Clinical research study
Relationship of Ethnic Origin, Gender, and Age to Blood Creatine Kinase Levels

https://doi.org/10.1016/j.amjmed.2008.08.033Get rights and content

Abstract

Background

Creatine kinase is expressed at high levels in muscle, where it plays a central role in energy metabolism. Highly elevated creatine kinase levels in blood may indicate muscle trauma or disease. However, it is known that baseline creatine kinase levels are higher in African Americans than in whites and that they are higher in men than in women. This analysis explores the relationship of ethnic origin, gender, and age to baseline blood creatine kinase levels in a large group of adults with hypercholesterolemia.

Methods

Data from the screening phases of 4 North American trials of statins, which included large numbers of specific racial/ethnic populations, were combined for analysis. The pooled population (N = 11,346) included 2760 African Americans, 3301 whites, 2930 Hispanics, and 2355 South Asians.

Results

Creatine kinase levels varied according to ethnic origin, gender, and age. African American participants had higher median creatine kinase levels than did individuals of the 3 other ethnicities. Within each ethnic group, men had higher median creatine kinase levels than women: African Americans, 135 versus 73 U/L; whites, 64 versus 42 U/L; Hispanics, 69 versus 48 U/L; and South Asians, 74 versus 50 U/L. An age-dependent decrease in creatine kinase levels was noted among men, but no such trend was seen among women. The median creatine kinase levels for younger African American men exceeded the standard upper limit of normal.

Conclusion

Physicians should use caution when interpreting creatine kinase levels that seem elevated, particularly when treating African American patients and younger men.

Section snippets

Screening

Data were collected during screening visits for entry into 1 of 4 studies conducted to assess rosuvastatin treatment of patients with hypercholesterolemia. For all studies, target populations were planned to include men and nonpregnant women who were aged 18 years or older and had been given a diagnosis of hypercholesterolemia. Individuals screened for the ARIES study (4522US/0002) described themselves as African American. Individuals screened for the IRIS study (4522US/0006) described

Participant Demographic Characteristics

Ethnicity, gender, and age distribution of the pooled population of screened individuals (N = 11,346) are shown in Table 1. Data relate to 2334 African American individuals in ARIES, 2355 South Asian individuals in IRIS, 3301 white individuals in SOLAR (and in the same study, 426 African American and 234 Hispanic individuals), and 2696 Hispanic individuals in STARSHIP. A greater number of men (n = 6058; 53.4%) than women (n = 5288; 46.6%) were included in the pooled population. The ratio of men

Discussion

This analysis of more than 11,000 individuals shows the effects of race/ethnicity, gender, and age on creatine kinase levels in adults with hypercholesterolemia. Separate studies have reported that Hispanic and Asian adults have creatine kinase levels similar to those of white adults.1, 5, 15 This is the first analysis in which creatine kinase levels among adults of South Asian origin were examined specifically; results show that creatine kinase levels in this group are similar to those of

Conclusions

This analysis of a large population of adults with hypercholesterolemia shows that typical creatine kinase levels vary significantly by racial/ethnic origin, gender, and age. African American individuals have higher creatine kinase levels than white, South Asian, or Hispanic individuals; within each ethnic group, men have higher creatine kinase levels than women. An age-dependent decrease in creatine kinase levels is seen among men but not among women. Physicians should keep these trends in

Acknowledgments

We gratefully acknowledge the investigators, co-investigators, study coordinators, and study participants. We thank the editorial staff of Scientific Connexions, Newtown, Pennsylvania, for assistance in the preparation of this article, funded by AstraZeneca.

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Funding: The ARIES, IRIS, SOLAR, and STARSHIP studies, as well as this analysis of pooled screening data, were funded by AstraZeneca LP, Wilmington, Delaware.

Conflict of Interest: Dr Neal is an active member of the Speakers' Bureau and consultant for AstraZeneca, with honoraria exceeding $50,000. Dr Ferdinand is an AstraZeneca consultant and member of the Speakers' Bureau, with honoraria totaling $50,000 for the past 3 years. Drs Yčas and Miller are employees of AstraZeneca.

Authorship: All authors had full access to the data and played a role in writing this article.

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