Abstract
Objective
To examine the effect of cigarette smoking (CS) status and total testosterone (TT) levels after testosterone replacement therapy (TRT) on all-cause mortality, myocardial infarction (MI), and stroke in male smokers and nonsmokers without history of MI and stroke.
Participants and Methods
Data from 18,055 males with known CS status and low TT levels who received TRT at the Veterans Health Administration between December 1, 1999, and May 31, 2014, were grouped into (1) current smokers with normalized TT, (2) current smokers with nonnormalized TT, (3) nonsmokers with normalized TT, and (4) nonsmokers with nonnormalized TT. Combined effect of CS status and TT level normalization after TRT on all-cause mortality, MI, and stroke was compared using propensity score–weighted Cox proportional hazard models.
Results
Normalization of serum TT levels in nonsmokers was associated with a significant decrease in all-cause mortality (hazard ratio [HR]=0.526; 95% CI, 0.477-0.581; P<.001) and MI (HR=0.717; 95% CI, 0.522-0.986; P<.001). Among current smokers, normalization of serum TT levels was associated with a significant decrease in only all-cause mortality (HR=0.563; 95% CI, 0.488-0.649; P<.001) without benefit in MI (HR=1.096; 95% CI, 0.698-1.720; P=.69). Importantly, compared with nonsmokers with normalized TT, all-cause mortality (HR=1.242; 95% CI, 1.104-1.396; P<.001), MI (HR=1.706; 95% CI, 1.242-2.342; P=.001), and stroke (HR=1.590; 95% CI, 1.013-2.495; P=.04) were significantly higher in current smokers with normalized TT.
Conclusion
We conclude that active CS may negate the protective effect of testosterone level normalization on all-cause mortality and MI after TRT.
Abbreviations and Acronyms: BMI, body mass index; DM, diabetes mellitus; CAD, coronary artery disease; CDW, Corporate Data Warehouse; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; CS, current smoking; CV, cardiovascular; CVD, cardiovascular disease; HR, hazard ratio; ICD-9, International Classification of Diseases, Ninth Revision; IPTW, inverse probability of treatment weights; LDL, low-density lipoprotein; MI, myocardial infarction; OSA, obstructive sleep apnea; PVD, peripheral vascular disease; TRT, testosterone replacement therapy; TT, total testosterone; VA, Veterans Administration; VHA, Veterans Health Administration
At any given age, men are more vulnerable than women to death from cardiovascular disease (CVD).1 Male gender is thought to be a strong independent risk factor for coronary artery disease (CAD), myocardial infarction (MI), and stroke.2 The male sex hormone testosterone is postulated to play a role in the observed incidence of CAD, MI, and stroke in men.2, 3, 4 Ex vivo studies showing increased human platelet thromboxane A2 receptor density and aggregation in response to testosterone lend support to this hypothesis.5 However, other studies have provided data that highlight the importance of normal testosterone levels for cardiovascular (CV) health specifically in symptomatic subjects with persistently low testosterone levels.6, 7, 8, 9 The significance of testosterone replacement therapy (TRT) in CV health is a topic of ongoing debate as several studies have reported higher CV events with TRT.10, 11 In contrast, we and others have found that normalization of testosterone levels after TRT is associated with a significant decrease in all-cause mortality and MI.6, 7
Lifestyle choices such as cigarette smoking (CS) could also contribute to this disparity in CVD between men and women. Historically, CS rates are higher in men than in women.12 Our group and others have shown that CS is associated with increased atherothrombotic events.13, 14, 15, 16, 17, 18 In an experimental study using rabbit aorta it was reported that physiologic levels of testosterone augmented the endothelial dysfunction associated with environmental tobacco smoke exposure.19 Therefore, it is conceivable that a combination of testosterone and CS could additively increase the risk of MI and stroke in male smokers via their reported prothrombotic effects. However, to our knowledge, no study has specifically examined the combined effect of CS and testosterone level on mortality, MI, or stroke in humans after TRT. It is also unclear whether normal testosterone levels indeed potentiate the active CS-related adverse effect on the mortality and CV events as suggested by some ex vivo and preclinical data.5, 19
In this study, we examined whether CS status modulated the risk for all-cause mortality, MI, and stroke in men in relation to normalized testosterone level after TRT.
Participants and Methods
We conducted a retrospective cohort study of male veterans who received medical care in the Veterans Health Administration (VHA) from December 1, 1999, to May 31, 2014. Data were retrieved from Veterans Administrations Corporate Data Warehouse (CDW) through the Veterans Administrations Informatics and Computing Infrastructure.20 The VHA provides care to veterans at more than 1400 establishments across the United States and each veteran is assigned a unique identifier in the CDW database. The Institutional Review Board of the Veterans Affairs Medical Center, Kansas City, MO, approved the study. The quality of data from these sources is well documented, and the data have been widely used by investigators for retrospective longitudinal studies.21
Study Design
This study was designed to determine the effect of the interaction between smoking and testosterone levels on CV events by determining the incidence of MI, stroke, and all-cause mortality in subpopulations of patients who received TRT. Cardiovascular events and comorbidities in patients were identified according to International Classification of Diseases, 9th Revision (ICD-9) codes. Patients included in the study had their testosterone levels checked on at least 2 separate occasions as recommended by guidelines.22
Determination of Exposure to TRT and Smoking
Patients' medical records were used to ascertain prescriptions for TRT administration. For this study, patients who received any form of TRT (injection, gel, or patch) were considered as treated. Smoking status was obtained from HealthFactors files in the Veterans Administrations Informatics and Computing Infrastructure database. Only those patients whose smoking status could be verified from the database were included in the study. Patients were classified as current smokers (smoking at the beginning of the study and at every encounter throughout the study period), nonsmokers (never smoked or had quit smoking at the beginning of the study and did not resume smoking throughout the study period).
Determination of Total Testosterone Levels
Total testosterone (TT) levels were considered low when the reported serum TT values were below the lower limit of normal laboratory reference range for each test result. This approach permitted inclusion of results from most laboratories in the Veterans Administration (VA) health system over the study period (≥14 years). The available test results from such a long period of follow-up lacked a uniform laboratory range for normal TT level and reporting units in the database. We chose to use this method rather than a discrete cutoff value because we found that facilities within the VHA system used different assay methods with different reference ranges and reporting units.23, 24 Even in the same hospital, the assay used could change over time. Moreover, lack of standardized values for serum testosterone levels and other stoichiometric measures made it difficult to select a single set of minimum and maximum values.25, 26 Thus, we categorized each test result as normal or low on the basis of their respective reference range reported with the test result, because this was the most accurate method to minimize the effect of use of multiple assays.
Outcome Measures
Primary outcome measures were (1) all-cause mortality, (2) the incidence of MI (ICD-9 codes 410.x0 and 410.x1), and (3) the incidence of ischemic-stroke (ICD-9 codes 433.x1 and 434 [excluding 434.x0], or 436) determined using dates of death in CDW data augmented with vital status files.
Confounding Factors Measured
Confounding measures included patients' demographic characteristics, comorbidities such as diabetes mellitus (DM), chronic obstructive pulmonary disease (COPD), obstructive sleep apnea (OSA), congestive heart failure (CHF), peripheral vascular disease (PVD), and CAD, and other factors. Other factors included the baseline body mass index (BMI), low-density lipoprotein (LDL), and use of aspirin, β-blockers, and statins. The International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes were used to capture the coexisting conditions.
Study Population
Inclusion Criteria
All male patients with TT levels lower than the corresponding normal laboratory reference range during initial laboratory assay were included.
Exclusion Criteria
(1) Females, (2) those who received TRT before the first available low-TT values, and (3) those who suffered MI or stroke before the first day of the study were excluded.
Eligible study patients were divided into 4 groups: (1) current smokers with normalized TT levels after TRT, (2) current smokers with nonnormalized TT levels after TRT, (3) nonsmokers with normalized TT levels after TRT, and (4) nonsmokers with nonnormalized TT levels after TRT. Normalized-treated are those whose TT levels normalized during follow-up visits and throughout the study. Nonnormalized-treated did not normalize throughout the study.
Statistical Analyses
Means and SDs were used to report continuous variables, whereas percentages were used for categorical variables. Nonparametric tests were used to compare nonnormally distributed baseline characteristics of study participants. Chi-square test and t test were used for normally distributed characteristics. First, we fitted models to determine the impact of smoking on mortality and MI. We then determined how TRT impacted the effects of smoking status on the same health outcomes. We conducted univariate and multivariable Cox proportional hazard regression analyses to determine the differences between each pair of the study groups. To correct for potential systematic differences between untreated and treated groups, propensity scores were computed. For each patient, propensity scores for receiving TRT were computed by adjusting for the covariates in a logistic regression analysis. The covariates included were age, BMI, hypertension, DM, OSA, COPD, PVD, CHF, LDL, CAD, and the use of aspirin, statins, and β-blockers. For a robust analysis of our data, propensity score–weighted stabilized inverse probability of treatment weights (IPTW) was used.27, 28 In addition, using the stabilized-IPTW approach, Kaplan-Meier survival curves were generated to compare event-free survival time between the groups. The SAS Enterprise Guide 7.1 supported on SAS 9.4 was used for statistical analyses with TRT as a time-varying factor. All hypothesis tests were 2-sided and carried out at a significance level of .05.
Results
Cohort Description
From our database, smoking status could be verified in 18,055 patients who received TRT. They were categorized into current smokers (5500) and nonsmokers (12,555). Each smoking status was further divided into normalized-treated and nonnormalized-treated depending on whether their testosterone levels normalized after receiving TRT. In the current smokers group, 3414 patients had normalized TT levels and 2086 patients had nonnormalized TT levels after TRT. In the nonsmokers group, 8137 patients had normalized TT levels and 4418 had nonnormalized TT levels after TRT.
Study Subjects
Table 1, Table 2, Table 3, Table 4 present the characteristics at baseline for different groups of patients: all patients, smokers, nonsmokers, and the normalized cohorts. Differences with respect to age, BMI, DM, hypertension, OSA, COPD, PVD, CHF, LDL, CAD, and use of aspirin, β-blockers, and statins between the study groups were normalized by using IPTW (P>.05).
Table 1.
| Characteristic | Unmatched cohort |
Propensity-matched cohort (stabilized IPTW) |
||||
|---|---|---|---|---|---|---|
| Current smokers (N=5500) | Nonsmokers (N=12,555) | P value | Current smokers (N=5509) | Nonsmokers (N=12,549) | P value | |
| Age ≥50 y | 4824 (87.7) | 11,558 (92.1) | <.001 | 4990 (90.7) | 11,386 (90.7) | 1.00 |
| Age (y), median | 63.0 | 67.0 | 63.0 | 67.0 | ||
| Body mass index ≥30 kg/m2 | 3276 (59.6) | 8,661 (69.0) | <.001 | 3658 (66.4) | 8,312 (66.2) | .84 |
| Body mass index (kg/m2), mean ± SD | 32.0±6.6 | 33.6±6.7 | 32.8±6.6 | 33.3±6.8 | ||
| Follow-up time (y), mean ± SD | 5.3±3.1 | 6.0±3.3 | 5.4±3.1 | 6.0±3.4 | ||
| Hypertension | 1312 (23.9) | 2,571 (20.5) | <.001 | 1196 (21.7) | 2,704 (21.6) | .81 |
| Diabetes mellitus | 1574 (28.6) | 4,632 (36.8) | <.001 | 1906 (34.6) | 4,320 (34.4) | .83 |
| Chronic obstructive pulmonary disease | 155 (2.8) | 162 (1.3) | <.001 | 98 (1.8) | 222 (1.8) | .94 |
| Obstructive sleep apnea | 123 (2.2) | 299 (2.4) | .55 | 134 (2.4) | 297 (2.4) | .79 |
| Congestive heart failure | 111 (2.0) | 323 (2.6) | .03 | 141 (2.6) | 304 (2.4) | .58 |
| Peripheral vascular disease | 96 (1.8) | 114 (0.9) | <.001 | 63 (1.2) | 145 (1.2) | .97 |
| Coronary artery disease | 358 (6.5) | 827 (6.6) | .85 | 370 (6.7) | 832 (6.6) | .82 |
| Depression | 854 (15.5) | 1,023 (8.2) | <.001 | 567 (10.3) | 1,297 (10.3) | .93 |
| LDL >100 mg/dL | 2851 (51.8) | 6,158 (49.1) | <.001 | 2751 (49.9) | 6,263 (49.9) | .97 |
| Concomitant therapy with | ||||||
| Antiplatelet agents (ASA) | 1869 (34.0) | 4,148 (33.0) | .22 | 1841 (33.4) | 4,186 (33.4) | .94 |
| β-Blockers | 2242 (40.8) | 5,345 (42.6) | .02 | 2325 (42.2) | 5,281 (42.1) | .88 |
| Statins | 3296 (59.9) | 8,158 (65.0) | <.001 | 3504 (63.6) | 7,967 (63.5) | .89 |
| All-cause mortality |
Myocardial infarction |
Stroke |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | P | HR | 95% CI | P | HR | 95% CI | P | |
| Univariate N=5500 vs 12,555 |
1.281 | 1.175-1.397 | <.001 | 1.358 | 1.047-1.760 | .02 | 1.693 | 0.973-2.946 | .06 |
| Propensity matched (stabilized IPTW) N=5509 vs 12,549 |
1.217 | 1.115-1.327 | <.001 | 1.396 | 1.079-1.806 | .01 | 1.739 | 1.201-2.519 | .003 |
ASA = aspirin; HR = hazard ratio; IPTW = inverse probability of treatment weights; LDL = low-density lipoprotein; Ref = reference.
Values represent n (%) unless otherwise indicated.
Table 2.
| Characteristic | Normalized-treated vs nonnormalized-treated (ref = nonnormalized-treated) |
|||||
|---|---|---|---|---|---|---|
| Unmatched cohort |
Propensity-matched cohort (stabilized IPTW) |
|||||
| Normalized-treated (N=3414) | Nonnormalized-treated (N=2086) | P value | Normalized-treated (N=3414) | Nonnormalized-treated (N=2086) | P value | |
| Age ≥50 y | 2988 (87.5) | 1836 (88.0) | .59 | 2995 (87.7) | 1830 (87.7) | 1.00 |
| Age (y), median | 63.0 | 63.0 | 63.0 | 63.0 | ||
| Body mass index ≥30 kg/m2 | 1992 (58.4) | 1284 (61.6) | .02 | 2034 (59.6) | 1242 (59.6) | 1.00 |
| Body mass index (kg/m2), mean ± SD | 31.8±6.6 | 32.3±6.7 | 31.8±6.6 | 32.3±6.7 | ||
| Follow-up time (y), mean ± SD | 5.8±3.0 | 4.5±3.0 | 5.8±3.0 | 4.5±3.0 | ||
| Hypertension | 775 (22.7) | 537 (25.7) | .01 | 815 (23.9) | 498 (23.9) | .99 |
| Diabetes mellitus | 920 (27.0) | 654 (31.4) | <.001 | 978 (28.6) | 598 (28.7) | 1.00 |
| Chronic obstructive pulmonary disease | 94 (2.8) | 61 (2.9) | .71 | 97 (2.8) | 60 (2.9) | .96 |
| Obstructive sleep apnea | 63 (1.9) | 60 (2.9) | .01 | 77 (2.3) | 47 (2.3) | 1.00 |
| Congestive heart failure | 63 (1.9) | 48 (2.3) | .24 | 70 (2.0) | 43 (2.0) | .99 |
| Peripheral vascular disease | 52 (1.5) | 44 (2.1) | .11 | 60 (1.7) | 36 (1.7) | 1.00 |
| Coronary artery disease | 213 (6.2) | 145 (7.0) | .30 | 223 (6.5) | 137 (6.6) | .96 |
| Depression | 514 (15.1) | 340 (16.3) | .22 | 530 (15.5) | 324 (15.5) | 1.00 |
| LDL >100 mg/dL | 1830 (53.6) | 1021 (49.0) | <.001 | 1769 (51.8) | 1080 (51.8) | .98 |
| Concomitant therapy with | ||||||
| Antiplatelet agents (ASA) | 1104 (32.3) | 765 (36.7) | .001 | 1162 (34.0) | 711 (34.1) | .98 |
| β-Blockers | 1337 (39.2) | 905 (43.4) | .002 | 1391 (40.7) | 849 (40.7) | .98 |
| Statins | 1998 (58.5) | 1298 (62.2) | .007 | 2047 (60.0) | 1250 (60.0) | 1.00 |
| All-cause mortality |
Myocardial infarction |
Stroke |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | P | HR | 95% CI | P | HR | 95% CI | P | |
| Univariate N=3414 vs 2086 |
0.534 | 0.462-0.616 | <.001 | 1.051 | 0.670-1.649 | .83 | 0.748 | 0.298-1.878 | .54 |
| Propensity-matched (stabilized IPTW) N= 3414 vs 2086 |
0.563 | 0.488-0.649 | <.001 | 1.096 | 0.698-1.720 | .69 | 0.792 | 0.424-1.481 | .47 |
ASA = aspirin; HR = hazard ratio; IPTW = inverse probability of treatment weights; LDL = low-density lipoprotein; ref = reference.
Values represent n (%) unless otherwise indicated.
Table 3.
| Characteristic | Normalized-treated vs nonnormalized-treated (ref = nonnormalized-treated) |
|||||
|---|---|---|---|---|---|---|
| Unmatched cohort |
Propensity-matched cohort (stabilized IPTW) |
|||||
| Normalized-treated (N=8137) | Nonnormalized-treated (N=4418) | P value | Normalized-treated (N=8137) | Nonnormalized-treated (N=4418) | P value | |
| Age ≥50 y | 7508 (92.3) | 4050 (91.7) | .24 | 7491 (92.1) | 4068 (92.1) | .99 |
| Age (y), median | 67.0 | 67.0 | 67.0 | 67.0 | ||
| Body mass index ≥30 kg/m2 | 5518 (67.8) | 3143 (71.1) | <.001 | 5613 (69.0) | 3047 (69.0) | .99 |
| Body mass index (kg/m2), mean ± SD | 33.3±6.5 | 34.1±7.1 | 33.3±6.5 | 34.1±7.1 | ||
| Follow-up time (y), mean ± SD | 6.6±3.3 | 5.0±3.2 | 6.6±3.3 | 5.0±3.2 | ||
| Hypertension | 1549 (19.0) | 1022 (23.1) | <.001 | 1667 (20.5) | 905 (20.5) | .99 |
| Diabetes mellitus | 2773 (34.1) | 1859 (42.1) | <.001 | 3001 (36.9) | 1628 (36.9) | .97 |
| Chronic obstructive pulmonary disease | 83 (1.0) | 79 (1.8) | <.001 | 105 (1.3) | 57 (1.3) | 1.00 |
| Obstructive sleep apnea | 153 (1.9) | 146 (3.3) | <.001 | 105 (2.4) | 194 (2.4) | .98 |
| Congestive heart failure | 166 (2.0) | 157 (3.6) | <.001 | 209 (2.6) | 113 (2.6) | .99 |
| Peripheral vascular disease | 58 (0.7) | 56 (1.3) | .002 | 74 (0.9) | 40 (0.9) | .98 |
| Coronary artery disease | 469 (5.8) | 358 (8.1) | <.001 | 538 (6.6) | 292 (6.6) | .97 |
| Depression | 632 (7.8) | 391 (8.9) | .03 | 665 (8.2) | 363 (8.2) | .95 |
| LDL >100 mg/dL | 4177 (51.3) | 1981 (44.8) | <.001 | 3990 (49.0) | 2166 (49.0) | .99 |
| Concomitant therapy with | ||||||
| Antiplatelet agents (ASA) | 2594 (31.9) | 1554 (35.2) | <.001 | 2688 (33.0) | 1461 (33.0) | .98 |
| β-Blockers | 3354 (41.2) | 1991 (45.1) | <.001 | 3465 (42.6) | 1883 (42.6) | .98 |
| Statins | 5141 (63.2) | 3017 (68.3) | <.001 | 5289 (65.0) | 2872 (65.0) | .99 |
| All-cause mortality |
Myocardial infarction |
Stroke |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | P | HR | 95% CI | P | HR | 95% CI | P | |
| Univariate N=8137 vs 4418 |
0.495 | 0.448-0.547 | <.001 | 0.622 | 0.455-0.852 | .003 | 1.000 | 0.466-2.147 | 1.00 |
| Propensity-matched (stabilized IPTW) N=8137 vs 4418 |
0.526 | 0.477-0.581 | <.001 | 0.717 | 0.522-0.986 | .04 | 1.069 | 0.652-1.754 | .79 |
ASA = aspirin; HR = hazard ratio; IPTW = inverse probability of treatment weights; LDL = low-density lipoprotein; ref = reference.
Values represent n (%) unless otherwise indicated.
Table 4.
| Characteristic | Current smokers vs nonsmokers (ref = nonsmokers) |
|||||
|---|---|---|---|---|---|---|
| Unmatched cohort |
Propensity-matched cohort (stabilized IPTW) |
|||||
| Current smokers (N=3414) | Nonsmokers (N=8137) | P value | Current smokers (N=3420) | Nonsmokers (N=8133) | P value | |
| Age ≥50 y | 2988 (87.5) | 7508 (92.3) | <.001 | 3108 (90.9) | 7391 (90.9) | 1.00 |
| Age (y), median | 63.0 | 67.0 | 63.0 | 67.0 | ||
| Body mass index ≥30 kg/m2 | 1992 (58.4) | 5518 (67.8) | <.001 | 2234 (65.3) | 5299 (65.2) | .85 |
| Body mass index (kg/m2), mean ± SD | 31.8±6.6 | 33.3±6.5 | 32.6±6.6 | 33.0±6.6 | ||
| Follow up time (y), mean ± SD | 5.8±3.0 | 6.6±3.3 | 5.9±3.0 | 6.5±3.3 | ||
| Hypertension | 775 (22.7) | 1549 (19.0) | <.001 | 696 (20.3) | 1639 (20.2) | .82 |
| Diabetes mellitus | 920 (27.0) | 2773 (34.1) | <.001 | 1105 (32.3) | 2604 (32.0) | .76 |
| Chronic obstructive pulmonary disease | 94 (2.8) | 83 (1.0) | <.001 | 53 (1.6) | 124 (1.5) | .91 |
| Obstructive sleep apnea | 63 (1.9) | 153 (1.9) | .90 | 68 (2.0) | 155 (1.9) | .78 |
| Congestive heart failure | 63 (1.9) | 166 (2.0) | .49 | 72 (2.1) | 162 (2.0) | .69 |
| Peripheral vascular disease | 58 (0.7) | 52 (1.5) | <.001 | 32 (0.9) | 75 (0.9) | .96 |
| Coronary artery disease | 213 (6.2) | 469 (5.8) | .32 | 206 (6.0) | 484 (6.0) | .87 |
| Depression | 514 (15.1) | 632 (7.8) | <.001 | 336 (9.8) | 801 (9.9) | .98 |
| LDL >100 mg/dL | 1830 (53.6) | 4177 (51.3) | .03 | 1781 (52.1) | 4232 (52.0) | .96 |
| Concomitant therapy with | ||||||
| Antiplatelet agents (ASA) | 1104 (32.3) | 2594 (31.9) | .63 | 1104 (32.3) | 2608 (32.1) | .83 |
| β-Blockers | 1337 (39.2) | 3354 (41.2) | .04 | 1390 (40.7) | 3303 (40,6) | .97 |
| Statins | 1998 (58.5) | 5141 (63.2) | <.001 | 2121 (62.0) | 5031 (61.9) | .88 |
| All-cause mortality |
Myocardial infarction |
Stroke |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | P | HR | 95% CI | P | HR | 95% CI | P | |
| Univariate N=3414 vs 8137 |
1.308 | 1.164-1.469 | <.001 | 1.639 | 1.187-2.261 | .003 | 1.573 | 0.804-3.080 | .19 |
| Propensity-matched (stabilized IPTW) N=3420 vs 8133 |
1.242 | 1.104-1.396 | <.001 | 1.706 | 1.242-2.342 | .001 | 1.590 | 1.013-2.495 | .04 |
ASA = aspirin; HR = hazard ratio; IPTW = inverse probability of treatment weights; LDL = low-density lipoprotein; ref = reference.
Values represent n (%) unless otherwise indicated.
Primary Outcome Based on Smoking Status in the Final Cohort
There were 18,055 patients who received TRT (Table 1). Of these, 5500 (30.5%) were smokers. Mean follow-up time (years) was 5.4±3.1 and 6.0±3.4 in the current smokers and nonsmokers groups, respectively. There were 2611 (95% CI, 2512-2713) vs 2118 (95% CI, 2029-2210) mortalities per 100,000 person-years; 302 (95% CI, 269-337) vs 218 (95% CI, 190-248) MI events per 100,000 person-years; and 67 (95% CI 52-85) vs 45 (95% CI 33-60) stroke events per 100,000 person-years in the current smokers and nonsmokers groups, respectively. Of the treated population, current smokers had a significantly higher mortality risk (hazard ratio [HR]=1.217; 95% CI, 1.115-1.327; P<.001), significantly higher MI risk (HR=1.396; 95% CI, 1.079-1.806; P=.011), and significantly higher stroke risk (HR=1.739; 95% CI, 1.201-2.519; P=.003) than did nonsmokers.
Effect of TRT on Current Smokers
In the treated group, there were 5500 current smokers of whom 3414 (62.07%) had their TT levels normalized after TRT (Table 2). Mean follow-up time (years) was 5.8±3.0 and 4.5±3.0 in the normalized-treated and nonnormalized groups, respectively. There were 2101 (95% CI, 2012-2193) vs 3675 (95% CI, 3557-3796) mortalities per 100,000 person-years; 303 (95% CI, 270-339) vs 298 (95% CI, 265-334) MI events per 100,000 person-years; and 66 (95% CI, 51-83) vs 75 (95% CI, 59-94) stroke events per 100,000 person-years in the normalized-treated and nonnormalized groups, respectively. In current smokers, normalization of testosterone with TRT resulted in a lower mortality risk compared with those who did not reach normalized testosterone levels (HR=0.563; 95% CI, 0.488-0.649; P<.001). However, there was no significant difference in the risk of MI (HR=1.096; 95% CI, 0.698-1.720; P=.69) and stroke (HR=0.792; 95% CI, 0.424-1.481; P=.47) between the normalized and nonnormalized current smokers.
Effect of TRT on Nonsmokers
In the treated group, there were 12,555 nonsmokers of whom 8137 (64.8%) had their TT levels normalized after TRT (Table 3). Mean follow-up time (years) was 6.6±3.3 and 5.0±3.2 in the normalized-treated and nonnormalized groups, respectively. There were 1687 (95% CI, 1607-1769) vs 3110 (95% CI, 3002-3221) mortalities per 100,000 person-years; 183 (95% CI, 157-211) vs 299 (95% CI, 266-334) MI events per 100,000 person-years; and 47 (95% CI, 35-63) vs 41 (95% CI, 29-56) stroke events per 100,000 person-years in the normalized-treated and nonnormalized groups, respectively. In the nonsmoking groups, normalization of testosterone with TRT resulted in a significantly lower mortality risk (HR=0.526; 95% CI, 0.477-0.581; P<.001) and significantly lower MI risk (HR=0.717; 95% CI, 0.522-0.986; P=.04) compared with their nonnormalized counterparts. Stroke events were not different between normalized and nonnormalized nonsmokers (HR=1.069; 95% CI, 0.652-1.754; P=.79).
Effect of Testosterone Normalization After TRT on Current Smokers vs Nonsmokers
There were 11,551 patients whose TT level normalized after TRT (Table 4). Of these, 3414 (29.6%) were smokers. Mean follow-up time (years) was 5.8±3.0 and 6.6±3.3 in the current smokers and nonsmokers groups, respectively. There were 2101 (95% CI, 2012-2193) vs 1687 (95% CI, 1607-1769) mortalities per 100,000 person-years; 303 (95% CI, 270-339) vs 183 (95% CI, 157-211) MI events per 100,000 person-years; and 66 (95% CI 51-83) vs 47 (95% CI, 35-63) stroke events per 100,000 person-years in the current smokers and nonsmokers groups, respectively. In these normalized-treated groups, current smokers had a significantly higher mortality risk (HR=1.242; 95% CI, 1.104-1.396; P<.001), higher MI risk (HR=1.706; 95% CI, 1.242-2.342; P=.001), and higher stroke risk (HR=1.590; 95% CI, 1.013-2.495; P=.04) than did nonsmokers.
Discussion
The present study compared CV events and all-cause mortality in smokers and nonsmokers after TRT. Our results showed the following: (1) There was a significant decrease in all-cause mortality and MI in nonsmokers who achieved normalized testosterone levels through TRT. (2) In current smokers, normalization of testosterone levels after TRT resulted in decreased incidence of all-cause mortality only compared with the current smokers who did not achieve normal testosterone levels after TRT. However, (3) the incidence of all-cause mortality, MI, and stroke in current smokers with normalized testosterone after TRT was significantly greater than that in nonsmokers with normalized testosterone after TRT. More importantly, (4) the incidence of MI or stroke between current smokers with normalized testosterone levels and smokers with nonnormalized testosterone levels after TRT was not different. Taken together, all these findings suggest that active CS nullifies the protective effect of normal testosterone levels after TRT on MI and all-cause mortality.
The role of testosterone and the effect of TRT in the pathophysiology of CVD remains controversial.6, 7, 8, 10, 11 It has been proposed that higher levels of testosterone predispose men to a 3 times greater risk of heart disease compared with women.3 Testosterone is considered to play a role in men developing cardiac diseases nearly a decade earlier compared with risk-matched women.4 Anabolic steroid abuse is associated with early MI and stroke.29 In addition, some observational studies support the notion that testosterone and TRT adversely affect CV health.10, 11, 30 In the National Institutes of Health–sponsored study Osteoporotic Fractures in Men, 697 subjects were divided into 4 groups on the basis of their testosterone levels and followed for nearly 4 years.30 Results showed that men with TT levels of 495 ng/dL or more had more than 2-fold greater risk of coronary disease compared with men with TT levels of less than 308 ng/dL. Four studies including 1 randomized placebo-controlled trial,11 2 retrospective trials,10, 31 and 1 meta-analysis32 suggest that TRT is associated with an increased risk of CV events.
However, recent research data question the conventional notion that testosterone is essentially harmful to the CV system. Accumulating data indicate the importance of optimal levels of testosterone for CV health.6, 7, 8 Indeed, a British study of 930 individuals with angiography-confirmed CAD showed the prevalence of low testosterone levels in 24% of subjects. This study also found that mortality due to CAD doubled in subjects with low testosterone levels.33 A Swedish study of more than 3000 men linked low testosterone levels to an increased risk of PVD.34 In addition, TRT was found to reduce total body fat, total cholesterol, and waist circumference.35, 36 In multiple studies, testosterone or TRT was shown to improve endothelial function, decreased systemic vascular resistance, and decrease left ventricular end-diastolic pressure, leading to increased cardiac output.7 TRT was also reported to decrease reperfusion injury via activation of signal transducer and activator of transcription 3.7 Recently, in a large cohort of US veterans, we demonstrated decreased all-cause mortality, stroke, and MI with normalization of testosterone levels after TRT.26
Several studies have examined the effect of CS on testosterone levels, but the data are conflicting. A cross-sectional study including a total of 255 men failed to show any significant association between CS and total, free, and bioavailable testosterone and sex-hormone–binding globulin.37 In contrast, a cross-sectional population-based study of 3427 men found that men who smoked had significantly higher levels of total and free testosterone compared with men had who never smoked. Testosterone levels were correlated directly with the number of cigarettes smoked daily.38 In the present study, this potential influence of CS on testosterone levels was not likely a factor in outcome measurements because only smokers and nonsmokers with baseline low TT levels (measured on at least 2 separate occasions) were included in the study. Inclusion criteria used for the present analyses provide confidence that the observed differences in mortality, MI, or stroke between smokers and nonsmokers are likely effects of CS per se and not the differences in TT levels before TRT.
Cigarette smoking is a major risk factor for MI and sudden cardiac death and it alters the interplay between prothrombotic/antithrombotic and profibrinolytic/antifibrinolytic factors.13, 15, 17, 18 Because the CS rate is higher among men, it is important to know how testosterone levels and TRT may affect mortality and MI in such populations. To our knowledge, the present investigation is the first study to examine the interaction between testosterone levels and CS in the context of CV events. During these analyses, we found that normalized testosterone levels after TRT in current smokers were associated with a decrease in all-cause mortality. But normalization of testosterone levels after TRT in smokers did not decrease the incidence of MI as observed in nonsmokers. In addition, a significant decrease in all-cause mortality (P<.001), MI (P=.001), and stroke (P=.04) among nonsmokers with normalized testosterone levels was noted compared with current smokers with normalized testosterone levels after TRT. Together, these data indicate that in current smokers with normal testosterone levels, MI or stroke events were driven by CS rather than by TT levels. Based on our previous studies,13, 17 it is reasonable to postulate that the proatherothrombotic effects of CS overwhelmed the potential beneficial effects of a normalized testosterone level. Consequently, no reduction in the incidence of MI among the current smokers was observed. Although a noticeable protective effect of testosterone normalization on all-cause-mortality was observed in current smokers after TRT, this effect was significantly lower when compared with that in nonsmokers. On the basis of these findings, we believe that it may be prudent to recommend CS cessation as an important pretreatment intervention in candidates for TRT.
An additional interesting and clinically relevant finding in our study is a lack of a significant difference in the incidence of MI (P=.69) and stroke (P=.47) between current smokers with normalized and current smokers without normalized TT levels. Thus, it appears unlikely that normal testosterone levels would potentiate CS-related adverse effects on the mortality and CV events as proposed by ex vivo and preclinical studies. On a similar note, in our recent study, we found that normalization of testosterone after TRT or TRT itself did not increase the incidence of deep venous thrombosis or pulmonary embolism.39
Study Limitations
The findings of our study have to be viewed in the context of the limitations of an observational study. Without assigning an order of significance, our study limitations include the following: (1) Unobserved confounding factors or hidden bias may be present. (2) We could not find the exact time of the day when samples for testosterone assays were collected. Samples for laboratory analysis are generally collected during morning hours in the VA health care system. Sample draw later in the day may result in lower TT values. If some subjects had their blood drawn after the morning hours, their TT levels would be underestimated. (3) Smoking status was obtained on the basis of self-reporting and documented in the HealthFactor data files in the VA database. (4) Laboratory measurements such as serum cotinine levels were not measured to confirm smoking status. (5) ICD-9 codes were used to determine entry criteria and outcomes. The VA cohort ICD-9 codes are valid for determining outcomes.
Conclusion
Our findings show that maintaining normal levels of testosterone in testosterone-deficient nonsmokers reduces all-cause mortality and MI. Cigarette smoking negates the beneficial effects of testosterone level normalization after TRT on MI and all-cause mortality. Adequately powered randomized clinical trials would be needed for conclusive determination of the effects of CS and TRT on CV risk and mortality. However, conducting such a randomized clinical trial in the United States would be prohibitive because smoking is an established risk factor for CVD. Based on the present study, counseling and treatment for smoking cessation would be an important intervention before and during TRT. Acknowledging the limitations of a retrospective analysis, results presented in the article provide insight and information that may be valuable in clinical practice.
Acknowledgments
We thank Ms Salwa Maalouf, MA, MPH, Data Analyst, Kansas City Veterans Affairs Medical Center, Kansas City, MO, for valuable suggestions during resubmission of the manuscript.
The contents of this article are those of the authors. These do not reflect the position and policies of the Department of Veterans Affairs or of the US government.
Footnotes
Grant Support: The study was supported by the Midwest Biomedical Research Foundation, VA Medical Center, Kansas City, MO. M.S. was supported by grant VA BX001037 from the Veterans Affairs Merit Review, Office of Research and Development, Veterans Health Administration, Department of Veterans Affairs, and through grant RO1DK1074901 from the National Institutes of Health/the National Institute of Diabetes and Digestive and Kidney Diseases.
Potential Competing Interests: The authors report no competing interests.
References
- 1.Mathers C.D., Boerma T., Ma Fat D. Global and regional causes of death. Br Med Bull. 2009;92:7–32. doi: 10.1093/bmb/ldp028. [DOI] [PubMed] [Google Scholar]
- 2.Nikiforov S.V., Mamaev V.B. The development of sex differences in cardiovascular disease mortality: a historical perspective. Am J Public Health. 1998;88(9):1348–1353. doi: 10.2105/ajph.88.9.1348. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Wingard D.L., Suarez L., Barrett-Connor E. The sex differential in mortality from all causes and ischemic heart disease. Am J Epidemiol. 1983;117(2):165–172. doi: 10.1093/oxfordjournals.aje.a113527. [DOI] [PubMed] [Google Scholar]
- 4.Njolstad I., Arnesen E., Lund-Larsen P.G. Smoking, serum lipids, blood pressure, and sex differences in myocardial infarction: a 12-year follow-up of the Finnmark Study. Circulation. 1996;93(3):450–456. doi: 10.1161/01.cir.93.3.450. [DOI] [PubMed] [Google Scholar]
- 5.Ajayi A.A., Mathur R., Halushka P.V. Testosterone increases human platelet thromboxane A2 receptor density and aggregation responses. Circulation. 1995;91(11):2742–2747. doi: 10.1161/01.cir.91.11.2742. [DOI] [PubMed] [Google Scholar]
- 6.Sharma R., Oni O.A., Gupta K. Normalization of testosterone level is associated with reduced incidence of myocardial infarction and mortality in men. Eur Heart J. 2015;36(40):2706–2715. doi: 10.1093/eurheartj/ehv346. [DOI] [PubMed] [Google Scholar]
- 7.Kloner R.A., Carson C., III, Dobs A., Kopecky S., Mohler E.R., III Testosterone and cardiovascular disease. J Am Coll Cardiol. 2016;67(5):545–557. doi: 10.1016/j.jacc.2015.12.005. [DOI] [PubMed] [Google Scholar]
- 8.Baillargeon J., Urban R.J., Kuo Y.F. Risk of myocardial infarction in older men receiving testosterone therapy. Ann Pharmacother. 2014;48(9):1138–1144. doi: 10.1177/1060028014539918. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Corona G., Maseroli E., Rastrelli G. Cardiovascular risk associated with testosterone-boosting medications: a systematic review and meta-analysis. Expert Opin Drug Saf. 2014;13(10):1327–1351. doi: 10.1517/14740338.2014.950653. [DOI] [PubMed] [Google Scholar]
- 10.Vigen R., O'Donnell C.I., Baron A.E. Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels. JAMA. 2013;310(17):1829–1836. doi: 10.1001/jama.2013.280386. [DOI] [PubMed] [Google Scholar]
- 11.Basaria S., Coviello A.D., Travison T.G. Adverse events associated with testosterone administration. N Engl J Med. 2010;363(2):109–122. doi: 10.1056/NEJMoa1000485. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Chen Z., Peto R., Zhou M., China Kadoorie Biobank (CKB) collaborative group Contrasting male and female trends in tobacco-attributed mortality in China: evidence from successive nationwide prospective cohort studies. Lancet. 2015;386(10002):1447–1456. doi: 10.1016/S0140-6736(15)00340-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Ambrose J.A., Barua R.S. The pathophysiology of cigarette smoking and cardiovascular disease: an update. J Am Coll Cardiol. 2004;43(10):1731–1737. doi: 10.1016/j.jacc.2003.12.047. [DOI] [PubMed] [Google Scholar]
- 14.Critchley J.A., Capewell S. Mortality risk reduction associated with smoking cessation in patients with coronary heart disease: a systematic review. JAMA. 2003;290(1):86–97. doi: 10.1001/jama.290.1.86. [DOI] [PubMed] [Google Scholar]
- 15.Morris P.B., Ference B.A., Jahangir E. Cardiovascular effects of exposure to cigarette smoke and electronic cigarettes: clinical perspectives from the Prevention of Cardiovascular Disease Section Leadership Council and Early Career Councils of the American College of Cardiology. J Am Coll Cardiol. 2015;66(12):1378–1391. doi: 10.1016/j.jacc.2015.07.037. [DOI] [PubMed] [Google Scholar]
- 16.Wolf P.A., D'Agostino R.B., Kannel W.B., Bonita R., Belanger A.J. Cigarette smoking as a risk factor for stroke. The Framingham Study. JAMA. 1988;259(7):1025–1029. [PubMed] [Google Scholar]
- 17.Barua R.S., Ambrose J.A. Mechanisms of coronary thrombosis in cigarette smoke exposure. Arterioscler Thromb Vasc Biol. 2013;33(7):1460–1467. doi: 10.1161/ATVBAHA.112.300154. [DOI] [PubMed] [Google Scholar]
- 18.Barua R.S., Sharma M., Dileepan K.N. Cigarette smoke amplifies inflammatory response and atherosclerosis progression through activation of the H1R-TLR2/4-COX2 axis. Front Immunol. 2015;6:572. doi: 10.3389/fimmu.2015.00572. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Hutchison S.J., Sudhir K., Chou T.M. Testosterone worsens endothelial dysfunction associated with hypercholesterolemia and environmental tobacco smoke exposure in male rabbit aorta. J Am Coll Cardiol. 1997;29(4):800–807. doi: 10.1016/s0735-1097(96)00570-0. [DOI] [PubMed] [Google Scholar]
- 20.US Department of Veterans Affairs VA Informatics and Computing Infrastructure (VINCI) http://www.hsrd.research.va.gov/for_researchers/vinci/default.cfm Available at: Accessed May 25, 2017.
- 21.Byrd J.B., Vigen R., Plomondon M.E. Data quality of an electronic health record tool to support VA cardiac catheterization laboratory quality improvement: the VA Clinical Assessment, Reporting, and Tracking System for Cath Labs (CART) program. Am Heart J. 2013;165(3):434–440. doi: 10.1016/j.ahj.2012.12.009. [DOI] [PubMed] [Google Scholar]
- 22.Bhasin S., Cunningham G.R., Hayes F.J., Task Force, Endocrine Society Testosterone therapy in men with androgen deficiency syndromes: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2010;95(6):2536–2559. doi: 10.1210/jc.2009-2354. [DOI] [PubMed] [Google Scholar]
- 23.Lazarou S., Reyes-Vallejo L., Morgentaler A. Wide variability in laboratory reference values for serum testosterone. J Sex Med. 2006;3(6):1085–1089. doi: 10.1111/j.1743-6109.2006.00334.x. [DOI] [PubMed] [Google Scholar]
- 24.Rosner W., Auchus R.J., Azziz R., Sluss P.M., Raff H. Position statement: utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. J Clin Endocrinol Metab. 2007;92(2):405–413. doi: 10.1210/jc.2006-1864. [DOI] [PubMed] [Google Scholar]
- 25.Wang C., Catlin D.H., Demers L.M., Starcevic B., Swerdloff R.S. Measurement of total serum testosterone in adult men: comparison of current laboratory methods versus liquid chromatography-tandem mass spectrometry. J Clin Endocrinol Metab. 2004;89(2):534–543. doi: 10.1210/jc.2003-031287. [DOI] [PubMed] [Google Scholar]
- 26.Vesper H.W., Botelho J.C. Standardization of testosterone measurements in humans. J Steroid Biochem Mol Biol. 2010;121(3-5):513–519. doi: 10.1016/j.jsbmb.2010.03.032. [DOI] [PubMed] [Google Scholar]
- 27.Austin P.C. An introduction to propensity score methods for reducing the effects of confounding in observational studies. Multivariate Behav Res. 2011;46(3):399–424. doi: 10.1080/00273171.2011.568786. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Harder V.S., Stuart E.A., Anthony J.C. Propensity score techniques and the assessment of measured covariate balance to test causal associations in psychological research. Psychol Methods. 2010;15(3):234–249. doi: 10.1037/a0019623. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Bagatell C.J., Bremner W.J. Androgens in men–uses and abuses. N Engl J Med. 1996;334(11):707–714. doi: 10.1056/NEJM199603143341107. [DOI] [PubMed] [Google Scholar]
- 30.Cawthon P.M., Ensrud K.E., Laughlin G.A., Osteoporotic Fractures in Men (MrOS) Research Group Sex hormones and frailty in older men: the osteoporotic fractures in men (MrOS) study. J Clin Endocrinol Metab. 2009;94(10):3806–3815. doi: 10.1210/jc.2009-0417. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Finkle W.D., Greenland S., Ridgeway G.K. Increased risk of non-fatal myocardial infarction following testosterone therapy prescription in men. PLoS One. 2014;9(1):e85805. doi: 10.1371/journal.pone.0085805. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Xu L., Freeman G., Cowling B.J., Schooling C.M. Testosterone therapy and cardiovascular events among men: a systematic review and meta-analysis of placebo-controlled randomized trials. BMC Med. 2013;11:108. doi: 10.1186/1741-7015-11-108. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Malkin C.J., Pugh P.J., Morris P.D., Asif S., Jones T.H., Channer K.S. Low serum testosterone and increased mortality in men with coronary heart disease. Heart. 2010;96(22):1821–1825. doi: 10.1136/hrt.2010.195412. [DOI] [PubMed] [Google Scholar]
- 34.Tivesten A., Mellstrom D., Jutberger H. Low serum testosterone and high serum estradiol associate with lower extremity peripheral arterial disease in elderly men. The MrOS Study in Sweden. J Am Coll Cardiol. 2007;50(11):1070–1076. doi: 10.1016/j.jacc.2007.04.088. [DOI] [PubMed] [Google Scholar]
- 35.Kapoor D., Goodwin E., Channer K.S., Jones T.H. Testosterone replacement therapy improves insulin resistance, glycaemic control, visceral adiposity and hypercholesterolaemia in hypogonadal men with type 2 diabetes. Eur J Endocrinol. 2006;154(6):899–906. doi: 10.1530/eje.1.02166. [DOI] [PubMed] [Google Scholar]
- 36.Heufelder A.E., Saad F., Bunck M.C., Gooren L. Fifty-two-week treatment with diet and exercise plus transdermal testosterone reverses the metabolic syndrome and improves glycemic control in men with newly diagnosed type 2 diabetes and subnormal plasma testosterone. J Androl. 2009;30(6):726–733. doi: 10.2164/jandrol.108.007005. [DOI] [PubMed] [Google Scholar]
- 37.Halmenschlager G., Rossetto S., Lara G.M., Rhoden E.L. Evaluation of the effects of cigarette smoking on testosterone levels in adult men. J Sex Med. 2009;6(6):1763–1772. doi: 10.1111/j.1743-6109.2009.01227.x. [DOI] [PubMed] [Google Scholar]
- 38.Suzuki R., Allen N.E., Appleby P.N. Lifestyle factors and serum androgens among 636 middle aged men from seven countries in the European Prospective Investigation into Cancer and Nutrition (EPIC) Cancer Causes Control. 2009;20(6):811–821. doi: 10.1007/s10552-009-9326-y. [DOI] [PubMed] [Google Scholar]
- 39.Sharma R., Oni O.A., Chen G. Association between testosterone replacement therapy and the incidence of DVT and pulmonary embolism: a retrospective cohort study of the Veterans Administration Database. Chest. 2016;150:563–571. doi: 10.1016/j.chest.2016.05.007. [DOI] [PubMed] [Google Scholar]