Key words
renin - stroke - myocardial infarction - general population
Introduction
Primary aldosteronism is accompanied by an increase in cardiovascular risk [1]
[2], which may not be fully balanced by treatment [3]
[4]. For instance, the association of primary aldosteronism with adverse
cardiovascular outcomes persisted after treatment with mineralocorticoid receptor
antagonists despite normalization of the blood pressure, as long as renin remained
suppressed [5], indicating that even
moderately increased mineralocorticoid receptor activation results in cardiovascular
alterations. The subsequent question whether plasma aldosterone levels are linked to
cardiovascular risk beyond (diagnosed) primary aldosteronism has mainly been
investigated in populations with a high risk of cardiovascular disease. For
instance, plasma aldosterone was associated with adverse outcomes, including acute
ischemic events and cardiovascular and all-cause mortality in patients submitted for
coronary angiography [6], referred for
elective coronary angioplasty [7], with
stable coronary artery disease [8], after
acute myocardial infarction [9] and with
chronic heart failure [2]. In line,
mineralocorticoid receptor blockade improved the cardiovascular adverse event rate
and survival of patients after myocardial infarction despite plasma aldosterone
levels in the normal range [10]
[11]
[12]
[13]
[14]. Preclinical studies elucidate
possible mechanisms behind these observations. In mice, cardiomyocyte-specific
mineralocorticoid receptor deficiency improved infarct healing and prevented adverse
cardiac remodeling [15], whereas
aldosterone infusion promoted atherosclerosis with an inflammatory plaque phenotype
[16]. Pro-atherogenic aldosterone
effects were mediated by elevated intercellular adhesion molecule 1 (ICAM-1)
expression [17]. Further, aldosterone
increased the expression of ICAM-1 and the adherence of monocytes on human coronary
endothelial cells [18] and interleukin
(IL)-6 production in human umbilical vein endothelial cells [19]. In primary aldosteronism, plasma IL-6
[19], as well as IL-6 and tumor
necrosis factor-α (TNF-α) in perirenal adipose tissue, were elevated
[20]. Thus, vascular adhesion,
inflammation and fibrosis are possible connections between aldosterone and
atherosclerosis [21].
Given the putative link of moderately elevated mineralocorticoid receptor activation
with atherosclerosis, adverse cardiovascular outcomes and mortality, we investigated
the association of aldosterone with cardiovascular events, cardiovascular and
all-cause mortality in the population-based KORA F4 study. Considering the
postulated proinflammatory effects of aldosterone on atherosclerosis, we further
examined the association of aldosterone with selected markers of subclinical
inflammation.
Methods
Study participants and definition of variables
The KORA (Cooperative Health Research in the Region of Augsburg) F4
(2006–2008) study included 3080 participants. The study was approved by
the Ethics Committees of the Bavarian Medical Association (approval number
06068) in adherence to the declaration of Helsinki. All participants gave
written informed consent. Recruitment and eligibility criteria, study design,
standardized sampling methods and data collection (medical history, medication,
anthropometric and blood pressure measurements) have been described in detail
elsewhere [22].
The outcomes all-cause and cardiovascular mortality (ICD-9 codes 390–459
and 798) were ascertained by regularly checking the status of the participants
through the population registries until 2016. Death certificates were obtained
from the local health authorities. The median (1st quartile; 3rd quartile)
follow-up time was 8.7 (8.2; 9.1) years. Myocardial infarction and stroke at
baseline were self-reported diagnoses. Incident myocardial infarction occurring
until the age of 74 years (for cases occurring before 2009) and until the age of
84 years (for cases occurring since 2009) was assessed by surveillance through
the local myocardial infarction registry. Incident non-fatal myocardial
infarction occurring in participants >74 and >84 years,
respectively, depending on the year of occurrence, or residing outside the study
area and non-fatal stroke were assessed by postal follow-up questionnaires. All
self-reported incident stroke and myocardial infarction cases occurring outside
the study area or in persons >74 or 84 years and the date of diagnosis
were validated using data from hospital records of participants and their
attending physicians. Incidents of stroke and myocardial infarction were pooled
to a combined endpoint, with only the first event taken into account in case of
several events. Participants with prevalent stroke (n=67) or prevalent
myocardial infarction (n=80), or missing data on incident stroke
(n=206) and myocardial infarction (n=24) were excluded from the
respective analyses. The follow-up time (median (1st quartile; 3rd quartile))
was 8.6 (8.1; 9.0) years for stroke and 8.6 (8.2; 9.1) years for myocardial
infarction. Arterial hypertension was defined as a systolic blood pressure
≥140 mmHg and/or a diastolic blood pressure
≥90 mmHg and/or intake of anti-hypertensive medication,
given that the participants were aware of being hypertensive. The definition of
the covariables, diabetes mellitus, smoking and physical activity were described
before [23].
Laboratory measurements
Measurements of high-sensitivity C-reactive protein (hsCRP) were available for
2931 participants; IL-6, TNF-α, IL-18, soluble intercellular adhesion
molecule-1 (sICAM-1), myeloperoxidase (MPO), IL-22 and IL-1 receptor antagonist
(IL-1RA) were available for 1076 participants aged ≥62 years. Blood
samples were collected after an overnight fast of at least eight hours in a
sitting position after a rest of 10 min (sitting) and were kept at room
temperature until centrifugation. Plasma was separated immediately and serum
after 30 min. Samples were assayed immediately or stored at −80
°C. Plasma renin concentrations were measured using the Liaison active
renin assay (Diasorin, Dietzenbach, Germany) using monoclonal antibodies to only
detect active renin molecules without interference with pro-renin. Intra- and
inter-assay coefficients of variation were less than 5.6% and
12.2%, respectively, and the functional sensitivity was
<2.0 μU/mL. Plasma aldosterone concentrations
were measured within 2 years from the sampling date with an in-house
immunoflurometric assay involving an extraction step before the measurements as
described previously [24]. Inter- and
intra-assay coefficients of variation were 15.2% and 7.3% in
low, and 8.0% and 4.4% in high concentrations, respectively.
Measurements procedures of serum creatinine, glucose, high-density lipoprotein
cholesterol (HDL), low-density lipoprotein cholesterol (LDL), hsCRP, IL-6,
TNF-α, IL-18, sICAM-1, MPO, IL-22, and Il-1RA are described elsewhere
[23]. Estimated glomerular
filtration rate (eGFR) was calculated using the Chronic Kidney Disease
Epidemiology Collaboration (CKD-EPI) equation (2009) based on serum
creatinine.
Statistical analyses
Characteristics of the study participants were compared between survivors and
non-survivors using t-tests in the case of approximately normally distributed
variables. Mann-Whitney U-tests were performed for variables with skewed
distributions. Binomial proportions were compared with Chi-square tests. The
associations of aldosterone with cardiovascular events and mortality were
examined using Cox proportional hazard models. The associations of aldosterone
with biomarkers of subclinical inflammation were assessed with linear regression
models. Continuous variables were transformed to approach Gaussian distribution
by the probability integral transformation followed by an inverse transform
sampling and were used in calculations per one standard deviation. The
associations were adjusted for renin, sex, age, body mass index (BMI), arterial
hypertension, diabetes, estimated glomerular filtration rate, low- and
high-density lipoprotein cholesterol, physical activity, smoking, use of
angiotensin-converting enzyme inhibitors, angiotensin receptor blockers,
beta-blockers, diuretics and calcium channel blockers. For power calculation for
Cox proportional hazards regression for nonbinary covariates, the formula
derived by Hsieh and Lavori was used [25]. The level of statistical significance was set at 5%
(two-sided). The calculations were performed using the statistical environment
R, version 3.6.0 (R Development Core Team. R: A Language and Environment for
Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing;
2019).
Results
[Table 1] displays the baseline
characteristics of the study population. There was no difference in renin and
aldosterone levels in non-survivors compared to survivors.
Table 1 Characteristics of the study participants; overall and
stratified by survival status 1.
|
Total study cohort (n=2935)
|
Survivors (n=2690)
|
All-cause death (n=245)
|
p-value
|
|
Male sex n (%)
|
1420 (48)
|
1272 (47)
|
148 (60)
|
<0.001 4
|
|
Age (years)
|
56.2±13.2
|
54.9±12.7
|
70.8±9.2
|
<0.001 2
|
|
BMI (kg/m2)
|
27.6±4.8
|
27.5±4.8
|
29.2±5.0
|
<0.001 2
|
|
eGFR (mL/min/1.73 m²)
|
89.2 (77.6; 100.0)
|
90.4 (78.9; 100.8)
|
73.9 (61.2; 86.4)
|
<0.001 3
|
|
Arterial hypertension n (%)
|
1125 (38)
|
959 (36)
|
166 (68)
|
<0.001 4
|
|
Type 2 diabetes n (%)
|
334 (11)
|
256 (10)
|
78 (32)
|
<0.001 4
|
|
Low-density lipoprotein (mmol/L)
|
3.44 (2.88; 4.06)
|
3.44 (2.87; 4.06)
|
3.41 (2.82; 3.95)
|
0.372 3
|
|
High-density lipoprotein (mmol/L)
|
1.40 (1.16; 1.68)
|
1.40 (1.16; 1.68)
|
1.34 (1.11; 1.60)
|
0.074 3
|
|
Smoker n (%) (current/former)
|
523 (18)/1189 (41)
|
491 (18)/1074 (40)
|
32 (13)/115 (47)
|
0.051/0.040 4
|
|
Physically inactive
|
1331 (45)
|
1178 (44)
|
153 (62)
|
<0.001 4
|
|
Plasma renin (µU/mL)
|
6.84 (3.72; 12.06)
|
6.78 (3.78; 11.82)
|
7.68 (3.06; 16.44)
|
0.111 3
|
|
Plasma aldosterone (ng/L)
|
38 (26; 58)
|
38 (26; 58)
|
38 (22; 66)
|
0.717 3
|
|
Aldosterone-to-renin ratio
|
5.65 (2.93; 10.75)
|
5.71 (3.02; 10.74)
|
4.91 (2.26; 11.71)
|
0.130 3
|
|
Angiotensin-converting enzyme inhibitors n (%)
|
223 (8)
|
196 (7)
|
27 (11)
|
0.050 4
|
|
Angiotensin receptor blockers n (%)
|
385 (13)
|
301 (11)
|
84 (34)
|
<0.001 4
|
|
Beta blockers n (%)
|
554 (19)
|
454 (17)
|
100 (41)
|
<0.001 4
|
|
Diuretics n (%)
|
522 (18)
|
420 (16)
|
102 (42)
|
<0.001 4
|
|
Calcium channel blockers n (%)
|
230 (8)
|
178 (7)
|
52 (21)
|
<0.001 4
|
1 mean±standard deviation, median (1st quartile; 3rd
quartile), or number of participants (proportion in %); 2
t-test; 3 Mann-Whitney U-test; 4 Chi-square test; the
p-value is related to the null hypothesis of no difference between survivors
and non-survivors.
In the fully adjusted model, aldosterone was not significantly associated with
incident stroke, myocardial infarction, the combined endpoint including stroke and
myocardial infarction, or with cardiovascular mortality ([Table 2]). The power analysis revealed
that given the observed event rate and hazard ratio of 1.18, 5216 participants
should have been included to detect a significant association of aldosterone with
the combined cardiovascular endpoint with a power of 0.8. With the available number
of study participants (n=2597 for the combined cardiovascular outcome), a
hazard ratio of at least 1.27 would have been necessary for a power of 0.8.
Table 2 Hazard ratios (95% confidence interval, CI) of
the association between aldosterone (per standard deviation) and
cardiovascular events, cardiovascular mortality, and all-cause
mortality.
|
Unadjusted analyses
|
Adjusted analyses 1
|
|
Outcome and numbers (total/events)
|
HR (95% CI)
|
p value
|
HR (95% CI)
|
p-value
|
|
Stroke n=2662/104
|
1.03 (0.84–1.25)
|
0.810
|
1.15 (0.93–1.43)
|
0.188
|
|
Myocardial infarction n=2831/90
|
0.92 (0.74–1.13)
|
0.422
|
0.99 (0.78–1.24)
|
0.937
|
|
Cardiovascular events (combined) n=2597/159
|
1.03 (0.88–1.21)
|
0.685
|
1.18 (0.99–1.41)
|
0.061
|
|
Cardiovascular mortalityn=2935/105
|
1.02 (0.84–1.24)
|
0.845
|
1.19 (0.97–1.47)
|
0.102
|
|
All-cause mortality n=2935/245
|
1.04 (0.92–1.19)
|
0.540
|
1.20 (1.04–1.37)
|
0.0099
|
1 The results are adjusted for sex, age, renin, body mass index,
hypertension, diabetes, estimated glomerular filtration rate, low-density
lipoprotein, high-density lipoprotein, smoking, physical activity, use of
angiotensin-converting enzyme inhibitors, angiotensin receptor blockers,
beta-blockers, diuretics and calcium channel blockers. The bold print
indicates significance in the fully adjusted model after correction for
multiple testing using the Bonferroni method (p<0.01 (0.05 ÷
5)).
There was a significant association between high aldosterone levels and all-cause
mortality (HR (95% CI) 1.20 (1.04–1.37); p=0.0099) that was
not substantially altered (HR (95% CI) 1.21 (1.05–1.39);
p=0.0098) by the exclusion of participants with aldosterone levels
>160 ng/L (n=59).
Renin and the aldosterone-to-renin ratio were not significantly associated with
all-cause-mortality (HR (95% CI) 0.97 (0.86–1.10) and 1.11
(0.98–1.26), respectively) or with cardiovascular events (Table
S1).
We stratified the study cohort by factors possibly influencing the association of
aldosterone with all-cause mortality (sex, age, BMI, diabetes mellitus and eGFR).
The association of aldosterone with all-cause mortality was only significant in men
(vs. women), participants ≥60 years (vs. <60 years), with a BMI
≥30 kg/m² (vs.
<30 kg/m²), without diabetes (vs. type 2 diabetes)
and with an eGFR ≥60 mL/min/1.73 m²
(vs. <60 mL/min/1.73). However, none of the
interaction terms were statistically significant (Table S2).
Aldosterone was not significantly associated with any of the analyzed markers of
subclinical inflammation (hsCRP, IL-6, TNF-α, IL-18, sICAM-1, MPO, IL-22 and
IL-1RA; Table S3).
Discussion
Higher aldosterone levels were moderately associated with all-cause mortality in the
KORA F4 study. There was a non-significant trend towards a positive association with
stroke, the combined cardiovascular endpoint and cardiovascular mortality, but not
with myocardial infarction. Aldosterone was not associated with any of the examined
markers of subclinical inflammation.
In contrast to populations at high risk for cardiovascular diseases, previous studies
investigating the association of aldosterone with cardiovascular events and
mortality in the general population yielded inconsistent results. Aldosterone was
associated with all-cause mortality in a population-based cohort from Olmsted
County, MN (n=1674), with an HR of 1.14 after adjustment for sex, age and
BMI [26]. However, this association was
no longer significant after the exclusion of participants with aldosterone levels
above the normal range (n=95). In contrast, the exclusion of participants
with aldosterone levels above the normal range did not alter the association of
aldosterone with all-cause mortality in the KORA F4 study. Interestingly, in a
Japanese population-based study (n=1310), the aldosterone-to-renin ratio was
inversely associated with all-cause mortality [27], whereas plasma renin activity was positively associated with
all-cause mortality [28]. However, in
KORA F4, neither the aldosterone-to-renin ratio nor renin was significantly
associated with cardiovascular events or mortality. The HR for the
aldosterone-to-renin ratio showed a positive association with all-cause mortality,
whereas the HR for renin was <1.00. In 3866 participants of the Chronic
Renal Insufficiency Cohort, aldosterone was not associated with atherosclerotic
events and all-cause mortality [29],
whereas in the Ludwigshafen Risk and Cardiovascular Health (LURIC) study (including
patients referred for coronary angiography), the association of aldosterone with
cardiovascular mortality was only present in participants with an eGFR in the lowest
tertile (mean eGFR 61.9 mL/min/1.73 m²), but
not in tertile 2 and 3 [30]. In the
current study, we found no significant interaction with the eGFR, although the
association of aldosterone with mortality was only present in participants with an
eGFR ≥60 mL/min/1.73 m² –
contrary to that observed in the LURIC study, but in line with the Chronic Renal
Insufficiency Cohort with no association of aldosterone with mortality in chronic
kidney disease.
Since experimental data suggest a role of mineralocorticoid receptor activation in
obesity-related endothelial dysfunction [31], Western diet-induced aortic stiffness, fibrosis and proinflammatory
responses [32], and coronary
vasoconstriction and atherosclerosis in metabolic syndrome [33], we further tested the interaction
with BMI and diabetes mellitus. Both were not significant, although the association
of aldosterone with mortality was stronger in participants with a BMI
≥30 kg/m² compared to participants with a BMI
<30 kg/m². However, the association of aldosterone
with mortality was only significant in participants without diabetes as compared to
participants with type 2 diabetes.
Our study included biomarkers reflecting diverse aspects of subclinical inflammation
(hsCRP, IL-6, TNF-α, IL-18), vascular inflammation (sICAM-1), oxidative
stress (MPO) and anti-inflammatory biomarkers (IL-22 and IL-1RA). However, none of
them showed a relevant association with aldosterone levels, so they may not
represent mediators in the relationship between aldosterone and mortality.
Limitation
Although the present analysis is based on a large, well-characterized sample from
the general adult population, the statistical analyses regarding the interaction
terms as well as cardiovascular events and cardiovascular mortality, seem to be
insufficiently powered to draw definitive conclusions. Plasma aldosterone
concentrations were measured using an in-house immunoflurometric assay. Today,
liquid chromatography-mass spectrometry is often preferred due to greater
accuracy, but it requires larger sample volumes and was not available to us at
the time of aldosterone measurements.
Conclusion
Aldosterone was associated with all-cause mortality in the population-based KORA F4
study but not clearly with cardiovascular events, cardiovascular mortality, or
biomarkers of subclinical inflammation, suggesting that the latter associations are
restricted to aldosterone excess and/or populations at high risk for
cardiovascular diseases. Beneficial effects of mineralocorticoid receptor blockade
in patients with heart failure and after myocardial infarction despite normal
aldosterone levels [10]
[11]
[12]
[13]
[14] might, therefore, be explained by the
elevated cardiovascular risk. Plasma measurements may poorly reflect increased
aldosterone tissue levels and paracrine mineralocorticoid effects, as observed in
isolated perfused rat hearts after myocardial infarction [34] and in human failing ventricles [35]. In this regard, the prognostic
clinical significance of mildly elevated plasma aldosterone levels in the general
population appears to be limited.
Author Contribution Statement
Author Contribution Statement
Conception and design of the study: M. Re, BT, CM, CH, MH, AP, WK and WR; collection
of data: BT, M. Re, MB, CT, CM, CH, MH, AP, WK, WR and M. Ro; data analysis,
interpretation of results and manuscript writing: CT, BT, CS, AP and M. Re; all
authors revised the manuscript critically for important intellectual content and
approved the final version.
Data Availability Statement
Data Availability Statement
The data are subject to national data protection laws; restrictions were imposed by
the Ethics Committee of the Bavarian Chamber of Physicians to ensure the data
privacy of the study participants. Therefore, data cannot be made freely available
in a public repository. However, data can be requested through an individual project
agreement with KORA via the online portal KORA.passt (https://epi.helmholtz-muenchen.de/).
