Conceived and designed the experiments: JL MW. Analyzed the data: JL ST RE MW CD KE WL. Contributed reagents/materials/analysis tools: JL MW. Wrote the paper: JL MW CD KE. Other: Approved the final version: JL RE WL ST KE CD MW.
Julio Licinio has been a consultant for Eli Lilly, but Eli Lilly did not in any way contribute to the design, analysis or writing of these data, and is not aware of these results, which have not been presented to Eli Lilly.
Major depressive disorder (MDD) is an independent risk factor for cardiovascular disease (CVD); the presence of MDD symptoms in patients with CVD is associated with a higher incidence of cardiac complications following acute myocardial infarction (MI). Stress-hemoconcentration, a result of psychological stress that might be a risk factor for the pathogenesis of CVD, has been studied in stress-challenge paradigms but has not been systematically studied in MDD.
Secondary analysis of stress hemoconcentration was performed on data from controls and subjects with mild to moderate MDD participating in an ongoing pharmacogenetic study of antidepressant treatment response to desipramine or fluoxetine. Hematologic and hemorheologic measures of stress-hemoconcentration included blood cell counts, hematocrit, hemoglobin, total serum protein, and albumin, and whole blood viscosity.
Subjects with mild to moderate MDD had significantly increased hemorheologic measures of stress-hemoconcentration and blood viscosity when compared to controls; these measures were correlated with depression severity. Measures of stress-hemoconcentration improved significantly after 8 weeks of antidepressant treatment. Improvements in white blood cell count, red blood cell measures and plasma volume were correlated with decreased severity of depression.
Our secondary data analyses support that stress-hemoconcentration, possibly caused by decrements in plasma volume during psychological stress, is present in Mexican-American subjects with mild to moderate MDD at non-challenged baseline conditions. We also found that after antidepressant treatment hemorheologic measures of stress-hemoconcentration are improved and are correlated with improvement of depressive symptoms. These findings suggest that antidepressant treatment may have a positive impact in CVD by ameliorating increased blood viscosity. Physicians should be aware of the potential impact of measures of hemoconcentration and consider the implications for cardiovascular risk in depressed patients.
Cardiovascular disease (CVD) risk has been linked to several emotional and psychological factors, including stress and depression. Mental stress can elicit acute coronary events and is considered a risk factor for CVD
A number of mechanisms underlying the link between stress, depression and cardiovascular disease have been proposed (for a comprehensive review, see reference
Behavioral/emotional stress and chronic anxiety have been shown to cause changes in hemorheologic measures, possibly due to increases in catecholamines and blood pressure
Despite the importance of the hemorheologic changes described in stress-hemoconcentration and the overlap between stress and depression in studies of cardiovascular disease risk, such changes have not been systematically studied in MDD. The present study is a secondary analysis of data from a randomized, double-blind trial of fluoxetine versus desipramine in a group of outpatients with mild to moderate MDD before and after antidepressant treatment compared to a group of ethnically-matched controls. The primary analysis focused on genetic markers of depression and antidepressant treatment response and has been reported elsewhere
This study was approved by the University of California, Los Angeles (UCLA) and University of Miami (UM) IRBs and has been registered in the public database clinicaltrials.gov (NCT00265291). The study population consisted of control and MDD individuals. All subjects gave written informed consent and received comprehensive psychiatric and medical assessment. We used diagnostic and ratings instruments that have been fully validated in English and in Spanish, and conducted all assessments in the subject's primary language.
We studied 146 outpatient depressed subjects, all of whom were Mexican-Americans (defined as having at least 3 grandparents born in Mexico) aged 19–65 years, who were participating in an ongoing randomized, double-blind pharmacogenetic study of antidepressant response to desipramine or fluoxetine and completed the 8-week treatment trial (see
Subject | Gender | N (%) | Variable | Mean±SD |
Controls | Female | 33 (72) | Age | 35.9±8.9 |
BMI | 28.6±4.5 | |||
Male | 13 (28) | Age | 33.2±7.7 | |
BMI | 29.4±4.6 | |||
All | 46 | Age | 35.2±8.6 | |
BMI | 28.8±4.5 | |||
MDD Subjects | Female | 97 (66) | Age | 36.4±9.7 |
BMI | 28.3±5.6 | |||
Male | 49 (34) | Age | 38.9±9.5 | |
BMI | 28.2±4.0 | |||
All | 146 | Age | 37.2±9.7 | |
BMI | 28.3±5.1 |
p for unpaired t-test is 0.194 for age and 0.543 for BMI between controls and MDD patients.
p for Chi-square test is 0.503 for gender ratio between controls and MDD patients.
Age in year; BMI: body mass index defined as weight in kilogram divided by the square of height in meters.
We studied 46 ethnically-matched control subjects (
All MDD subjects reported here completed 8 weeks of a randomized, double-blind trial of antidepressant treatment response to desipramine or fluoxetine as part of a pharmacogenetic study. The treatment had two phases. Phase 1 was a 1-week, single-blind placebo lead-in phase to eliminate placebo responders. Subjects who continued to meet the inclusion criteria after Phase 1 were randomly assigned to one of two treatment groups in a double-blind manner in Phase 2 during which they received fluoxetine 10–40 mg/day or desipramine 50–200 mg/day, for 8 weeks, with a dose escalation based on clinical outcomes. All subjects had 9 weeks of structured follow-up assessments. Our primary clinical outcome measure within the depressed group receiving antidepressant treatment was the HAM-D21. Remitter was defined as the patients who had a final HAM-D21 score <8.
Blood was collected from a vein in the antecubital fossa before beginning antidepressant treatment (week −2) and at the end of treatment (week 8). All samples were drawn after the subjects had rested in a supine position for 5–10 minutes. Samples for white blood cell (WBC) and red blood cell (RBC) count, hematocrit (HCT) and hemoglobin (HGB) levels were drawn into 7 ml ethylenediaminetetraacetic acid (K2 EDTA) BD-Vacutainer® tubes. Total serum protein (TSP) and albumin samples were drawn into chilled 7-ml K2 EDTA-treated BD-Vacutainer® tubes and placed on ice until centrifuged at 3000 rpm for 10 minutes at 4°C. Blood count and protein analysis were performed by the UCLA Clinical Laboratories and Pathology Services using a Sysmex XE-2100 (Sysmex Co, Kobe, Japan) and Synchron LX®20 (Beckman Coulter, Fullerton, CA), respectively.
WBV was determined in centipoises (cP) at a shear rate of 208 seconds−1 using the following equation: WBV = 0.12×HCT (%)+0.17×serum proteins (g/dL)
This equation has been validated by de Simone
Estimates in plasma volume changes before and after 8-weeks antidepressant treatment was calculated using the following formula:
Variables used for secondary data analyses included HAM-D21 scores and the following measurements: RBC, HGB, HCT, WBC, TSP, albumin levels and estimation of WBV. MDD subjects were analyzed before (week −2) and after treatment (week 8), and control subjects were measured at one time point for comparison.
To assess similarity between depressed and control subjects, unpaired t-tests were used to compare age and BMI means and a χ2 test was used to compare gender ratios. To examine the potential effects of gender and age, unpaired t-tests were also performed for the difference in blood measurements between female and male, and Pearson correlation analysis was conducted for the correlation of age with blood measurements. To adjust for gender and age, a general linear model (GLM) was employed to conduct multivariate tests (MANOVA) to compare blood measurements between MDD subjects and controls or between desipramine- and fluoxetine- treated MDD subjects. Paired T-tests were used to compare blood measurements before and after treatment in MDD subjects. Spearman partial correlation was used to measure the degree of association of HAM-D21 score with the blood measurements by controlling for age and gender. Stepwise logistic regression analysis was conducted to screen the predictors that allow a differentiation between remitter and non-remitter patients using the baseline HAM-D21 score, baseline blood measurements, antidepressant medication, age, and gender variables.
All analyses were performed using SPSS version 14.0 (SPSS Inc., Chicago, IL, USA), except for Spearman partial correlation analysis which was conducted with SAS version 9.1 (SAS Institute Inc., Cary, NC, USA). As HAM-D21 score is an ordinal measurement rated on a 5-point scale for each item (from “0 – not present” to “4 – severe”) and did not follow normal distribution when used as an interval variable, Spearman partial correlation was used. A significance level of 0.05 was used for all statistical testing, and the Bonferroni post-hoc method of correction was used to correct for multiple testing.
This study was funded by the National Institute of General Medical Sciences (NIGMS), the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and the National Center for Research Resources (NCRR). The sponsors were not involved in the study design; the collection analysis and interpretation of data; the writing of the report; or the decision to publish.
Our data are compatible with classical findings that gender influences red blood cell (RBC) measurements and albumin levels. RBC measurements are correlated with gender; female subjects had lower RBC count (
Therefore, we performed multivariate analysis of variance (MANOVA) to compare group differences in hemorheologic measures and WBC count by controlling for gender and age (
Hemorheologic Measures | Controls (N = 46) | MDD Subjects (N = 146) | |
RBC count −106/µL | 4.6±0.5 | 4.7±0.4 | |
HGB – g/dL | 13.4±1.6 | 14.0±1.4 | |
HCT −% | 39.5±4.2 | 41.4±3.5 | |
TSP – g/dL | 7.1±0.5 | 7.3±0.5 | |
Albumin – g/dL | 4.1±0.4 | 4.2±0.3 | 0.052 |
WBV – cP | 5.9±0.5 | 6.2±0.4 | |
WBC count −106/µL | 6.8±1.5 | 7.5±2.1 | 0.052 |
Values are means±SD.
p was based on MANOVA using GLM model by adjusting for age and gender.
In MDD subjects, hemorheologic parameters of stress-hemoconcentration improved after 8 weeks of antidepressant treatment (
Hemorheologic Measures | Number of Patients | Before Treatment | After Treatment | |
RBC count −106/µL | 146 | 4.7±0.4 | 4.6±0.4 | |
HGB – g/dL | 146 | 14.0±1.4 | 13.8±1.4 | |
HCT −% | 146 | 41.4±3.5 | 40.6±3.6 | |
TSP – g/dL | 146 | 7.3±0.5 | 7.1±0.4 | |
Albumin – g/dL | 146 | 4.2±0.3 | 4.0±0.3 | |
WBV – cP | 146 | 6.2±0.4 | 6.1±0.5 | |
WBC count −106/µL | 146 | 7.5±2.1 | 6.7±1.7 |
Subjects with no missing data.
Values are means±SD.
p was based on paired t-test.
Measures of stress-hemoconcentration were not significantly different in subjects treated with desipramine or fluoxetine in MANOVA analysis. Our analyses showed that total RBC count, HBG, HCT, total WBC, TSP and albumin did not differ between the two groups in the final week of treatment.
Hemorheologic Measures before Treatment | HAM-D21 Score before Treatment | Change in Hemorheologic Measures with treatment | Change in HAM-D21 Score | ||
RBC count −106/µL | 0.18 | RBC count −106/µL | 0.22 | ||
HGB – g/dL | 0.14 | 0.105 | HGB – g/dL | 0.18 | |
HCT −% | 0.24 | HCT −% | 0.22 | ||
TSP – g/dL | 0.26 | TSP – g/dL | 0.14 | 0.086 | |
Albumin – g/dL | 0.22 | Albumin – g/dL | 0.13 | 0.115 | |
WBV – cP | 0.29 | WBV – cP | 0.21 | ||
Plasma volume | 0.20 | ||||
WBC count −106/µL | 0.21 | 0.010 | WBC count −106/µL | 0.23 | 0.007 |
p was based on Spearman partial correlation by controlling for age and gender.
Plasma volume change % after treatment based on the method provided by Dill and Costill.27
Stepwise logistic regression analysis revealed that the significant predictors of remission included HAM-D21 score (OR = 0.85, 95%CI = 0.77–0.93,
Our secondary data analyses indicate that hemorheologic measures of stress-hemoconcentration are present in Mexican-American individuals with mild to moderate MDD and that these measures decrease significantly after 8 weeks of antidepressant treatment to levels which were the same as those of controls. Measures we obtained in depressed subjects at rest (in the absence of any deliberate psychological challenge) are comparable to those elicited after a stressful challenge in other studies
Psychological stress has been identified as a risk factor for CVD, as a trigger of acute coronary events, and as a contributor to the pathogenesis of atherosclerosis and hypertension
During stress, hemoconcentration can be at least partially explained by sympathetic nervous system activation (for a comprehensive review see reference
Stress hemoconcentration has not been systematically studied in MDD. Several studies on relatively small numbers of depressed subjects (30–50) examining other systemic aspects of depression – inflammation and the acute phase response – have reported on some measures that overlap with those we examined. Total serum protein
Importantly, the changes in hemorheologic measures that we report in our depressed subjects improved with treatment. Treatment of depression has been reported to lessen the risk of MI associated with depression
Normal individuals can display hemorheologic measures of stress-hemoconcentration after acute psychological stress. Those measures return to baseline levels within minutes after the stress situation is terminated. Subjects with major depressive disorder (MDD) display stress-hemoconcentration at baseline, non-stressed conditions and those measures return to baseline levels in responders to an 8-week treatment with antidepressants.
Our data based on secoondary analyses support the notion that successful antidepressant treatment ameliorates hemorheologic measures of stress-hemoconcentration, which indicates that factors consistent with increased blood viscosity and the advancement of atherosclerotic plaque in low-pressure sites in the arterial tree may be alleviated following the improvement of MDD symptomatology. Our results suggest that hemorheologic changes in patients suffering from MDD could contribute to an increased risk for CVD. Antidepressant treatment reduces not only the psychological symptoms of depression, but it also may reduce this potentially important depression-associated risk factor for CVD. Hemorheologic measures of stress-hemoconcentration are of low cost and often contained in routine lab assessments, but they have not yet been considered as a relevant biomarker of CVD risk in depression. We suggest here that physicians who assess major depression and provide antidepressant treatment should consider stress hemoconcentration when evaluating the cardiovascular risk factors of depressed patients.
Trial Protocol
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