Low serum magnesium and the development of atrial fibrillation in the community: the Framingham Heart Study.

BACKGROUND: Low serum magnesium has been linked to increased risk of atrial fibrillation (AF) after cardiac surgery. It is unknown whether hypomagnesemia predisposes to AF in the community. METHODS AND RESULTS: We studied 3530 participants (mean age, 44 years; 52% women) from the Framingham Offspring Study who attended a routine examination and were free of AF and cardiovascular disease. We used Cox proportional hazard regression analysis to examine the association between serum magnesium at baseline and risk of incident AF. Analyses were adjusted for conventional AF risk factors, use of antihypertensive medications, and serum potassium. During up to 20 years of follow-up, 228 participants developed AF. Mean serum magnesium was 1.88 mg/dL. The age- and sex-adjusted incidence rate of AF was 9.4 per 1000 person-years (95% confidence interval, 6.7-11.9) in the lowest quartile of serum magnesium (≤1.77 mg/dL) compared with 6.3 per 1000 person-years (95% confidence interval, 4.1-8.4) in the highest quartile (≥1.99 mg/dL). In multivariable-adjusted models, individuals in the lowest quartile of serum magnesium were ~50% more likely to develop AF (adjusted hazard ratio, 1.52; 95% confidence interval, 1.00-2.31; P=0.05) compared with those in the upper quartiles. Results were similar after the exclusion of individuals on diuretics. CONCLUSIONS: Low serum magnesium is moderately associated with the development of AF in individuals without cardiovascular disease. Because hypomagnesemia is common in the general population, a link with AF may have potential clinical implications. Further studies are warranted to confirm our findings and to elucidate the underlying mechanisms.

Plasma resistin, adiponectin, and risk of incident atrial fibrillation: the Framingham Offspring Study.

BACKGROUND: We sought to investigate whether higher concentrations of resistin and lower concentrations of adiponectin relate to incident atrial fibrillation (AF) and whether this association is mediated by AF risk factors and inflammation. Resistin and adiponectin are adipokines that have been associated with multiple known risk factors for AF including diabetes, obesity, inflammation, and heart failure. METHODS: We studied the relations between circulating concentrations of both adipokines and incident AF in participants of the Framingham Offspring Study. RESULTS: Participants (n = 2,487) had a mean age of 61 ± 10 years, and 54% were women. During a mean follow-up of 7.6 ± 2.0 years, 206 (8.3%) individuals (96 women) developed incident AF. Plasma resistin concentration was significantly associated with incident AF (multivariable-adjusted hazard ratio [HR] 1.17 per SD [0.41 ng/mL] of natural logarithmically transformed resistin, 95% CI 1.02-1.34, P = .028). The resistin-AF association was attenuated after further adjustment for C-reactive protein (HR per SD increase resistin 1.14, 95% CI 0.99-1.31, P = .073). Adiponectin concentrations were not significantly associated with incident AF (multivariable-adjusted HR of 0.95 per SD [0.62 µg/mL] of logarithmically transformed adiponectin, 95% CI 0.81-1.10, P = .478). CONCLUSION: In our community-based longitudinal study, higher mean concentrations of resistin were associated with incident AF, but the relation was attenuated by adjustment for C-reactive protein. We did not detect a statistically significant association between adiponectin and incident AF. Additional studies are needed to clarify the potential role of adipokines in AF and mechanisms linking adiposity to AF.

Bias reduction in conditional logistic regression.

We employ a general bias preventive approach developed by Firth (Biometrika 1993; 80:27-38) to reduce the bias of an estimator of the log-odds ratio parameter in a matched case-control study by solving a modified score equation. We also propose a method to calculate the standard error of the resultant estimator. A closed-form expression for the estimator of the log-odds ratio parameter is derived in the case of a dichotomous exposure variable. Finite sample properties of the estimator are investigated via a simulation study. Finally, we apply the method to analyze a matched case-control data from a low birthweight study.

Genome-wide association study of personality traits in the long life family study.

Personality traits have been shown to be associated with longevity and healthy aging. In order to discover novel genetic modifiers associated with personality traits as related with longevity, we performed a genome-wide association study (GWAS) on personality factors assessed by NEO-five-factor inventory in individuals enrolled in the Long Life Family Study (LLFS), a study of 583 families (N up to 4595) with clustering for longevity in the United States and Denmark. Three SNPs, in almost perfect LD, associated with agreeableness reached genome-wide significance (p < 10(-8)) and replicated in an additional sample of 1279 LLFS subjects, although one (rs9650241) failed to replicate and the other two were not available in two independent replication cohorts, the Baltimore Longitudinal Study of Aging and the New England Centenarian Study. Based on 10,000,000 permutations, the empirical p-value of 2 × 10(-7) was observed for the genome-wide significant SNPs. Seventeen SNPs that reached marginal statistical significance in the two previous GWASs (p-value <10(-4) and 10(-5)), were also marginally significantly associated in this study (p-value <0.05), although none of the associations passed the Bonferroni correction. In addition, we tested age-by-SNP interactions and found some significant associations. Since scores of personality traits in LLFS subjects change in the oldest ages, and genetic factors outweigh environmental factors to achieve extreme ages, these age-by-SNP interactions could be a proxy for complex gene-gene interactions affecting personality traits and longevity.

Personality factors in the Long Life Family Study.

OBJECTIVES: To evaluate personality profiles of Long Life Family Study participants relative to population norms and offspring of centenarians from the New England Centenarian Study. METHOD Personality domains of agreeableness, conscientiousness, extraversion, neuroticism, and openness were assessed with the NEO Five-Factor Inventory in 4,937 participants from the Long Life Family Study (mean age 70 years). A linear mixed model of age and gender was implemented adjusting for other covariates. RESULTS: A significant age trend was found in all five personality domains. On average, the offspring generation of long-lived families scored low in neuroticism, high in extraversion, and within average values for the other three domains. Older participants tended to score higher in neuroticism and lower in the other domains compared with younger participants, but the estimated scores generally remained within average population values. No significant differences were found between long-lived family members and their spouses. DISCUSSION: Personality factors and more specifically low neuroticism and high extraversion may be important for achieving extreme old age. In addition, personality scores of family members were not significantly different from those of their spouses, suggesting that environmental factors may play a significant role in addition to genetic factors.

Risk assessment for incident heart failure in individuals with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is a strong risk factor for heart failure (HF); HF onset in patients with AF is associated with increased morbidity and mortality. Risk factors that predict HF in individuals with AF in the community are not well established. METHODS AND RESULTS: We examined clinical variables related to the 10-year incidence of HF in 725 individuals (mean 73.3 years, 45% women) with documented AF in the Framingham Heart Study. Event rates for incident HF (n = 161, 48% in women) were comparable in women (4.30 per 100 person-years) and men (3.34 per 100 person-years). Age, body mass index, ECG LV hypertrophy, diabetes, significant murmur, and history of myocardial infarction were positively associated with incident HF in multivariable models (C-statistic 0.71; 95% confidence interval 0.67-0.75). We developed a risk algorithm for estimating absolute risk of HF in AF patients with good model fit and calibration (adjusted calibration χ2 statistic 7.29; P(χ2) = 0.61). Applying the algorithm, 47.6% of HF events occurred in the top tertile in men compared with 13.1% in the bottom tertile, and 58.4% in women in the upper tertile compared with 18.2% in the lowest category. For HF type, women had a non-significantly higher incidence of HF with preserved EF compared with men. CONCLUSIONS: We describe advancing age, LV hypertrophy, body mass index, diabetes, significant heart murmur, and history of myocardial infarction as clinical predictors of incident HF in individuals with AF. A risk algorithm may help identify individuals with AF at high risk of developing HF.

Naïve Bayesian Classifier and Genetic Risk Score for Genetic Risk Prediction of a Categorical Trait: Not so Different after all!

One of the most popular modeling approaches to genetic risk prediction is to use a summary of risk alleles in the form of an unweighted or a weighted genetic risk score, with weights that relate to the odds for the phenotype in carriers of the individual alleles. Recent contributions have proposed the use of Bayesian classification rules using Naïve Bayes classifiers. We examine the relation between the two approaches for genetic risk prediction and show that the methods are mathematically related. In addition, we study the properties of the two approaches and describe how they can be generalized to include various models of inheritance.

White blood cell count and risk of incident atrial fibrillation (from the Framingham Heart Study).

Several studies have reported that inflammatory markers are associated with atrial fibrillation (AF). The white blood cell (WBC) count is a widely available and broadly used marker of systemic inflammation. We sought to investigate the association between an increased WBC count and incident AF and whether this association is mediated by smoking, myocardial infarction, and heart failure. We examined the participants in the Framingham Heart Study original cohort. Cox proportional hazard regression analysis was used to examine the relation between the WBC count and incident AF during a 5-year follow-up period. We adjusted for standard AF risk factors, smoking, previous myocardial infarction, and interim myocardial infarction and heart failure before the incident AF. Our sample consisted of 936 participants (mean age 76 ± 6 years and 61% women). The median WBC count was 6.4 × 10(9)/L (25th to 75th percentile 5.6 × 10(9)/L to 7.8 × 10(9)/L). During a median 5-year follow-up period, 82 participants (9%) developed new-onset AF. After adjusting for standard risk factors for AF, an increased WBC count was significantly associated with incident AF, with a hazard ratio per SD (0.26 × 10(9)/L) increase of 2.22 (95% confidence interval 1.10 to 4.48; p = 0.03). We found no substantive differences adjusting for smoking, previous myocardial infarction, interim myocardial infarction, or heart failure. In conclusion, in our community-based sample, an increased WBC count was associated with incident AF during 5 years of follow-up. Our findings provide additional evidence for the relation between systemic inflammation and AF.