Hyperuricemia and incident atrial fibrillation in a normotensive elderly population in Taiwan

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Abstract

Background and aim

Atrial fibrillation (AF) is an important cardiovascular disease in the elderly. The association between hyperuricemia and AF is unclear. Therefore, we aimed to investigate the prospective relationship between uric acid and development of AF in a nationally representative cohort of elderly people.

Methods and results

A total of 1485 elderly people (age ≥ 65 yrs) from the Elderly Nutrition and Health Survey in Taiwan (1999–2000) were without AF on “electrocardiography” at baseline. Incident AF events (International Classification of Diseases, Ninth Revision, Clinical Modification, ICD-9-CM: 427.31) were identified using data from the National Health Insurance Dataset. Hyperuricemia was defined as levels of uric acid >7.0 mg/dL in men and 6.0 mg/dL in women. A Cox proportional hazards model was used to evaluate the association between hyperuricemia and incident AF.

The follow-up period was from 1999 to 2000 to 2008. During the follow-up period (median: 9.16 yrs), 90 AF events occurred (44 in men and 46 in women). Older age, elevated systolic blood pressure, being an ex-smoker, and high uric acid were positively associated with incident AF. Hyperuricemia was positively associated with incident AF in normotensive (age-adjusted hazard ratio (HR): 2.65 and 95% confidence intervals: 1.05–6.69), but not in (1.20:0.74–1.94) hypertensive individuals (systolic blood pressure ≥130 or diastolic blood pressure ≥85 or using hypertensive medicine). A significant association between hyperuricemia and AF (3.78; 1.24–11.59) remained after adjusting for other potential confounders among normotensive older persons.

Conclusion

Hyperuricemia is associated with the development of AF in elderly people with normal blood pressure.

Introduction

Atrial fibrillation (AF) is one of the most prevalent types of heart disease in the elderly population, with a reported prevalence of 20% in persons aged 80 years and over in the USA [1]. Individuals with AF have medical costs that are 73% higher than normal controls, with an estimated incremental cost of >$8000 per individual with AF in the USA [2].

AF increases the risk of cardiovascular outcomes such as heart failure and stroke and has harmful effects on quality of life, functional status, and cognition [3]. AF is associated with a twofold higher risk of stroke [4], silent cerebral infarction [5], and impaired cognitive function and dementia [6]. Therefore, an understanding of factors associated with the development of AF through longitudinal studies is essential for the design of preventive strategies [2].

Current known risk factors for AF include older age, male sex, smoking, obesity, hypertension, diabetes mellitus, myocardial infarction, heart failure, valvular heart disease, and cardiac surgery [2]. Prior studies have also reported a positive association between hyperuricemia and AF. However, as hyperuricemia is more prevalent in men and is associated with obesity, hypertension, diabetes mellitus, and myocardial infarction, it is unclear whether the association between hyperuricemia and AF is independent of these potential confounding factors. Moreover, the association has been inconsistent, and observed in studies of cross-sectional design or small sample size. Few studies have investigated the relationship between hyperuricemia and AF in an elderly population, where there is a higher incidence of AF.

Therefore, we aimed to investigate the relationship between hyperuricemia and AF in a national representative cohort of elderly people.

Section snippets

Study population

Data were obtained from the Elderly Nutrition and Health Survey in Taiwan (1999–2000) (Elderly NAHSIT) which was a national survey aimed at studying the nutrition and health status of noninstitutionalized people aged 65 yrs and over in Taiwan. Three hundred and fifty-five townships in Taiwan were divided into 13 strata according to the dietary patterns of residents, urbanization index, and geographic characteristics. A total of 1937 persons completed the interview and health examination [7]. Of

Prevalence of hyperuricemia

The prevalence of hyperuricemia was 52.66% (n = 782) and there was no gender difference (52.76% for men and 52.55% for women, p-value = 0.9350). Of them, 104 persons (13.3%) were using UA-lowering drugs.

Incidence of AF

The follow-up period was from 1999 to 2000 to 2008. The median follow-up time was 9.16 years (inter-quarters: 3.56 years (6.00–9.45)). During follow-up, 90 AF (AF) events occurred, giving an incidence rate of 7.75 per 1000 person-years (PYs) in men (n = 44) and 8.02 per 1000 PYs in women (n = 46

Main findings

In this study, we found a high incidence of AF among elderly patients of Chinese origin. Age, elevated BP, smoking status, inflammatory predisposition, and hyperuricemia were significantly associated with incidence of AF. Moreover, we found that hyperuricemia was an independent risk factor for AF in the normotensive elderly population.

Incidence of AF

Racial differences in AF remain poorly understood [3]. The atherosclerosis risk in communities study (ARCI) study reported that the cumulative risk of AF at 80

Conclusion

Among the normotensive elderly population, older subjects with hyperuricemia had significantly higher risk of AF. Hyperuricemia may be sign of AF in normotensive elderly.

Interests to disclose

None for all authors.

Acknowledgments

This work was supported by a grant from the National Health Research Institutes (no. PH-100-PP-55, PH-101-PP-24 and PH-102-PP-18), and was partially supported by the Korea Research Foundation Grant funded by the Korean Government (MEST) (KRF-2009-220-E00023). This study was conducted in part using data from the National Health Insurance Research Database provided by the Bureau of National Health Insurance, Department of Health, and managed by National Health Research Institutes. No potential

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