Early-life exposure to ambient air pollutants and kidney function in adolescents: a cohort study based on the 'Children of 1997' Hong Kong birth cohort

OBJECTIVES

Air pollution is increasingly linked to impaired kidney function in adults. However, little is known about how early-life exposure to air pollutants affects kidney function in adolescents.

STUDY DESIGN

Cohort study.

METHODS

We leveraged data from the 'Children of 1997' Hong Kong population-representative birth cohort (N = 8327). Residential exposure to average ambient levels of four air pollutants, including inhalable particle (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), and nitrogen monoxide (NO), during in utero, infancy, and childhood periods was estimated using the inverse distance weighting. Kidney function was assessed using estimated glomerular filtration rate (eGFR) calculated from age-adjusted equations for adolescents. Generalized linear regression was used to examine the association of air pollutant exposure in each period with kidney function at 17.6 years. Two-pollutant models tested the robustness of the association.

RESULTS

Of the 3350 participants included, 51.4% were boys. Exposure to PM10 was associated with poorer kidney function. Each interquartile range increment in PM10 was inversely associated with eGFR (β: -2.933, 95% confidence interval -4.677 to -1.189) in utero, -2.362 (-3.992 to -0.732) infancy, -2.708 (-4.370 to -1.047) childhood, and -2.828 (-4.409 to -1.247) overall. Exposure to PM10 and SO2in utero had a stronger inverse association with kidney function in males. The associations were robust to PM10 exposure in two-pollutant models.

CONCLUSIONS

Our findings suggest that early-life exposure to ambient PM10 and SO2 is associated with reduced kidney function in adolescents, especially exposure in utero.

Insights into Causal Cardiovascular Risk Factors from Mendelian Randomization

PURPOSE OF THE REVIEW

This review summarizes major insights into causal risk factors for cardiovascular disease (CVD) by using Mendelian randomization (MR) to obtain unconfounded estimates, contextualized within its strengths and weaknesses.

RECENT FINDINGS

MR studies have confirmed the role of major CVD risk factors, including alcohol, smoking, adiposity, blood pressure, type 2 diabetes, lipids, and possibly inflammation, but added that the relation with alcohol is likely linear, confirmed the role of diastolic blood pressure, identified apolipoprotein B as the major target lipid, and foreshadowed results of some trials concerning anti-inflammatories. Identifying a healthy diet and the role of early life influences, such as birth weight, has proved more difficult. Use of MR has winnowed empirically driven hypotheses about CVD into a set of genetically validated targets of intervention. Greater inclusion of global diversity in genetic studies and the use of an overarching framework would enable even more informative MR studies.

Investigating the effects of statins on ischemic heart disease allowing for effects on body mass index: a Mendelian randomization study

Despite effective lipid reduction and corresponding benefits for cardiovascular disease prevention and treatment, statins have pleiotropic effects potentially increasing the risk of ischemic heart disease (IHD), particularly by increasing body mass index (BMI). We assessed whether the effects of genetically mimicked statins on IHD were strengthened by adjusting for BMI in men and women. We also assessed if increasing BMI was specific to statins in comparison to other major lipid-lowering treatments in current use, i.e., proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors and ezetimibe. Using univariable and multivariable Mendelian randomization (MR) we found genetically mimicked effects of statins increased BMI (0.33, 95% confidence interval (CI) 0.28 to 0.38), but genetically mimicked PCSK9 inhibitors and ezetimibe did not. Genetically mimicked effects of statins on IHD reduction in both sexes (odds ratio (OR) 0.55 per unit decrease in effect size of low-density lipoprotein cholesterol (LDL-c), 95% confidence interval (CI) 0.40 to 0.76), was largely similar after adjusting for BMI, in both men (OR 0.48, 95% CI 0.38 to 0.61) and women (OR 0.66, 95% CI 0.53 to 0.82). Compared with variations in PCSK9 and NPC1L1, only variation in HMGCR was associated with higher BMI. The effects on IHD of mimicking statins were similar after adjusting for BMI in both men and women. The BMI increase due to statins does not seem to be a concern as regards the protective effects of statins on IHD, however other factors driving BMI and the protective effects of statins could be.

Impact of Liability to Periodontitis on Glycemic Control and Type II Diabetes Risk: A Mendelian Randomization Study

While the association of periodontitis with Type II diabetes (T2DM) is well-established, the causal relationship remains uncertain. We examined the causal association of periodontitis with glycemic traits (HbA1c, fasting glucose, and fasting insulin) and T2DM using Mendelian randomization (MR) taking advantage of large genome-wide association studies of European and East Asian adults, i.e., the UK Biobank (n ≈ 350,000) (HbA1c), trans-ancestral MAGIC (HbA1c, fasting glucose, and insulin), and DIAMANTE (74,124 cases/824,006 controls), and AGEN for T2DM in Europeans and East Asians, respectively. Periodontitis was instrumented using single-nucleotide polymorphisms (SNPs), strongly and independently predicting liability to periodontitis in each ancestry group. SNP-specific Wald estimates were combined using inverse variance weighting. Sensitivity analyses were performed using the weighted median and MR-Egger with meta-analysis of MR estimates for Europeans and East Asians. Genetically instrumented liability to periodontitis was not associated with glycemic traits or T2DM in either ancestry or when ancestry specific estimates were meta-analyzed. Our findings do not support a causal association of liability to periodontitis with glycemic traits or T2DM. However, further research is required confirming these findings among other racial/ethnic groups, especially groups who carry a heavy burden of both periodontitis and T2DM.

Investigating the association of testosterone with survival in men and women using a Mendelian randomization study in the UK Biobank

Life expectancy in the developed West is currently stagnated and remains shorter in men than women. Well-established evolutionary biology theory suggests lifespan trades-off against reproductive success, possibly sex-specifically. We examined whether a key driver of reproductive success, testosterone, affected survival using a Mendelian randomization longevity study in the UK Biobank to obtain unbiased estimates, along with control exposures. We applied published genetic instruments for testosterone to obtain inverse variance weighted estimates of associations with survival to (i.e., age at) recruitment, in 167,020 men and 194,174 women. We similarly obtained estimates for a positive control (smoking initiation), and a negative control (absorbate), a marker of vitamin C metabolism. Testosterone was associated with poorer survival (0.10 years younger at recruitment per effect size of testosterone, 95% confidence interval (CI) 0.004 to 0.20). As expected, smoking initiation was also associated with poorer survival (0.37 years younger, 95% CI 0.25 to 0.50), but not absorbate (0.01 years younger, 95% CI - 0.09 to 0.11). Several aspects of a healthy lifestyle (low animal fat diet) and several widely used medications (statins, metformin, dexamethasone and possibly aspirin) may modulate testosterone. Explicitly designing interventions sex-specifically based on these insights might help address stagnating life expectancy and sexual disparities.

Use of Multivariable Mendelian Randomization to Address Biases Due to Competing Risk Before Recruitment

Background: Mendelian randomization (MR) provides unconfounded estimates. MR is open to selection bias when the underlying sample is selected on surviving to recruitment on the genetically instrumented exposure and competing risk of the outcome. Few methods to address this bias exist. Methods: We show that this selection bias can sometimes be addressed by adjusting for common causes of survival and outcome. We use multivariable MR to obtain a corrected MR estimate for statins on stroke. Statins affect survival, and stroke typically occurs later in life than ischemic heart disease (IHD), making estimates for stroke open to bias from competing risk. Results: In univariable MR in the UK Biobank, genetically instrumented statins did not protect against stroke [odds ratio (OR) 1.33, 95% confidence interval (CI) 0.80-2.20] but did in multivariable MR (OR 0.81, 95% CI 0.68-0.98) adjusted for major causes of survival and stroke [blood pressure, body mass index (BMI), and smoking initiation] with a multivariable Q-statistic indicating absence of selection bias. However, the MR estimate for statins on stroke using MEGASTROKE remained positive and the Q statistic indicated pleiotropy. Conclusion: MR studies of harmful exposures on late-onset diseases with shared etiology need to be conceptualized within a mechanistic understanding so as to identify any potential bias due to survival to recruitment on both genetically instrumented exposure and competing risk of the outcome, which may then be investigated using multivariable MR or estimated analytically and results interpreted accordingly.

A phenome-wide association study of ABO blood groups

BACKGROUND

ABO blood group is associated with differences in lifespan, cardiovascular disease, and some cancers, for reasons which are incompletely understood. To gain sex-specific additional insight about potential mechanisms driving these common conditions for future interventions, we characterized associations of ABO blood group antigen across the phenotype sex-specifically.

METHODS

We performed a phenome-wide association study (PheWAS) assessing the association of tag single nucleotide polymorphisms (SNPs) for ABO blood group antigens (O, B, A1, and A2) with 3873 phenotypes.

RESULTS

The tag SNP for the O antigen was inversely associated with diseases of the circulatory system (particularly deep vein thrombosis (DVT)), total cholesterol, low-density lipoprotein cholesterol (LDL-C), and ovarian cancer, and positively associated with erythrocyte traits, leukocyte counts, diastolic blood pressure (DBP), and healthy body composition; the tag SNP for the A1 antigen tended to have associations in reverse to O. Stronger associations were more apparent for men than women for DVT, DBP, leukocyte traits, and some body composition traits, whereas larger effect sizes were found for women than men for some erythrocyte and lipid traits.

CONCLUSION

Blood group has a complex association with cardiovascular diseases and its major risk factors, including blood pressure and lipids, as well as with blood cell traits and body composition, with some differences by sex. Lower LDL-C may underlie some of the benefits of blood group O, but the complexity of associations with blood group antigen suggests overlooked drivers of common chronic diseases.

Investigating pleiotropic effects of statins on ischemic heart disease in the UK Biobank using Mendelian randomisation

We examined whether specifically statins, of the major lipid modifiers (statins, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors and ezetimibe) have pleiotropic effects on ischemic heart disease (IHD) via testosterone in men or women. As a validation, we similarly assessed whether a drug that unexpectedly likely increases IHD also operates via testosterone. Using previously published genetic instruments we conducted a sex-specific univariable and multivariable Mendelian randomization study in the UK Biobank, including 179918 men with 25410 IHD cases and 212080 women with 12511 IHD cases. Of these three lipid modifiers, only genetically mimicking the effects of statins in men affected testosterone, which partly mediated effects on IHD. Correspondingly, genetically mimicking effects of anakinra on testosterone and IHD presented a reverse pattern to that for statins. These insights may facilitate the development of new interventions for cardiovascular diseases as well as highlighting the importance of sex-specific explanations, investigations, prevention and treatment.

Reproduction and longevity: A Mendelian randomization study of gonadotropin-releasing hormone and ischemic heart disease

Background

According to well-established evolutionary biology theory there is a trade-off between reproduction and longevity, implying that upregulating the reproductive axis might drive major diseases. We assessed whether the central driver of reproduction gonadotropin-releasing hormone 1 (GnRH1) had a causal effect on the leading cause of global morbidity and mortality, i.e. ischemic heart disease (IHD). As a contrast we similarly examined the role of GnRH2 because it is more a driver of female sexual behavior.

Methods

We applied strong (p-value <5 × 10^-6) and independent genetic predictors of GnRH1 and GnRH2 to an extensively genotyped IHD case (n = 76,014) - control (n = 264,785) study and combined the genetic variant specific Wald estimates using inverse variance weighting (IVW) with multiplicative random effects, and as a sensitivity analysis used weighted median, MR-Egger and MR-PRESSO estimates, and repeated the analysis only using genome wide significant genetic predictors.

Findings

GnRH1, predicted by 11 genetic variants, was positively associated with IHD (IVW odds ratio (OR) 1.04 per effect size, 95% confidence interval (CI) 1.01 to 1.08), but GnRH2, predicted by 15 genetic variants, was not (IVW OR 0.98, 95% CI 0.95 to 1.02). Estimates from sensitivity analysis were similar.

Interpretation

GnRH1 is a potential IHD genetic target. Apart from demonstrating a central tenet of evolutionary biology in humans, our study suggests that existing treatments and environmental factors targeting GnRH1, its drivers or consequences could be re-purposed to prevent and treat IHD. Given, the importance of reproduction to the human species, many such exposures likely exist.

ADAMTS-13 activity and ischemic heart disease: a Mendelian randomization study

Essentials Cardiovascular disease remains the leading cause of global mortality despite progress in control. We assessed the role of ADAMTS-13 in ischemic heart disease using Mendelian randomization. Genetically instrumented ADAMTS-13 activity reduced ischemic heart disease. Therapeutics targeting ADAMTS-13 activity could perhaps be repurposed in ischemic heart disease.

BACKGROUND

Despite great progress in the prevention and control of cardiovascular disease, it remains the leading cause of global mortality and morbidity, with new unexpected risk factors emerging and few effective new pharmaceutical treatments. ADAMTS-13 is involved in a clotting disorder, thrombotic thrombocytopenic purpura, for which new treatments are being developed. Observationally, ADAMTS-13 activity is inversely associated with ischemic heart disease (IHD) but positively associated with diabetes.

OBJECTIVES

To obtain unconfounded estimates of the effect of ADAMTS-13 on IHD, diabetes and lipids.

METHODS

We applied genetic variants strongly, (P < 5 × 10-8 ), solely and independently associated with ADAMTS-13 to the largest available extensively genotyped case-control studies of IHD and diabetes and to a large study of lipids to obtain Mendelian randomization inverse variance weighted (IVW) estimates. Sensitivity was evaluated through weighted median and MR-Egger estimates.

RESULTS

Genetically predicted ADAMTS-13 activity, based on three genetic variants, was consistently inversely associated with IHD (IVW odds ratio [OR] 0.91 per effect size; 95% confidence interval [CI] 0.86-0.97) but not with diabetes (OR 0.94, 95% CI 0.88-1.01) or high or low-density lipoprotein cholesterol (0.01, 95% CI -0.02 to 0.04; -0.01, 95% CI -0.04 to 0.02, respectively). ADAMTS-13 antigen, based on four genetic variants, was not associated with any outcome.

CONCLUSIONS

This genetic validation of ADAMTS-13 activity as a target of intervention in IHD raises the possibility of new ways of prevention and treatment being developed by repurposing therapeutics that raise ADAMTS-13 activity, or by other environmental or dietary interventions that raise ADAMTS-13 activity.

In utero exposure to gestational diabetes and adiposity: does breastfeeding make a difference?

BACKGROUND/OBJECTIVES

Short-term breastfeeding from mothers with gestational diabetes (GDM) may programme metabolism and increase offspring diabetes risk. We examined the association of in utero GDM exposure with adiposity from infancy to adolescence, and whether any association was modified by breastfeeding during early infancy.

METHODS

In the prospective Chinese birth cohort "Children of 1997" (n = 7342, 88% follow-up rate), generalised estimate equations with multiple imputation were used to assess associations of in utero GDM exposure with age- and sex-specific body mass index (BMI) z-score during infancy (3 and 9 months), childhood (2- < 8 years) and adolescence (8-16 years), adjusted for sex, parity, maternal age, birth place, preeclampisa, smoking, and family socio-economic position. We also tested whether the associations differed by mode of infant feeding (always formula-fed, mixed, always breastfed) during the first three months of life.

RESULTS

In utero GDM exposure (7.5%) was associated with a lower BMI z-score during infancy (-0.13, 95% confidence interval (CI) -0.22, -0.05) but higher BMI z-scores during childhood (0.14, 95% CI 0.03, 0.25) and adolescence (0.25 95% CI 0.11, 0.38). Breastfeeding for the first three months did not modify the association of in utero GDM status with subsequent BMI (all p values for interaction >0.4).

CONCLUSIONS

In utero GDM exposure was associated with greater adiposity during childhood and adolescence. Breastfeeding in early infancy from mothers with GDM was not associated with greater adiposity in children and thus should still be encouraged.

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.

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

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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.

Migrant status and childhood hospitalizations for asthma and other wheezing disorders

BACKGROUND

In developed Western settings, asthma is more prevalent among second-generation compared to first-generation migrants. However, these studies are difficult to interpret as they include migrants of various ethnicities and countries of origin.

OBJECTIVE

We assessed the association of parental migrant status with wheezing disorders among children born in Hong Kong, a developed non-Western setting, where many children have migrant parents from mainland China of the same ethnicity.

METHODS

We used Cox regression to examine the adjusted associations of parental migrant status with time to first public hospital admission for asthma, bronchitis and bronchiolitis (International Classification of Diseases, Ninth Version Clinical Modification 466, 490 and 493) from 9 days to 12 years in a population-representative birth cohort of 8327 Chinese children in Hong Kong.

RESULTS

Having both parents as migrants was associated with higher risk of hospitalization for asthma and other wheezing disorders, compared to both parents being Hong Kong born (hazard ratio 1.30, 95% confidence interval 1.05-1.60 from 9 days to 6 years), adjusted for type of hospital at birth, parental history of allergies, mother's age at birth, father's age at birth and highest parental education.

CONCLUSIONS AND CLINICAL RELEVANCE

In the unique, non-Western context of Hong Kong, second-generation migrants had higher risk of hospitalization for childhood wheezing disorders compared to the native population, particularly before 6 years of age. Further study is required to clarify the underlying mechanisms involved.

Homocysteine-reducing B vitamins and ischemic heart disease: a separate-sample Mendelian randomization analysis

BACKGROUND/OBJECTIVES

Observationally, homocysteine is positively associated with ischemic heart disease (IHD) and unhealthy lipids; folate and vitamin B12, which reduce homocysteine, are associated with lower IHD risk and healthy lipids. Randomized controlled trials have shown no benefits of folate and vitamin B12 for IHD. To clarify the role of these potential targets of intervention in IHD we assessed how genetically determined homocysteine, folate and vitamin-B12-affected IHD and lipids.

SUBJECTS/METHODS

Separate-sample instrumental variable analysis with genetic instruments, that is, Mendelian randomization, was used to obtain unconfounded estimates (based on strongly related single-nucleotide polymorphisms (SNPs)) using CARDIoGRAMplusC4D, a large coronary artery disease/myocardial infarction (CAD/MI) case (n=64 374)-control (n=130 681) study with extensive genotyping, and the Global Lipids Genetics Consortium Results (n=196 475).

RESULTS

Homocysteine was unrelated to CAD/MI (odds ratio (OR) 1.07 per log-transformed s.d., 95% confidence interval (CI) 0.96 to 1.19) based on 14 SNPs, as was folate (OR 1.18 per s.d., 95% CI 0.80 to 1.75) based on rs153734, and vitamin B12 (OR 0.98 per log-transformed s.d., 95% CI 0.85 to 1.14) based on rs602662, rs9473555, rs526934 and rs11254363. Homocysteine and folate were not clearly associated with lipids, vitamin B12 was associated with higher inverse normal transformed low-density lipoprotein cholesterol (0.07, 95% CI 0.02 to 0.12) and triglycerides (0.05, 95% CI 0.004 to 0.09).

CONCLUSIONS

Our findings do not corroborate the observed positive association of homocysteine or negative associations of folate and vitamin B12 with CAD/MI. Vitamin B12 might be associated with an unfavorable lipid profile.

The effect of hematocrit and hemoglobin on the risk of ischemic heart disease: A Mendelian randomization study

Hematocrit and hemoglobin affect viscosity, and have been considered as risk factors for ischemic heart disease (IHD), although observations are inconsistent; randomized controlled trials targeting hematocrit or hemoglobin have not been definitive. To clarify their role, the risk of IHD was assessed according to genetically determined hematocrit and hemoglobin. We applied single nucleotide polymorphisms (SNPs) strongly determining hematocrit and hemoglobin, from a genome wide association study, to a large case (64,746) control (130,681) study of coronary artery disease, CARDIoGRAMplusC4D, to obtain unconfounded estimates using instrumental variable analysis by combining the Wald estimators for each SNP taking into account any correlation between SNPs using weighted generalized linear regression. Hematocrit was positively associated with IHD, odds ratio (OR) 1.07 per %, 95% confidence interval (CI) 1.03 to 1.11, before and after excluding SNPs from gene regions directly functionally relevant to IHD. However, hematocrit was not associated with IHD (OR 0.99, 0.94 to 1.04) after also excluding SNPs associated with lipids at genome wide significance. Hemoglobin was not associated with IHD (OR 1.06 per g/dL, 0.97 to 1.15) which was similar (OR 1.02, 0.94 to 1.11) after excluding SNPs from gene regions directly functionally relevant to IHD. Hemoglobin was negatively associated with IHD after also excluding SNPs associated with lipids at genome wide significance (OR 0.86, 0.78 to 0.94). In conclusion, hematocrit shares genetic determinants with IHD, but whether the genes contribute to IHD via hematocrit or other mechanisms is not entirely clear. Higher Hemoglobin is unlikely to cause IHD.

Plasma levels of vitamin K and the risk of ischemic heart disease: a Mendelian randomization study

Essentials Vitamin K plays a role in coagulation, and deficiency may promote coronary artery calcification. The role of vitamin K1 in heart disease was assessed using Mendelian randomization in Caucasians. Genetically higher vitamin K1 was associated with a higher risk of ischemic heart disease. Further research elucidating the role of vitamin K1 in ischemic heart disease could be useful.

SUMMARY

Background Vitamin K1 is a nutrient in green leafy vegetables; deficiency may promote coronary artery calcification. Warfarin, an anticoagulant used in secondary prevention of thrombotic events, is a vitamin K antagonist. Thrombotic and coronary events may share risk factors. Objectives To clarify the role of vitamin K1 in ischemic heart disease, the risk of coronary artery disease/myocardial infarction (CAD/MI) was assessed according to genetically determined vitamin K1 levels. Given vitamin K1 is fat soluble, associations with lipids were similarly assessed to assess pleotropic effects via lipids. Methods Separate sample instrumental variable analysis with genetic instruments (Mendelian randomization) was used to obtain an unconfounded estimate of the association of vitamin K1 (based on rs2108622 [CYP4F2], rs4645543 [KCNK9] and rs2192574 [CTNNA2] from a genome-wide association study) with CAD/MI using CARDIoGRAMplusC4D (cases = 64 374; controls = 130 681) and with lipids using Global Lipids Genetics Consortium Results (n = 196 475). Results Vitamin K1 single nucleotide polymorphisms were positively associated with CAD/MI (odds ratio [OR], 1.17 per unit [nmol L(-1) ] of natural log-transformed genetically predicted vitamin K1 ; 95% confidence interval [CI], 1.08-1.26), but not with inverse normal transformed low-density lipoprotein cholesterol (-0.0003; 95% CI, -0.03 to 0.03), high-density lipoprotein cholesterol (0.02; 95% CI, -0.01 to 0.05) or triglycerides (-0.01; 95% CI, -0.04 to 0.02). Considering only rs2108622, which is functionally relevant to vitamin K1 , the association for CAD/MI was stronger (OR, 1.21; 95% CI, 1.08-1.36). Conclusions Vitamin K may cause CAD/MI; whether vitamin K or other determinants of coagulation could be relevant to primary prevention might be worth considering.

Mode of delivery and childhood hospitalizations for asthma and other wheezing disorders

BACKGROUND

Observationally, delivery by Caesarean section is associated with higher risk of childhood asthma and wheeze in developed Western settings, but associations are less consistent in other settings.

OBJECTIVE

To examine the association of mode of delivery with hospitalizations for asthma and other wheezing disorders in a developed non-Western setting with high rates of Caesarean section.

METHODS

Using Cox regression, we examined the adjusted association of mode of delivery with public hospital admissions for asthma, bronchitis, and bronchiolitis (International Classification of Diseases, Ninth Version Clinical Modification 466, 490 and 493) from 9 days to 12 years of age in a population-representative prospective birth cohort of 8327 Chinese children in Hong Kong. Confounders included sex, birth and parental characteristics, and socio-economic position (SEP).

RESULTS

Delivery by Caesarean section accounted for 27% of all births and was not clearly associated with hospitalizations for asthma and other wheezing disorders to 12 years [hazard ratio (HR) 1.11, 95% confidence interval (CI) 0.91 to 1.36] compared to vaginal delivery. Similarly, there were no clear associations to 2 years (HR 1.07, 95% CI 0.83 to 1.38) or 6 years (HR 1.12, 95% CI 0.91 to 1.37), although we cannot rule out residual confounding by SEP.

CONCLUSIONS AND CLINICAL RELEVANCE

We cannot rule out an association, but our findings suggest that the observed associations of delivery by Caesarean section with childhood wheezing disorders may vary with setting and may not be biologically mediated. Further studies with different designs are needed to clarify the role of the microbiome and mode of delivery in the aetiology of asthma and other childhood wheezing disorders.

Liver enzymes and incident diabetes in China: a prospective analysis of 10 764 participants in the Guangzhou Biobank Cohort Study

BACKGROUND

Impaired liver function has been shown to be associated with incident diabetes. The independent role of the different liver enzymes, including γ-glutamyltransferase (GGT), alanine transaminase (ALT) and aspartate transaminase (AST), has not been addressed properly, taking into account their high collinearity. We used partial least squares (PLS) regression to identify the contribution of ALT, AST and GGT, which appears causally associated with diabetes as a validation factor, to incident diabetes in a South China population where liver impairment and diabetes are common.

METHODS

Participants were from the Guangzhou Biobank Cohort Study recruited in 2003-2008, with follow-up re-examination up to the end of 2012. Multivariable generalised linear models and PLS were used to examine the adjusted associations of ALT, AST and GGT with diabetes. Incident diabetes was defined as self-reported diabetes, and/or initiation of hypoglycaemia medication or insulin during follow-up, or fasting glucose ≥7.0 mmol/L, or 2 h oral glucose tolerance test, glucose ≥11.1 mmol/L at follow-up examination.

RESULTS

In 10 764 Chinese participants aged ≥50 years with no diabetes at baseline, 1228 (11.4%) developed diabetes during the median 4 years of follow-up. Using PLS, the risk for incident diabetes was higher by 18% (95% CI 8% to 27%) per 1 SD increment in log-ALT, and expectedly higher by 36% (95% CI 26% to 52%) for log-GGT, adjusted for age, sex, education, smoking, alcohol, physical activity, waist circumference and body mass index. Similarly adjusted, no association for log-AST (relative risk 0.92, 95% CI 0.85 to 1.01) was found.

CONCLUSIONS

ALT but not AST was associated with incident diabetes. Further experimental studies are needed to confirm the causal association and clarify the underlying mechanisms.

The Association of Infant Growth Patterns with Adiposity in Adolescence: Prospective Observations from Hong Kong's 'Children of 1997' Birth Cohort

BACKGROUND

The role of infant growth in adiposity remains unclear.

METHODS

We used multivariable linear regression, with inverse probability weighting and multiple imputation to account for loss to follow-up, in a population-representative Chinese birth cohort, 'Children of 1997' in Hong Kong, to examine, in terms births, the adjusted association of infant (birth to 12 months) weight growth trajectories with body mass index (BMI) (n = 6861, 88% follow-up), waist-to-height ratio (WHtR), and waist-to-hip ratio (WHR) (n = 5398, 69% follow-up) at ∼ 14 years.

RESULTS

Infant weight growth trajectories had graded associations with adolescent BMI and WHtR but not with WHR, such that compared with adolescents born light with slow infant growth, adolescents born heavy with fast infant growth had higher BMI z-score [0.60, 95% confidence interval (CI) 0.49, 0.70], higher WHtR z-score (0.17, 95% CI 0.08, 0.26) but similar WHR z-score (-0.02, 95% CI -0.11, 0.08), adjusted for sex, gestational age, parental education, parental BMI, parental height, and parental place of birth.

CONCLUSIONS

Varying associations of infant growth with different adiposity measures suggest a complex role of infant growth in long-term health, perhaps because infant growth, or its underlying drivers, influences build and body composition as well as adiposity.

Adolescent testosterone, muscle mass and glucose metabolism: evidence from the 'Children of 1997' birth cohort in Hong Kong

AIMS

Diabetes rates are high in Asia despite relatively low rates of obesity, which might be related to lower muscle mass. Muscle mass plays an important role in glucose metabolism. Peak muscle mass is obtained in late adolescence. We tested the hypothesis that pubertal testosterone is negatively associated with glucose metabolism mediated by muscle mass.

METHODS

Participants aged 15 years (278 boys and 223 girls) were recruited from the Hong Kong's 'Children of 1997' birth cohort in 2012. Multivariable linear regression with multiple imputation and inverse probability weighting was used to examine the adjusted associations of pubertal testosterone with skeletal muscle index, body fat percentage, fasting glucose, insulin and homeostasis model of assessment - insulin resistance.

RESULTS

Total testosterone was negatively associated with fasting glucose (-0.008, 95% confidence interval -0.015 to -0.002), insulin (-0.43, 95% confidence interval -0.56 to -0.30) and insulin and homeostasis model of assessment - insulin resistance (-0.09, 95% confidence interval -0.12 to -0.06) adjusted for sex, birth weight, highest parental education, mother's place of birth and physical activity. These associations were attenuated by additional adjustment for skeletal mass index or body fat percentage.

CONCLUSIONS

Adolescent glucose metabolism may be influenced by testosterone, perhaps partially via skeletal muscle mass.

Does falling testosterone with age among men underlie the increase in ischaemic heart disease

BACKGROUND

Observationally, testosterone falls with age among men and ischaemic heart disease (IHD) increases with age, so testosterone is commonly assumed to protect against IHD. Here we examined whether IHD mortality rates among men increased faster with age in the USA than China, where testosterone in men remains stable throughout adulthood, and also whether the increase with age in mortality rates for IHD is faster than for other causes of death.

METHODS

Age-specific mortality rates from all causes, IHD, pneumonia and prostate cancer for men in the USA and China from 1991 to 1995 were obtained from the WHO, and considered in age groups because of non-linearity.

RESULTS

The risk of death from IHD in US men increased with age at the same rate as the risk of death from any cause. In China, the risk of death from IHD increased with age faster than the risk of death from any cause.

CONCLUSION

The data are not consistent with the assumption that a fall in testosterone with age causes IHD.

Cohort Profile: Hong Kong Department of Health Elderly Health Service Cohort

The Department of Health Elderly Health Service Cohort in Hong Kong was set up to promote understanding of ageing in a global context, to exploit the role of Hong Kong as a sentinel for populations currently experiencing very rapid economic development, to provide a developed non-Western 'social laboratory' where empirically derived hypotheses can be tested and to leverage the different patterns of common chronic diseases between East and West to generate novel hypotheses about their determinants. The initial cohort enrolled from July 1998 to the end of December 2001 includes 66 820 people aged 65 years or older, forming about 9% of the population of this age. A comprehensive health assessment was made at enrollment and then repeated regularly on an ongoing basis. The health assessment included a comprehensive assessment of lifestyle, social circumstances, physical health and mental health, including an assessment of cognition and depressive symptoms. Health services use and deaths have been obtained by record linkage and confirmed, where necessary, by telephone interview. Currently, the data are not publicly available; we would welcome collaborations and research proposals.

Breast cancer incidence and mortality in a transitioning Chinese population: current and future trends

BACKGROUND

Projections of future trends in cancer incidence and mortality are important for public health planning.

METHODS

By using 1976-2010 data in Hong Kong, we fitted Poisson age-period-cohort models and made projections for future breast cancer incidence and mortality to 2025.

RESULTS

Age-standardised breast cancer incidence (/mortality) is projected to increase (/decline) from 56.7 (/9.3) in 2011-2015 to 62.5 (/8.6) per 100,000 women in 2021-2025.

CONCLUSIONS

The incidence pattern may relate to Hong Kong's socio-economic developmental history, while falling mortality trends are, most likely, due to improvements in survival from treatment advancement and improved health service delivery.

Height, its components, and coagulability among older Chinese: the Guangzhou biobank cohort study

OBJECTIVES

The causal role of some cardiovascular risk factors, such as HDL cholesterol, has been increasingly challenged and attention is returning to all elements of Virchow's triad, i.e., hypercoagulability (including viscosity) as well as endothelial function and blood flow. We examined the life course origins of coagulability.

METHODS

We used multivariable linear regression to assess whether childhood influences, proxied by height and its components, were associated with hematocrit (Hct), hemoglobin (HGB), and other hematological parameters in 28,595 older Chinese adults (mean age = 61.8 years) from the Guangzhou Biobank Cohort Study.

RESULTS

Adjusted for age, sex, and recruitment phase, leg length was negatively associated with platelets (PLT) (-0.83 × 10(9) /l per centimeter (cm), 95% confidence interval (CI) -1.01 to -0.65). Sitting height and height were positively associated with Hct (0.05% per cm, 95% CI 0.04-0.07 for sitting height; 0.02% per cm, 95% CI 0.01-0.02 for height), HGB (0.21 g/l per cm, 95% CI 0.17-0.25; 0.07 g/l per cm, 95% CI 0.04-0.09) and negatively associated with PLT (-1.2 × 10(9) /l per cm, 95% CI -1.4 to -1.0; -0.83 × 10(9) /l per cm, 95% CI -0.95 to -0.70). Further adjustment for potential confounders did little to change the estimates.

CONCLUSIONS

For the first time we provide anthropometric evidence for the different roles of prepubertal and pubertal influences in relation to Hct and HGB. Whether factors that promote leg growth but reduce growth of sitting height may help to prevent cardiovascular events, via effects on hypercoagulability or viscosity, overall or in specific subgroups, remains to be determined.