cohen's kappa was used to assess agreement.

Results

We identified 173 autosomal genes associated with IHD and 236 autosomal genes with products targeted by current IHD treatments, only 8 genes (PCSK9, EDNRA, PLG, LPL, CXCL12, LRP1, CETP and ADORA2A) overlapped, i.e. were both associated with IHD and had products targeted by current IHD treatments. The Cohen's kappa was 0.03. Interventions related to another 29 IHD genes exist, including dietary factors, environmental exposures and existing treatments for other indications.

Conclusions

Closer alignment of IHD treatments with genetically validated physiological targets may represent a major opportunity for combating a leading cause of global morbidity and mortality through repurposing existing interventions.

•

Pharmacological treatments for ischemic heart disease (IHD) target < 5% (8/173) of genes strongly predicting IHD.

•

Treatments or nutraceuticals targeting products of another 17% (29/173) of genes strongly predicting IHD exist.

•

Repurposing represents a major opportunity to prevent and treat a leading cause of global morbidity and mortality.

Development of drugs to mitigate ischemic heart disease, a leading cause of global morbidity and mortality, has stalled. We examined the relation between the physiological targets of current drugs for ischemic heart disease and the genetic predictors of ischemic heart disease. We found little correspondence between the genes with products targeted by current ischemic heart disease drugs and the genes associated with ischemic heart disease, but found several drugs for other purposes relevant to ischemic heart disease genes. Refocusing ischemic heart disease drug development on genetically valid targets and repurposing existing drugs represents a major opportunity to improve population health.

Age-period-cohort analysis of trends in blood pressure and body mass index in children and adolescents in Hong Kong

BACKGROUND

The declining or fluctuating trend in blood pressure (BP) despite the rising trend in body mass index (BMI) during childhood and adolescence is unexplained. We decomposed trends in BP and BMI to identify the relevance of early-life and contemporaneous factors.

METHODS

We assessed the relative contribution of age, period and cohort to secular trends in BP in children and adolescents (9-18 years) from 1999 to 2014 and BMI (6-18 years) from 1996 to 2014 in Hong Kong, China.

RESULTS

After accounting for age, period effects contributed more than cohort effects to the overall fluctuating BP trend and the rising BMI trend observed in this Chinese population. For both sexes, BP fell from the start of period to a low point in 2003-2005 but then rose. BMI rose strongly across the period before levelling off in 2009-2010. Earlier cohorts (born in 1983-1984) had higher BP and BMI than later cohorts.

CONCLUSION

With globalisation and associated lifestyle changes, successive generations of children and adolescents in a recently developed Chinese setting had lower BP and BMI, but this fall was offset until recently by population-wide increase in BMI. School-based health promotion efforts could have partly mitigated the population-wide rise in child and adolescent BMI, while socioeconomic transition or other factors could be relevant to changes in BP between generations. Explaining these trends will help identify early-life factors that may contribute to a healthier start as well as contemporaneous factors that may protect against rising trends in adiposity.

Pathways from parental educational attainment to adolescent blood pressure

OBJECTIVES

Lower parental education is associated with higher adolescent blood pressure (BP). We examined the contribution of modifiable risk factors from infancy to adolescence that could potentially explain the link between parental education and SBP and DBP in the offspring.

METHODS

In a prospective Chinese birth cohort, 'Children of 1997' of 5604 adolescents (68% follow-up), we analyzed the relation between parental educational attainment and sex-specific, age-specific and height-specific BP z-scores at ∼13 years. Using mediation analysis, we examined the contribution of household income at birth (both absolute income and relative income deprivation), exposures during infancy (breastfeeding and early life second-hand smoking), lifestyles during childhood (diet, physical activity and screen-time), weight or BMI status during fetal, infancy, childhood and puberty, pubertal stage as well as parental BMI.

RESULTS

We found that adolescent BMI, but not birth weight or infant growth or childhood BMI, mediated the inverse association of parental education with adolescent SBP (proportion mediated: 24%), followed by maternal BMI (proportion mediated: 18%). Factors explaining the link between parental education and DBP were less clear. Absolute income, breastfeeding, childhood diet and physical activity, pubertal stage and paternal BMI did not mediate the association between parental education and adolescent BP.

CONCLUSION

Low parental education is a risk factor for high SBP and, to a lesser extent, DBP in adolescents. Important mediators of this relation include adolescent and maternal body weight.

The association of breastfeeding with insulin resistance at 17 years: Prospective observations from Hong Kong's "Children of 1997" birth cohort

Breastfeeding has many benefits for mother and infant. Whether breastfeeding also protects against type 2 diabetes is unclear. To clarify the role of breastfeeding in type 2 diabetes, we assessed the association of breastfeeding with insulin resistance in late adolescence in a birth cohort from a non-Western setting where breastfeeding was not associated with higher socio-economic position. We used multivariable linear regression, with multiple imputation and inverse probability weighting, to examine the adjusted associations of contemporaneously reported feeding in the first 3 months of life (exclusively breastfed, mixed feeding, or always formula-fed) with fasting glucose, fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) at 17 years in a subset (n = 710, 8.6% of entire cohort) of the Hong Kong Chinese birth cohort "Children of 1997." We found a graded association of breastfeeding exclusivity in the first 3 months of life with lower fasting insulin and HOMA-IR (p-for-trend < .05), but not fasting glucose, at 17 years. Exclusively breastfed adolescents (7%) had nonsignificantly lowest fasting insulin and HOMA-IR, adjusted for sex, birth weight, parity, length of gestation, pregnancy characteristics, parents' education, and mother's place of birth. Exclusively breastfeeding for 3 months may be causally associated with lower insulin resistance in late adolescence. Further follow-up studies into adulthood are required to clarify the long-term protection of breastfeeding from type 2 diabetes.

Pubertal testis volume, age at pubertal onset, and adolescent blood pressure: Evidence from Hong Kong's "Children of 1997" birth cohort

OBJECTIVES

A warning from Health Canada suggests that testosterone increases blood pressure (BP). No evidence from large randomized controlled trials is available, and observational studies are confounded by ill-health lowering serum testosterone. To address the evidence gap, we assessed the association of pubertal testicular volume, as a reflection of testosterone production, with BP.

METHODS

We examined whether testicular volume was associated with sex-, age-, and height-standardized BP z-score at ∼13 years in a population-representative Chinese birth cohort (n = 5195, 63% follow-up). We used age at pubertal onset, determined as the earliest age when Tanner stage II for genitalia, breast, or pubic hair, or testicular volume of 4 mL occurred, as control exposures. These exposures were expected to produce findings different from testicular volume because they are not direct measures of testosterone. They were used to ascertain specificity of exposure and to detect residual confounding.

RESULTS

Greater testicular volume was associated with higher systolic BP by 0.03 z-score, which is equivalent to 1.40 mm Hg per standard deviation of testicular volume (95% CI 0.02-0.04), adjusted for infant characteristics, socioeconomic position, and childhood body mass index. Similarly adjusted, earlier pubertal onset was not associated with higher systolic BP z-score in boys or girls.

CONCLUSIONS

Greater pubertal testicular volume is related to higher BP, consistent with a potential role of androgens in the higher BP in boys than girls that emerges during puberty. Our finding provides preliminary evidence supportive of more definitive studies to clarify the warning on testosterone from Health Canada.

Glucose-6-Phosphate Dehydrogenase Deficiency and Physical and Mental Health until Adolescence

Background

To examine the association of glucose-6-phosphate dehydrogenase (G6PD) deficiency with adolescent physical and mental health, as effects of G6PD deficiency on health are rarely reported.

Methods

In a population-representative Chinese birth cohort: “Children of 1997” (n = 8,327), we estimated the adjusted associations of G6PD deficiency with growth using generalized estimating equations, with pubertal onset using interval censored regression, with hospitalization using Cox proportional hazards regression and with size, blood pressure, pubertal maturation and mental health using linear regression with multiple imputation and inverse probability weighting.

Results

Among 5,520 screened adolescents (66% follow-up), 4.8% boys and 0.5% girls had G6PD deficiency. G6PD-deficiency was not associated with birth weight-for-gestational age or length/height gain into adolescence, but was associated with lower childhood body mass index (BMI) gain (-0.38 z-score, 95% confidence interval (CI) -0.57, -0.20), adjusted for sex and parental education, and later onset of pubic hair development (time ratio = 1.029, 95% CI 1.007, 1.050). G6PD deficiency was not associated with blood pressure, height, BMI or mental health in adolescence, nor with serious infectious morbidity until adolescence.

Conclusions

G6PD deficient adolescents had broadly similar physical and mental health indicators, but transiently lower BMI gain and later pubic hair development, whose long-term implications warrant investigation.