Measures of Body Size and Composition and Risk of Incident Atrial Fibrillation in Older People: The Cardiovascular Health Study

Diabetes, prediabetes, and atrial fibrillation-A population-based cohort study based on national and regional registers

BACKGROUND

Previous studies have shown an increased risk for atrial fibrillation and atrial flutter (AF) in people with type 2 diabetes and prediabetes. It is unclear whether this increase in AF risk is independent of other risk factors for AF.

OBJECTIVE

To investigate the association between diabetes and different prediabetic states, as independent risk factors for the onset of AF.

METHODS

We performed a population-based cohort study in Northern Sweden, including data on fasting plasma glucose, oral glucose tolerance test, major cardiovascular risk factors, medical history, and lifestyle factors. Participants were divided into six groups depending on glycemic status and followed through national registers for AF diagnosis. Cox proportional hazard model was used to assess the association between glycemic status and AF, using normoglycemia as reference.

RESULTS

The cohort consisted of 88,889 participants who underwent a total of 139,661 health examinations. In the model adjusted for age and sex, there was a significant association between glycemic status and development of AF in all groups except the impaired glucose tolerance group, with the strongest association for the group with known diabetes (p-value <0.001). In a model adjusted for sex, age, systolic blood pressure, body mass index, antihypertensive drugs, cholesterol, alcohol, smoking, education level, marital status, and physical activity, there was no significant association between glycemic status and AF.

CONCLUSIONS/INTERPRETATION

The association between glycemic status and AF disappears upon adjustment for potential confounders. Diabetes and prediabetes do not appear to be independent risk factors for AF.

Body Composition and Risk of Incident Heart Failure in 1 Million Adults: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies

Background The aim of this systematic review was to quantify the associations between body composition measures and risk of incident heart failure (HF) and its subtypes in the general population. Methods and Results We searched Medline, Embase, and Global Health databases from each database inception to January 19, 2023 for prospective studies reporting on body composition and HF risk. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Newcastle-Ottawa scale was used to assess the risk of bias of included studies. Fixed-effects models were used for meta-analysis. Thirty-five studies were included (ntotal=1 137 044; ncases=34 422). Summary relative risk (RR) per 5-kg/m2 higher body mass index was 1.42 (95% CI, 1.40-1.42; 𝜁2=0.02, I2=94.4%), 1.28 (95% CI, 1.26-1.31; 𝜁2=0.01, I2=75.8%) per 10-cm higher waist circumference, and 1.33 (95% CI, 1.28-1.37; 𝜁2=0.04, I2=94.9%) per 0.1-unit higher waist-hip ratio. Pooled estimates of the few studies that reported on regional fat suggested significant positive association between HF risk and both visceral fat (RR, 1.08 [95% CI, 1.04-1.12]) and pericardial fat (RR, 1.08 [95% CI, 1.06-1.10]). Among HF subtypes, associations were stronger for HF with preserved ejection fraction than HF with reduced ejection fraction. No study reported on lean mass. Conclusions Pooled data suggested strong associations between adiposity and HF. The association with adiposity is stronger for HF with preserved ejection fraction than HF with reduced ejection fraction, indicating that different mechanisms may be at play in etiopathogenesis of HF subtypes. Future studies are needed to investigate role of regional fat mass and lean mass in HF risk. Registration Information REGISTRATION: URL: www.crd.york.ac.uk/prospero/. Unique identifier: CRD42020224584.

Genetics of atrial fibrillation

PURPOSE OF REVIEW

Atrial fibrillation is the most common cardiac arrhythmia worldwide. There is considerable interest in better understanding the molecular genetics and biology of atrial fibrillation to inform the development of new therapies and improve clinical management. This review summarizes recent advances in our understanding of the genetic basis of atrial fibrillation and new efforts to utilize genetics to inform clinical management.

RECENT FINDINGS

Genome-wide association studies in diverse populations have increased the number of genetic loci associated with atrial fibrillation and its specific subtypes. Large-scale biobanks with deep phenotyping have provided invaluable data to study the impact of both common and rare variants on atrial fibrillation, susceptibility, and prognosis. Polygenic risk scores help improve individual atrial fibrillation risk stratification and prognostication.

SUMMARY

Our understanding of atrial fibrillation genetics is rapidly improving with larger and more diverse genome-wide association studies. Translating genetic discoveries into molecular pathways and new therapeutic targets remains a bottleneck in the development of new therapies for atrial fibrillation. Genetic risk scores have shown early promise in improving atrial fibrillation risk stratification; however, their broader utility for the general population remains unclear.

Circulating Androgen Concentrations and Risk of Incident Heart Failure in Older Men: The Cardiovascular Health Study

Background

Circulating androgen concentrations in men decline with age and have been linked to diabetes and atherosclerotic cardiovascular disease (ASCVD). A similar relationship has been reported for low total testosterone and incident heart failure (HF) but remains unstudied for free testosterone or the more potent androgen dihydrotestosterone (DHT). We hypothesized that total/free testosterone are inversely related, sex hormone–binding globulin is positively related, and total/free DHT bear a U‐shaped relationship with incident HF.

Methods and Results

In a sample of men from the CHS (Cardiovascular Health Study) without atherosclerotic cardiovascular disease or HF, serum testosterone and DHT concentrations were measured by liquid chromatography–tandem mass spectrometry, and sex hormone–binding globulin by immunoassay. Free testosterone or DHT was calculated from total testosterone or total DHT, sex hormone–binding globulin, and albumin. We used Cox regression to estimate relative risks of HF after adjustment for potential confounders. In 1061 men (aged 76±5 years) followed for a median of 9.6 years, there were 368 HF events. After adjustment, lower calculated free testosterone was significantly associated with higher risk of HF (hazard ratio [HR], 1.14 [95% CI, 1.01–1.28]). Risk estimates for total testosterone (HR, 1.12 [95% CI, 0.99–1.26]), total DHT (HR, 1.10 [95% CI, 0.97–1.24]), calculated free dihydrotestosterone (HR, 1.09 [95% CI, 0.97–1.23]), and sex hormone–binding globulin (HR, 1.07 [95% CI, 0.95–1.21]) were directionally similar but not statistically significant.

Conclusions

Calculated free testosterone was inversely associated with incident HF, suggesting a contribution of testosterone deficiency to HF incidence among older men. Additional research is necessary to determine whether testosterone replacement therapy might be an effective strategy to lower HF risk in older men.

Sex Differences in Atrial Fibrillation Risk: The VITAL Rhythm Study

Importance

Women have a lower incidence of atrial fibrillation (AF) compared with men in several studies, but it is unclear whether this sex difference is independent of sex differences in prevalent cardiovascular disease (CVD), body size, and other risk factors.

Objective

To examine sex differences in AF incidence and whether AF risk factors differ by sex in a contemporary cohort of men and women without prevalent CVD.

Design, Setting, and Participants

This was a prospective cohort analysis within the Vitamin D and Omega-3 Trial (VITAL) Rhythm Study, a randomized trial that examined the effect of vitamin D and ω-3 fatty acid supplementation on incident AF among men 50 years or older and women 55 years or older without a prior history of prevalent AF, CVD, or cancer at baseline. Data were analyzed from September 29, 2020, to June 29, 2021.

Exposures

Sex, height, weight, body mass index (BMI), body surface area (BSA), and other AF risk factors at study enrollment.

Main Outcomes and Measures

Incident AF confirmed by medical record review.

Results

A total of 25 119 individuals (mean [SD] age, 67.0 [7.1] years; 12 757 women [51%]) were included in this study. Over a median (IQR) follow-up of 5.3 (5.1-5.7) years, 900 confirmed incident AF events occurred among 12 362 men (495 events, 4.0%) and 12 757 women (405 events, 3.2%). After adjustment for age and treatment assignment, women were at lower risk for incident AF than men (hazard ratio [HR], 0.68; 95% CI, 0.59-0.77; P < .001). The inverse association between female sex and AF persisted after adjustment for race and ethnicity, smoking, alcohol intake, hypertension, diabetes (type 1, type 2, gestational), thyroid disease, exercise, and BMI (HR, 0.73; 95% CI, 0.63-0.85; P <.001). However, female sex was positively associated with AF when height (HR, 1.39; 95% CI, 1.14-1.72; P = .001), height and weight (HR 1.49, 95% CI, 1.21-1.82; P <.001), or BSA (HR, 1.25; 95% CI, 1.06-1.49; P = .009) were substituted for BMI in the multivariate model. In stratified models, risk factor associations with incident AF were similar for women and men.

Conclusions and Relevance

In this cohort study, findings suggest that after controlling for height and/or body size, women without CVD at baseline were at higher risk for AF than men, suggesting that sex differences in body size account for much of the protective association between female sex and AF. These data underscore the importance of AF prevention in women.

Independent effects of adiposity measures on risk of atrial fibrillation in men and women: a study of 0.5 million individuals

BACKGROUND

Atrial fibrillation (AF) has a higher prevalence in men than in women and is associated with measures of adiposity and lean mass (LM). However, it remains uncertain whether the risks of AF associated with these measures vary by sex.

METHODS

Among 477 904 UK Biobank participants aged 40-69 without prior AF, 23 134 incident AF cases were identified (14 400 men, 8734 women; median follow-up 11.1 years). Cox proportional hazards models were used to estimate the covariate adjusted hazard ratios (HRs) describing the association of AF with weight, measures of adiposity [fat mass (FM), waist circumference (WC)] and LM, and their independent relevance, by sex.

RESULTS

Weight and WC were independently associated with risk of AF [HR: 1.25 (1.23-1.27) per 10 kg, HR: 1.11 (1.09-1.14) per 10 cm, respectively], with comparable effects in both sexes. The association with weight was principally driven by LM, which, per 5 kg, conferred double the risk of AF compared with FM when mutually adjusted [HR: 1.20 (1.19-1.21), HR: 1.10 (1.09-1.11), respectively]; however, the effect of LM was weaker in men than in women (p-interaction = 4.3 x 10-9). Comparing the relative effects of LM, FM and WC identified different patterns within each sex; LM was the strongest predictor for both, whereas WC was stronger than FM in men but not in women.

CONCLUSIONS

LM and FM (as constituents of weight) and WC are risk factors for AF. However, the independent relevance of general adiposity for AF was more limited in men than in women. The relevance of both WC and LM suggests a potentially important role for visceral adiposity and muscle mass in AF development.

Body Composition and Incident Heart Failure in Older Adults: Results From 2 Prospective Cohorts

Background Aging is associated with central fat redistribution and skeletal muscle decline, yet the relationships of tissue compartments with heart failure (HF) remain incompletely characterized. We assessed the contribution of body composition to incident HF in elders. Methods and Results Participants from 2 older cohorts who completed dual-energy X-ray absorptiometry (DEXA) and, in one cohort, computed tomography were included. We evaluated associations with incident HF for DEXA principal components (PCs) and total lean, appendicular lean, total fat and trunk fat mass; and for computed tomography measures of abdominal visceral and subcutaneous fat, thigh muscle, intermuscular fat area and thigh muscle density. DEXA analysis included 3621, and computed tomography analysis 2332 participants. During median follow-up of 11.8 years, 927 participants developed HF. DEXA principal components showed no relationship with HF. After adjustment for height, weight, and cardiovascular risk factors, total lean mass was near significantly associated with higher HF (hazard ratio [HR], 1.25 per SD [1.00-1.56]), whereas total fat mass and thigh muscle density were significantly related to lower HF (HR, 0.82 [0.68-0.99] and HR, 0.87 [0.78-0.97], respectively). Patterns were similar for HF subtypes. The relationships with HF for total lean and fat mass were attenuated after adjusting for intercurrent atrial fibrillation or excluding high natriuretic peptide levels. Conclusions Total lean mass was positively associated, while total fat mass and thigh muscle density were inversely associated, with incident HF. These findings highlight the limitations of DEXA for assessment of HF risk in elders and support the preeminence of computed tomography-measured skeletal muscle quality over mass as a determinant of HF incidence.

Anthropometric measures and the risk of developing atrial fibrillation: a Swedish Cohort Study

Aims

Obesity is a risk factor for several cardiovascular diseases (CVDs), including atrial fibrillation (AF). However, it is less clear whether overall fat or abdominal fat distribution are most important for risk of developing AF. This study investigates how different anthropometric measures correlate to the risk of developing clinical AF in the Malmö Diet and Cancer cohort (MDC-cohort).

Methods

The MDC-cohort (n = 25,961) was examined in 1991–1996. The endpoint was clinical AF diagnosed in a hospital setting, and retrieved via linkage with national registers. Hazard Ratios (HR) for incident AF was calculated in relation to quartiles of body mass index (BMI), waist circumference, waist hip ratio, waist height ratio, body fat percentage, weight and height, using Cox regression with adjustment for age, biological (e.g. blood pressure, diabetes, blood lipid levels), and socioeconomic risk factors.

Results

After adjustment for multiple risk factors, the risk of AF was significantly increased in the 4th versus 1st quartile of weight (HR for men/women = 2.02/1.93), BMI (HR = 1.62/1.52), waist circumference (HR = 1.67/1.63), waist to hip ratio (HR = 1.30/1.24), waist to height ratio (1.37/1.39) and body fat percentage (HR = 1.21/1.45) in men/women. Measures of overall weight (BMI, weight) were slightly more predictive than measures of abdominal obesity (waist hip ratio and waist height ratio) both in men and women.

Conclusion

All measures of obesity were associated with increased risk of developing AF. Both overall obesity and abdominal obesity were related to incidence of AF in this population-based study, although the relationship for overall obesity was stronger.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02415-6.

Adverse cardiac mechanics and incident coronary heart disease in the Cardiovascular Health Study

OBJECTIVES

Speckle-tracking echocardiography enables detection of abnormalities in cardiac mechanics with higher sensitivity than conventional measures of left ventricular (LV) dysfunction and may provide insight into the pathogenesis of coronary heart disease (CHD). We investigated the relationship of LV longitudinal strain, LV early diastolic strain rate (SR) and left atrial (LA) reservoir strain with long-term CHD incidence in community-dwelling older adults.

METHODS

The association of all three strain measures with incidence of non-fatal and fatal CHD (primary outcome of revascularisation, non-fatal and fatal myocardial infarction) was examined in the population-based Cardiovascular Health Study using multivariable Cox proportional hazards models. Follow-up was truncated at 10 years.

RESULTS

We included 3313 participants (mean (SD) age 72.6 (5.5) years). During a median follow-up of 10.0 (25th-75th percentile 7.7-10.0) years, 439 CHD events occurred. LV longitudinal strain (HR=1.25 per SD decrement, 95% CI 1.09 to 1.43) and LV early diastolic SR (HR=1.31 per SD decrement, 95% CI 1.14 to 1.50) were associated with a significantly greater risk of incident CHD after adjustment for potential confounders. By contrast, LA reservoir strain was not associated with incident CHD (HR=1.06 per SD decrement, 95% CI 0.94 to 1.19). Additional adjustment for biochemical and echocardiographic measures of myocardial stress, dysfunction and remodelling did not meaningfully alter these associations.

CONCLUSION

We found an association between echocardiographic measures of subclinically altered LV mechanics and incident CHD. These findings inform the underlying biology of subclinical LV dysfunction and CHD. Early detection of asymptomatic myocardial dysfunction may offer an opportunity for prevention and early intervention.

Adult height and incidence of atrial fibrillation and heart failure in older men: The British Regional Heart Study

Aims

Taller stature has been associated with increased risk of atrial fibrillation (AF). AF and heart failure (HF) often co-occur but the association between height and risk of HF in older adults has not been well studied. We have examined the association between height and incident AF and incident HF in older adults.

Methods

Prospective study of 3346 men aged 60–79 years with no diagnosed HF, myocardial infarction or stroke at baseline (1998–2000) followed up for a mean period of 16 years, in whom there were 294 incident HF cases and 456 incident AF. Men were divided into 5 height groups: <168.2, 168.2–172.5, 172.6–176.9, 177.0–183.0 and >183.0 cms based on the 25th, 50th, 75th and 95th centiles distribution of height.

Results

CVD risk factors tended to decrease with increasing height but a positive association was seen between height and electrocardiographic QRS duration and incident AF. Both short stature (<168.2 cm) and tall stature (>183.0 cm) was associated with significantly increased risk of HF in age-adjusted analysis compared to those in the second height quartile [HR (95 %CI) = 1.62 (1.15, 2.26) and 2.04 (1.23, 3.39) respectively]. In short men the increased risk remained after adjustment for adverse CVD risk factors; in tall men the association was largely associated with AF and QRS duration.

Conclusion

Tall stature is associated with significantly increased risk of AF leading to increased risk of HF. Short stature was associated with increased HF risk which was not explained by known adverse CVD risk factors.

A Systematic Review of Scaling Left Atrial Size: Are Alternative Indexation Methods Required for an Increasingly Obese Population?

BACKGROUND

Left atrial (LA) size indexed to body surface area (BSA) is a clinically important marker of cardiovascular prognosis. However, indexation using a scaling variable such as BSA has inherent flaws, particularly in an obese population. The aim of this study was to determine whether alternative indexation methods may more accurately scale for LA size.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to execute a structured search of medical databases, to identify articles discussing alternative methods of LA indexation in echocardiography. Articles that stratified indexed LA size by obesity class were also included. Two independent reviewers identified relevant articles and extracted baseline characteristics, alternative indexation methods, scaling variables, obesity class characteristics, and correlation coefficients.

RESULTS

A total of 3,804 articles were found in the database search after removing duplicates. After abstract and full-text screening, 13 relevant articles were identified. Twelve studies used alternative methods of LA indexation, of which nine reported allometric indices. Seven of the included studies reported LA size by obesity class, of which six reported alternative indices. Correlation coefficients plotted for indexed LA size against absolute measured LA size showed that allometric indices (specifically to height) were more likely to maintain proportionality to body size compared with isometric indices such as BSA. Allometric indices were less likely to overcorrect for body size compared with isometric indices.

CONCLUSIONS

Compared with isometric indexation to BSA, allometric indexation (specifically to height) improves scaling of LA volumes to maintain proportionality and avoid overcorrection for body size.

Joint Associations Between Body Mass Index and Waist Circumference With Atrial Fibrillation in Men and Women

Background Associations between adiposity and atrial fibrillation (AF) might differ between sexes. We aimed to determine precise estimates of the risk of AF by body mass index (BMI) and waist circumference (WC) in men and women. Methods and Results Between 2008 and 2013, over 3.2 million adults attended commercial screening clinics. Participants completed health questionnaires and underwent physical examination along with cardiovascular investigations, including an ECG. We excluded those with cardiovascular and cardiac disease. We used multivariable logistic regression and determined joint associations of BMI and WC and the risk of AF in men and women by comparing likelihood ratio χ2 statistics. Among 2.1 million included participants 12 067 (0.6%) had AF. A positive association between BMI per 5 kg/m2 increment and AF was observed, with an odds ratio of 1.65 (95% CI, 1.57-1.73) for men and 1.36 (95% CI, 1.30-1.42) for women among those with a BMI above 20 kg/m2. We found a positive association between AF and WC per 10 cm increment, with an odds ratio of 1.47 (95% CI, 1.36-1.60) for men and 1.37 (95% CI, 1.26-1.49) for women. Improvement of likelihood ratio χ2 was equal after adding BMI and WC to models with all participants. In men, WC showed stronger improvement of likelihood ratio χ2 than BMI (30% versus 23%). In women, BMI showed stronger improvement of likelihood ratio χ2 than WC (23% versus 12%). Conclusions We found a positive association between BMI (above 20 kg/m2) and AF and between WC and AF in both men and women. BMI seems a more informative measure about risk of AF in women and WC seems more informative in men.

Race, Body Mass Index, and the Risk of Atrial Fibrillation: The Multi-Ethnic Study of Atherosclerosis

Background

Higher body mass index (BMI) is associated with increased risk of incident atrial fibrillation (AF), but it is not known whether this relationship varies by race/ethnicity.

Methods and Results

Eligible participants (6739) from MESA (Multi‐Ethnic Study of Atherosclerosis) were surveilled for incident AF using MESA hospital surveillance, scheduled MESA study ECG, and Medicare claims data. After a median 13.8 years of follow‐up, 970 participants (14.4%) had incident AF. With BMI modeled categorically in a Cox proportional hazards model, only those with grade II and grade III obesity had increased risks of AF (hazard ratio [HR], 1.50; 95% CI, 1.14–1.98, P=0.004 for grade II obesity and HR, 2.13; 95% CI, 1.48–3.05, P<0.0001 for grade III obesity). The relationship between BMI and AF risk was J‐shaped. However, the risk of AF as a function of BMI varied substantially by race/ethnicity (P value for interaction=0.02), with Chinese‐American participants having a much higher risk of AF with higher BMI and Black participants having minimal increased risk of AF with higher BMI.

Conclusions

Obesity is associated with an increased risk of incident AF, but the relationship between BMI and the risk of AF is J‐shaped and this relationship differs by race/ethnicity, such that Chinese‐American participants have a more pronounced increased risk of AF with higher BMI, while Black participants have minimal increased risk. Further exploration of the differential effects of BMI by race/ethnicity on cardiovascular outcomes is needed.

The height as an independent risk factor of atrial fibrillation: A review

Atrial fibrillation (AF) is characterized by abnormal heart rhythm. Among other well-known associations, recent studies suggest an association of AF with height. Height is related to 50 diseases spanning different body systems, AF is one of them. Since AF, a heterogeneous disease process, is influenced by structural, neural, electrical, and hemodynamic factors, height alters this process through its contribution to increasing atrial and ventricular size, leading to altered conduction patterns, autonomic dysregulation, and development of AF. Multiple underlying mechanisms associate height with AF. Apart from these indirect mechanisms, genome-wide association studies suggest the involvement of the same genes in AF and growth pathways. Tall stature is independently associated with a higher risk of AF development in healthy individuals. Since adult height is achieved much earlier than the onset of AF, protective measures can be taken in individuals with increased height to monitor, manage, and prevent the progression of AF.

Genetics of height and risk of atrial fibrillation: A Mendelian randomization study

BACKGROUND

Observational studies have identified height as a strong risk factor for atrial fibrillation, but this finding may be limited by residual confounding. We aimed to examine genetic variation in height within the Mendelian randomization (MR) framework to determine whether height has a causal effect on risk of atrial fibrillation.

METHODS AND FINDINGS

In summary-level analyses, MR was performed using summary statistics from genome-wide association studies of height (GIANT/UK Biobank; 693,529 individuals) and atrial fibrillation (AFGen; 65,446 cases and 522,744 controls), finding that each 1-SD increase in genetically predicted height increased the odds of atrial fibrillation (odds ratio [OR] 1.34; 95% CI 1.29 to 1.40; p = 5 × 10-42). This result remained consistent in sensitivity analyses with MR methods that make different assumptions about the presence of pleiotropy, and when accounting for the effects of traditional cardiovascular risk factors on atrial fibrillation. Individual-level phenome-wide association studies of height and a height genetic risk score were performed among 6,567 European-ancestry participants of the Penn Medicine Biobank (median age at enrollment 63 years, interquartile range 55-72; 38% female; recruitment 2008-2015), confirming prior observational associations between height and atrial fibrillation. Individual-level MR confirmed that each 1-SD increase in height increased the odds of atrial fibrillation, including adjustment for clinical and echocardiographic confounders (OR 1.89; 95% CI 1.50 to 2.40; p = 0.007). The main limitations of this study include potential bias from pleiotropic effects of genetic variants, and lack of generalizability of individual-level findings to non-European populations.

CONCLUSIONS

In this study, we observed evidence that height is likely a positive causal risk factor for atrial fibrillation. Further study is needed to determine whether risk prediction tools including height or anthropometric risk factors can be used to improve screening and primary prevention of atrial fibrillation, and whether biological pathways involved in height may offer new targets for treatment of atrial fibrillation.

Atrial fibrillation is associated with lean body mass in postmenopausal women

This study investigated the association between body composition and risk of atrial fibrillation (AF) in postmenopausal women. In a retrospective analysis we assessed data from 5704 postmenopausal women (age 70.7 ± 6.5 yrs.) who in 1999–2001 participated in The Prospective Epidemiological Risk Factor study with body composition assessed by dual-energy X-ray absorptiometry. Outcomes were obtained from Danish Health Registries and body composition association to risk of AF was evaluated by univariable and multivariable Cox Hazard regression. 850 women developed AF after baseline. High lean body mass was associated with increased risk of AF in multivariable analyses, adjusting for body mass index (BMI), height or weight (adjusted for: BMI, hazard ratio (HR) 1.49, 95% Confidence Interval (1.22–1.80); height, HR 1.27 (1.03–1.56); weight, 1.33 (1.06–1.65)). Height and weight were associated with increased risk of AF in multivariable analyses adjusting for body composition measures. When adjusting for total lean mass, only height remained statistically significant (HR 1.34 (1.09–1.64)). In a cohort of elderly Caucasian women, high lean body mass, height and weight were associated with increased risk of AF and the variables remained significant after adjusting for age and other known risk factors of AF.

Exploring the causal pathway from ischemic stroke to atrial fibrillation: a network Mendelian randomization study

BACKGROUND AND PURPOSE

Previous studies have found ischemic stroke is associated with atrial fibrillation. However, the causal association between ischemic stroke and atrial fibrillation is not clear. Furthermore, the network relationship among ischemic stroke, atrial fibrillation and its risk factors need further attention. This study aims to examine the potential causal association between ischemic stroke and atrial fibrillation and further to explore potential mediators in the causal pathway from ischemic stroke to atrial fibrillation.

METHODS

Summary statistics from the ISGC (case = 10,307 and control = 19,326) were used as ischemic stroke genetic instruments, AFGen Consortium data (case = 65,446 and control = 522,744) were used for atrial fibrillation, and other consortia data were used for potential mediators (fasting insulin, white blood cell count, procalcitonin, systolic and diastolic blood pressure, body mass index, waist circumference, and height). Under the framework of network Mendelian randomization, two-sample Mendelian randomization study was performed using summary statistics from several genome-wide association studies. Inverse-variance weighted method was performed to estimate causal effect.

RESULTS

Blood pressure mediates the causal pathways from ischemic stroke to atrial fibrillation. The total odds ratio of ischemic stroke on atrial fibrillation was 1.05 (95% confidence interval [CI], 1.02 to 1.07; P = 1.3 × 10-5). One-unit increase of genetically determined ischemic stroke was associated with 0.02 (DBP: 95% CI, 0.001 to 0.034, P = 0.029; SBP: 95% CI, 0.006 to 0.034, P = 0.003) upper systolic and diastolic blood pressure levels. Higher genetically determined systolic and diastolic blood pressure levels were associated with higher atrial fibrillation risk (DBP: RR, 1.18; 95% CI, 1.03 to 1.35; P = 0.012. SBP: RR, 1.18; 95% CI, 1.01 to 1.38; P = 0.04). Specially, we also found the bidirectional causality between blood pressure and ischemic stroke.

CONCLUSIONS

Our study provided a strong evidence that raised blood pressure in stroke patients increases the risk of atrial fibrillation and active acute blood pressure lowering can improve the outcome in ischemic stroke patients.

Biochemical markers of bone turnover and risk of incident hip fracture in older women: the Cardiovascular Health Study

The relationships of osteocalcin (OC) and C-telopeptide of type I collagen (CTX) with long-term incidence of hip fracture were examined in 1680 post-menopausal women from a population-based study. CTX, but not OC, levels were associated with incident hip fracture in these participants, a relationship characterized by an inverted U-shape.

INTRODUCTION

We sought to investigate the relationships of OC, a marker of bone formation, and CTX, a marker of bone resorption, with long-term incidence of hip fracture in older women.

METHODS

We included 1680 women from the population-based Cardiovascular Health Study (mean [SD] age 74.5 [5.0] years). The longitudinal association of both markers with incidence of hip fracture was examined using multivariable Cox models.

RESULTS

During a median follow-up of 12.3 years, 288 incident hip fractures occurred. Linear spline analysis did not demonstrate an association between OC levels and incident hip fracture. By contrast, increasing levels of CTX up to the middle-upper range were associated with a significantly greater risk of hip fracture (HR = 1.52 per SD increment, 95% CI = 1.10-2.09), while further increases were associated with a marginally non-significant lower risk (HR = 0.80 per SD increment, 95% CI = 0.63-1.01), after full adjustment for potential confounders. In analyses of quartiles, CTX exhibited a similar inverted U-shaped relationship with incident fracture after adjustment, with a significant association observed only for the comparison of quartile 3 to quartile 1 (HR = 1.63, 95% CI = 1.10-2.43). In a subset with available measures, both OC and CTX were inversely associated with bone mineral density of the hip.

CONCLUSION

CTX, but not OC, levels were associated with incident hip fracture in post-menopausal women, a relationship characterized by an inverted U-shape. These findings highlight the complex relationship of bone turnover markers with hip fracture risk.

Body composition and atrial fibrillation: a Mendelian randomization study

AIMS

Increases in fat-free mass and fat mass have been associated with higher risk of atrial fibrillation (AF) in observational studies. It is not known whether these associations reflect independent causal processes. Our aim was to evaluate independent causal roles of fat-free mass and fat mass on AF.

METHODS AND RESULTS

We conducted a large observational study to estimate the associations between fat-free mass and fat mass on incident AF in the UK Biobank (N = 487 404, N events = 10 365). Genome-wide association analysis was performed to obtain genetic instruments for Mendelian randomization (MR). We evaluated the causal effects of fat-free mass and fat mass on AF with two-sample method by using genetic associations from AFGen consortium as outcome. Finally, we evaluated independent causal effects of fat-free mass and fat mass with multivariate MR. Both fat-free mass and fat mass had observational associations with incident AF [hazard ratio (HR) = 1.77, 95% confidence interval (CI) 1.72-1.83; HR = 1.40, 95% CI 1.37-1.43 per standard deviation increase in fat-free and fat mass, respectively]. The causal effects using the inverse-variance weighted method were 1.55 (95% CI 1.38-1.75) for fat-free mass and 1.30 (95% CI 1.17-1.45) for fat mass. Weighted median, Egger regression, and penalized methods showed similar estimates. The multivariate MR analysis suggested that the causal effects of fat-free and fat mass were independent of each other (causal risk ratios: 1.37, 95% CI 1.06-1.75; 1.28, 95% CI 1.03-1.58).

CONCLUSION

Genetically programmed increases in fat-free mass and fat mass independently cause an increased risk of AF.

Biochemical Markers of Bone Turnover and Risk of Incident Diabetes in Older Women: The Cardiovascular Health Study

OBJECTIVE

To investigate the relationship of osteocalcin (OC), a marker of bone formation, and C-terminal cross-linked telopeptide of type I collagen (CTX), a marker of bone resorption, with incident diabetes in older women.

RESEARCH DESIGN AND METHODS

The analysis included 1,455 female participants from the population-based Cardiovascular Health Study (CHS) (mean [SD] age 74.6 [5.0] years). The cross-sectional association of serum total OC and CTX levels with insulin resistance (HOMA-IR) was examined using multiple linear regression. The longitudinal association of both markers with incident diabetes, defined by follow-up glucose measurements, medications, and ICD-9 codes, was examined using multivariable Cox proportional hazards models.

RESULTS

OC and CTX were strongly correlated (r = 0.80). In cross-sectional analyses, significant or near-significant inverse associations with HOMA-IR were observed for continuous levels of OC (β = -0.12 per SD increment; P = 0.004) and CTX (β = -0.08 per SD; P = 0.051) after full adjustment for demographic, lifestyle, and clinical covariates. During a median follow-up of 11.5 years, 196 cases of incident diabetes occurred. After full adjustment, both biomarkers exhibited inverse associations with incident diabetes (OC: hazard ratio 0.85 per SD [95% CI 0.71-1.02; P = 0.075]; CTX: 0.82 per SD [0.69-0.98; P = 0.031]), associations that were comparable in magnitude and approached or achieved statistical significance.

CONCLUSIONS

In late postmenopausal women, lower OC and CTX levels were associated with similarly increased risks of insulin resistance at baseline and incident diabetes over long-term follow-up. Further research to delineate the mechanisms linking abnormal bone homeostasis and energy metabolism could uncover new approaches for the prevention of these age-related disorders.

Prevalence of atrial fibrillation and cardiovascular risk factors in a 63-65 years old general population cohort: the Akershus Cardiac Examination (ACE) 1950 Study

OBJECTIVES

To investigate the sex-specific prevalence of atrial fibrillation (AF), including subclinical AF found by screening in a general population aged 63-65 years. The prevalence of cardiovascular risk factors and their association with AF will also be investigated.

DESIGN

Cross-sectional analysis of an observational, prospective, longitudinal, population-based cohort study.

SETTING

General population in Akershus county, Norway.

PARTICIPANTS

Women and men born in 1950. We included 3706 of 5827 eligible individuals (63.6%); 48.8% were women.

METHODS

All participants underwent extensive cardiovascular examinations, including 12-lead ECG. History of AF and other cardiovascular diseases were self-reported. Subsequent validation of all reported or detected AF diagnoses was performed.

RESULTS

Mean age was 63.9±0.7 years. Prevalence of ECG-verified AF was 4.5% (women 2.4%, men 6.4%; p<0.001), including screen-detected AF in 0.3% (women 0.1%, men 0.6%; p<0.01). Hypertension was found in 62.0% (women 57.8%, men 66.0%; p<0.001). Overweight or obesity was found in 67.6% (women 59.8%, men 74.9%; p<0.001). By multivariate logistic regression, risk factors associated with AF were height (OR 1.67 per 10 cm; 95% CI 1.26 to 2.22; p<0.001), weight (OR 1.15 per 10 kg; 95% CI 1.01 to 1.30; p=0.03), hypertension (OR 2.49; 95% CI 1.61 to 3.86; p<0.001), heart failure (OR 3.51; 95% CI 1.71 to 7.24; p=0.001), reduced estimated glomerular filtration rate (OR 2.56; 95% CI 1.42 to 4.60; p<0.01) and at least one first-degree relative with AF (OR 2.32; 95% CI 1.63 to 3.31; p<0.001), whereas male sex was not significantly associated (OR 1.00; 95% CI 0.59 to 1.68; p=0.99).

CONCLUSION

In this cohort from the general population aged 63-65 years, we found a higher prevalence of known AF than previously reported below the age of 65 years. The additional yield of single time point screening for AF was low. Body size and comorbidity may explain most of the sex difference in AF prevalence at this age.

TRIAL REGISTRATION NUMBER

NCT01555411; Results.

Body size and risk of atrial fibrillation: a cohort study of 1.1 million young men

BACKGROUND

Whilst tall stature has been related to lower risk of vascular disease, it has been proposed as a risk factor for atrial fibrillation. Little is known about other anthropometric measures and their joint effects on risk of atrial fibrillation.

OBJECTIVES

We aim to investigate associations and potential joint effects of height, weight, body surface area (BSA) and body mass index (BMI) with risk of atrial fibrillation.

METHODS

In a cohort covering 1 153 151 18-year-old men participating in the Swedish military conscription (1972-1995), Cox regression was used to investigate associations of height, weight, BSA and BMI with risk of atrial fibrillation.

RESULTS

During a median of 26.3 years of follow-up, higher height was associated with higher risk of atrial fibrillation (hazard ratio [HR] 2.80; 95% CI 2.63-2.98; for 5th vs. 1st quintile) and so was larger BSA (HR 3.05; 95% CI 2.82-3.28; for 5th vs. 1st quintile). Higher weight and BMI were to a lesser extent associated with risk of atrial fibrillation (BMI: 1.42; 95% CI 1.33-1.52, for 5th vs. 1st quintile). We found a multiplicative joint effect of height and weight. Adjusting for muscle strength, exercise capacity and diseases related to atrial fibrillation attenuated these measures.

CONCLUSIONS

Higher height and weight are strongly associated with higher risk of atrial fibrillation. These associations are multiplicative and independent of each other and are summarized in a strong association of body surface area with risk of atrial fibrillation. The mechanisms remain unknown but may involve increased atrial volume load with larger body size.

Height, Weight, and Aerobic Fitness Level in Relation to the Risk of Atrial Fibrillation

Tall stature and obesity have been associated with a higher risk of atrial fibrillation (AF), but there have been conflicting reports of the effects of aerobic fitness. We conducted a national cohort study to examine interactions between height or weight and level of aerobic fitness among 1,547,478 Swedish military conscripts during 1969-1997 (97%-98% of all 18-year-old men) in relation to AF identified from nationwide inpatient and outpatient diagnoses through 2012 (maximal age, 62 years). Increased height, weight, and aerobic fitness level (but not muscular strength) at age 18 years were all associated with a higher AF risk in adulthood. Positive additive and multiplicative interactions were found between height or weight and aerobic fitness level (for the highest tertiles of height and aerobic fitness level vs. the lowest, relative excess risk = 0.51, 95% confidence interval (CI): 0.40, 0.62; ratio of hazard ratios = 1.50, 95% CI: 1.34, 1.65). High aerobic fitness levels were associated with higher risk among men who were at least 186 cm (6 feet, 1 inch) tall but were protective among shorter men. Men with the combination of tall stature and high aerobic fitness level had the highest risk (for the highest tertiles vs. the lowest, adjusted hazard ratio = 1.70, 95% CI: 1.61, 1.80). These findings suggest important interactions between body size and aerobic fitness level in relation to AF and may help identify high-risk subgroups.

Young women, body size and risk of atrial fibrillation

Background A large body size in early adult life has been associated with an increased risk of atrial fibrillation (AF) later in life in men; however, this has not yet been investigated in women.

DESIGN

Prospective cohort study.

METHODS

We included all women in the Swedish Medical Birth Registry with known weight and height from 1982 to 2014. The main exposure body surface area (BSA) was calculated as the square root of (height [cm]  ×  weight [kg]/3600). Information on hospital diagnoses of AF were obtained from the Patient Registry. The study population comprised 1,522,329 women (mean age 28.3 years).

RESULTS

A total of 6993 women (0.5%) were diagnosed with AF during a maximum follow-up of 33.6 years (mean 16.6 years, confidence interval [CI] 16.6-16.6). Risk of AF rose linearly with increasing BSA, body mass index (BMI) and height, with up to a threefold increased risk in the biggest women. Hazard ratios associated with BSA were 1.21 (95% CI 1.12-1.30), 1.45 (95% CI 1.35-1.56) and 2.11 (95% CI 1.97-2.26) when comparing the second, third and fourth quartiles, respectively, with the first. The elevated risk persisted after stratifying for different levels of BMI, even among women with low-normal BMI. Conclusion A larger body size measured early in adulthood was, independent from BMI, associated with an increased risk of AF in women during follow-up of up to 33 years.

Lean Body Mass Is the Predominant Anthropometric Risk Factor for Atrial Fibrillation

BACKGROUND

Obesity is repeatedly emphasized as a risk factor for atrial fibrillation or flutter (AF). However, the underlying evidence may be questioned, as the obvious correlations between various anthropometric measures hamper identification of the characteristics that are biologically driving AF risk, and recent studies suggest that fat carries limited or no independent risk of AF.

OBJECTIVES

This study sought to assess mutually adjusted associations among AF risk and height, weight, body mass index, hip and waist circumference, waist-to-hip ratio, and bioelectrical impedance-derived measures of fat mass, lean body mass, and fat percentage.

METHODS

Anthropometric measures and self-reported life-style information were collected from 1993 to 1997 in a population-based cohort including 55,273 persons age 50 to 64 years who were followed in Danish registers until June 2013.

RESULTS

During a median of 17 years of follow-up, 3,868 persons developed AF. Adjusted hazard ratios per population SD difference (HRs) showed highly statistically significant, positive associations for all 9 anthropometric measures (HRs ranging from 1.08 [95% confidence interval (CI): 1.05 to 1.12] for waist-to-hip ratio to 1.37 [95% CI: 1.33 to 1.42] for lean body mass). Pairwise mutual adjustment of the 9 measures left the association for lean body mass virtually unchanged (lowest HR: 1.33 [95% CI: 1.28 to 1.39] when adjusting for height), whereas no other association remained substantial when adjusted for lean body mass (highest HR: 1.05 [95% CI: 1.01 to 1.10] for height).

CONCLUSIONS

Lean body mass was the predominant anthropometric risk factor for AF, whereas no association was observed for either of the obesity-related anthropometric measures after adjustment for lean body mass.

Anthropometric parameters and the incidence of atrial fibrillation in older people: the PRO.V.A study

BACKGROUND

Atrial fibrillation (AF) has been associated with body size and central obesity, but the impact of different anthropometric measures in this relationship has been inadequately investigated.

HYPOTHESIS

In this study, we examined the association between baseline anthropometric parameters with the incidence of AF in older people, hypothesizing that body size could impact the onset of AF more than fat distribution.

METHODS

Our study included 1764 participants with a mean age of 74.3 ± 6.9 years and no AF at baseline. Body mass index (BMI), body height, body surface area (BSA), waist and hip circumference, waist-to-stature ratio, waist-to-hip ratio, and mid-upper arm circumference (MUAC) were measured by trained physicians. AF was assessed after a 4.4-year follow-up.

RESULTS

There were 115 new cases of AF observed after the follow-up. Taking lower values of these measures for reference, the adjusted AF risk was 2.42 (95% confidence interval [CI]:1.88-3.12) for the highest stature quartile, 1.36 (95% CI:1.15-1.62) for BMI ≥30 kg/m2 , 2.12 (95% CI:1.73-2.59) for the highest BSA quartile, 1.38 (95% CI: 1.21-1.56) for higher MUAC, and 1.39 (95% CI: 1.23-1.58, P < 0.0001) for higher hip circumference values. Central obesity did not seem to relevantly predict the onset of AF in our sample. Stature revealed the strongest impact on the onset of AF (5% higher risk of developing AF per 1 cm increase in height).

CONCLUSIONS

Body size, particularly tall stature and obesity, but not fat distribution, seems to be associated with the risk of AF in the elderly.

Relation of the Myocardial Contraction Fraction, as Calculated from M-Mode Echocardiography, With Incident Heart Failure, Atherosclerotic Cardiovascular Disease and Mortality (Results from the Cardiovascular Health Study)

We evaluated the association between 2-dimensional (2D) echocardiography (echo)-determined myocardial contraction fraction (MCF) and adverse cardiovascular outcomes including incident heart failure (HF), atherosclerotic cardiovascular disease (ASCVD), and mortality. The MCF, the ratio of left ventricular (LV) stroke volume (SV) to myocardial volume (MV), is a volumetric measure of myocardial shortening that can distinguish pathologic from physiological hypertrophy. Using 2D echo-guided M-mode data from the Cardiovascular Health Study, we calculated MCF in subjects with LV ejection fraction (EF) ≥55% and used Cox models to evaluate its association with incident HF, ASCVD, and all-cause mortality after adjusting for clinical and echo parameters. We assessed whether log₂(SV) and log₂(MV) were consistent with the expected 1:-1 ratio used in the definition of MCF. Among 2,147 participants (age 72 ± 5 years), average MCF was 59 ± 13%. After controlling for clinical and echo variables, each 10% absolute increment in MCF was associated with lower risk of HF (hazard ratio [HR] 0.88; 95% confidence interval [CI] 0.82, 0.94), ASCVD (HR 0.90; 95% CI 0.85, 0.95), and death (HR 0.93; 95% CI 0.89, 0.97). Moreover, the MCF was still significantly associated with ASCVD and mortality, but not HF, after adjustment for percent-predicted LV mass. Significant departure from the 1:-1 ratio was not observed for ASCVD or death, but did occur for HF, driven by a stronger association for MV than SV. In conclusion, among older adults without CVD or low LV ejection fraction, 2D echo-guided M-mode-derived MCF was independently associated with lower risk of adverse cardiovascular outcomes, but this ratiometric index may not capture the full relation that is apparent when its components are modeled separately in the case of HF.

Body mass index, abdominal fatness, fat mass and the risk of atrial fibrillation: a systematic review and dose-response meta-analysis of prospective studies

Different adiposity measures have been associated with increased risk of atrial fibrillation, however, results have previously only been summarized for BMI. We therefore conducted a systematic review and meta-analysis of prospective studies to clarify the association between different adiposity measures and risk of atrial fibrillation. PubMed and Embase databases were searched up to October 24th 2016. Summary relative risks (RRs) were calculated using random effects models. Twenty-nine unique prospective studies (32 publications) were included. Twenty-five studies (83,006 cases, 2,405,381 participants) were included in the analysis of BMI and atrial fibrillation. The summary RR was 1.28 (95% confidence interval: 1.20-1.38, I² = 97%) per 5 unit increment in BMI, 1.18 (95% CI: 1.12-1.25, I² = 73%, n = 5) and 1.32 (95% CI: 1.16-1.51, I² = 91%, n = 3) per 10 cm increase in waist and hip circumference, respectively, 1.09 (95% CI: 1.02-1.16, I² = 44%, n = 4) per 0.1 unit increase in waist-to-hip ratio, 1.09 (95% CI: 1.02-1.16, I² = 94%, n = 4) per 5 kg increase in fat mass, 1.10 (95% CI: 0.92-1.33, I² = 90%, n = 3) per 10% increase in fat percentage, 1.10 (95% CI: 1.08-1.13, I² = 74%, n = 10) per 5 kg increase in weight, and 1.08 (95% CI: 0.97-1.19, I² = 86%, n = 2) per 5% increase in weight gain. The association between BMI and atrial fibrillation was nonlinear, p _nonlinearity < 0.0001, with a stronger association at higher BMI levels, however, increased risk was observed even at a BMI of 22-24 compared to 20. In conclusion, general and abdominal adiposity and higher body fat mass increase the risk of atrial fibrillation.