We appreciate the insightful commentary by Drs. Schneider and Michos (1). We have reanalyzed the data from our study (2) with adjustment for 3 categories of race/ethnicity: white, black, and other. The point estimates for the association between vitamin D and cardiovascular events were not appreciably altered by this substitution (Table 1). However, our participants were primarily white men; therefore, future studies in more racially diverse samples would be of interest to further explore racial differences, especially in light of the recent work by Powe et al. (3).
Table 1.
Association Between Baseline 25-Hydroxyvitamin D Level (<20 ng/mL vs. ≥20 ng/mL) and Subsequent Cardiovascular Eventsa (n = 323) After Multivariate Adjustment, by Race/Ethnicity, Among 946 Participants in the Heart and Soul Study, 2000–2012
| Modelb | 2 Race Categories (White vs. Nonwhite) |
3 Race Categories (White, Black, or Other) |
||
|---|---|---|---|---|
| HR | 95% CI | HR | 95% CI | |
| Model 3c | 1.30 | 1.01, 1.67 | 1.25 | 0.97, 1.63 |
| Model 4d | 1.11 | 0.85, 1.44 | 1.12 | 0.85, 1.46 |
Abbreviations: CI, confidence interval; HR, hazard ratio.
a Subsequent cardiovascular events were defined as heart failure, myocardial infarction, stroke, or cardiovascular mortality.
c Results were adjusted for age, sex, season of blood draw, college graduation, tobacco use, multivitamin use, physical activity, diabetes, hypertension, body mass index, and depression.
d Results were adjusted for all model 3 covariates plus systolic blood pressure, diastolic blood pressure, hemoglobin A1c, triglycerides, high-density lipoprotein cholesterol, C-reactive protein, phosphorus, parathyroid hormone, and fibroblast growth factor 23.
We appreciate the authors’ reference to the methodological considerations involved in analyzing the data by season. We would like to clarify that in our study, we adjusted for season (not date) of blood draw, with 4 different categories: spring (March–May), summer (June–August), fall (September–November), and winter (December–February). Analyzing the data using the cosinor approach (4) did not appreciably alter the point estimate (Table 2).
Table 2.
Association Between Baseline 25-Hydroxyvitamin D Level (<20 ng/mL vs. ≥20 ng/mL) and Subsequent Cardiovascular Eventsa (n = 323) After Multivariate Adjustment, by Season of Blood Draw, Among 946 Participants in the Heart and Soul Study, 2000–2012
| Modelb | Adjusted for Season of Blood Draw |
Adjusted by Consignor Approach |
||
|---|---|---|---|---|
| HR | 95% CI | HR | 95% CI | |
| Model 3c | 1.30 | 1.01, 1.67 | 1.35 | 1.05, 1.73 |
| Model 4d | 1.11 | 0.85, 1.44 | 1.15 | 0.89, 1.50 |
Abbreviations: CI, confidence interval; HR, hazard ratio.
a Subsequent cardiovascular events were defined as heart failure, myocardial infarction, stroke, or cardiovascular mortality.
c Results were adjusted for age, sex, white race/ethnicity, college graduation, tobacco use, multivitamin use, physical activity, diabetes, hypertension, body mass index, and depression.
d Results were adjusted for all model 3 covariates plus systolic blood pressure, diastolic blood pressure, hemoglobin A1c, triglycerides, high-density lipoprotein cholesterol, C-reactive protein, phosphorus, parathyroid hormone, and fibroblast growth factor 23.
ACKNOWLEDGMENTS
Author affiliations: Division of General Internal Medicine, Department of Medicine, School of Medicine, University of California, San Francisco, San Francisco, California (Christine C. Welles, Mary A. Whooley); Department of Family and Preventive Medicine and Division of Nephrology-Hypertension, Department of Medicine, School of Medicine, University of California, San Diego, San Diego, California (Joachim H. Ix); Division of General Medicine and Primary Care (Kenneth J. Mukamal) and Division of Nephrology (Tammy Hod, S. Ananth Karumanchi), Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Pathology, Beth Israel Deaconess Medical Center, Boston, Massachusetts (Anders H. Berg); and Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts (Ravi Thadhani).
Dr. Christine C. Welles was supported by the Veterans Affairs National Quality Scholars Program. The Heart and Soul Study was supported by the Department of Veterans Affairs, the National Heart, Lung, and Blood Institute, the American Federation for Aging Research, the Robert Wood Johnson Foundation, and the Ischemia Research and Education Foundation. Dr. S. Ananth Karumanchi is an investigator of the Howard Hughes Medical Institute. Dr. Ravi Thadhani was supported by National Institutes of Health grants DK094486 and DK094872.
Conflict of interest: none declared.
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