Large-scale meta-analysis of interleukin-1 beta and interleukin-1 receptor antagonist polymorphisms on risk of radiographic hip and knee osteoarthritis and severity of knee osteoarthritis

OBJECTIVE

To clarify the role of common genetic variation in the Interleukin-1β (IL1B) and Interleukin-1R antagonist (IL1RN) genes on risk of knee and hip osteoarthritis (OA) and severity of knee OA by means of large-scale meta-analyses.

METHODS

We searched PubMed for articles assessing the role of IL1B and IL1RN polymorphisms/haplotypes on the risk of hip and/or knee OA. Novel data were included from eight unpublished studies. Meta-analyses were performed using fixed- and random-effects models with a total of 3595 hip OA and 5013 knee OA cases, and 6559 and 9132 controls respectively. The role of ILRN haplotypes on radiographic severity of knee OA was tested in 1918 cases with Kellgren-Lawrence (K/L) 1 or 2 compared to 199 cases with K/L 3 or 4.

RESULTS

The meta-analysis of six published studies retrieved from the literature search and eight unpublished studies showed no evidence of association between common genetic variation in the IL1B or IL1RN genes and risk of hip OA or knee OA (P>0.05 for rs16944, rs1143634, rs419598 and haplotype C-G-C (rs1143634, rs16944 and rs419598) previously implicated in risk of hip OA). The C-T-A haplotype formed by rs419598, rs315952 and rs9005, previously implicated in radiographic severity of knee OA, was associated with reduced severity of knee OA (odds ratio (OR)=0.71 95%CI 0.56-0.91; P=0.006, I(2)=74%), and achieved borderline statistical significance in a random-effects model (OR=0.61 95%CI 0.35-1.06 P=0.08).

CONCLUSION

Common genetic variation in the Interleukin-1 region is not associated with prevalence of hip or knee OA but our data suggest that IL1RN might have a role in severity of knee OA.

Retinal vascular caliber and risk of dementia: the Rotterdam study

BACKGROUND

Retinal vessels provide a unique opportunity to study both systemic and cerebrovascular disease. Smaller retinal arteriolar calibers are strongly related to hypertension, whereas larger retinal venular calibers are more related to inflammation, cerebral hypoperfusion, and cerebrovascular disease. Whether retinal vessel calibers are related to dementia remains unclear.

METHODS

We investigated whether retinal arteriolar and venular calibers are associated with risk of dementia, and its subtypes Alzheimer disease (AD) and vascular dementia, in the prospective population-based Rotterdam Study. Digitized retinal images were available in 5,553 participants aged 55 years or over and dementia-free at baseline (1990-1993). Participants were re-examined in 1993-1994, 1997-1999, and 2002-2004 and were continuously monitored for development of dementia.

RESULTS

During a mean follow-up of 11.6 years, 655 participants developed dementia. AD was diagnosed in 519 and vascular dementia in 73 participants. Larger venular calibers were associated with an increased risk of dementia, in particular vascular dementia (age- and sex-adjusted hazard ratio per SD increase: 1.31; 95% confidence interval 1.06-1.64), but not AD. The association remained significant after adjustment for stroke and cardiovascular risk factors. Smaller arteriolar calibers were also associated with an increased risk of vascular dementia, yet only when adjusted for venular calibers.

CONCLUSIONS

Retinal venular widening is associated with an increased risk of vascular dementia. Our findings are in line with previous observations in stroke and cerebral small-vessel disease and suggest that the association between larger retinal venular calibers and dementia may reflect cerebral hypoperfusion and subsequent ischemia.

Does aortic stiffness improve the prediction of coronary heart disease in elderly? The Rotterdam Study

It has been demonstrated that aortic stiffness is an independent predictor of cardiovascular disease. We investigated whether this measure is of use in cardiovascular risk stratification in clinical practice for elderly subjects (mean age 71.5 years). Within the framework of the Rotterdam Study, we stratified subjects free of coronary heart disease (CHD) at baseline into categories of low (<10%), intermediate (10-20%) and high (>20%) 10-year risk of CHD based on Framingham risk factors. Within each risk category, we determined the percentages of subjects moving into a higher or lower risk category when adding aortic stiffness to the Framingham risk factors. Among 2849 participants, 223 CHD events occurred during a median follow-up of 7.9 years. In the low risk group, 5% of the subjects could be reclassified and in the high-risk group, 6% of the subjects could be reclassified to the intermediate-risk group. In the intermediate-risk group 3% could be reclassified to the high-risk group and 6% to the low-risk group. In a population of elderly subjects, aortic stiffness measurement in addition to Framingham risk factors leads to a limited reclassification of subjects in 10-year cardiovascular disease-risk categories. Therefore, aortic stiffness is associated with the risk of CHD in elderly, but provides no additional value in cardiovascular risk stratification.

Folic acid is positively associated with uteroplacental vascular resistance: the Generation R study

BACKGROUND AND AIMS

Periconception folic acid supplementation may influence early placentation processes and thereby the occurrence of hypertensive pregnancy disorders. For this reason we examined the associations between periconception folic acid supplementation and uteroplacental vascular resistance, blood pressure, and the risks of gestational hypertension and preeclampsia, in 5993 pregnant women, participating in a population-based cohort study.

METHODS AND RESULTS

Folic acid supplementation was assessed by questionnaire. Mean pulsatility index (PI) and resistance index (RI) of the uterine (UtA) and umbilical arteries (UmA) were measured by Doppler ultrasound in mid- and late pregnancy. Systolic and diastolic blood pressures (SBP, DBP) were measured in early, mid- and late pregnancy. Compared to women who did not use folic acid, preconception folic acid users had a slightly lower UtA-RI in mid-pregnancy [β -0.02, 95% confidence interval (CI) -0.03, -0.01] and late pregnancy [β -0.02, 95% CI -0.03, -0.001], a lower UtA-PI in mid-pregnancy [β -0.06, 95% CI -0.1, -0.03] and late pregnancy [β -0.03, 95% CI -0.05, -0.01], as well as tendencies towards a lower UmA-PI in mid-pregnancy [β -0.02, 95% CI -0.04, -0.001] and late pregnancy [β -0.01, 95% CI -0.02, 0.01]. Additionally, these women had slightly higher SBP and DBP throughout pregnancy. Neither the patterns of blood-pressure change during pregnancy, nor the risk of gestational hypertension and preeclampsia differed between the folic acid categories.

CONCLUSION

Periconception folic acid supplementation is associated with lower uteroplacental vascular resistance and higher blood pressures during pregnancy. The effects are small and within physiologic ranges and seem not associated with the risk of hypertensive pregnancy disorders.

Is there an association between wheezing and constipation in preschool children? Explanations from a longitudinal birth cohort

OBJECTIVE

To assess whether wheezing and atopic dermatitis were associated with constipation in preschool children and to what extent shared risk factors contribute to this relationship.

METHODS

A population-based sample of 4651 preschool children was used. At the age of 24, 36 and 48 months, a parental report of functional constipation was available according to the Rome II criteria, and data on atopic dermatitis and wheezing were available using age-adapted questionnaires from the International Study of Asthma and Allergies in Childhood. Stepwise multivariate analyses were performed to assess whether body mass index, infection exposure, food allergy and infant nutrition, and parental stress explained the association between wheezing, atopic dermatitis and constipation.

RESULTS

Out of 4651 children, 12-17% had functional constipation between 24 and 48 months. Symptoms of wheezing decreased from 20% to 12% and atopic dermatitis decreased from 30% to 18% at the age of 24 and 48 months respectively. Between the age of 24 and 48 months, wheezing symptoms were significantly associated with functional constipation (OR 1.17; 1.02 to 1.34) but these results were mainly explained by the child's exposure to infections and use of antibiotics (adjusted odds ratio 1.08; 95% CI 0.95 to 1.24). No significant association was found between symptoms of atopic dermatitis and functional constipation (OR 1.08; 95% CI 0.94 to 1.23).

CONCLUSIONS

These findings suggest that functional constipation coexists with wheezing in childhood but is mainly explained by the child's infection exposure and use of antibiotics. Therefore, an independent association between respiratory symptoms and functional bowel disorders as suggested in previous studies is questionable.

No association of obesity gene FTO with body composition at the age of 6 months. The Generation R Study

BACKGROUND

Genome-wide association studies on body mass index (BMI) have identified an FTO polymorphism (rs9939609) as having the strongest effect.

AIM

We examined the effect of FTO genotype on body composition at the age of 6 months using skinfold thickness measurements and dual energy X-ray absorptiometry (DXA).

MATERIAL/SUBJECTS AND METHODS

This study was embedded in a population-based prospective cohort study from early fetal life onwards. FTO genotype was related to anthropometric measurements (weight and height), subcutaneous fat mass measured by skinfold thickness, and total, truncal, and peripheral fat mass and lean mass measured by DXA. Analyses for skinfold thickness and DXA were performed in 695 and 216 children, respectively.

RESULTS

Genotype frequency was TT 40.3%, TA 45.5%, and AA 14.2%. No significant differences between FTO genotypes were found in weight, height or BMI. Furthermore, FTO genotype was not associated with any skinfold thickness. Finally, no associations between FTO genotype and body composition measures (fat and lean mass) assessed by DXA were found.

CONCLUSIONS

We observed no association between this FTO polymorphism and body composition at the age of 6 months. Longer follow-up studies are necessary to examine at which age and by which mechanisms FTO genotype starts to influence fat mass and body composition.

Agreement between maternal cannabis use during pregnancy according to self-report and urinalysis in a population-based cohort: the Generation R Study

AIM

To verify self-reported information on prenatal drug use in urine because reporting in pregnancy is sensitive to stigma and might lead to misclassification.

METHODS

Using semiquantitative immunochemical analysis, the presence of the urinary metabolite (11-nor-Δ9-tetrahydrocannabinol- 9-carboxylic acid) was compared to self-reported prenatal cannabis use. Sensitivity and specificity for self-report and urinalysis outcomes were calculated and Yule's Y was used as an agreement measure.

RESULTS

Urine samples were available for 3,997 pregnant women. Of these women, 92 reported having used cannabis during pregnancy (2.3%) and 71 had positive urine screens (1.8%). In total 35% of the 92 women with self-reported cannabis use also had a positive urine screen. Positive urines were relatively frequent in women reporting cannabis use before pregnancy only (7.6%) and in women with missing information (2.6%). Sensitivity and specificity of urinalysis compared to self-report were 0.46 and 0.98. Sensitivity and specificity of self-report compared to urinalysis were 0.36 and 0.99. Yule's Y amounted to 0.77, indicating substantial agreement between the measures.

CONCLUSIONS

Our findings illustrate the difficulties in obtaining valid information on prenatal cannabis use. To improve the quality of cannabis use data, we suggest a 2-step approach starting with self-report.

Insulin metabolism and the risk of Alzheimer disease: the Rotterdam Study

OBJECTIVE

Diabetes mellitus has been associated with an increased risk of Alzheimer disease (AD), but how it exerts its effect remains controversial. Possible pathophysiologic mechanisms are glucose toxicity and a direct effect of insulin on amyloid metabolism. Most studies had short follow-up, and longer-term effects of diabetes on AD risk are unknown. We investigated whether fasting glucose and insulin levels and insulin resistance are associated with the risk of AD and whether this risk is constant over time.

METHODS

The study was based on 3,139 participants of the Rotterdam Study, a population-based cohort study. All subjects were free from dementia, did not have a history of diabetes, and had fasting levels of glucose and insulin measured at baseline. Insulin resistance was estimated with the homeostasis model assessment. We investigated how fasting glucose, insulin, and insulin resistance are related to the risk of AD in 3 different strata according to time-to-event, using Cox proportional hazards models.

RESULTS

During follow-up, 211 participants developed AD, 71 of them within 3 years of baseline. Levels of insulin and insulin resistance were associated with a higher risk of AD within 3 years of baseline. After 3 years, the risk was no longer increased. Glucose was not associated with a higher risk of AD. There was no interaction of APOE ε4 carriership and insulin metabolism on the risk of AD.

CONCLUSIONS

Our findings suggest that insulin metabolism influences the clinical manifestation of AD only within 3 years.

Perinatal complications increase the risk of postpartum depression. The Generation R Study

OBJECTIVE

  To examine whether specific pregnancy and delivery complications are risk factors for postpartum depression.

DESIGN

  A prospective longitudinal study.

SETTING

 Rotterdam, the Netherlands.

POPULATION

 A cohort of 4941 pregnant women who enrolled in the Generation R Study.

METHODS

  Information on perinatal complications was obtained from the midwife and hospital registries or by questionnaire. Logistic regression analyses were used to calculate the risk of postpartum depression for the separate perinatal complications.

MAIN OUTCOME MEASURES

Postpartum psychiatric symptoms were assessed 2 months after delivery using the Edinburgh postnatal depression scale.

RESULTS

 Several perinatal complications were significantly associated with postpartum depression, namely: pre-eclampsia (adjusted OR, aOR 2.58, 95% CI 1.30-5.14), hospitalization during pregnancy (aOR 2.25, 95% CI 1.19-4.26), emergency caesarean section (aOR 1.53, 95% CI 1.02-2.31), suspicion of fetal distress (aOR 1.56, 95% CI 1.08-2.27), a medically indicated delivery provided by an obstetrician (aOR 2.43, 95% CI 1.56-3.78), and hospital admission of the baby (aOR 1.45, 95% CI 1.10-1.92). Unplanned pregnancy, thrombosis, meconium-stained amniotic fluid, and Apgar score were not associated with postpartum depression after adjustment for confounding factors, such as pre-existing psychopathological symptoms and sociodemographic characteristics. The risk of postpartum depression increased with the number of perinatal complications women experienced (P < 0.001).

CONCLUSIONS

 We showed that several pregnancy and delivery complications present a risk for women's mental health in the postpartum period. Obstetricians, midwives, general practitioners, and staff at baby well clinics should be aware that women who experienced perinatal complications-especially those with a number of perinatal complications-are at risk for developing postpartum depression.

Insights into the genetic architecture of osteoarthritis from stage 1 of the arcOGEN study

Objectives

The genetic aetiology of osteoarthritis has not yet been elucidated. To enable a well-powered genome-wide association study (GWAS) for osteoarthritis, the authors have formed the arcOGEN Consortium, a UK-wide collaborative effort aiming to scan genome-wide over 7500 osteoarthritis cases in a two-stage genome-wide association scan. Here the authors report the findings of the stage 1 interim analysis.

Methods

The authors have performed a genome-wide association scan for knee and hip osteoarthritis in 3177 cases and 4894 population-based controls from the UK. Replication of promising signals was carried out in silico in five further scans (44 449 individuals), and de novo in 14 534 independent samples, all of European descent.

Results

None of the association signals the authors identified reach genome-wide levels of statistical significance, therefore stressing the need for corroboration in sample sets of a larger size. Application of analytical approaches to examine the allelic architecture of disease to the stage 1 genome-wide association scan data suggests that osteoarthritis is a highly polygenic disease with multiple risk variants conferring small effects.

Conclusions

Identifying loci conferring susceptibility to osteoarthritis will require large-scale sample sizes and well-defined phenotypes to minimise heterogeneity.

Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

Maternal psychological distress and fetal growth trajectories: the Generation R Study

BACKGROUND

Previous research suggests, though not consistently, that maternal psychological distress during pregnancy leads to adverse birth outcomes. We investigated whether maternal psychological distress affects fetal growth during the period of mid-pregnancy until birth.

METHOD

Pregnant women (n=6313) reported levels of psychological distress using the Brief Symptom Inventory (anxious and depressive symptoms) and the Family Assessment Device (family stress) at 20.6 weeks pregnancy and had fetal ultrasound measurements in mid- and late pregnancy. Estimated fetal weight was calculated using head circumference, abdominal circumference and femur length.

RESULTS

In mid-pregnancy, maternal distress was not linked to fetal size. In late pregnancy, however, anxious symptoms were related to fetal size after controlling for potential confounders. Anxious symptoms were also associated with a 37.73 g [95% confidence interval (CI) -69.22 to -6.25, p=0.019] lower birth weight. When we related maternal distress to fetal growth curves using multilevel models, more consistent results emerged. Maternal symptoms of anxiety or depression were associated with impaired fetal weight gain and impaired fetal head and abdominal growth. For example, depressive symptoms reduced fetal weight gain by 2.86 g (95% CI -4.48 to -1.23, p<0.001) per week.

CONCLUSIONS

The study suggests that, starting in mid-pregnancy, fetal growth can be affected by different aspects of maternal distress. In particular, children of prenatally anxious mothers seem to display impaired fetal growth patterns during pregnancy. Future work should address the biological mechanisms underlying the association of maternal distress with fetal development and focus on the effects of reducing psychological distress in pregnancy.

Single nucleotide polymorphisms in genes that are associated with a modified response to statin therapy: the Rotterdam Study

The objective of this study was to investigate whether common variation in genes involved in lipid metabolism modify the effect of statins on serum total cholesterol concentration. Statin users were identified in the Rotterdam Study, a prospective population-based cohort study of subjects >55 years of age. We studied the association between single nucleotide polymorphisms (SNPs) in genes involved in lipid metabolism and total cholesterol response to statin therapy, using linear regression analysis and adjusting for potential confounders. Replication was performed in an independent extended cohort of the Rotterdam Study. Genotype data and total cholesterol concentrations after start of statin therapy were available for 554 newly started statin users. Two SNPs were associated with a significantly higher cholesterol concentration under statin therapy: SNP rs1532624 in the CETP gene (β: 0.141  mmol l(-1), P=0.004 per additional allele) and SNP rs533556 in the APOA1 gene (β: 0.138  mmol l(-1), P=0.005 per additional allele). In the replication sample, only the CETP rs1532624 SNP again showed a significant association. The SNPs were not related to baseline total cholesterol in non-statin users. In conclusion, we found that the CETP rs1532624 polymorphism is associated with cholesterol response to statin therapy in a cohort of elderly subjects in the general population.

Hedgehog-interacting protein is a COPD susceptibility gene: the Rotterdam Study

The Hedgehog signalling pathway plays an important role in lung morphogenesis and cellular responses to lung injury. A genome-wide association study has demonstrated that two single nucleotide polymorphisms (SNPs) near the Hedgehog-interacting protein (Hip) gene, SNP identifiers rs1828591 and rs13118928, are associated with risk of chronic obstructive pulmonary disease (COPD). The aim of the present study was to validate the observed association between genetic variation near the Hip gene and COPD, and to investigate whether risk estimates were modified by smoking behaviour. The association between the Hip gene SNPs and COPD was investigated in the Rotterdam Study by logistic regression analyses, adjusted for several covariates. In addition, an association meta-analysis was performed that included data from the genome-wide association study on COPD. Both SNPs were significantly associated with risk of COPD (OR 0.80; 95% CI 0.72-0.91). Homozygosity for the minor G allele resulted in a decreased risk of COPD of approximately 40% (95% CI 0.47-0.78). There was a significant interaction with the number of pack-years of smoking (p = 0.004). The meta-analysis yielded an odds ratio for COPD of 0.80 per additional G allele (p = 3.4 x 10(-9)). Genetic variation near the Hip gene was significantly associated with risk of COPD, depending on the number of pack-years of smoking.

Abdominal fat in children measured by ultrasound and computed tomography

The prevalence of childhood obesity is increasing rapidly. Visceral fat plays an important role in the pathogenesis of metabolic and cardiovascular diseases. Currently, computed tomography (CT) is broadly seen as the most accurate method of determining the amount of visceral fat. The main objective was to examine whether measures of abdominal visceral fat can be determined by ultrasound in children and whether CT can be replaced by ultrasound for this purpose. To assess whether preperitoneal fat thickness and area are good approximations of visceral fat at the umbilical level, we first retrospectively examined 47 CT scans of nonobese children (body mass index <30kg/m(2); median age 7.9 y [95% range 1.2 to 16.2]). Correlation coefficients between visceral and preperitoneal fat thickness and area were 0.58 (p<0.001) and 0.76 (p<0.001), respectively. Then, to assess how preperitoneal and subcutaneous fat thicknesses and areas measured by ultrasound compare with these parameters in CT, we examined 34 nonobese children (median age 9.5 [95% range 0.3 to 17.0]) by ultrasound and CT. Ultrasound measurements of preperitoneal and subcutaneous fat were correlated with CT measurements, with correlation coefficients ranging from 0.75-0.97 (all p<0.001). Systematic differences of up to 24.0cm(2) for preperitoneal fat area (95% confidence interval -29.9 to 77.9cm(2)) were observed when analyzing the results described by the Bland-Altman method. Our findings suggest that preperitoneal fat can be used as an approximation for visceral fat in children and that measuring abdominal fat with ultrasound in children is a valid method for epidemiological and clinical studies. However, the exact agreement between the ultrasound and CT scan was limited, which indicates that ultrasound should be used carefully for obtaining exact fat distribution measurements in individual children.

Cathepsin D gene and the risk of Alzheimer's disease: a population-based study and meta-analysis

Cathepsin D (CTSD) is a gene involved in amyloid precursor protein processing and is considered a candidate for Alzheimer's disease (AD). The aim of the current study was to examine if variation in CTSD increases the risk of AD. We performed a candidate-gene analysis in a population-based cohort study (N=7983), and estimated the effect of CTSD on the risk of AD. Additionally, a large meta-analysis was performed incorporating our data and previously published data. The T-allele of CTSD rs17571 was associated with an increased risk of AD (p-value 0.007) in the Rotterdam Study. This association was predominantly found in APOE ε4 noncarriers. A meta-analysis of previously published data showed a significantly increased risk of AD in carriers of the T-allele of rs17571 (OR 1.22, 95% CI 1.03-1.44), irrespective of APOE ε4 carrier status. This study adds to the evidence that CTSD increases the risk of AD, although the effect size is moderate.

Induction of antibodies by Staphylococcus aureus nasal colonization in young children

In order to develop novel antistaphylococcal strategies, understanding the determinants of carriage and how humans respond to Staphylococcus aureus exposure is essential. Here, the primary S. aureus-specific humoral immune response and its association with nasal colonization was studied in young children. Sera from 57 colonized or non-colonized children, serially collected at birth and at 6, 14 and 24 months, were analysed for IgG, IgA and IgM binding to 19 staphylococcal proteins, using flow cytometry-based technology. The antibody responses showed extensive inter-individual variability. On average, the levels of antistaphylococcal IgA and IgM increased from birth until the age of 2 years (p <0.05), whereas the levels of IgG decreased (p <0.001). Placentally transferred maternal IgG did not protect against colonization. In colonized children, IgG and IgA levels for a number of proteins were higher than in non-colonized children. At both 14 and 24 months, the levels of IgG against chemotaxis inhibitory protein of S. aureus (at 24 months; median fluorescence intensity, 4928 vs. 24, p <0.05), extracellular fibrinogen-binding protein (987 vs. 604, p <0.05), and iron-responsive surface determinant H (62 vs. 5, p <0.05) were significantly higher in colonized children. The levels of IgA against CHIPS, IsdH and IsdA were higher (p <0.05). Therefore, CHIPS, Efb, IsdA and IsdH seem to play a role in nasal colonization of young children.

Superficial siderosis in the general population

BACKGROUND

Superficial siderosis is a rare radiologic diagnosis of hemosiderin deposition in subpial brain layers. In case studies, an association between superficial siderosis and cerebral amyloid angiopathy (CAA) has been described. Also, a potential role of superficial siderosis in Alzheimer disease (AD) was hypothesized. All previously reported cases of superficial siderosis were detected because of overt clinical symptoms. We studied the occurrence of superficial siderosis on brain MRI in a general population of nondemented elderly.

METHODS

In 1,062 persons (mean age 69.6 years) from the population-based Rotterdam Scan Study, we performed T2*-weighted MRI to assess the presence of superficial siderosis. Furthermore, the presence, number, and location of cerebral microbleeds were rated, as lobar microbleeds are thought to be indicative of CAA.

RESULTS

We found that superficial siderosis was present in 7 (0.7%) individuals, all of whom had cerebral microbleeds in lobar locations. Furthermore, in all 7 persons, microbleeds were located in close vicinity to superficial siderosis.

CONCLUSIONS

Our results provide further indirect support for the presumed link between superficial siderosis and cerebral amyloid angiopathy (CAA). Whether superficial siderosis may be a marker for severity or worse prognosis of CAA needs to be further evaluated in longitudinal follow-up.

Genetic variation in the organic cation transporter 1 is associated with metformin response in patients with diabetes mellitus

The organic cation transporter 1, encoded by the SLC22A1 gene, is responsible for the uptake of the anti-hyperglycaemic drug, metformin, in the hepatocyte. We assessed whether a genetic variation in the SLC22A1 gene is associated with the glucose-lowering effect of metformin. Incident metformin users in the Rotterdam Study, whose HbA1c measurements were available, were identified. Associations between 11 tagging single nucleotide polymorphisms in the SLC22A1 gene and change in the HbA1c level were analyzed. A total of 102 incident metformin users were included in this study sample. Except for the rs622342 A>C polymorphism, no significant differences in metformin response were observed. For each minor C allele at rs622342, the reduction in HbA1c levels was 0.28% less (95% CI 0.09-0.47, P=0.005). After Bonferroni correction, the P-value was 0.050. To conclude, genetic variation at rs622342 in the SLC22A1 gene was associated with the glucose-lowering effect of metformin in patients with diabetes mellitus.

No modification of the beneficial effect of NSAIDs on colorectal cancer by CYP2C9 genotype

BACKGROUND

CYP2C9 enzymes are involved in non-steroidal anti-inflammatory drug (NSAID) metabolism. Therefore, we investigated whether CYP2C9*2 and *3 variant alleles, encoding for enzymes with lower activity, increased the protective effect of NSAIDs on colorectal cancer.

METHODS

Individual and combined associations of NSAIDs and CYP2C9*2 and *3 variant alleles with colorectal cancer were studied in 7757 Caucasian individuals of The Rotterdam Study, a population-based prospective cohort since 1990. Additive and multiplicative effect modification models were used to examine drug-gene interactions.

RESULTS

There were 212 incident cases of colorectal cancer during follow-up. A reduced risk of colorectal cancer was observed in individuals who used NSAIDs for more than a year (HR 0.45; 95% CI 0.28 to 0.71), and in carriers of an CYP2C9 variant allele associated with lower enzymatic activity (HR 0.67; 95% CI 0.47 to 0.96). The combination of both determinants was associated with a further risk reduction but without synergy.

CONCLUSION

Both NSAID use and CYP2C9*2 and/ or *3 carriage are associated with a reduced risk of colorectal cancer. However, no interaction between the determinants was found, which might indicate independent pathophysiological mechanisms.

Protective effect of NSAIDs on cancer and influence of COX-2 C(-765G) genotype

PURPOSE

Inhibition of COX-2 enzymes is a frequently suggested mechanism for the beneficial effects of NSAIDs on carcinogenesis. The aim of this study was to explore the role of cumulative NSAID use on four common non-skin related cancers and modification by COX-2 G(-765)C genotype.

PATIENTS AND METHODS

7621 participants of The Rotterdam Study were included. In a mean follow up period of 10 years, 720 colorectal, lung, breast or prostate cancers occurred. Cumulative NSAID use was calculated per NSAID class. Individual associations of NSAID use and COX-2 G(-765)C genotype on cancer risk were explored with Cox' proportional hazard models. Next, the association of NSAIDs and cancer stratified by COX-2 genotype was studied. Finally, the effect of combinations of NSAID use and COX-2 genotype on survival times was investigated.

RESULTS

All NSAID classes were associated with a reduced risk of colorectal cancer but not of other cancers. No associations between COX-2 genotype and incident cancer, overall or cancer specific mortality were observed. COX-selective NSAIDs showed modest further risk reduction. Survival times were more than twice as long for carriers of a COX-2 C(-765) allele with colorectal cancer who used NSAIDs in the five years prior to diagnosis than for patients homozygous for the wild type (G(-765)) without NSAID use (p = 0.007).

CONCLUSION

Our results confirm the protective effect of NSAID use on colorectal cancer. Individuals diagnosed with colorectal cancer who carry a COX-2 C(-765) allele and are on NSAIDs have an increased survival in comparison to non-users with the wild type (G(-765)).

Duration of antihypertensive drug use and risk of dementia: A prospective cohort study

BACKGROUND

The evidence from prospective observational research for a protective effect of antihypertensive drug use on the risk of dementia is far from uniform. Duration of follow-up was limited and relied mainly on baseline drug exposure data without information on duration of use. We investigated the association between the duration of antihypertensive use and risk of dementia.

METHODS

We followed 6,249 participants (mean 68.4 years, 60% women) of a prospective, population-based cohort from baseline (1990-1993) until 2005 for incident dementia. Continuous data on filled prescriptions came from pharmacy records. Total cumulative duration of antihypertensive use was expressed in years. We subtracted a latent 4-year period before the date of dementia diagnosis in the quantification of exposure duration to avoid potential bias in antihypertensive prescription due to prodromal changes in blood pressure or cognition. With Cox regression models, we calculated crude and adjusted hazard ratios (HRs) of all dementia and Alzheimer disease (AD) with antihypertensive use vs never used.

RESULTS

Compared to never used, antihypertensive use was associated with a reduced risk of all dementia (adjusted HR per year of use 0.95; 95% confidence interval [CI] 0.91-0.99). We observed an 8% (95% CI -15% to -1%) risk reduction per year of use for persons < or =75 years, whereas for persons >75 years this was 4% (95% CI -11% to 4%). Equivalent estimates were observed for AD. No apparent differences were observed among different types of antihypertensive drugs.

CONCLUSIONS

Antihypertensive drug use was associated with 8% risk reduction of dementia per year of use for persons < or =75 years.

Statins are associated with a reduced risk of Alzheimer disease regardless of lipophilicity. The Rotterdam Study

BACKGROUND

Cross-sectional reports suggest that statin users are less likely to have Alzheimer disease (AD). Prospective studies have provided inconsistent evidence. Moreover, it is unclear whether the association differs for lipophilic statins, those that could more easily pass the blood-brain barrier and hydrophilic statins.

OBJECTIVES

To prospectively evaluate whether use of statins is associated with the risk of AD, and to determine whether associations differ for lipophilic and hydrophilic statins.

METHOD

6992 participants of the prospective, population-based Rotterdam Study were followed, from baseline (1990-1993) until January 2005 for incident AD. Data on all filled prescriptions came from pharmacy records. For each date on which each event occurred, cholesterol-lowering drug use for the person who experienced the event and all remaining persons in the cohort was categorised as "any" or "never" use. A distinction was made between statin, lipophilic and hydrophilic statins, and non-statin cholesterol-lowering drugs. Data were analysed with the Cox regression analysis, adjusting for sex, age and potential confounders.

RESULTS

During follow-up (mean 9 years), 582 persons developed AD. Compared with never use of cholesterol-lowering drugs, statin use was associated with a decreased risk of AD (HR 0.57; 95% CI 0.37 to 0.90), but non-statin cholesterol-lowering drug use was not (HR 1.05; 95% CI 0.45 to 2.44). HRs were equal for lipophilic (HR 0.54; 95% CI 0.32 to 0.89) and hydrophilic statins (HR 0.54; 95% CI 0.26 to 1.11).

CONCLUSION

In the general population, the use of statins, but not of non-statin cholesterol-lowering drugs, was associated with a lower risk of AD compared with never use of cholesterol-lowering drugs. The protective effect was independent of the lipophilicity of statins.

Explaining educational inequalities in preterm birth: the generation r study

BACKGROUND

Although a low socioeconomic status has consistently been associated with an increased risk of preterm birth, little is known about the pathways through which socioeconomic disadvantage influences preterm birth.

AIM

To examine mechanisms that might underlie the association between the educational level of pregnant women as an indicator of socioeconomic status, and preterm birth.

METHODS

The study was nested in a population-based cohort study in the Netherlands. Information was available for 3830 pregnant women of Dutch origin.

FINDINGS

The lowest-educated pregnant women had a statistically significant higher risk of preterm birth (odds ratio (OR) = 1.89 (95% CI 1.28 to 2.80)) than the highest educated women. This increased OR was reduced by up to 22% after separate adjustment for age, height, preeclampsia, intrauterine growth restriction, financial concerns, long-lasting difficulties, psychopathology, smoking habits, alcohol consumption, and body mass index (BMI) of the pregnant women. Joint adjustment for these variables resulted in a reduction of 89% of the increased risk of preterm birth among low-educated pregnant women (fully adjusted OR = 1.10 (95% CI 0.66 to 1.84)).

CONCLUSIONS

Pregnant women with a low educational level have a nearly twofold higher risk of preterm birth than women with a high educational level. This elevated risk could largely be explained by pregnancy characteristics, indicators of psychosocial well-being, and lifestyle habits. Apparently, educational inequalities in preterm birth go together with an accumulation of multiple adverse circumstances among women with a low education. A number of explanatory mechanisms unravelled in the present study seem to be modifiable by intervention programmes.

Salivary cortisol is related to atherosclerosis of carotid arteries

BACKGROUND

Dysregulation of the hypothalamic-pituitary-adrenal axis has been suggested as an independent risk factor for ischemic heart disease. The aim of our study was to evaluate whether two markers of the hypothalamic-pituitary-adrenal axis activity, the level of salivary cortisol and the diurnal salivary cortisol pattern, are associated with atherosclerosis of the carotid arteries in an elderly population.

METHODS AND RESULTS

A total of 1866 participants of the Rotterdam Study, a population-based cohort study in the elderly, provided four salivary cortisol samples throughout 1 d, and underwent ultrasonography to examine the presence of plaques in the common, internal, and bifurcation sites of both carotid arteries. Two summary measures of the separate cortisol values were computed: area under the curve (AUC), which is a measure of total cortisol exposure while awake; and the slope, which is a measure of diurnal cortisol decline.

RESULTS

Total cortisol exposure while awake (AUC) was associated with higher plaque scores (beta = 0.08 per sd of AUC, 95% confidence interval 0.00-0.16; P = 0.04) in a fully adjusted linear regression model. Persons with an AUC in the highest tertile had a higher number of plaques of carotid arteries compared with those in the lowest tertile (3.08 vs. 2.80, 95% confidence interval of difference 0.09-0.48; P = 0.005). There was no relation between diurnal cortisol decline and plaque score.

CONCLUSION

Our results support the hypothesis that increased total cortisol exposure is independently associated with atherosclerosis of the carotid arteries.

Depressive symptoms and risk of stroke: the Rotterdam Study

BACKGROUND

Previous studies that have assessed whether the presence of depressive symptoms predisposes to stroke in the general elderly population have been contradictory. Moreover, they did not distinguish between men and women and did not perform psychiatric workups in those with depressive symptoms. This study examines the association between depressive symptoms, depressive disorder and the risk of stroke in the general population.

METHODS

This prospective population based cohort study included 4424 participants from the third Rotterdam Study Survey (1997-1999) who, at that time, were > or =61 years of age and free from stroke. Depressive symptoms were assessed using the Centre for Epidemiological Studies Depression Scale (CESD) and considered present if the CESD score was > or =16. Participants with depressive symptoms had a diagnostic interview for depressive disorder. Follow-up was complete until 1 January 2005. Data were analysed using Cox proportional hazards models with adjustment for relevant confounders.

RESULTS

Men with depressive symptoms (n = 73) were at increased risk of stroke (adjusted hazard ratio (HR) 2.17; 95% CI 1.11 to 4.23) and ischaemic stroke (adjusted HR 3.21; 95% CI 1.62 to 6.38). These associations were at least partly attributable to men who reported depressive symptoms but who did not fulfil Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV diagnostic criteria for depressive disorder (n = 32): they had a very high risk of stroke (adjusted HR 2.70; 95% CI 1.15 to 6.33) and ischaemic stroke (adjusted HR 4.01; 95% CI 1.68 to 9.57). In women there was no association between presence of depressive symptoms and risk of stroke.

CONCLUSIONS

Presence of depressive symptoms is a strong risk factor for stroke in men but not in women.

White matter atrophy and lesion formation explain the loss of structural integrity of white matter in aging

The importance of macrostructural white matter changes, including white matter lesions and atrophy, in intact brain functioning is increasingly being recognized. Diffusion tensor imaging (DTI) enables measurement of the microstructural integrity of white matter. Loss of white matter integrity in aging has been reported, but whether this is inherent to the aging process itself or results from specific white matter pathology is unknown. In 832 persons aged 60 years and older from the population-based Rotterdam Study, we measured fractional anisotropy (FA) and directional diffusivities in normal-appearing white matter using DTI. All subjects' DTI measures were projected onto a common white matter skeleton to enable robust voxelwise comparison. With increasing age, multiple regions showed significant decreases in FA or increases in axial or radial diffusivity in normal-appearing white matter. However, nearly all of these regional changes were explained by either white matter atrophy or by white matter lesions; each of which related to changes in distinct brain regions. These results indicate that loss of white matter integrity in aging is primarily explained by atrophy and lesion formation and not by the aging process itself. Furthermore, white matter atrophy and white matter lesion formation relate to loss of integrity in distinct brain regions, indicating the two processes are pathophysiologically different.

An RBP4 promoter polymorphism increases risk of type 2 diabetes

AIMS/HYPOTHESIS

Retinol-binding protein 4 (RBP4), originally known for retinol transport, was recently identified as an adipokine affecting insulin resistance. The RBP4 -803GA promoter polymorphism influences binding of hepatic nuclear factor 1alpha and is associated with type 2 diabetes in case-control studies. We hypothesised that the RBP4 -803GA polymorphism increases type 2 diabetes risk at a population-based level. In addition, information on retinol intake and plasma vitamin A levels enabled us to explore the possible underlying mechanism.

METHODS

In the Rotterdam Study, a prospective, population-based, follow-up study, the -803GA polymorphism was genotyped. In Cox proportional hazards models, associations of the -803GA polymorphism and retinol intake with type 2 diabetes risk were examined. Moreover, the interaction of the polymorphism with retinol intake on type 2 diabetes risk was assessed. In a subgroup of participants the association of the polymorphism and vitamin A plasma levels was investigated.

RESULTS

Homozygous carriers of the -803A allele had increased risk of type 2 diabetes (HR 1.83; 95% CI 1.26-2.66). Retinol intake was not associated with type 2 diabetes risk and showed no interaction with the RBP4 -803GA polymorphism. Furthermore, there was no significant association of the polymorphism with plasma vitamin A levels.

CONCLUSIONS/INTERPRETATION

Our results provide evidence that homozygosity for the RBP4 -803A allele is associated with increased risk of type 2 diabetes in the Rotterdam population. This relationship was not clearly explained by retinol intake and vitamin A plasma levels. Therefore, we cannot differentiate between a retinol-dependent or -independent mechanism of this RBP4 variant.

Cerebrovascular risk factors and incident depression in community-dwelling elderly

OBJECTIVE

The 'vascular depression' hypothesis suggests that late-life depression results from vascular brain damage. We studied the longitudinal association between cerebrovascular risk factors and incident depression in a large population-based study.

METHOD

Two thousand nine hundred and thirty-one persons with the age of > or =61 years were followed up. Data on a comprehensive set of cerebrovascular risk factors were collected at baseline. Participants received a psychiatric assessment 5 years later to establish DSM-IV diagnoses.

RESULTS

Only current smoking and antihypertensive drug use were independently associated with incident depressive symptoms. Diabetes mellitus and the Framingham stroke risk score were related to incident depressive disorder. No relation with depression was observed for cholesterol, diastolic and systolic blood pressure, history of cardiovascular disease, atrial fibrillation, left ventricular hypertrophy or the use of statins and anticoagulants.

CONCLUSION

These results moderately support the 'vascular depression' hypothesis.

Ankle brachial index combined with Framingham Risk Score to predict cardiovascular events and mortality: a meta-analysis

CONTEXT

Prediction models to identify healthy individuals at high risk of cardiovascular disease have limited accuracy. A low ankle brachial index (ABI) is an indicator of atherosclerosis and has the potential to improve prediction.

OBJECTIVE

To determine if the ABI provides information on the risk of cardiovascular events and mortality independently of the Framingham risk score (FRS) and can improve risk prediction.

DATA SOURCES

Relevant studies were identified. A search of MEDLINE (1950 to February 2008) and EMBASE (1980 to February 2008) was conducted using common text words for the term ankle brachial index combined with text words and Medical Subject Headings to capture prospective cohort designs. Review of reference lists and conference proceedings, and correspondence with experts was conducted to identify additional published and unpublished studies.

STUDY SELECTION

Studies were included if participants were derived from a general population, ABI was measured at baseline, and individuals were followed up to detect total and cardiovascular mortality.

DATA EXTRACTION

Prespecified data on individuals in each selected study were extracted into a combined data set and an individual participant data meta-analysis was conducted on individuals who had no previous history of coronary heart disease.

RESULTS

Sixteen population cohort studies fulfilling the inclusion criteria were included. During 480,325 person-years of follow-up of 24,955 men and 23,339 women, the risk of death by ABI had a reverse J-shaped distribution with a normal (low risk) ABI of 1.11 to 1.40. The 10-year cardiovascular mortality in men with a low ABI (< or = 0.90) was 18.7% (95% confidence interval [CI], 13.3%-24.1%) and with normal ABI (1.11-1.40) was 4.4% (95% CI, 3.2%-5.7%) (hazard ratio [HR], 4.2; 95% CI, 3.3-5.4). Corresponding mortalities in women were 12.6% (95% CI, 6.2%-19.0%) and 4.1% (95% CI, 2.2%-6.1%) (HR, 3.5; 95% CI, 2.4-5.1). The HRs remained elevated after adjusting for FRS (2.9 [95% CI, 2.3-3.7] for men vs 3.0 [95% CI, 2.0-4.4] for women). A low ABI (< or = 0.90) was associated with approximately twice the 10-year total mortality, cardiovascular mortality, and major coronary event rate compared with the overall rate in each FRS category. Inclusion of the ABI in cardiovascular risk stratification using the FRS would result in reclassification of the risk category and modification of treatment recommendations in approximately 19% of men and 36% of women.

CONCLUSION

Measurement of the ABI may improve the accuracy of cardiovascular risk prediction beyond the FRS.

Haplotypes of the fibrinogen gene and cerebral small vessel disease: the Rotterdam scan study

OBJECTIVE

Fibrinogen levels and fibrinogen clot structure have been implicated in the pathogenesis of vascular disease. We examined fibrinogen levels and variation in fibrinogen genes (fibrinogen gamma (FGG), alpha (FGA) and beta (FGB)), which have been associated with fibrin clot structure and fibrinogen levels, in relation to cerebral small vessel disease (SVD).

METHODS AND RESULTS

This study was performed as part of the Rotterdam Scan Study, a population based study in 1077 elderly patients undergoing cerebral MRI. Plasma fibrinogen levels and haplotypes were determined. We examined the association between fibrinogen levels and haplotype with silent brain infarcts and white matter lesions using logistic regression models. We constructed seven haplotypes (frequency >0.01) that describe the total common variation in the FGG and FGA genes. Haplotype 2 (GATAGTG) was associated with the presence of silent brain infarcts compared with the most frequent haplotype (GGTGGTA) (OR 1.41, 95% CI 1.03 to 1.94). Haplotype 3 (GGCGATA) was associated with periventricular white matter lesions in the highest tertile of the distribution (OR 1.40, 95% CI 1.01 to 1.92). No association was found between plasma fibrinogen levels and SVD.

CONCLUSIONS

Our study provides evidence for an association of common variation in the FGG and FGA genes with cerebral SVD. It is possible that the structure of the fibrin clot rather than plasma fibrinogen levels plays a role in the pathogenesis of cerebral SVD.

Tracking and determinants of subcutaneous fat mass in early childhood: the Generation R Study

OBJECTIVES

To examine the development and tracking of subcutaneous fat mass in the first 2 years of life and to examine which parental, fetal and postnatal characteristics are associated with subcutaneous fat mass.

DESIGN

This study was embedded in the Generation R Study, a prospective cohort study from early fetal life onward. Subcutaneous fat mass was measured by skinfold thickness (biceps, triceps, suprailiacal, subscapular) at the ages of 1.5, 6 and 24 months in 1012 children. Information about parental, fetal and postnatal growth characteristics was collected by physical and fetal ultrasound examinations and questionnaires.

RESULTS

Normal values of subcutaneous fat mass are presented. Total subcutaneous fat mass was higher in girls than in boys at the age of 24 months (P=0.01). Subjects in the lowest and highest quartiles at the age of 6 months tended to keep their position in the same quartile at the age of 24 months (odds ratios 1.86 (95% confidence interval (CI) 1.3, 2.7)) and 1.84 (95% CI: 1.3, 2.6), respectively). Maternal height and weight, paternal weight, fetal weight at 30 weeks, birth weight and weight at the age of 6 weeks were each inversely associated with subcutaneous fat mass at the age of 24 months after adjustment for current weight at 24 months.

CONCLUSION

This study shows for the first time that subcutaneous fat mass tends to track in the first 2 years of life. Furthermore, the results suggest that an adverse fetal environment and growth are associated with increased subcutaneous fat mass at the age of 24 months. Further studies are needed to examine whether these associations persist in later life.

History of depression, depressive symptoms, and medial temporal lobe atrophy and the risk of Alzheimer disease

BACKGROUND

Depression may increase risk for Alzheimer disease (AD), but it is not clear whether this risk is mediated by structural brain changes. We determined whether history of depressive episodes and presence of depressive symptoms were associated with smaller hippocampal and amygdalar volumes and with increased risk for incident AD.

METHODS

Within the Rotterdam Scan Study 503 persons, aged 60-90 years at baseline and without dementia, reported their history of depressive episodes. Depressive symptoms were assessed with the Center for Epidemiologic Studies Depression Scale. Volumetric assessment of the hippocampus and amygdala was performed using three-dimensional MRI. All subjects were followed for an average of 6 years for development of AD, diagnosed according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria.

RESULTS

A total of 134 subjects (26.6%) reported a history of depression (88 reported an onset <60 years and 46 a late onset). Multiple linear regression analyses did not reveal a significant association with hippocampal or amygdalar volume for any of the depression parameters. During follow-up, 33 persons developed AD. Cox regression analyses showed that subjects with early onset depression had an increased risk for AD (HR 3.76; 95% CI 1.41 to 10.06), independent of hippocampal and amygdalar volume, whereas this risk was 2.34 (95% CI 0.82 to 6.69) in subjects with a late-onset depression. Depressive symptoms at baseline were not associated with increased risk for AD.

CONCLUSION

History of depression, and particularly an early onset, but not presence of depressive symptoms increased the risk for Alzheimer disease. This risk was not mediated by smaller hippocampal or amygdalar volumes.

Bone mineral density, osteoporosis, and osteoporotic fractures: a genome-wide association study

BACKGROUND

Osteoporosis is diagnosed by the measurement of bone mineral density, which is a highly heritable and multifactorial trait. We aimed to identify genetic loci that are associated with bone mineral density.

METHODS

In this genome-wide association study, we identified the most promising of 314 075 single nucleotide polymorphisms (SNPs) in 2094 women in a UK study. We then tested these SNPs for replication in 6463 people from three other cohorts in western Europe. We also investigated allelic expression in lymphoblast cell lines. We tested the association between the replicated SNPs and osteoporotic fractures with data from two studies.

FINDINGS

We identified genome-wide evidence for an association between bone mineral density and two SNPs (p<5x10(-8)). The SNPs were rs4355801, on chromosome 8, near to the TNFRSF11B (osteoprotegerin) gene, and rs3736228, on chromosome 11 in the LRP5 (lipoprotein-receptor-related protein) gene. A non-synonymous SNP in the LRP5 gene was associated with decreased bone mineral density (rs3736228, p=6.3x10(-12) for lumbar spine and p=1.9x10(-4) for femoral neck) and an increased risk of both osteoporotic fractures (odds ratio [OR] 1.3, 95% CI 1.09-1.52, p=0.002) and osteoporosis (OR 1.3, 1.08-1.63, p=0.008). Three SNPs near the TNFRSF11B gene were associated with decreased bone mineral density (top SNP, rs4355801: p=7.6x10(-10) for lumbar spine and p=3.3x10(-8) for femoral neck) and increased risk of osteoporosis (OR 1.2, 95% CI 1.01-1.42, p=0.038). For carriers of the risk allele at rs4355801, expression of TNFRSF11B in lymphoblast cell lines was halved (p=3.0x10(-6)). 1883 (22%) of 8557 people were at least heterozygous for these risk alleles, and these alleles had a cumulative association with bone mineral density (trend p=2.3x10(-17)). The presence of both risk alleles increased the risk of osteoporotic fractures (OR 1.3, 1.08-1.63, p=0.006) and this effect was independent of bone mineral density.

INTERPRETATION

Two gene variants of key biological proteins increase the risk of osteoporosis and osteoporotic fracture. The combined effect of these risk alleles on fractures is similar to that of most well-replicated environmental risk factors, and they are present in more than one in five white people, suggesting a potential role in screening.