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CLIN. CHEM. 33/4, 518-523 (1987)
518 CLINICALCHEMISTRY,Vol.33, No.4, 1987
Prevalenceof Magnesiumand PotassiumDeficienciesinthe Elderly
Yvan Toultou,’ Jean-Pierre Godard,1 OlMer Ferment,1Claude Chastang,2 Jacques Proust3 Andr#{233}Bogdan,’ Andr#{233}Auz#{233}by,’and
CatherineToultou’
Concentrations of magnesium and potassium in erythrocytes
and plasma were determinedina population of 381 unselect-
ed elderly men and women, most of them in their eighties.
The effects of biological factors (age, sex, weight) and a large
set of pathological conditions, malignant or not, were exam-
ined. Analyses of variance showed a relation between age
and concentrations of plasma potassium and between weight
and concentrations of plasma magnesium. The chi-square
test showed correlations between low concentrations of
plasma magnesium and diabetes, abuse of alcohol and
tobacco, and also between low values for erythrocyte mag-
nesium and hypertension. Low values for plasma potassium
were correlated with hypertension whereas high values were
correlated with cardiovascular disease. Although some of the
differences in the mean concentrations observed were statis-
tically significant, these differences were always small. Most
interesting was the distribution of the concentrations of the
cations. This study shows that assays of both of these
cations in erythrocytes were better than assays in plasma to
evidence a deficiency. Indeed, about 20% of the studied
population had low concentrations of both erythrocyte potas-
sium and magnesium, whereas 2 and 10% had lowvalues for
plasma potassium and magnesium, respectively. This study
underlines the large prevalence of magnesium and potassi-
um deficiencies in the elderly, an observation we could not
attribute to pathology or treatment. Routine electrolyte stud-
ies therefore appear to be justified in aged human subjects.
Addftlonal Keyphrases: variation, source of .age-related ef-
feds electrolytes reference values eiythrocytes di-
abetes alcohol and tobacco abuse
Age is an important variable to take into account in
interpreting biologicaldata.Data dealingwith elderly peo-
ple are often related to subjects in theirsixties(1-6) and the
few people of ages 75 or over are usually integrated into
large age groups, e.g., “older than 60 years.” Reference
values for some biological variables, however, can change
with advanced age, as previously demonstrated for some of
them (7, 8).
As part of a broad study on the biology of aging (7-10), we
wanted to document the cumulative effectsof both age and
pathology on the concentrations of magnesium and potassi-
um in plasma and erythrocytes of an institutionalized
elderly population, taking into account medical history,
biological data, and autopsy findings.
Subjects, MaterIals, and Methods
Plasma and erythrocytes were assayed for magnesium
and potassium over a three-month period (December
‘Department of Biochemistry,Facult#{233}deM#{233}decinePitie-Salp#{234}-
tri#{232}re91, bd. de l’h#{244}pital-75634Paris Cedex13, France.
2Department of Biostatistics, Faculte de Medecine Lariboisiere-
Saint-Louis, Paris, France.
3H#{244}pitalCharles Foix, Ivry, France.
Received June 23, 1986;acceptedJanuary 14, 1987.
through February). The samples were from 381 unselected
elderly subjects (422 for plasma potassium), 75% of whom
were 75 years or older (range 79.9 ±9.5 years) (Table 1
below). All the subjects had the same schedule for meals and
bed rest. The mean daily dietary regimen was as follows:
total calories 1700; proteins 57 g; lipids 81 g; carbohydrates
184 g; Na 64 mmol; K 68 mmol; Ca 18 mmol; and Mg 10
mmol. Most of the patients were hospitalized in long-term-
care units for various diseases that required constant medi-
cal assistance, and therefore they could not be regarded as
representative of a normal, healthy, elderly population. All
had documented medical records from which relevant data
were computer-processed for this study: age, sex, smoking
and (or) alcohol habits, history of respiratory disease (chron-
ic bronchitis, asthma, emphysema, tuberculosis, exposure to
pulmonary toxins), cardiovascular disease (myocardial in-
farction, severe angina pectoris, cardiac failure), gastroin-
testinal disease (ulcer, colitis, diverticulitis, polyposis,
chronic irritable bowel syndrome), liver and biliary disease
(viral hepatitis, cirrhosis, biliaryobstruction), neurological
disease (stroke, senile dementia, chronic hypertensive
encephalopathy, Parkinson’s disease),bone andjoint disease
(severe arthritis, Paget’s disease, gout, pseudogout), chronic
renal failure, diabetes, hypertension, inflammatory syn-
drome (hyper a2-globulinemia, sedimentation rate >80
mm), and malignancy (Table 2 below). Twenty of these
subjects, three men and 17 women (5.2% of the population),
were free of any pathological condition and (or) alcoholic and
smoking habits, and were therefore considered as a control
group (mean age 80.9, SD 8.9 years).
To avoid the effect of circadian variations (11), we collect-
ed venous blood samples at a fixed time (08.00 to 09.30
hours), without inducing stasis, so that correction for a
constant plasma protein concentration was not necessary
(12, 13). “Venoject” tubes containing 150 USP units of
lithium heparin (Terumo Europe NV, Leuven, Belgium)
were used in collecting the 10-mL blood specimens, which
were immediately centrifuged (2000 x g, 10 mm). After
separating the plasma, we carefully removed the buffy coat,
then washed the erythrocytes in choline-Ringer’s solution
(composition, in mmol/L: choline Cl 146; MgC12 1; CaCl2 1;
NaC1 5; orthophosphoric acid 2.5; Tris buffer 2.5 topH 7.4),
then storing them at -20 #{176}C.We then processed all samples
in one large series at the end of the protocol.
Erythrocytes were diluted 50-fold with de-ionized water
for potassium determination. Normal and pathological com-
mercial control sera were included in each series of analy-
ses. We used an IL 143 flamephotometer(Instrumentation
Laboratory, Lexington, MA) for both plasma and erythro-
cyte potassium determinations, with lithium as internal
standard. The CVs were 1.4 and 1.0% for potassium concen-
trations of 4.6 and 6.3 mmol/L, respectively. For magnesium
determinations we diluted plasma and erythrocyte samples
50-fold with a 5 g/L solution of lanthanum chloride, then
used an atomic absorption spectrophotometer (Model 372;
Perkin-Elmer SA, Division Instruments, Bois d’Arcy,
France): X =285 nm; slit width 7 nm. The CV was 1.3%.
Plasma creatinine was determined by the Jaff#{233}reaction
Ergthrocytss Plasma
patients Prcentag. ofpatientshavingMg Co
mean±SO
Percentage of patients having Mg Co
mean±SO<074 0.74-0.90 >0.90
<2.05 2.05-2.62 >2.62
Age, years’
s64 26 23.1 69.2 7.7 2.29 ±0.32 7.7 84.6 7.7 0.82 ±0.07
65-74 69 14.5 78.3 7.2 2.34 ±0.27 14.5 79.7 5.8 0.82 ±0.07
75-84 162 21.0 70.4 8.6 2.29 ±0.29 9.1 87.2 3.7 0.82 ±0.07
85 124 23.4 60.5 16.1 2.33 ±0.32 8.1 87.9 4.0 0.83 ±0.07
Allsubjects
AllSUbjectsb 381
198 20.7
19.4 68.5
66.8 10.8
13.7 2.31 ±0.30
2.33 ±0.30 9.7
5.5 85.9
90.8 4.4
3.7 0.82 ±0.07
0.83 ±0.07
Sex’ Men 90 20.0 71.1 8.9 2.30 ±0.30 14.4 81.1 4.4 0.81 ±0.07
Women 291 21.0 67.7 11.3 2.32 ±0.30 8.2 87.4 4.4 0.83 ±0.07
Weight, kg’
39 21 14.3 76.2 9.5 2.32 ±0.30 5.0 80.0 15.0 0.87 ±0.07
40-49 82 19.7 66.7 13.6 2.34 ±0.29 6.2 92.6 1.2 0.80 ±0.06
50-59 110 19.4 69.4 11.1 2.31 ±0.28 4.6 89.9 5.5 0.83 ±0.07
60-69 90 19.1 71.9 9.0 2.31 ±0.31 14.6 80.9 4.5 0.82 ±0.07
70-79 56 27.3 65.4 7.3 2.26 ±0.32 12.5 83.9 3.6 0.80 ±0.06
80-89 16 25.0 56.3 18.7 2.28 ±0.34 18.8 81.2 0.0 0.81 ±0.07
90-100 6 50.0 33.3 16.7 2.31 ±0.35 16.7 83.3 0.0 0.85 ±0.08
‘An effectof weight, but not ofsexor age,wasvalidatedon plasmavaluesbyANOVA(see Results).
bRiCJi8ted dataafterexclusionof patientswithtreatment,diseases,or addictionsknowntoafterthe cationconcentration(seetext).
CLINICAL CHEMISTRY,Vol. 33, No. 4, 1987 519
Table 1. DIstribution and Mean Concentrations (mmol/L) of Magnesium In Erythrocytee and Plasma of 381 PatIents
According to Age, Sex, and WeIght
with an AutoAnalyzer (Technicon Co., Domont, France).
The CVs were 2.6 and 1.3% forcreatinine concentrations of
119 and 501 pinol/L, respectively.
The statistical significance of the relation between the
different pathological conditions and concentrations of mag-
nesium and potassium in plasma and erythrocytes was
assessedby the chi-square test. Student’s t-test was used for
comparing the means. We submitted the data to analysis of
variance (ovA), using the GLM program (S.A.S. Institute,
Cary, NC).
During the follow-up to this study, some of the patients
died; a complete autopsy was done on 112. The relation
between significantautopsy findings (occult chronic disease,
undiagnosed neoplasms, and the like) and cation concentra-
tions in plasma or erythrocyte was assessed by the chi-
square test.
Results
We determined plasma creatinine to assess the renal
function of the subjects of this study; values were in the so-
callednormal range in subjects who were free of chronic
renal failure (8).
Magnesium
Effect ofage, sex and weight. As Table 1 shows, about 30%
of the population studied had abnormal values for erythro-
cyte magnesium, either low (20.7%) or high (10.8%), and
about 14% had abnormal values for plasma magnesium
(low: 9.7%, high: 4.4%)
A two-way ANOVA showed no effect of age, sex, or sex-age
interaction on plasma or erythrocyte magnesium.
Aone-way ANOVA showed the prevalence of low values of
plasma magnesium (p =0.005) with increased weight
(Table 1).
Effect of alcohol addiction and cigarette smoking. Forty-
four subjects(11.5%of the population)were considered tobe
heavy smokers (0.5-2.0 packs a day for more than 10 years)
and 25(6.5%) were known to be chronic abusers of alcohol.
Their plasma magnesium values were significantly lower (p
<0.05) than in the non-smoking and non-drinking popula-
tion (Table 2). Accordingly, the number of subjects with low
concentrations of plasma magnesium was significantly
greater among the population of smokers and alcoholics (p
<0.05 and p <0.008, respectively).We observed no differ-
ence in the values for erythrocyte magnesium in smokers
and alcoholics.
Effects of illness. The number of patients with low concen-
trations of plasma magnesium was significantly greater in
patients with diabetes (p <0.01).
We found no relation between abnormal values for mag-
nesium in plasma or erythrocytes and autopsy findings in
the 112 patients who were autopsied among the population
studied (Table 3).
Exclusion of patients with abnormal cation concentrations
explicable by known causes. The relatively high percentage
of elderly subjectswith low values for Mg in plasma and
erythrocytes (9.7 and 20.7%, respectively) and the differ-
ences related to weight (plasma magnesium) could be the
results of all the causes we have shown (Table 2) to alter the
levels of the cation-i.e., diabetes, smoking, and (or) alcohol
addiction. The data were thus recalculated after exclusion of
both such diseased patients, patients with renal failure, and
patients being treated with diuretics or antihypertensive
drugs. The distribution of the patients with low and high
concentrations of Mg in plasma and erythrocytes was not
noticeably modified thereby (Table 1).
Potassium
Effect of age, sex, and weight. About 11% of the subjects
had abnormal values for plasma potassium, either low
(1.9%) or high (9.7%), and 22.6% had low values for erythro-
cyte potassium (Table 4).
ANOVA showed that age, sex, and weight did not influence
erythrocyte potassium, whereas we observed arelation
between age and the incidence of high values for plasma
potassium (p <0.05).
Effects of akohol addiction and cigarette smoking. We
observed no significant difference in values for erythrocyte
21.3
15.4 67.0
82.1
No. of
20
342
39
276
105
281
56
44
310
46
25
307
74
Percentageofpatientshaving Mg Concn,
mean ± SD
2.13 ±0.29
Percentageof patientshaving Mg Concn,
mean ±SD
0.84 ±0.06
<2.05
40.0 2.05-2.62
60.0 >2.62
0.0 <0.74
5.0 0.74-0.90
95.0 >0.90
0.0
11.7
2.5 2.31 ±0.31
2.32 ±0.25 8.4
20.5k 86.6
795
18.5
26.7k 70.9
61.9 8.3
13.3 87.7
81.0
21.9
21.8
14.0
66.2
67.3
83.7
11.9
10.9
2.3
2.32 ±0.31
2.32 ±0.30
2.30 ±0.26
8.9
7.3
18.6
86.8
87.3
76.7
30.1
28.3
16.0
69.2
58.7
80.0
10.7
13.0
4.0
2.31 ±0.30
2.27 ±0.31
2.33 ±0.27
8.1
12.8
24.0k
86.7
85.1
76.0
19.9
24.3 69.6
63.5 10.5
12.2 2.31 ±0.29
2.31 ±0.34 9.7
9.5 86.0
85.1 4.2
5.4 0.82 ±0.07
0.81 ±0.07
21.7
5.6
15.4
67.1
88.9
76.9
10.3
0.0
7.1
85.8
100.0
71.4
4.0
0.0
21,4
0.82 ±0.07
0.83 ±0.05
0.84 ±0.09
20.1
25.0 69.3
63.5 9.4
11.5 85.8
86.5
20.4
22.2 69.2
65.1 86.6
82.5
21.3
16.7 67.3
77.1 86.5
81.6
20.4
22.6 69.3
64.5 85.7
87.1
20.6
21.2 69.2
65.2 85.8
86.6
24.1
17.1 66.8
70.3 83.5
85.3
20.5
21.4 68.4
69.1
Table 2. Effects of Pathology on DistributIon and Mean Concentrations of Erythrocyte and Plasma MagnesIum In
520 CLINICALCHEMISTRY, Voi. 33, No. 4, 1987
381 Elderly Subjects
Pathology
None
Diabetes9
no
yes
Hypertension9
no
yes
Smokers’
never
past
current
Alcoholics9
never
past
current
Heart diseases
no
yes
Cancerno 350
past 18
evoiutive 13
Renal failure
no 329
yes 52
Inflammatory syndrome
no 318
yes 63
Gastro-intestinaldiseases
no 333
yes 48
Liver and biliaty diseases
no 319
yes 62
Bone and joint diseases
no 315
yes 66
Neurologic diseases
no 199
yes 182
Respiratory diseases
no 297
yes 84
Erythrocytes
10.6 2.32 ±0.28
11.4 2.28 ±0.34
11.1 2.31±0.30
5.5 2.35 ±0.27
7.7 2.29 ±0.36
10.6 2.31 ±0.30
11.5 2.28 ±0.31
10.4 2.31 ±0.30 9.1
12.7 2.30 ±0.30 12.7
11.4 2.31 ±0.31 9.3
6.2 2.32 ±0.25 12.2
10.3 2.31 ±0.30 9.3
12.9 2.31 ±0.32 11.3
10.2 2.31 ±0.30 9.5
13.6 2.32 ±0.32 10.4
9.1 2.28 ±0.31 11.0
12.6 2.35 ±0.29 8.2
11.1 2.31 ±0.30 9.7 85.6
9.5 2.31 ±0.29 9.5 86.9
Plasma
4.9 0.83 ±0.07
0.0 0.79 ±007D
4.0 0.83 ±0.07
5.7 0.82 ±0.08
4.3 0.83 ±0.07
5.5 0.83 ±0.07
4.7 0.80 ±007b
5.2 0.83 ±0.07
2.1 0.82 ±0.07
0.0 0.79 ±007b
4.8 0.82 ±0.07
1.9 0.82 ±0.07
4.4 0.83 ±0.07
4.8 0.82 ±0.07
4.2 0.82 ±0.07
6.1 0.82 ±0.08
5.0 0.82 ±0.07
1.6 0.82 ±0.07
4.7 0.82 ±0.07
3.0 0.82 ±0.07
5.5 0.82 ±0.07
3.3 0.82 ±0.06
4.7 0.82 ±0.07
3.6 0.81 ±0.06
‘Relationvalidatedby chi-squaretest (see Results). bMeen concentrationssignificantlydifferedby Student’s ttest.
and plasma potassium in smokers or alcoholics (Table 5).
Effect of illness. The number of patients with low values
for plasma potassium was significantly greater among the
hypertensivepatients(p<0.02). However, this relation was
no longer demonstrable when we took into account treat-
ment with diuretics and antthypertensive drugs.
We also found a relation between high values for plasma
potassium (5 mmol/L) and cardiovascular disease (p
<0.02), which persisted even when the data were recalculat-
ed after the exclusion of treated patients (p <0.003).
Potassium concentrations in plasma and erythrocytes
were not altered in other pathological conditions, including
cancer, whatever the localization (Tables 3 and 5) and
autopsy findings (Table 3).
Exclusion of patients with abnormal cation levels explica-
ble by known causes. The proportion of elderly subjects with
low and high values for potassium in plasma and erythro-
cytes was not modified (Table 4) by excluding patients with
hypertension or cardiovascular disease, those being treated
with diuretics and antihypertensive drugs, and (or) those
with alcohol or tobacco addiction-all of which are known to
alter the cation concentration.
DIscussIon
This study points out the unexpectedly high prevalenceof
magnesium and potassium deficiencies in erythrocytes of an
unselected elderly population, a finding not attributable to
either pathology or treatment.
The lower reference limits we used for plasma magnesium
and potassium were 0.74 and 3.5 mmol/L, respectively,
values commonly admitted as defining hypomagnesemia
and hypokalemia (14, 15). Differences between concentra-
tions of potassium in serum and plasma, with higher values
in serum, have been reported (reviewed in 16). This increase
ofpotassium in serum correlated positively with the platelet
and leukocyte counts,but the increase could not be predicted
Table 3. Mean (± SD) ConcentratIons of MagnesIum and PotassIum (mmol/L) In Erythrocytes and Plasma of Elderly
Patients with Malignant DIseases (n =30) and In Autopsied PatIents (n =112)
No. of
patients Erythrocytea
Magnesium Potassium
Piasma Erythrocytss Plasma
Cancer type
SkIn 72.34 ±0.21 0.82 ±0.05 89.7 ±3.7 4.4 ±0.2
Colon 42.46 ±0.32 0.88 ±0.09 91.5 ±1.9 4.6 ±0.6
Bladder 42.31 ±0.16 0.82 ±0.04 93.0 ±3.8 4.6 ±0.3
Breast 22.24 ± 0.24 0.93 ± 0.09 93.0 ±1.4 4.6 ±0.1
Stomach 2 2.03 ±0.34 0.83 ±0.05 91.0 ±4.2 4.6 ±0.3
Prostate 2 2.28 ±0.70 0.74 ±0.03 90.0 ±5.7 4.5 ±0.2
Rectum 1 2.16 0.77 92.0 4.3
Ovary 1 2.61 0.90 98.0 4.6
Uver 1 2.55 0.74 96.0 4.3
KIdney 1 2.18 0.90 96.0 4.2
Metastases of 1 1.63 0.86 86.0 4.4
unproven origin
Other 42.46 ±0.27 0.84 ±0.03 91.5 ±4.4 4.5 ±0.5
Autopsy findings
Gall-bladder llthiasis 32 2.34 ±0.32 0.80 ±0.07 91.1 ±3.4 4.4 ±0.5
Biliary obstruction 9 2.21 ±0.43 0.80 ± 0.08 90.2 ±2.7 4.3 ±0.6
Dlverticulitls 8 2.24 ±0.37 0.82 ±0.06 92.5 ±3.7 4.6 ±0.3
Uversteatosis 11 2.36 ±0.30 0.83 ±0.10 93.3 ±3.4 4.5 ±0.5
Chronic pancreatitis 92.20 ±0.39 0.83 ±0.08 93.8 ±4.1 4.4 ±0.5
Uver fibrosis 9 2.47 ±0.16 0.79 ±0.08 91.8 ±3.5 4.4 ±0.3
Uterine lelomyomata 8 2.37 ± 0.25 0.82 ± 0.06 92.0 ±3.0 4.5 ±0.4
Uver cirrhosis 7 2.14 ±0.31 0.77 ±0.05 92.9 ±4.3 4.4 ±0.5
Ovariancyst 4 2.11 ±0.19 0.81 ±0.03 93.5 ±3.8 4.6 ±0.4
KidneyIlthiasis 42.30 ± 0.47
Variousnon-malignant 11 2.25 ±0.27 0.82 ±0.09 90.5 ±4.1
0.78 ±0.09 91.5 ±4.2 4.6 ±0.3
4.4 ± 0.4
tumors
Table 4. DIstribution and Mean Concentrations (mmol/L) of PotassIum In Erythrocytes (n =381) and Plasma (n =
422) of PatIents AccordIng to Age, Sex, and WeIght
Erythrocytes Plasma
Percentage of patients having
K
No. of
patients <90 90-100 >100
26 30.8
69 23.2
162 21.6
124 21.8
381 22.6
179 17.9
Percentage of patients
having K
Concn, No. of
mean ±SD patients <3.5 3.5-5.0 >5.0
69.2
73.9
77.8
77.4
76.4
81.6
Age. yearsa
64
65-74
75-84
85
all subjects
all subjects1’
Sex’ Men
Women
Weight, kg9
39
40-49
50-59
60-69
70-79
80-89
90-100
90 22.2 76.7
291 22.7 76.3
27
74
184
137
422
193
0.0 96.3
4.1 93.2
1.1 92.4
2.2 78.8
1.9 88.4
1.0 89.1
Concn,
mean±SD
4.3 ±0.4
4.3 ±0.4
4.4 ± 0.4
4.5 ±0.4
4.4 ±0.4
4.4 ±0.4
3.7
2.7
6.5
19.0
9.7
9.9
0.0 90.6 ±4.2
2.9 91.5 ±3.7
0.6 91.9 ±3.6
0.8 91.9 ±3.6
1.0 91.7 ±3.6
0.5 92.1 ±3.5
1.1 91.7±3.5
1.0 91.8 ±3.7
0.0 91.8 ±3.6
1.2 91.7±3.5
1.8 92.2 ±4.0
1.1 91.5±3.7
0.0 91.7 ±3.1
0.0 90.5 ±3.5
0.0 90.7 ±3.5
21 28.6
82 21.0
110 20.4
90 23.6
56 21.8
16 37.5
633.3
71.4
77.8
77.8
75.3
78.2
62.5
66.7
99 3.0 90.9 6.1 4.3 ±0.4
323 1.6 87.6 10.8 4.4 ±0.4c
26 0.0 84.6
90 2.2 84.4
122 1.6 86.1
98 4.1 87.8
59 0.0 98.3
16 0.0 100.0
6 0.0 83.3
‘An effectofage,butnotof weightorsex,was validatedonplasmavaluesbyANOVA (see Results).
data afterexclusionof patientswithtreatmentdiseases,or addictionsknown to alterthe cation concentration(seetext).
significantlydifferentbyStudent’s f-test.
15.4
13.3
12.3
8.2
1.7
0.0
16.7
4.3 ±0.5
4.4 ±0.5
4.5 ±0.4
4.4 ±0.4
4.3 ±0.3
4.3 ±0.3
4.6 ±0.3
CLINICALCHEMISTRY,Vol.33, No.4, 1987 521
from these values. The useofplasma specimens is therefore
essential to accurate analysis for potassium, as stated by
Ladenson et al. (16). The lower reference limits we used for
erythrocyte magnesium and potassium were 2.05 and 90
mniol/L, respectively, in good agreement with data in the
literature(17-19).
Arelation was found between low values for plasma
magnesium and body weight that we could not attribute to
pathologyor treatmentwith diuretics and antihypertensive
drugs (20,21). Indeed, this relation persisted when the data
were recalculated after such patients were excluded. In
addition, magnesium concentrations were low in plasma of
patients with diabetes and in patients addicted to alcohol
and tobacco. In agreement with our data, hypomagnesemia
has been reported in diabetic (22-24) and chronic alcoholic
patients (25-29). Whereas the precise mechanism of diabet-
422) PotassIum in Elderly Subjects
Erythrocytes Plasma
Percentage of patients
havingK
No. of Concn, No.of
patients <90 90-99 100 mean ±SD patients
20 10.0 90.0 0.0 92.0 ±3.1 25
342 21.3 77.5 1.2 91.9 ±3.7 380
39 33.3 66.7 0.0 90.9 ±3.2 41
276 18.2 80.4 1.4 92.2 ±3.5 305
105 34.3 65.7 0.0 90.7 ±116
281 23.4 75.5 1.1 91.7 ±3.7
56 23.6 76.4 0.0 91.6 ±3.5
44 16.3 81.4 2.3 92.4 ±3.5
310 22.7 76.0 1.3 91.8 ±3.7
46 21.7 78.3 0.0 91.7 ±3.4
25 24.0 76.0 0.0 91.6 ±3.6
307 21.9 77.1 1.0 91.8 ±3.6
74 25.7 73.0 1.3 91.5 ±3.7
Percentage of patients
having K Concn,
<3.5 3.5-4.9 5.0 mean ±SD
0.0 88.0 12.0 4.4 ±0.4
2.1 87.7 10.2 4.4 ±0.4
0.0 95.1 4.9 4.4 ±Q.3
1.0 82.2 10.8 4.4 ±0.4
439 88.8 6.9 4.3 ±0.5
310
60
47
345
50
25
337
84
386
20
16
1.9 87.4
1.7 91.7
2.1 91.5
1.7 87.8
2.0 94.0
4.0 88.0
1.8 89.9
2.4 82.1
2.1 87.8
0.0 95.0
0.0 93.8
10.7 4.4 ±0.4
6.7 4.5 ±0.4
6.4 4.4 ±0.4
10.4 4.4 ±0.4
4.0 4.4 ±0.4
8.0 4.4 ±0.5
8.3 4.4 ±0.4
15.5’ 4.4 ±0.5
10.1 4.4 ±0.4
5.0 4.4 ±0.3
6.2 4.5 ±0.4
22.0 76.9 1.1 91.8 ±3.6
27.8 72.2 0.0 91.2 ±3.5
30.8 69.2 0.0 91.9 ±4.1
23.1 76.0 0.9 91.7 ±3.7
19.2 78.8 1.9 92.1 ±3.2
23.6 75.8 0.6 91.6 ± 3.6
17.5 79.4 3.2 92.7 ±3.71’
76.3 1.2 91.7 ±3.7
77.1 0.0 92.0 ±3.6
2.3 88.3
0.0 88.8
1.9 88.1
1.9 90.6
2.2 87.7
0.0 92.2
342
80
369
53
358
64
348
74
232
190
9.4 4.4 ±0.4
11.2 4.5±0.4
10.0 4.4 ±0.4
7.5 4.3 ±0.4
10.1 4.4 ±0.4
7.8 4.4 ±0.4
23.5 75.2 1.3 91.6 ± 3.6
18.2 81.8 0.0 92.3 ±3.9
19.6 79.4 1.0 92.1 ±3.6
25.8 73.1 1.1 91.4± 3.7
24.2 75.1 0.7 91.6 ±3.7
16.7 81.0 2.4 92.4 ±3.5
‘Relationvalidatedby chi-squaretest (see Results).
bMean concentrationssignificantly differentby Student’s f-test.
1.7 88.8 9.5 4.4 ±0.4
2.7 86.5 10.8 4.4 ± 0.5
1.7 87.1
2.1 90.0 11.2 4.4±0.4
7.9 4.4 ±0.4
334 1.5 88.3 10.2 4.4 ±0.4
88 3.4 88.6 8.0 4.4 ±0.5
Table 5. Effect of Pathology on DIstrIbution and Mean ConcentratIons of Erythrocyte(n =381) and Plasma (n =
522 CLINICALCHEMISTRY, Vol.33, No. 4, 1987
Pathology
None
Diabetes
no
yes
Hypertension9
no
yes
Smokers
never
past
current
Alcoholics
never
past
current
Heart diseases9
no
yes
Cancerno 350
past 18
evoiutive 13
Renal failure
no 329
yes 52
Inflammatory syndrome
no 318
yes 63
Gastro-intestinal diseases
no 333
yes 48
Liver and biliary diseases
no 319
yes 62
Bone andjoint diseases
no 315
yes 66
Neurologic diseases
no 199
yes 182
Respiratory diseases
no 297
yes 84
22.5
22.9
23.5 75.5
17.7 80.6 0.9 91.7 ±3.7
1.6 92.2 ±3.5
ic hypomagnesemia still remains obscure, magnesium defi-
ciency in chronic alcoholics appears to be due to the in-
creased urinary excretion of magnesium resulting from a
direct inhibitory effect of alcohol on renal tubular absorption
(26-29). Although we did not observe a relation between
magnesium concentration and renal failure in this study, it
is to be noted that hypomagnesemia has been observed
during early chronic renalinsufficiencyand renaltubular
acidosis (30, 31), because in these conditions the renal
tubules cannot effectively conserve magnesium. In advanced
renal failure, however, hypermagnesemia usually occurs
due to a reduction of the glomerular ifitrationrate and
retention of magnesium (30-31). We were unable to find in
the literature any study concerning the effect of cigarette
smoking on plasma magnesium concentrations that we
observed.
Magnesium and potassium interact on blood vessels and
thus are involved in the genesis of hypertension (reviewed
361 1.7 88.1
61 3.3 90.2 10.2 4.4 ±0.4
6.6 4.4 ±0.4
in 32). We found a relation between hypertension and low
values for erythrocyte magnesium and potassium and plas-
ma potassium. High values for plasma potassium were
related to cardiovascular diseases and age. We did not find
any relation to cancer, a subject on which observations are
largely conflicting (33).
Hypokalemia is common in the elderly (34,35). From our
study it appears thaterythrocyte potassium concentration is
abetter index of potassium deficiency (22.6% of the popula-
tion had low concentrations) than is plasma potassium
(1.9% of the population had low values). In the same way,
erythrocyte magnesium is a better index of magnesium
deficiency, because 20.7% of the patients had low concentra-
tions whereas 8% had low values for plasma Mg.
In conclusion, the present study underlines the high
prevalence of magnesium and potassium deficiencies in the
elderly as reflected by their concentrations in erythrocytes,
CLINICAL CHEMISTRY, Vol. 33, No.4, 1987 523
afinding that was not attributable to pathology or treat-
ment. Reduction in the dietary intake (36) and decreased
intestinal absorption may explain, at least in part, these
deficiencies we observedin the elderly population. Routine
assessment of electrolytes seems to be justified in the
elderly, because recent studies on unselected hospitalized
patients-but without any reference to age-have shown
that hypomagnesemia occurs concurrently with hypokale-
mia, hypophosphatemia, hyponatremia, and hypocalcemia
(14,37). Whether magnesium and potassium supplementa-
tion is worthwhile in the elderly stillremains a question to
be answered (36).
This workwas assistedby a grant from le Conseil Scientifique de
l’Umversit#{234}P. et M. Curie (Formation Recommandee par la Direc-
tionde la Recherche)et Ia Caisse Regionale d’Assurance Maladies
d’fle de France.
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