The Rotterdam Study: 2012 objectives and design update

PLS3 mutations in X-linked osteoporosis with fractures

Plastin 3 (PLS3), a protein involved in the formation of filamentous actin (F-actin) bundles, appears to be important in human bone health, on the basis of pathogenic variants in PLS3 in five families with X-linked osteoporosis and osteoporotic fractures that we report here. The bone-regulatory properties of PLS3 were supported by in vivo analyses in zebrafish. Furthermore, in an additional five families (described in less detail) referred for diagnosis or ruling out of osteogenesis imperfecta type I, a rare variant (rs140121121) in PLS3 was found. This variant was also associated with a risk of fracture among elderly heterozygous women that was two times as high as that among noncarriers, which indicates that genetic variation in PLS3 is a novel etiologic factor involved in common, multi-factorial osteoporosis.

Apolipoprotein E genotype influences spatial distribution of cerebral microbleeds

In cerebral amyloid angiopathy patients, microbleeds often cluster, mostly occipital, and are associated with apolipoprotein E (APOE) genotype. Microbleeds also frequently occur in the asymptomatic, general population. In this population, we investigated spatial distribution of microbleeds and whether this is influenced by APOE genotype. In 292 persons with microbleeds, we labeled microbleeds on baseline and follow-up magnetic resonance images. We calculated distance between incident and prevalent microbleeds within and between persons and performed lobar segmentation on the magnetic resonance images. Subsequently, we investigated proximity and lobar distribution in strata of APOE genotype. Microbleeds occurred closer within persons than between persons (-42.2 mm, 95% confidence interval, -44.6 to -39.9; p < 0.001). Microbleeds within APOE ε2 and ε4 carriers occurred closer than those in persons with ε3ε3 genotype (-11.9 mm, 95% confidence interval, -24.4 to 0.6; p = 0.06). Persons with ε2 and ε4 alleles had a larger proportion of microbleeds in the occipital lobe than persons with ε3ε3 genotype. Similar to cerebral amyloid angiopathy patients, microbleeds in the general population cluster and the distribution is affected by APOE genotype.

Systematic identification of trans eQTLs as putative drivers of known disease associations

Identifying the downstream effects of disease-associated SNPs is challenging. To help overcome this problem, we performed expression quantitative trait locus (eQTL) meta-analysis in non-transformed peripheral blood samples from 5,311 individuals with replication in 2,775 individuals. We identified and replicated trans eQTLs for 233 SNPs (reflecting 103 independent loci) that were previously associated with complex traits at genome-wide significance. Some of these SNPs affect multiple genes in trans that are known to be altered in individuals with disease: rs4917014, previously associated with systemic lupus erythematosus (SLE), altered gene expression of C1QB and five type I interferon response genes, both hallmarks of SLE. DeepSAGE RNA sequencing showed that rs4917014 strongly alters the 3' UTR levels of IKZF1 in cis, and chromatin immunoprecipitation and sequencing analysis of the trans-regulated genes implicated IKZF1 as the causal gene. Variants associated with cholesterol metabolism and type 1 diabetes showed similar phenomena, indicating that large-scale eQTL mapping provides insight into the downstream effects of many trait-associated variants.

Cerebral microbleeds and the risk of mortality in the general population

Presence of cerebral microbleeds indicates underlying vascular brain disease and has been implicated in lobar hemorrhages and dementia. However, it remains unknown whether microbleeds also reflect more systemic vascular burden. We investigated the association of microbleeds with all-cause and cardiovascular related mortality in the general population. We rated the brain magnetic resonance imaging scans of 3979 Rotterdam Scan Study participants to determine presence, number, and location of microbleeds. Cox proportional hazards models, adjusted for age, sex, subcohort, vascular risk factors, and other MRI markers of cerebral vascular disease, were applied to quantify the association of microbleeds with mortality. After a mean follow up of 5.2 (±1.1) years, 172 (4.3 %) people had died. Presence of microbleeds, and particularly deep or infratentorial microbleeds, was significantly associated with an increased risk of all-cause mortality [sex-, age-, subcohort adjusted hazard ratio (HR) 2.27; CI 1.50-3.45], independent of vascular risk factors (HR 1.87; 95 % CI 1.20-2.92). The presence of deep or infratentorial microbleeds strongly associated with the risk of cardiovascular related mortality (HR 4.08; CI 1.78-9.39). Mortality risk increased with increasing number of microbleeds. The presence of microbleeds, particularly multiple microbleeds and those in deep or infratentorial regions, indicates an increased risk of mortality, independent of other MRI markers of cerebral vascular disease. Our data suggest that microbleeds may mark severe underlying vascular pathology associated with poorer survival.

Clopidogrel use is associated with an increased prevalence of cerebral microbleeds in a stroke-free population: the Rotterdam study

BACKGROUND

Although clopidogrel reduces the incidence of atherothrombotic events, its use is associated with an increased risk of major bleeding. Cerebral microbleeds (CMBs) are indicative of subclinical microangiopathy in the brain and may prelude symptomatic intracerebral hemorrhage. We examined the association between use of clopidogrel and CMBs in persons without a history of stroke.

METHODS AND RESULTS

We performed a cross-sectional analysis using data from the Rotterdam Study, a prospective population-based cohort of persons aged 45 years and older. Among 4408 stroke-free individuals who underwent brain magnetic resonance imaging for the detection of CMBs, we identified 121 ever-users and 4287 never-users of clopidogrel before magnetic resonance imaging. We used multiple logistic regression to analyze the association between clopidogrel and CMBs with adjustment for age, sex, cardiovascular risk factors, and common cardiovascular medication. Users of clopidogrel had a higher prevalence of CMBs (odd ratio 1.55, 95% CI 1.01 to 2.37) than nonusers and more often had a high number (> 4) of CMBs (odds ratio 3.19, 95% CI 1.52 to 6.72). Clopidogrel use was associated with a significantly higher prevalence of deep or infratentorial CMBs (odd ratio 1.90, 95% CI 1.05 to 3.45). Among clopidogrel users, we were unable to demonstrate differences in the prevalence of CMBs by indication of prescription, history of coronary heart disease, or common genetic variants in CYP2C19.

CONCLUSIONS

In stroke-free individuals, clopidogrel use was associated with a higher prevalence and higher number of CMBs. Whether this association is causal requires confirmation in prospective studies, especially given the small number of participants taking clopidogrel and the possibility of residual confounding in this study.

Common genetic loci influencing plasma homocysteine concentrations and their effect on risk of coronary artery disease

BACKGROUND

The strong observational association between total homocysteine (tHcy) concentrations and risk of coronary artery disease (CAD) and the null associations in the homocysteine-lowering trials have prompted the need to identify genetic variants associated with homocysteine concentrations and risk of CAD.

OBJECTIVE

We tested whether common genetic polymorphisms associated with variation in tHcy are also associated with CAD.

DESIGN

We conducted a meta-analysis of genome-wide association studies (GWAS) on tHcy concentrations in 44,147 individuals of European descent. Polymorphisms associated with tHcy (P < 10(⁻⁸) were tested for association with CAD in 31,400 cases and 92,927 controls.

RESULTS

Common variants at 13 loci, explaining 5.9% of the variation in tHcy, were associated with tHcy concentrations, including 6 novel loci in or near MMACHC (2.1 × 10⁻⁹), SLC17A3 (1.0 × 10⁻⁸), GTPB10 (1.7 × 10⁻⁸), CUBN (7.5 × 10⁻¹⁰), HNF1A (1.2 × 10⁻¹²)), and FUT2 (6.6 × 10⁻⁹), and variants previously reported at or near the MTHFR, MTR, CPS1, MUT, NOX4, DPEP1, and CBS genes. Individuals within the highest 10% of the genotype risk score (GRS) had 3-μmol/L higher mean tHcy concentrations than did those within the lowest 10% of the GRS (P = 1 × 10⁻³⁶). The GRS was not associated with risk of CAD (OR: 1.01; 95% CI: 0.98, 1.04; P = 0.49).

CONCLUSIONS

We identified several novel loci that influence plasma tHcy concentrations. Overall, common genetic variants that influence plasma tHcy concentrations are not associated with risk of CAD in white populations, which further refutes the causal relevance of moderately elevated tHcy concentrations and tHcy-related pathways for CAD.

External validation of the fatty liver index for identifying nonalcoholic fatty liver disease in a population-based study

BACKGROUND & AIMS

We aimed to validate the fatty liver index (FLI), an algorithm that is based on waist circumference, body mass index, and levels of triglyceride and γ-glutamyltransferase. We calculated its ability to identify fatty liver disease from any cause or nonalcoholic fatty liver disease (NAFLD) in a large population of white elderly persons.

METHODS

We collected ultrasonography and FLI data from participants of the Rotterdam Study from February 2009 to February 2012; 2652 subjects (mean age, 76.3 ± 6.0 years) were interviewed and received a clinical examination that included abdominal ultrasound, analysis of blood samples during fasting, and anthropometric assessment. The ability of the FLI to detect (nonalcoholic) fatty liver was assessed by using area under the receiver operator characteristic (AUROC) curve analysis.

RESULTS

FLI score was associated with NAFLD in multivariable analysis (odds ratio, 1.05; 95% confidence interval [CI], 1.04-1.05; P < .001). FLI identified patients with NAFLD with an AUROC curve of 0.813 (95% CI, 0.797-0.830) and those with fatty liver from any cause with an AUROC curve of 0.807 (95% CI, 0.792-0.823).

CONCLUSIONS

The FLI (an algorithm that is based on waist circumference, body mass index, and levels of triglyceride and γ-glutamyltransferase) accurately identifies NAFLD, confirmed via ultrasonography, in a large, white, elderly population.

Scheuermann disease: evaluation of radiological criteria and population prevalence

STUDY DESIGN

Observational population-based study.

OBJECTIVE

To determine the prevalence of radiographical Scheuermann disease in a Dutch population and evaluate the consistency of diagnostic criteria.

SUMMARY OF BACKGROUND DATA

Scheuermann disease is a form of osteochondrosis characterized by increased posterior rounding of the thoracic spine with structural vertebral deformity. Different expert opinion-based radiological criteria exist, yet these have not been validated. The prevalence in the general population reported ranged from 1% to 10%.

METHODS

Lateral spine radiographs of 2753 Rotterdam Study participants (aged 45-89 yr) were assessed for Scheuermann disease using Sørensen and Sachs' radiographical criteria in 2 phases. Cohen κ statistics were calculated for interrater agreement. Prevalence estimates were calculated and sex differences were tested with Pearson χ test. We evaluated whether varying the kyphosis angle criterion would change the prevalence estimate.

RESULTS

A total of 677 (24.6%) individuals had endplate irregularities and 140 (5.1%) individuals had vertebral wedging. Abnormalities were significantly more prevalent among males (P < 0.05). The interrater agreement κ statistics were 78.8% for vertebral wedging and 79.4% for endplate irregularity. A total of 127 individuals had both criteria, of which 111 had a kyphosis angle greater than 45°, resulting in a prevalence of 4.0% (95% confidence interval [CI]: 3.3%-4.7%). The disease prevalence was 4.5% in males versus 3.6% in females, yet this difference was not statistically significant (P = 0.23). Adjustment of the kyphosis angle criterion from 45° to 40° or 35° increased the number of cases marginally, corresponding to prevalence estimates not significantly different from the estimates using original criteria (4.2% [95% CI: 3.3%-4.7%] and 4.4% [95% CI: 3.6%-5.2%]).

CONCLUSION

Our results revealed a prevalence of 4.0% of radiographical Scheuermann disease in Dutch individuals aged 45 years and older. Although there is no current "gold standard" for the radiographical definition, standardized scoring of independent features resulted in substantial interobserver agreement, and different applications of diagnostic criteria did not significantly alter the classification.

Serum potassium levels and the risk of atrial fibrillation: the Rotterdam Study

BACKGROUND

Atrial fibrillation is the most common sustained arrhythmia in the elderly. Serum potassium is associated with ventricular arrhythmias and cardiac arrest. Little is known about the association of serum potassium with atrial fibrillation. The objective of this study was to investigate the association of serum potassium and the risk of atrial fibrillation in a population based setting.

METHODS

The study was performed within the prospective population-based Rotterdam Study. The study population consisted of 4059 participants without atrial fibrillation at baseline for whom baseline levels of serum potassium were measured. Atrial fibrillation was ascertained from centre visit ECG assessments as well as medical records.

RESULTS

During a mean follow up of 11.8 years (SD=5.2 yr), 474 participants developed atrial fibrillation. Participants with hypokalemia (<3.5 mmol/l) had a higher risk of atrial fibrillation (HR: 1.63, 95%CI: 1.03-2.56) than those with normokalemia (3.5-5.0 mmol/l). This association was independent of age, sex, serum magnesium, and other potential confounders. Especially in participants with a history of myocardial infarction, those with hypokalemia had a higher risk of atrial fibrillation than those with normokalemia (HR: 3.81, 95%-CI: 1.51-9.61).

CONCLUSIONS

In this study low serum levels of potassium were associated with a higher risk of atrial fibrillation.

Stability and fragmentation of the activity rhythm across the sleep-wake cycle: the importance of age, lifestyle, and mental health

The rhythms of activity across the 24-h sleep-wake cycle, determined in part by the circadian clock, change with aging. Few large-scale studies measured the activity rhythm objectively in the general population. The present population-based study in middle-aged and elderly persons evaluated how activity rhythms change with age, and additionally investigated sociodemographics, mental health, lifestyle, and sleep characteristics as determinants of rhythms of activity. Activity rhythms were measured objectively with actigraphy. Recordings of at least 96 h (138 ± 14 h, mean ± SD) were collected from 1734 people (age: 62 ± 9.4 yrs) participating in the Rotterdam Study. Activity rhythms were quantified by calculating interdaily stability, i.e., the stability of the rhythm over days, and intradaily variability, i.e., the fragmentation of the rhythm relative to its 24-h amplitude. We assessed age, gender, presence of a partner, employment, cognitive functioning, depressive symptoms, body mass index (BMI), coffee use, alcohol use, and smoking as determinants. The results indicate that older age is associated with a more stable 24-h activity profile (β = 0.07, p = 0.02), but also with a more fragmented distribution of periods of activity and inactivity (β = 0.20, p < 0.001). Having more depressive symptoms was related to less stable (β = -0.07, p = 0.005) and more fragmented (β = 0.10, p < 0.001) rhythms. A high BMI and smoking were also associated with less stable rhythms (BMI: β = -0.11, p < 0.001; smoking: β = -0.11, p < 0.001) and more fragmented rhythms (BMI: β = 0.09, p < 0.001; smoking: β = 0.11, p < 0.001). We conclude that with older age the 24-h activity rhythm becomes more rigid, whereas the ability to maintain either an active or inactive state for a longer period of time is compromised. Both characteristics appear to be important for major health issues in old age.

Nine loci for ocular axial length identified through genome-wide association studies, including shared loci with refractive error

Refractive errors are common eye disorders of public health importance worldwide. Ocular axial length (AL) is the major determinant of refraction and thus of myopia and hyperopia. We conducted a meta-analysis of genome-wide association studies for AL, combining 12,531 Europeans and 8,216 Asians. We identified eight genome-wide significant loci for AL (RSPO1, C3orf26, LAMA2, GJD2, ZNRF3, CD55, MIP, and ALPPL2) and confirmed one previously reported AL locus (ZC3H11B). Of the nine loci, five (LAMA2, GJD2, CD55, ALPPL2, and ZC3H11B) were associated with refraction in 18 independent cohorts (n = 23,591). Differential gene expression was observed for these loci in minus-lens-induced myopia mouse experiments and human ocular tissues. Two of the AL genes, RSPO1 and ZNRF3, are involved in Wnt signaling, a pathway playing a major role in the regulation of eyeball size. This study provides evidence of shared genes between AL and refraction, but importantly also suggests that these traits may have unique pathways.

Association of heat shock proteins with all-cause mortality

Experimental mild heat shock is widely known as an intervention that results in extended longevity in various models along the evolutionary lineage. Heat shock proteins (HSPs) are highly upregulated immediately after a heat shock. The elevation in HSP levels was shown to inhibit stress-mediated cell death, and recent experiments indicate a highly versatile role for these proteins as inhibitors of programmed cell death. In this study, we examined common genetic variations in 31 genes encoding all members of the HSP70, small HSP, and heat shock factor (HSF) families for their association with all-cause mortality. Our discovery cohort was the Rotterdam study (RS1) containing 5,974 participants aged 55 years and older (3,174 deaths). We assessed 4,430 single nucleotide polymorphisms (SNPs) using the HumanHap550K Genotyping BeadChip from Illumina. After adjusting for multiple testing by permutation analysis, three SNPs showed evidence for association with all-cause mortality in RS1. These findings were followed in eight independent population-based cohorts, leading to a total of 25,007 participants (8,444 deaths). In the replication phase, only HSF2 (rs1416733) remained significantly associated with all-cause mortality. Rs1416733 is a known cis-eQTL for HSF2. Our findings suggest a role of HSF2 in all-cause mortality.

High serum thyrotropin levels are associated with current but not with incident hypertension

BACKGROUND

Recent data from a population-based study in children and adolescents suggest that serum thyrotropin (TSH) levels are associated with arterial blood pressure and hypertension. These results are in agreement with some but not all population-based studies in adults. Discrepancies in results might be explained by drug intake, different iodine supplies, and sizes of populations investigated. In addition, it is not clear whether an association between TSH and hypertension exists longitudinally or only cross-sectionally. Thus, our aim was to investigate cross-sectional and longitudinal associations between thyroid function and arterial blood pressure in a large consortium of cohort studies in adults.

METHODS

Data from five population-based studies were pooled resulting in 17,023 individuals being available for cross-sectional and 10,048 individuals for longitudinal analyses. Associations of baseline TSH with baseline blood pressure or hypertension were analyzed by multivariable median or logistic regression models. Multivariable median or Poisson regression models were used to investigate associations of baseline TSH with five-year change in arterial blood pressure or incident hypertension.

RESULTS

There was a cross-sectional positive association of TSH with arterial blood pressure (p<0.001) and hypertension (odds ratio [OR]=1.76 [confidence interval (CI) 1.24-2.50], p=0.002). Likewise, hypothyroidism was associated with systolic (β=1.1 [CI 0.1-2.1], p=0.040) and diastolic blood pressure (β=1.4 [CI 0.7-2.0], p<0.001). TSH, however, was not consistently associated with a five-year change in blood pressure or incident hypertension.

CONCLUSIONS

High serum TSH levels were associated with current hypertension and blood pressure but not with a five-year change in blood pressure and incident hypertension. This argues for only a short-term effect of thyroid hormone levels on arterial blood pressure or a spurious association that needs further evaluation in population-based studies.

Association between genetic variation in the ABCB1 gene and switching, discontinuation, and dosage of antidepressant therapy: results from the Rotterdam Study

The objective of this study was to investigate whether polymorphisms in the ABCB1 gene were associated with switching, with discontinuation of antidepressants within 45 days after starting therapy, and/or with dose change in a large prospective population-based cohort study. Between April 1, 1991, and December 31, 2007, there were 1257 incident users of antidepressants with known ABCB1 genotypes (1236C>T, 2677G>T/A, 3435C>T) in the population-based Rotterdam Study. Logistic regression models were used to estimate the genotype and haplotype effect on the risk of switching and discontinuation. In addition, the association between the haplotypes and the prescribed drug dosage was assessed per drug class. The separate polymorphisms in the ABCB1 gene were associated with increased risks of switching and discontinuation but reached only statistical significance for the association between the 3435C>T polymorphism and switching. In a model adjusted for age and sex, homozygous carriers of the T-T-T haplotype had an increased risk of switching (odds ratio, 4.22; 95% confidence interval, 1.30-13.7; P = 0.017) and discontinuation (odds ratio, 1.47; 95% confidence interval, 0.98-2.22; P = 0.063). Explained variance was 10.4% for switching and 2.5% for discontinuation. In contrast, no association was observed between the T-T-T haplotype and the prescribed dosage. In summary, this study showed that genetic variation in the ABCB1 gene might play a role in the risk of switching and discontinuation of antidepressant therapy but the clinical relevance is limited.

Projections on the number of individuals with atrial fibrillation in the European Union, from 2000 to 2060

AIMS

Since atrial fibrillation (AF) is associated with increased risks of cardiovascular and cerebrovascular complications, estimations on the number of individuals with AF are relevant to healthcare planning. We aimed to project the number of individuals with AF in the Netherlands and in the European Union from 2000 to 2060.

METHODS AND RESULTS

Age- and sex-specific AF prevalence estimates were obtained from the prospective community-based Rotterdam Study. Population projections for the Netherlands and the European Union were obtained from the European Union's statistics office. In the age stratum of 55-59 years, the prevalence of AF was 1.3% in men (95% CI: 0.4-3.6%) and 1.7% in women (95% CI: 0.7-4.0%). The prevalence of AF increased to 24.2% in men (95% CI: 18.5-30.7%), and 16.1% in women (95% CI: 13.1-19.4%), for those >85 years of age. This age- and sex-specific prevalence remained stable during the years of follow-up. Furthermore, we estimate that in the European Union, 8.8 million adults over 55 years had AF in 2010 (95% CI: 6.5-12.3 million). We project that this number will double by 2060 to 17.9 million (95% CI: 13.6-23.7 million) if the age- and sex-specific prevalence remains stable.

CONCLUSION

We estimate that from 2010 to 2060, the number of adults 55 years and over with AF in the European Union will more than double. As AF is associated with significant morbidities and mortality, this increasing number of individuals with AF may have major public health implications.

Best practices and joint calling of the HumanExome BeadChip: the CHARGE Consortium

Genotyping arrays are a cost effective approach when typing previously-identified genetic polymorphisms in large numbers of samples. One limitation of genotyping arrays with rare variants (e.g., minor allele frequency [MAF] <0.01) is the difficulty that automated clustering algorithms have to accurately detect and assign genotype calls. Combining intensity data from large numbers of samples may increase the ability to accurately call the genotypes of rare variants. Approximately 62,000 ethnically diverse samples from eleven Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium cohorts were genotyped with the Illumina HumanExome BeadChip across seven genotyping centers. The raw data files for the samples were assembled into a single project for joint calling. To assess the quality of the joint calling, concordance of genotypes in a subset of individuals having both exome chip and exome sequence data was analyzed. After exclusion of low performing SNPs on the exome chip and non-overlap of SNPs derived from sequence data, genotypes of 185,119 variants (11,356 were monomorphic) were compared in 530 individuals that had whole exome sequence data. A total of 98,113,070 pairs of genotypes were tested and 99.77% were concordant, 0.14% had missing data, and 0.09% were discordant. We report that joint calling allows the ability to accurately genotype rare variation using array technology when large sample sizes are available and best practices are followed. The cluster file from this experiment is available at www.chargeconsortium.com/main/exomechip.

Cognition and gait show a distinct pattern of association in the general population

BACKGROUND

With brain aging, cognition and gait deteriorate in several domains. However, the interrelationship between cognitive and gait domains remains unclear. We investigated the independent associations between cognitive and gait domains in a community-dwelling population.

METHODS

In the Rotterdam Study, 1232 participants underwent cognitive and gait assessment. Cognitive assessment included memory, information processing speed, fine motor speed, and executive function. Gait was summarized into seven independent domains: Rhythm, Variability, Phases, Pace, Tandem, Turning, and Base of Support. With multivariate linear regression, independent associations between cognitive and gait domains were investigated.

RESULTS

Information processing speed associated with Rhythm, fine motor speed with Tandem, and executive function with Pace. The effect sizes corresponded to a 5- to 10-year deterioration in gait.

CONCLUSIONS

Cognition and gait show a distinct pattern of association. These data accentuate the close, but complicated, relation between cognition and gait, and they may aid in unraveling the broader spectrum of the effects of brain aging.

Brain cortical thickness in the general elderly population: the Rotterdam Scan Study

Cortical thickness is considered a potentially relevant marker for neurodegenerative diseases. However, the relationship of demographic and vascular risk factors with cortical thickness remains unclear. In a population-based sample of 1022 non-demented elderly persons (mean age 68.4±7.3 years), we examined aging effects on global and lobar cortical thickness and the relationship with demographic variables and cardiovascular risk factors. We used a validated model-based approach to calculate mean cortical thickness (μm) in brain MR-images. We found that women had a significant thicker cortex than men (p<0.01). Further, with increasing age, cortical thickness decreased (approximately 0.2% per year), with the largest age effects for the occipital and temporal lobes, and the decrease in the frontal lobe being more apparent in men than in women (p-interaction<0.001). Additionally, higher education, higher diastolic blood pressure and larger intra-cranial volume were related to a larger cortical thickness, whilst diabetes mellitus and higher HDL cholesterol levels were related to a thinner cortex.

Common carotid intima-media thickness does not add to Framingham risk score in individuals with diabetes mellitus: the USE-IMT initiative

AIMS/HYPOTHESIS

The aim of this work was to investigate whether measurement of the mean common carotid intima-media thickness (CIMT) improves cardiovascular risk prediction in individuals with diabetes.

METHODS

We performed a subanalysis among 4,220 individuals with diabetes in a large ongoing individual participant data meta-analysis involving 56,194 subjects from 17 population-based cohorts worldwide. We first refitted the risk factors of the Framingham heart risk score on the individuals without previous cardiovascular disease (baseline model) and then expanded this model with the mean common CIMT (CIMT model). The absolute 10 year risk for developing a myocardial infarction or stroke was estimated from both models. In individuals with diabetes we compared discrimination and calibration of the two models. Reclassification of individuals with diabetes was based on allocation to another cardiovascular risk category when mean common CIMT was added.

RESULTS

During a median follow-up of 8.7 years, 684 first-time cardiovascular events occurred among the population with diabetes. The C statistic was 0.67 for the Framingham model and 0.68 for the CIMT model. The absolute 10 year risk for developing a myocardial infarction or stroke was 16% in both models. There was no net reclassification improvement with the addition of mean common CIMT (1.7%; 95% CI -1.8, 3.8). There were no differences in the results between men and women.

CONCLUSIONS/INTERPRETATION

There is no improvement in risk prediction in individuals with diabetes when measurement of the mean common CIMT is added to the Framingham risk score. Therefore, this measurement is not recommended for improving individual cardiovascular risk stratification in individuals with diabetes.

GWAS of 126,559 individuals identifies genetic variants associated with educational attainment

A genome-wide association study (GWAS) of educational attainment was conducted in a discovery sample of 101,069 individuals and a replication sample of 25,490. Three independent single-nucleotide polymorphisms (SNPs) are genome-wide significant (rs9320913, rs11584700, rs4851266), and all three replicate. Estimated effects sizes are small (coefficient of determination R(2) ≈ 0.02%), approximately 1 month of schooling per allele. A linear polygenic score from all measured SNPs accounts for ≈2% of the variance in both educational attainment and cognitive function. Genes in the region of the loci have previously been associated with health, cognitive, and central nervous system phenotypes, and bioinformatics analyses suggest the involvement of the anterior caudate nucleus. These findings provide promising candidate SNPs for follow-up work, and our effect size estimates can anchor power analyses in social-science genetics.

Serum testosterone levels in males are not associated with entrepreneurial behavior in two independent observational studies

Previous research has suggested a positive association between testosterone (T) and entrepreneurial behavior in males. However, this evidence was found in a study with a small sample size and has not been replicated. In the present study, we aimed to verify this association using two large, independent, population-based samples of males. We tested the association of T with entrepreneurial behavior, operationalized as self-employment, using data from the Rotterdam Study (N=587) and the Study of Health in Pomerania (N=1697). Total testosterone (TT) and sex hormone-binding globulin (SHBG) were measured in the serum. Free testosterone (FT), non-SHBG-bound T (non-SHBG-T), and the TT/SHBG ratio were calculated and used as measures of bioactive serum T, in addition to TT adjusted for SHBG. Using logistic regression models, we found no significant associations between any of the serum T measures and self-employment in either of the samples. To our knowledge, this is the first large-scale study on the relationship between serum T and entrepreneurial behavior.

High bone mineral density and fracture risk in type 2 diabetes as skeletal complications of inadequate glucose control: the Rotterdam Study

OBJECTIVE

Individuals with type 2 diabetes have increased fracture risk despite higher bone mineral density (BMD). Our aim was to examine the influence of glucose control on skeletal complications.

RESEARCH DESIGN AND METHODS

Data of 4,135 participants of the Rotterdam Study, a prospective population-based cohort, were available (mean follow-up 12.2 years). At baseline, 420 participants with type 2 diabetes were classified by glucose control (according to HbA1c calculated from fructosamine), resulting in three comparison groups: adequately controlled diabetes (ACD; n = 203; HbA1c <7.5%), inadequately controlled diabetes (ICD; n = 217; HbA1c ≥ 7.5%), and no diabetes (n = 3,715). Models adjusted for sex, age, height, and weight (and femoral neck BMD) were used to test for differences in bone parameters and fracture risk (hazard ratio [HR] [95% CI]).

RESULTS

The ICD group had 1.1-5.6% higher BMD, 4.6-5.6% thicker cortices, and -1.2 to -1.8% narrower femoral necks than ACD and ND, respectively. Participants with ICD had 47-62% higher fracture risk than individuals without diabetes (HR 1.47 [1.12-1.92]) and ACD (1.62 [1.09-2.40]), whereas those with ACD had a risk similar to those without diabetes (0.91 [0.67-1.23]).

CONCLUSIONS

Poor glycemic control in type 2 diabetes is associated with fracture risk, high BMD, and thicker femoral cortices in narrower bones. We postulate that fragility in apparently "strong" bones in ICD can result from microcrack accumulation and/or cortical porosity, reflecting impaired bone repair.

High Blood Pressure and Cerebral White Matter Lesion Progression in the General Population

High blood pressure is considered an important risk factor for cerebral white matter lesions (WMLs) in the aging population. In a longitudinal population-based study of 665 nondemented persons, we investigated the longitudinal relationship of systolic blood pressure, diastolic blood pressure, and pulse pressure with annual progression of WMLs. Means of blood pressure were calculated over a 5-year period before longitudinal MRI scanning. WML progression was subsequently measured on 2 scans 3.5 years apart. We performed analyses with linear regression models and evaluated adjustments for age, sex, cardiovascular risk factors, and baseline WML volume. In addition, we evaluated whether treatment of hypertension is related to less WML progression. Both systolic and diastolic blood pressures were significantly associated with annual WML progression (regression coefficient [95% confidence interval], 0.08 [0.03; 0.14] mL/y and 0.09 [0.03; 0.15] mL/y per SD increase in systolic and diastolic blood pressure, respectively). Pulse pressure was also significantly associated with WML progression, but not independent from hypertension. After adjustment for baseline WML volume, only systolic blood pressure remained significantly associated: 0.05 (0.00; 0.09) mL/y per SD increase. People with uncontrolled untreated hypertension had significantly more WML progression than people with uncontrolled treated hypertension (difference [95% confidence interval], 0.12 [0.00; 0.23] mL/y). The present study further establishes high blood pressure to precede WMLs and implies that hypertension treatment could reduce WML progression in the general population.

Impact of Inherited Genetic Variants Associated With Lipid Profile, Hypertension, and Coronary Artery Disease on the Risk of Intracranial and Abdominal Aortic Aneurysms

Background—

Epidemiological studies show that an unfavorable lipid profile and coronary artery disease (CAD) are risk traits for abdominal aortic aneurysms (AAAs) but not for intracranial aneurysms (IAs), and that hypertension is a main risk trait for IAs but not for AAAs. To evaluate these observations, we investigated single-nucleotide polymorphisms associated with serum lipid levels, hypertension, and CAD and tested their contribution to AAA and IA risk.

Methods and Results—

We defined sets of single-nucleotide polymorphisms previously reported to be associated with serum lipid levels, CAD, and blood pressure. From previously collected genome-wide data, we extracted genotypes for these single-nucleotide polymorphism sets in 709 IA cases and 2692 controls and 807 AAA cases and 1905 controls (all of Dutch origin). We computed genetic scores for each individual by summing the observed number of risk alleles weighted by their previously published effect size. Using logistic regression, we tested the genetic scores for association with IAs and AAAs and found significant associations for genetic scores of total cholesterol ( P =3.6×10 -6 ), low-density lipoprotein-cholesterol ( P =5.7×10 -7 ), and CAD ( P =0.0014) with AAAs and for the blood pressure score with IAs ( P =0.0030).

Conclusions—

We demonstrate that genetic risk profiles of lipid factors and CAD are associated with AAAs but not with IAs, and the genetic risk profile of blood pressure is associated with IAs but not with AAAs. These findings are consistent with epidemiological observations.

Molecular genetics and subjective well-being

Subjective well-being (SWB) is a major topic of research across the social sciences. Twin and family studies have found that genetic factors may account for as much as 30-40% of the variance in SWB. Here, we study genetic contributions to SWB in a pooled sample of ≈ 11,500 unrelated, comprehensively-genotyped Swedish and Dutch individuals. We apply a recently developed method to estimate "common narrow heritability": the fraction of variance in SWB that can be explained by the cumulative additive effects of genetic polymorphisms that are common in the population. Our estimates are 5-10% for single-question survey measures of SWB, and 12-18% after correction for measurement error in the SWB measures. Our results suggest guarded optimism about the prospects of using genetic data in SWB research because, although the common narrow heritability is not large, the polymorphisms that contribute to it could feasibly be discovered with a sufficiently large sample of individuals.

Association of atherosclerosis with presence and progression of osteoarthritis: the Rotterdam Study

OBJECTIVE

This study examined whether vascular alterations are associated with the presence and progression of osteoarthritis of the knee, the hip and the different hand joints in a large prospective cohort study.

METHODS

In this population-based study involving participants aged 55 years and older (Rotterdam Study I), men (n=2372) and women (n=3278) were analysed separately. x-Rays of the knee, hip and hand were scored using the Kellgren and Lawrence score for osteoarthritis at baseline, after 6.6 years and 10 years. Measures of atherosclerosis (carotid intima media thickness (IMT) and carotid plaque) and data on covariates (age, body mass index, hypertension, cholesterol ratio, diabetes mellitus and smoking) were collected at baseline. Multivariate logistic regression models with generalised estimated equations were used to calculate OR and corresponding 95% CI. Secondary multiple comparison adjustment resulted in a significance level of p<0.0021.

RESULTS

In women, IMT showed an independent association with the prevalence of knee osteoarthritis (adjusted OR (aOR) 1.7, 1.1 to 2.7), and carotid plaque with distal interphalangeal (DIP) osteoarthritis (aOR 1.4, 1.2 to 1.7) and with metacarpophalangeal osteoarthritis (aOR 1.5, 1.1 to 2.2). An independent association for IMT with progression of metacarpophalangeal osteoarthritis was found in women (aOR 2.9, 1.18 to 6.93). Additional adjustment for multiple testing yielded a significant association between carotid plaque and DIP osteoarthritis in women (p<0.001).

CONCLUSIONS

This study showed independent associations of atherosclerosis with osteoarthritis of the knee and hand joints in women. The evidence was most solid for a relation with DIP osteoarthritis. More research is needed to confirm the associations and examine the differential association with various joints.

Resting Heart Rate and the Risk of Heart Failure in Healthy Adults

Background—

An elevated resting heart rate is associated with rehospitalization for heart failure and is a modifiable risk factor in heart failure patients. We aimed to examine the association between resting heart rate and incident heart failure in a population-based cohort study of healthy adults without pre-existing overt heart disease.

Methods and Results—

We studied 4768 men and women aged ≥55 years from the population-based Rotterdam Study. We excluded participants with prevalent heart failure, coronary heart disease, pacemaker, atrial fibrillation, atrioventricular block, and those using β-blockers or calcium channel blockers. We used extended Cox models allowing for time-dependent variation of resting heart rate along follow-up. During a median of 14.6 years of follow-up, 656 participants developed heart failure. The risk of heart failure was higher in men with higher resting heart rate. For each increment of 10 beats per minute, the multivariable adjusted hazard ratios in men were 1.16 (95% confidence interval, 1.05–1.28; P =0.005) in the time-fixed heart rate model and 1.13 (95% confidence interval, 1.02–1.25; P =0.017) in the time-dependent heart rate model. The association could not be demonstrated in women ( P for interaction=0.004). Censoring participants for incident coronary heart disease or using time-dependent models to account for the use of β-blockers or calcium channel blockers during follow-up did not alter the results.

Conclusions—

Baseline or persistent higher resting heart rate is an independent risk factor for the development of heart failure in healthy older men in the general population.

A genome-wide association study of depressive symptoms

BACKGROUND

Depression is a heritable trait that exists on a continuum of varying severity and duration. Yet, the search for genetic variants associated with depression has had few successes. We exploit the entire continuum of depression to find common variants for depressive symptoms.

METHODS

In this genome-wide association study, we combined the results of 17 population-based studies assessing depressive symptoms with the Center for Epidemiological Studies Depression Scale. Replication of the independent top hits (p<1×10(-5)) was performed in five studies assessing depressive symptoms with other instruments. In addition, we performed a combined meta-analysis of all 22 discovery and replication studies.

RESULTS

The discovery sample comprised 34,549 individuals (mean age of 66.5) and no loci reached genome-wide significance (lowest p = 1.05×10(-7)). Seven independent single nucleotide polymorphisms were considered for replication. In the replication set (n = 16,709), we found suggestive association of one single nucleotide polymorphism with depressive symptoms (rs161645, 5q21, p = 9.19×10(-3)). This 5q21 region reached genome-wide significance (p = 4.78×10(-8)) in the overall meta-analysis combining discovery and replication studies (n = 51,258).

CONCLUSIONS

The results suggest that only a large sample comprising more than 50,000 subjects may be sufficiently powered to detect genes for depressive symptoms.

Plasma amyloid β, depression, and dementia in community-dwelling elderly

Plasma amyloid β (Aβ) levels have been associated with an increased risk of Alzheimer's disease (AD). As depression is common before the onset of AD, a few clinical studies tested the cross-sectional association of Aβ levels with depression in elderly and showed incongruous findings. Hence, we tested the longitudinal association between Aβ levels and depressive symptoms in community-dwelling elderly. The study is embedded in a population-based cohort of 980 participants aged 60 years or older from the Rotterdam Study with Aβ levels. Participants were evaluated for depressive symptoms with the Centre for Epidemiological Studies-Depression scale at baseline and repeatedly over the mean follow-up of 11 years. We first performed cross-sectional analyses. Then, we tested the longitudinal association between Aβ levels and depressive symptoms after excluding participants with dementia during follow-up. In cross-sectional analyses, persons with high Aβ(1-40) levels had more clinically relevant depressive symptoms. However, this association was accounted for by persons with clinically relevant depressive symptoms who developed dementia within the next 11 years. In longitudinal analyses, persons with low levels of Aβ(1-40) and Aβ(1-42) without dementia had a higher risk of clinically relevant depressive symptoms during the follow-up. These findings suggest that the cross-sectional association between high plasma Aβ levels and clinically relevant depressive symptoms in the elderly is due to prodromal dementia. In contrast, the longitudinal association between low plasma Aβ levels and depressive symptoms could not be explained by dementia during follow-up suggesting that Aβ peptides may play a distinct role on depression etiology.

Gait patterns in a community-dwelling population aged 50 years and older

Poor gait is an important risk factor for falls and associated with higher morbidity and mortality. It is well established that older age is associated with worse gait, but it remains unclear at what age this association is first seen. Moreover, previous studies focused mainly on normal walking, but gait also encompasses turning and tandem walking. In a large study of community-dwelling middle-aged and elderly persons we investigated the association of age with gait, focusing on normal walking, turning and tandem walking. In 1500 persons aged 50 years and over, we measured gait using an electronic walkway. Participants performed normal walks, turning and a tandem walk. With principal components analysis of 30 variables we summarized gait into five known gait factors: Rhythm, Variability, Phases, Pace and Base of Support; and uncovered two novel gait factors: Tandem and Turning. The strongest associations with age were found for Variability (difference in Z-score -0.29 per 10 years increase (95% confidence interval: -0.34; -0.24)), Phases (-0.31 per 10 years (-0.36; -0.27)) and Tandem (-0.25 per 10 years (-0.30; -0.20)). Additionally, these factors already showed association with the youngest age groups, from 55 to 60 years of age and older. Our study shows that Variability, Phases and Tandem have the strongest association with age and are the earliest to demonstrate a poorer gait pattern with higher age. Future research should further investigate how these gait factors relate with gait-related diseases in their earliest stages.

Normal spirometry values in healthy elderly: the Rotterdam Study

Although many different reference values for spirometry are available from various studies, the elderly are usually underrepresented. Therefore, our objective was to assess reference values in a sample of healthy participants from a prospective population-based cohort study, including a large proportion of elderly. We included spirometry measurements of healthy, never smokers, from the Rotterdam Study and excluded participants with respiratory symptoms or prescriptions for respiratory medication. Age- and height-specific curves for the 5th (lower limit of normal) and the 50th (median) percentile of Forced Expiratory Volume in 1 s (FEV1), Forced Vital Capacity (FVC), and the ratio (FEV1/FVC) were calculated by quantile regression models. The group of healthy elderly study subjects consisted of 1,125 individuals, with a mean age of 68 years, ranging from 47 to 96 years of age. Sex stratified equations for the median and the lower limit of normal were calculated adjusted for age and height. In this study, we report age- and height-dependent reference limits for FEV1, FVC, and FEV1/FVC in a large population, and prediction equations for the lower limit of normal and median values for a sample containing a large proportion of healthy elderly.

Improving alignment in Tract-based spatial statistics: evaluation and optimization of image registration

Anatomical alignment in neuroimaging studies is of such importance that considerable effort is put into improving the registration used to establish spatial correspondence. Tract-based spatial statistics (TBSS) is a popular method for comparing diffusion characteristics across subjects. TBSS establishes spatial correspondence using a combination of nonlinear registration and a “skeleton projection” that may break topological consistency of the transformed brain images. We therefore investigated feasibility of replacing the two-stage registration-projection procedure in TBSS with a single, regularized, high-dimensional registration.

To optimize registration parameters and to evaluate registration performance in diffusion MRI, we designed an evaluation framework that uses native space probabilistic tractography for 23 white matter tracts, and quantifies tract similarity across subjects in standard space. We optimized parameters for two registration algorithms on two diffusion datasets of different quality. We investigated reproducibility of the evaluation framework, and of the optimized registration algorithms. Next, we compared registration performance of the regularized registration methods and TBSS. Finally, feasibility and effect of incorporating the improved registration in TBSS were evaluated in an example study.

The evaluation framework was highly reproducible for both algorithms (R² 0.993; 0.931). The optimal registration parameters depended on the quality of the dataset in a graded and predictable manner. At optimal parameters, both algorithms outperformed the registration of TBSS, showing feasibility of adopting such approaches in TBSS. This was further confirmed in the example experiment.

Prevalence of actinic keratosis and its risk factors in the general population: the Rotterdam Study

Limited data are available on the prevalence and risk factors of actinic keratoses (AKs). Within the Rotterdam Study, full-body skin examinations were performed among participants aged 45 years or older to estimate the age- and sex-standardized prevalence of AK and its associated risk factors. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for associations between risk factors and the presence of 1-3, 4-9, and ≥ 10 AKs. Of the 2,061 inspected cohort members (mean age 72 years), 21% had 1-3, 9% had 4-9, and 8% had ≥ 10 AKs. AK prevalence was 49% (95% CI: 46-52%) for men and 28% (26-31%) for women. Male gender, older age, light pigmentation status, severe baldness, skin wrinkling, and high tendency for sunburn were significantly associated with extensive actinic damage (≥ 10 AKs) in the multivariate analyses. Especially bald males were at an increased risk of severe actinic skin damage (adjusted OR=7.0 (3.8-13.1)). The prevalence of AK is very high, especially among elderly bald males. The prevention and management of AK is a true challenge for patients, physicians, and health-care policymakers.

The relation of uric acid to brain atrophy and cognition: the Rotterdam Scan Study

BACKGROUND

Uric acid has been associated with focal vascular brain disease. However, it is unknown whether uric acid also relates to global brain changes such as brain atrophy. We therefore studied the relation of uric acid to brain atrophy and whether this is accompanied by worse cognitive function.

METHODS

In 814 persons of the population-based Rotterdam Study (mean age 62.0 years), we studied the relation of uric acid levels to brain tissue atrophy and cognition using linear regression models adjusted for age, sex and putative confounders. Brain atrophy was assessed using automated processing of magnetic resonance imaging. Cognition was assessed using a validated neuropsychological test battery and we computed compound scores of cognitive domains.

RESULTS

Higher uric acid levels were associated with white matter atrophy [difference in Z-score of white matter volume per standard deviation increase in uric acid: -0.07 (95% CI: -0.12; -0.01)], but not with gray matter atrophy. This was particularly marked when comparing hyperuricemic to normouricemic persons [Z-score difference: -0.27 (-0.43; -0.11)]. Worse cognition was primarily found in persons with hyperuricemia [-0.28 (-0.48; -0.08)].

CONCLUSIONS

Hyperuricemia is related to white matter atrophy and worse cognition.

Liposomes and nanotechnology in drug development: focus on neurological targets

Neurological diseases represent a medical, social, and economic problem of paramount importance in developed countries. Although their etiology is generally known, developing therapeutic interventions for the central nervous system is challenging due to the impermeability of the blood-brain barrier. Thus, the fight against neurological diseases usually struggles "at the gates" of the brain. Flooding the bloodstream with drugs, where only a minor fraction reaches its target therapeutic site, is an inefficient, expensive, and dangerous procedure, because of the risk of side effects at nontargeted sites. Currently, advances in the field of nanotechnology have enabled development of a generation of multifunctional molecular platforms that are capable of transporting drugs across the blood-brain barrier, targeting specific cell types or functional states within the brain, releasing drugs in a controlled manner, and enabling visualization of processes in vivo using conventional imaging systems. The marriage between drug delivery and molecular imaging disciplines has resulted in a relatively new discipline, known as theranostics, which represents the basis of the concept of personalized medicine. In this study, we review the concepts of the blood-brain barrier and the strategies used to traverse/bypass it, the role of nanotechnology in theranostics, the wide range of nanoparticles (with emphasis on liposomes) that can be used as stealth drug carriers, imaging probes and targeting devices for the treatment of neurological diseases, and the targets and targeting strategies envisaged in the treatment of different types of brain pathology.

Alzheimer's disease genes and cognition in the nondemented general population

BACKGROUND

Genome-wide association studies have established 11 genes for late-onset Alzheimer's disease (AD). We investigated whether these genes jointly affect cognition in a nondemented population and improve prediction of AD.

METHODS

In 5171 nondemented people (age 45-99 years) from the population-based Rotterdam Study, we genotyped APOE-ε4 and single nucleotide polymorphisms from the genes CLU, PICALM, BIN1, CR1, ABCA7, MS4A6A, MS4A4E, CD2AP, EPHA1, and CD33. We constructed a genetic risk score by adding the risk alleles per individual weighted by the reported effect sizes. All people underwent cognitive testing. With linear regression we investigated the relationship between the genetic risk score and cognition, with and without APOE. In a subcohort, with more than 10 years of follow-up, we assessed whether the risk score predicted AD.

RESULTS

The genetic risk score was primarily associated with memory (standardized difference [95% confidence interval] per SD increase in genetic risk score: -.05[-.07; -.02], p = 1.5 * 10(-4)). This association attenuated when APOE was excluded from the genetic risk score (-.03[-.05; .00], p = .047) and would not survive a multiple-testing correction. Similarly, we found that although the genetic risk score without APOE was associated with the development of AD (p = .010), it only marginally improved prediction of AD beyond age, sex, APOE (area under the curve: .8159 vs. .8148).

CONCLUSIONS

In nondemented people, there is only a marginal joint effect of AD genes on memory independent from APOE. Moreover, although associated with AD, these genes jointly hardly improve prediction of AD.

Genome-wide association study meta-analysis of chronic widespread pain: evidence for involvement of the 5p15.2 region

BACKGROUND AND OBJECTIVES

Chronic widespread pain (CWP) is a common disorder affecting ∼10% of the general population and has an estimated heritability of 48-52%. In the first large-scale genome-wide association study (GWAS) meta-analysis, we aimed to identify common genetic variants associated with CWP.

METHODS

We conducted a GWAS meta-analysis in 1308 female CWP cases and 5791 controls of European descent, and replicated the effects of the genetic variants with suggestive evidence for association in 1480 CWP cases and 7989 controls. Subsequently, we studied gene expression levels of the nearest genes in two chronic inflammatory pain mouse models, and examined 92 genetic variants previously described associated with pain.

RESULTS

The minor C-allele of rs13361160 on chromosome 5p15.2, located upstream of chaperonin-containing-TCP1-complex-5 gene (CCT5) and downstream of FAM173B, was found to be associated with a 30% higher risk of CWP (minor allele frequency=43%; OR=1.30, 95% CI 1.19 to 1.42, p=1.2×10(-8)). Combined with the replication, we observed a slightly attenuated OR of 1.17 (95% CI 1.10 to 1.24, p=4.7×10(-7)) with moderate heterogeneity (I2=28.4%). However, in a sensitivity analysis that only allowed studies with joint-specific pain, the combined association was genome-wide significant (OR=1.23, 95% CI 1.14 to 1.32, p=3.4×10(-8), I2=0%). Expression levels of Cct5 and Fam173b in mice with inflammatory pain were higher in the lumbar spinal cord, not in the lumbar dorsal root ganglions, compared to mice without pain. None of the 92 genetic variants previously described were significantly associated with pain (p>7.7×10(-4)).

CONCLUSIONS

We identified a common genetic variant on chromosome 5p15.2 associated with joint-specific CWP in humans. This work suggests that CCT5 and FAM173B are promising targets in the regulation of pain.

Electrolyte disorders in community subjects: prevalence and risk factors

BACKGROUND

Electrolyte disorders have been studied mainly in hospitalized patients, whereas data in the general population are limited. The aim of this study was to determine the prevalence and risk factors of common electrolyte disorders in older subjects recruited from the general population.

METHODS

A total of 5179 subjects aged 55 years or more were included from the population-based Rotterdam Study. We focused on hyponatremia, hypernatremia, hypokalemia, hyperkalemia, and hypomagnesemia. Multivariable logistic regression was used to study potential associations with renal function, comorbidity, and medication. The adjusted mortality also was determined for each electrolyte disorder.

RESULTS

A total of 776 subjects (15.0%) had at least 1 electrolyte disorder, with hyponatremia (7.7%) and hypernatremia (3.4%) being most common. Diabetes mellitus was identified as an independent risk factor for hyponatremia and hypomagnesemia, whereas hypertension was associated with hypokalemia. Diuretics were independently associated with several electrolyte disorders: thiazide diuretics (hyponatremia, hypokalemia, hypomagnesemia), loop diuretics (hypernatremia, hypokalemia), and potassium-sparing diuretics (hyponatremia). The use of benzodiazepines also was associated with hyponatremia. Hyponatremic subjects who used both thiazides and benzodiazepines had a 3 mmol/L lower serum sodium concentration than subjects using 1 or none of these drugs (P < .001). Hyponatremia and hypomagnesemia were independently associated with an increased mortality risk.

CONCLUSIONS

Electrolyte disorders are common among older community subjects and mainly associated with diabetes mellitus and diuretics. Subjects who used both thiazides and benzodiazepines had a more severe degree of hyponatremia. Because even mild electrolyte disorders were associated with mortality, monitoring of electrolytes and discontinuation of offending drugs may improve outcomes.

Changes in normal-appearing white matter precede development of white matter lesions

BACKGROUND AND PURPOSE

It is unknown whether white matter lesions (WML) develop abruptly in previously normal brain areas, or whether tissue changes are already present before WML become apparent on MRI. We therefore investigated whether development of WML is preceded by quantifiable changes in normal-appearing white matter (NAWM).

METHODS

In 689 participants from the general population (mean age 67 years), we performed 2 MRI scans (including diffusion tensor imaging and Fluid Attenuation Inversion Recovery [FLAIR] sequences) 3.5 years apart using the same 1.5-T scanner. Using automated tissue segmentation, we identified NAWM at baseline. We assessed which NAWM regions converted into WML during follow-up and differentiated new WML into regions of WML growth and de novo WML. Fractional anisotropy, mean diffusivity, and FLAIR intensity of regions converting to WML and regions of persistent NAWM were compared using 3 approaches: a whole-brain analysis, a regionally matched approach, and a voxel-wise approach.

RESULTS

All 3 approaches showed that low fractional anisotropy, high mean diffusivity, and relatively high FLAIR intensity at baseline were associated with WML development during follow-up. Compared with persistent NAWM regions, NAWM regions converting to WML had significantly lower fractional anisotropy (0.337 vs 0.387; P<0.001), higher mean diffusivity (0.910 × 10(-3) mm(2)/s vs 0.729 × 10(-3) mm(2)/s; P<0.001), and relatively higher normalized FLAIR intensity (1.233 vs -0.340; P<0.001). This applied to both NAWM developing into growing and de novo WML.

CONCLUSIONS

White matter changes in NAWM are present and can be quantified on diffusion tensor imaging and FLAIR before WML develop. This suggests that WML develop gradually, and that visually appreciable WML are only the tip of the iceberg of white matter pathology.

The association between physical activity and dementia in an elderly population: the Rotterdam Study

Several studies have associated physical activity with the risk of dementia, but mostly did so during short follow-up. It remains unclear whether physical activity also affects dementia during longer follow-up. We examined the association between physical activity and risk of dementia during a follow-up period up to 14 years. From 1997 to 1999, physical activity was assessed using a validated questionnaire in 4,406 elderly persons (age range 61-97) from the prospective, population-based Rotterdam Study. Follow-up for dementia was complete until January 1, 2011. We used Cox proportional hazards models to assess the association between physical activity and incident dementia. Next, we stratified follow-up time using a cut-off of 4 years. We separately investigated dementia due to Alzheimer disease. During 38,631 person-years, 583 participants developed dementia. When adjusting for age and sex, we found a borderline significant association between higher physical activity and lower risk of dementia (HR 0.95; 95% CI 0.87-1.04). This association was confined to follow-up up to 4 years (HR 0.82; 95% CI 0.71-0.95), and not to follow-up of at least 4 years (HR 1.04; 95% CI 0.93-1.16). Additional adjustments only slightly attenuated the associations. A similar pattern was present for Alzheimer disease. We found a higher level of physical activity to be associated with a lower risk of dementia. This association was confined to follow-up for up to 4 years and not to longer follow-up, suggesting either a role for reverse causality or only a short term effect of late-life physical activity in an elderly population.