- Email: [email protected]
Serum uric acid and ischemic heart disease incidence
Letters to the Editor
381
Serum uric acid and ischemic heart disease incidence Tomoyuki Kawada ⁎ Department of Hygiene and Public Health, Nippon Medical School, Japan
a r t i c l e
i n f o
Article history: Received 21 November 2011 Accepted 26 November 2011 Available online 20 December 2011 Keywords: Ischemic heart disease incidence Serum uric acid Metabolic components Cox proportional hazard analysis
To the Editor Chuang et al. presented a 7-year follow-up study on the effect of uric acid on the occurrence of ischemic heart disease (IHD), adjusted by age, metabolic factors, lifestyles, medication and working type [1]. They used popular variables in the health examination targeting 128,569 subjects. Kim et al. recently overviewed and conducted metaanalysis on this association precisely, and concluded that hyperuricemia may increase the risk of IHD events, independently of traditional IHD risk factors [2]. But sub-analysis stratified by sex presented that the significance of relative risk disappeared in men, and only Chinese cohort kept significance in case of women. On this point, Chuang et al. handled big cohort and I want to make some queries on their analysis. 1) They compiled IHD death (n = 116) and IHD events (n = 1933), and 2049 subjects who developed IHD subjects were used for the analysis. Are there any differences in the risk factors between the two groups? 2) They conducted Cox proportional hazard model regression analysis for subjects with and without metabolic risk factors, separately (Table 3 in [1]). In case of women without metabolic risk actors, the effect of hyperuricemia on IHD incidence showed
⁎ Department of Hygiene and Public Health, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-Ku, Tokyo 113-8602, Japan. Tel.: +81 3 3822 2131; fax: +81 3 5685 3065. E-mail address: [email protected]. 0167-5273/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2011.11.040
no significance. They quoted their past report as a mortality study [3], and Chen et al. also mentioned that the hazard ratio of hyperuricemia for total cardiovascular mortality did not reach significance in a low metabolic risk subgroup. As the serum uric acid was categorized binary, I recommend for classifying several grades of uric acid for the risk assessment of IHD to check dose– response relationship such as blood pressure or total cholesterol in their study. I suppose that the number of evens is satisfactory for the Cox proportional hazard model regression analysis. 3) They used waist circumference and body mass index for obesity. They also used serum total cholesterol as one of the indicators of dyslipidemia. Although these variables were not used simultaneously in Table 2 [1], I suppose that adjustment of metabolic components, total cholesterol and body mass index for subjects with and without metabolic risk factors in Table 3 [1] should be paid attention for over-adjustment. 4) As the numbers of samples for subjects with and without metabolic risk factors are described as 83,135 and 45,434 in Table 3 [1], the number of risk factors for 83,135 subjects would be ranged from 1 to 5. As an alternative analysis, the number of metabolic risk factors can be adopted as one of the independent or explanatory variables. I suppose that continuous follow-up of the baseline subjects would present more information for the IHD incidence in their big cohort study, and it is also possible to conduct sub-analysis by stratification of variables because of the satisfactory number of events. I wish to express my appreciation to the members of Hygiene and Public Health, Nippon Medical School, for the preparation of this study. The author of this manuscript has certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology (2010;144:1–2.). References [1] Chuang SY, Chen JH, Yeh WT, Wu CC, Pan WH. Hyperuricemia and increased risk of ischemic heart disease in a large Chinese cohort. Int J Cardiol 2012;154(3): 326–31. [2] Kim SY, Guevara JP, Kim KM, Choi HK, Heitjan DF, Albert DA. Hyperuricemia and coronary heart disease: a systematic review and meta-analysis. Arthritis Care Res (Hoboken) 2010;62:170–80. [3] Chen JH, Chuang SY, Chen HJ, Yeh WT, Pan WH. Serum uric acid level as an independent risk factor for all-cause, cardiovascular, and ischemic stroke mortality: a Chinese cohort study. Arthritis Rheum 2009;61:225–32.
381
Serum uric acid and ischemic heart disease incidence Tomoyuki Kawada ⁎ Department of Hygiene and Public Health, Nippon Medical School, Japan
a r t i c l e
i n f o
Article history: Received 21 November 2011 Accepted 26 November 2011 Available online 20 December 2011 Keywords: Ischemic heart disease incidence Serum uric acid Metabolic components Cox proportional hazard analysis
To the Editor Chuang et al. presented a 7-year follow-up study on the effect of uric acid on the occurrence of ischemic heart disease (IHD), adjusted by age, metabolic factors, lifestyles, medication and working type [1]. They used popular variables in the health examination targeting 128,569 subjects. Kim et al. recently overviewed and conducted metaanalysis on this association precisely, and concluded that hyperuricemia may increase the risk of IHD events, independently of traditional IHD risk factors [2]. But sub-analysis stratified by sex presented that the significance of relative risk disappeared in men, and only Chinese cohort kept significance in case of women. On this point, Chuang et al. handled big cohort and I want to make some queries on their analysis. 1) They compiled IHD death (n = 116) and IHD events (n = 1933), and 2049 subjects who developed IHD subjects were used for the analysis. Are there any differences in the risk factors between the two groups? 2) They conducted Cox proportional hazard model regression analysis for subjects with and without metabolic risk factors, separately (Table 3 in [1]). In case of women without metabolic risk actors, the effect of hyperuricemia on IHD incidence showed
⁎ Department of Hygiene and Public Health, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-Ku, Tokyo 113-8602, Japan. Tel.: +81 3 3822 2131; fax: +81 3 5685 3065. E-mail address: [email protected]. 0167-5273/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2011.11.040
no significance. They quoted their past report as a mortality study [3], and Chen et al. also mentioned that the hazard ratio of hyperuricemia for total cardiovascular mortality did not reach significance in a low metabolic risk subgroup. As the serum uric acid was categorized binary, I recommend for classifying several grades of uric acid for the risk assessment of IHD to check dose– response relationship such as blood pressure or total cholesterol in their study. I suppose that the number of evens is satisfactory for the Cox proportional hazard model regression analysis. 3) They used waist circumference and body mass index for obesity. They also used serum total cholesterol as one of the indicators of dyslipidemia. Although these variables were not used simultaneously in Table 2 [1], I suppose that adjustment of metabolic components, total cholesterol and body mass index for subjects with and without metabolic risk factors in Table 3 [1] should be paid attention for over-adjustment. 4) As the numbers of samples for subjects with and without metabolic risk factors are described as 83,135 and 45,434 in Table 3 [1], the number of risk factors for 83,135 subjects would be ranged from 1 to 5. As an alternative analysis, the number of metabolic risk factors can be adopted as one of the independent or explanatory variables. I suppose that continuous follow-up of the baseline subjects would present more information for the IHD incidence in their big cohort study, and it is also possible to conduct sub-analysis by stratification of variables because of the satisfactory number of events. I wish to express my appreciation to the members of Hygiene and Public Health, Nippon Medical School, for the preparation of this study. The author of this manuscript has certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology (2010;144:1–2.). References [1] Chuang SY, Chen JH, Yeh WT, Wu CC, Pan WH. Hyperuricemia and increased risk of ischemic heart disease in a large Chinese cohort. Int J Cardiol 2012;154(3): 326–31. [2] Kim SY, Guevara JP, Kim KM, Choi HK, Heitjan DF, Albert DA. Hyperuricemia and coronary heart disease: a systematic review and meta-analysis. Arthritis Care Res (Hoboken) 2010;62:170–80. [3] Chen JH, Chuang SY, Chen HJ, Yeh WT, Pan WH. Serum uric acid level as an independent risk factor for all-cause, cardiovascular, and ischemic stroke mortality: a Chinese cohort study. Arthritis Rheum 2009;61:225–32.