Readmission and mortality one year after acute hospitalization in older patients with explained and unexplained anemia - a prospective observational cohort study
Abrahamsen et al. BMC Geriatrics
Readmission and mortality one year after acute hospitalization in older patients with explained and unexplained anemia - a prospective observational cohort study
Jenny Foss Abrahamsen 0 1
Anne-Lise Bjorke Monsen 2
Francesco Landi 6
Cathrine Haugland 5
Roy Miodini Nilsen 4
Anette Hylen Ranhoff 3
0 Department of Nursing Home Medicine , Municipality of Bergen , Norway
1 Kavli Research Centre for Geriatrics and Dementia, Haraldsplass Deaconess Hospital , Ulriksdal 8, Bergen 5009 , Norway
2 Laboratory of Clinical Biochemistry, Haukeland University Hospital , Bergen , Norway
3 Departement of Clinical Science, University of Bergen , Bergen , Norway
4 Centre for Clinical Research, Haukeland -University Hospital , Bergen , Norway
5 Municipality of Bergen , Bergen , Norway
6 Facoltà di Medicina e chirurgia, Universita Cattoloca del Sacro Cuore , Rome , Italy
Background: Few studies have examined whether specific subtypes of anemia in older persons are more related to adverse outcomes such as hospital readmissions and death after acute hospitalization and post-acute care. Methods: An observational prospective cohort study was conducted between 2011 and 2014. A total of 884 community-dwelling patients, ≥70 years of age were transferred from acute medical and orthopaedic hospital departments to a skilled nursing home where they were examined by comprehensive geriatric assessment and had laboratory tests taken for the investigation of anemia. They were divided into three major groups and compared; 1) no anemia (reference group), 2) explained anemia (renal insufficiency, iron deficiency, vitaminB12/folate deficiency or multifactorial anemia) and 3) unexplained anemia. The groups were compared, and association of anemia with hospital readmission and death was estimated by logistic regression analyses. Results: Compared to the patients with unexplained anemia (n=135), patients with explained anemia (n=275) had more often died (22 % vs. 14 %, p=0.05) and had more frequenlty been readmitted to hospital (39 % vs. 27 %, p=0.03). Compared to the patients without anemia (n=474), the patients with explained anemia had increased odds of hospital readmissions (OR = 1.54 (95 % CI: 1.05-2.25), p=0.03), while patients with unexplained anemia, (n=135), had neither increased odds of hospital readmissions, (OR=0.83, 95 % CI: 0.51-1.34, p=0.44) nor death (OR = 0.74, 95 % CI: 0.41-1.31, p=0.30), in adjusted regression analysis. Conclusion: Since no increased risk of hospital readmissions or death was seen in older patients with unexplained anemia in the first year after acute hospitalization, no further invasive investigations might be necessary to investigate the cause of anemia in these patients. A close clinical follow up might be the best way to care for older patients with a mild and unexplained anemia.
Unexplained anemia; Readmission; Mortality; Elderly; Hospitalization
The prevalence of anemia in older persons increases
with age, and multifactorial causes related to
age-associated renal insufficiency, microscopic bleeding, chronic
inflammation, hormonal insufficiency and qualitative bone
marrow alterations, like an age-associated diminished
hematopoietic stem cell proliferative capacity or
myelodysplastic syndrome, play important roles in the
]. Anemia has been associated with several
unfavorable outcomes, such as death [
], the worsening
of cardiovascular disease , cognitive impairment [
] and functional dependence [
Most studies have focused on the risk of anemia in
general, and have not examined whether specific
subtypes of anemia are more related to unfavorable
outcomes. In approximately one third of older persons no
specific cause for the anemia, such as renal insufficiency,
nutritional deficiency (iron, vitamin B12, folate) or a
combination of these could be found, and the anemia is
called unexplained anemia [
]. Two studies of
community dwelling older people with unexplained anemia
have described that people with unexplained anemia did
not have any increased risk of mortality as compared to
older people without anemia [
]. However, to our
knowledge, no study has investigated both the increased
risk of hospital readmission and death in hospitalized
home-dwelling elderly people with explained and
A different clinical outcome in patients with explained
and unexplained anemia may imply different threshold
for further investigation into the causes of anemia [
as well as different follow-up and treatment.
This study is part of a prospective, observational, cohort
study, taking place during 2011–2014. It enrolled
consecutively older patients who were originally
homedwelling but suffered an acute trauma or illness, were
admitted to the hospital and thereafter to a post-acute
nursing home ward, before returning to their home [
In this sub-study 884 patients that could be analysed for
anemia and anemia subtypes were included. The patient
flow chart is shown in Fig. 1. The patients in the main
study, described in detail in a recent paper [
been admitted acutely to the two hospitals in Bergen.
Both medical patients (from the departments of internal
medicine, including cardiology and pulmonology) and
orthopaedic patients, with need for further medical
treatment or rehabilitation before discharge to own
home, were included (Table 1). Most of the orthopaedic
patients had suffered a fall, and none were admitted after
elective surgery. No patients with active cancer were
admitted. The inclusion criteria were as follows: 1) The
patients were ≥ 70 years of age and considered to have
respiratory and circulatory stability. 2) The hospital
doctor expected that the patients would be able to return
home within 2 weeks of treatment in the post-acute care
unit, and 3) the patients did not have major cognitive
impairment or delirium.
The morning after arrival to the nursing home, they
had a venous blood sample drawn. If the results of the
blood test indicated that the patients had signs of iron
deficiency anemia, and they had no occult blood loss
suggestive of gastrointestinal malignancy, they were
prescribed iron tablets. If the patients had folate or vitamin
B12 deficiency, they were prescribed folate or vitamin
B12 substitution. At discharge, all patients with anemia
were asked to follow up with their general practitioner.
The data on patient’s demographic and baseline clinical
characteristics were obtained from hospital records.
During the first week in the nursing home comprehensive
geriatric assessment was performed on >90 % of the
patients using the Barthel index sumscore (BI) [
Norwegian version of the Mini Mental Status Examination,
], Geriatric Depression Scale GDS , and
Mini Nutritional Assessment- Short Form; MNA-SF [
Data regarding hospital readmissions were obtained
from electronic patient registers and digital health
records at Haukeland and Haraldsplass hospitals (data
obtained from 80 % of the patients). Mortality information
(whether the patients were alive or dead 12 months after
hospital discharge), was collected from the patient
administrative system in the municipality (data obtained
from 98 % of the patients).
Blood was collected into EDTA Vacutainer Tubes (Becton
Dickinson) and hematological parameters (Hemoglobin
level (Hb), MCV (mean corpuscular volume), white blood
cells (WBS) and platelets,) were analyzed with an
automated hematology analyzer (ADVIA 120, Bayer
Diagnostics, Tarrytown, NY, USA).
Serum was obtained by collecting blood into Vacutainer
Tubes with no additive (Becton Dickinson). Serum levels
of creatinine (CV 1.8 %), C-reactive protein (CRP) (CV
3.3 %) and soluble transferrin receptor (TfR) (CV 3.5 %)
were analyzed with Modular P, levels of cobalamin (vitamin
B12) (CV 4.4 %), folate (CV 7.5 %) and NT-proBNP
(NTerminal pro brain-type natriuretic peptide) (CV 4.8 %)
with Modular E and serum ferritin (CV 4.5 %) by Modular
PP (F. Hoffman-La Roche Ltd, Basel, Switzerland).
The Modification of Diet in Renal Disease (MDRD)
Study equation; GFR (glomerular filtration rate) (mL/min/
1.73 m2) = 175 × (Scr)-1.154 × (Age)-0.203 × (0.742 if female),
was used for estimating GFR. The equation does not
Homedwelling patients admitted for nursing home
postacute care after acute hospitalization, n=1082
Study population, n=958
Patients that could be analysed for anemia subtypes, n= 884
Anemia, n= 410 (46%)
require weight or height variables because the results are
reported normalized to 1.73 m2 body surface area, which
is an accepted average adult surface area. The equation
has been validated in Caucasian populations between
the ages of 18 and 70 with impaired kidney function
(eGFR < 60 mL/min/1.73 m2) and has shown good
performance for patients with all common causes of
kidney disease [
Iron deficiency was assessed by measuring Ferritin and
TfR, since other studies have demonstrated that these
measurements give a more sensitive measure of
irondeficiency than the more commonly used Transferrin
saturation (Serum-iron/Total Iron Binding Capacity
]. Transferrin receptor rise, independent
of inflammation, when the iron level available for
erythropoiesis decrease .
N-Terminal pro brain-type natriuretic hormone
(proBnP) (level > 225 pg/L [
]) has been demonstrated to
be a sensitive marker clinical cardiovascular disease [
and renal dysfunction [
], and was included as a
measure of these comorbidities.
Definitions and subdivision of anemia subtypes
Anemia was classified according to the World
Health Organization (WHO) definition as a
haemoglobin concentration of less than 12 g/dL in
women and less than 13 g/dL in men.
Severe anemi was defined as having a haemoglobin
concentration in the lowest gender-specific tertile
of the anemia patients. The 33.3 percentile of
haemoglobin concentration both for men and women
OR odds ratio, CI confidence interval, Hb hemoglobin concentration
aAdjustment for age, > 5 diagnoses, Barthel index, influence of 5 different admission diagnoses
bAdjustment for age, > 5 diagnoses, Barthel index, influence of 5 different admission diagnoses, gender, MMSE, renal insufficiency
cComparing patients with or without anemia, defined by WHO
dComparing patients with and without severe anemia, defined as Hb in lowest gender –specific anemia tertile, (<10.6 g/dL)
eComparing patients with unexplained anemia versus patients without anemia (WHO defined)
fComparing patients with explained anemia versus patients without anemia (WHO defined)
with anemia was 10.6 g/dL, and this value was used as
cut-off for defining patients with severe anemia.
Renal anemia was defined as anemia combined with
eGFR < 60 ml/min/1.73 m2 and normal levels of
ferritin, folate and cobalamin
Iron deficiency anemia was defined as anemia
combined with ferritin < 35 μg/L or TfR > 4.5 mg/L
Vitamin B12 or folate anemia was defined as anemia
with vit B12 < 200 pmol/L or folate < 8 nmol/L, and
normal levels for creatinine and ferritin and TfR
Multifactorial anemia was defined as anemia with
more than one of the above explainable causes of
Explainable anemia were defined as either renal
anemia, iron deficiency anemia, vit B12/folate
deficiency anemia or multiple cause anemia
Unexplainable anemia was defined as anemia without
any known cause listed for the explained anemias.
Continuous data with a normal distribution was presented
as mean (standard deviation) and compared with two
sample t-test. Continuous data with a non-normal distribution
was presented as median (interquartile range) and
compared with the Mann–Whitney U test. Categorical data was
presented as numbers (percentages) and compared with
the chi-square test.
For identifying the clinical characteristics that were
independently associated with hospital readmissions and
death, odds ratios (ORs) with 95 % confidence intervals
(CIs) were estimated using logistic regression models.
The characteristics associated with p < 0.25 in univariate
analysis were noted as likely predictors and included in
multivariate, adjusted logistic regression models. When
analysing hospital readmission as the outcome, the
covariates age, >5 diagnoses, Barthel index, and the
influence of five different admission diagnoses groups were
included in the multivariate analysis. When analyzing
mortality as outcome, the additional covariates male sex,
hemoglobin concentration, renal failure and MMSE
score were also included in multivariate analysis.
All analyses were performed using the Statistical
Package for Social Science (IBM SPSS), version 20 for
Baseline patient characteristics and difference between patients with and without anemia
As shown in Table 1, the patients in general had rather
good physical, cognitive and nutritional status, but still
wide inter-individual variations were present in geriatric
Anemia based on the WHO criterias was present in
410 (46 %) of the patients while severe anemia was
present in 130 (15 %) of the patients.
Compared to the patients without anemia, the anemic
patients were older, more often male sex, more of them
had suffered a hip fracture, they had worse ADL
function (lower BI), they had more diagnoses and were using
more medications. Their CRP and pro-BnP levels were
higher, and more of them had renal insufficiency.
There was no significant difference in the prevalence of
hospital readmission or death in patients with and without
anemia (Table 1). As shown in Table 2, no association was
shown between anemia and death and anemia and
hospital readmissions in regression analysis. However,
sub-analyses of patients with severe anemia (Hb < 10.6),
demonstrated an increased odds for death but no
increased odds of hospital readmission, when patients with
severe anemia were compared to non-anemic patients.
Difference in baseline characteristics and outcome in patients with subgroups of explainable anemia
As indicated in Fig. 1, one or more explainable cause (s)
could be found for 275 (67 %) of all the patients with
anemia. Renal insufficiency was the most common
cause, and was present in 208 (76 %) of the patients with
other orthopaedic trauma
other medical diseases
Vitamin B12, pmol/L
Transferrin receptor, ml/L
12 months follow up
> 2 hospital admissions
35 (51 %)**
3 (4 %)
10 (15 %)
20 (29 %)
15 (22 %)
21 (30 %)
aanemia + estimated GFR (described in methods) < 60 mL/min/1.73 m2
banemia + ferritin < 35 ug/L or transferrin receptor > 4.5 mg/L
canemia + Vit B12 < 200 pmol/L or folate <8 nmol/L
drenal anemia and iron deficiency anemia (n=40), renal anemia + B12/folater deficiency anemia (n=11) or renal anemia + iron deficiency anemia + B12/folate
deficiency anemia (n=6)
Continous parameters are presented as mean (standard deviation) or median (interquartile range), categorical data are presented as numbers (percentages)
Hb haemoglobin, MCV mean corpuscular volume, CRP C-reactive protein, NT pro- BnP N-Terminal pro brain-type natriuretic peptide, *p < 0.05, **p < 0.01 when
patients with each of the anemia subtypes were compared to patients without anemia
explained anemia (139 pure renal anemias + 69
multifactorial anemias), more often in men than in women.
As shown in Table 3, the patients with pure iron
deficiency anemia had the lowest hemoglobin and 50 % of
them had been admitted to hospital the first year. Only
9 % of them had been operated on for a hip fracture.
Difference in baseline characteristics and outcome in patients with unexplained and explained anemia
As shown in Table 4, the hemoglobin was comparable
between the patients with unexplainable and explainable
anemias, and both groups had significantly increased
CRP, as compared to patients without anemia.
Compared to the patients with explained anemia, the
patients with unexplained anemias were more often
women, were admitted after a fall and had suffered a hip
fracture, but they had fewer diagnoses and were using
less drugs. None of them (per definition) had iron
deficiency nor renal insufficiency, and most of them did not
have elevated NT-pro BnP, indicating no heart failure.
The patients with unexplained anemia had no more
hospitals admission or death than patients with no anemia.
As shown in Table 2, no significant association was
demonstrated between unexplained anemia and hospital
admissions and unexplained anemia and death. When the
analysis was repeated for patients with severe
unexplained anemia, the results were not materially different.
As shown in Table 4, patients with explained anemia
had more frequently been readmitted to hospital or had
died during the first 12 months than patients without
anemia. Furthermore, a significant association was
demonstrated between explained anemia and hospital
readmission in adjusted regression analysis, while no
significant association between explained anemia and
death was demonstrated in adjusted regression analysis
The main finding in the present study is that no increased
risk of 1-year mortality and hospital readmissions could
be demonstrated in older patients that had unexplained
anemia, when they were discharged from acute
hospitalization, compared to patients with no anemia. On
the other hand, more patients with explained anemia died
during the first year, and they had a higher risk of hospital
readmissions, compared to patients without anemia.
These findings imply that it is clinically important to
distinguish between these two groups of anemias, because
patients with unexplained and explained anemia may
require different follow up and treatment.
To our knowledge no earlier studies have reported risk of
hospital readmissions and death in older patients with
explained and unexplained anemia, one year after acute
hospitalization. However, our results are in agreement with
the Leiden 85 plus study, which demonstrated no increased
risk of mortality in 86 year old community dwelling persons
with unexplained anemia compared to no anemia, after a
6-years follow-up [
]. Similarly, the Women’s Health and
Aging Study I, which included moderately to severely
disabled women > 65 years of age, could not demonstrate
increased mortality after five years in patients with
unexplained anemia compared to non-anemic women [
Several other studies characterize a group of explained
anemias related to chronic disease/chronic inflammation
10, 13, 26
]. However, the definition for this anemia
subtype is not uniform [
]. Since a majority of our
patients had chronic diseases, all of them had suffered an
acute trauma or illness, and 80 % of them had an
elevated CRP > 5, we decided, in line with the Leiden study
, not to conduct any subgrouping of anemia patients
with acute/chronic inflammation or chronic disease, but
rather subdivide patients with explained and unexplained
anemias based on simple, standardized laboratory
measurements. The fractions of patients with unexplained and
explained anemia in our study are in accordance with
other studies of older patients living in the community
13, 14, 27
], and with a small cohort of older patients from
an acute medical hospital unit [
], and an university
anemia clinic [
Our patients, with a mean age of 85 years, were living
in the community, and 80 % of them returned home
after a short stay in the hospital followed by post-acute
]. Thus they may be partly comparable to both
anemic persons living in the community [
3, 13, 14, 29
and anemia patients from hospital cohorts [
but not strictly representative of a normal, home-dwelling
elderly population. The overall prevalence of anemia in
our study (47 %) was similar to other studies reporting
anemia in a hospital setting [
28, 32, 33
], but lower than
reported from long term care [
While no overall risk of mortality was demonstrated in
the anemic population when applying the WHO
definition, a significant association with mortality was
demonstrated for the anemia patients with a hemoglobin
concentration in the lower anemia tertile (10.6 g/dL). This
is partly in agreement with a large study of 17 030
community dwelling older patients, reporting increased
mortality in patients with a hemoglobin < 11gd/L [
], and with
a previous study from long-term care demonstrating an
association between high levels of hemoglobin and better
]. Unfortunately, no recording of the causes of
death was recorded, thus we were unable to investigate
whether different types of anemi were related to different
causes of death.
Like other studies on anemia, renal insufficiency
and iron deficiency were the most common causes of
the explainable anemias, often together [
our study patients with iron deficiency anemia had
the lowest Hb and the most frequent hospital
readmissions, compared with the other anemia subgroups.
Thus, the recognition of patients with iron deficiency
anemia is particularly important to diagnose, as these
patients may be more prone to hospital readmissions,
and this type of anemia may be susceptible to
Clinical baseline differences were demonstrated
between patients with unexplained and explained anemias.
While both patient groups had rather mild anemia and
elevated CRP, the patients with unexplained anemias
more often had suffered a fall, even though they had
fewer diagnoses, were using fewer drugs and had a lower
pro-BnP, indicative of less cardiovascular disease. This
suggests that the unexplained anemia in these patients
might be more associated with frailty and the
proinflammatory state of ageing, whereas the explained
anemia is more related to multimorbidity. Although the
reason for the observed differences in hospital
readmission and mortality between patients with explained and
unexplained anemia is not obvious from our study, we
may speculate that the influence of both renal
dysfunction, and possible heart failure, in combination with
anemia, may influence the increased readmssion and
mortality seen in the patients with explained anemia.
The findings in the present study may have clinical
importance for the follow up and treatment of older
patients diagnosed with anemia. When anemia is found in
the elderly, it is important to determine if it is explained
by age related physiological degeneration of bone
marrow function or if there is an underlying disease of
which the treatment can improve the anemia. We
recommend that all patients with a subnormal hemoglobin
level should have a repeated simple biochemical
standard blood test including the measurements of Hb, MCV,
eGFR, Ferritin, s-TfR (or se-Fe and TIBC), CRP, B12 and
folate, to indicate whether the patients have an explained
or unexplained anemia. If the patients have an explained
anemia, further care should be directed towards
handling these explained causes. For patients with iron
deficiency, further search for GI disease or cancer should be
sought before iron administration. If the patients have a
renal anemia, particular care should be directed towards
the use of nephrotoxic drugs and drug dosages, and
treatment with Erythropoietin might be considered if blood
serum levels are not elevated. For older patients with
unexplained anemia, we support the conclusion from the
Leiden study, that no further invasive investigations might
be necessary in determining the cause of the anemia [
However, we recommend that these patients are followed
clinically, and that a screening test for frailty is included,
as the anemia may precede, predispose or accelerate the
development of frailty [
A limitation of the present study is that the follow up
time of 12 months might be too short to assess the
mortality risk in anemia patients. Furthermore, no formal
assessment of multi-morbidity or frailty was done. The
strength of our study is the prospective follow-up setting
and the inclusion of a complete baseline geriatric
evaluation, laboratory investigations and a one year follow-up.
This enables new knowledge of both the clinical patient
characteristics and the future clinical unfavourable
outcomes, in older patients with unexplained and explained
In contrast to patients with an explained anemia, older
anemic patients ≥ 70 years of age, without the presence
of renal insufficiency, iron deficiency and B12/folate
deficiency, had no increased risk of hospital readmission
and death the first year after an acute hospitalization,
compared to patients without anemia. This suggests that
no further invasive investigations might be necessary to
investigate the cause of the anemia, and that a close
clinical follow up might be the best way to care for these
older patients with a mild and unexplained anemia.
BI, Barthel index sumscore; CI, confidence interval; CRP, C-reactive protein;
GDS, Geriatric Depression Scale; GFR, glomerular filtration rate; Hb,
hemoglobin level; MCV, mean corposcular volume; MMSE, Mini Mental Status
Examination; MNA-SF, mini nutritional assessment-short form; NT-pro BNP,
N-Terminal pro brain-type natriuretic peptide; OR, odds ratio; TfR, transferrin
receptor; WBS, white blood cells.
We thank Håkon Ersland and Arne Johannesen for their cooperation and
work in providing data from the hospital’s electronic patient registers and
digital health records, and Alex Sisto for assistance in the final preparation of
This study was funded by Western Norway Regional Health Authority (Grant
number 911926). The funding source had no role in the study design, in the
collection, analysis and interpretation of data, in the writing of the report or
in the decision to submit the article for publication.
Availability of data material
The data will not be shared since sharing of dataset with other researchers
was not included in the application and approval to the Regional
Committee for Medical and Health Research.
JFA is the initiator, project leader and the first author of the manuscript.
ALBM is responsible for the biochemical analysis and has contributed in the
analyses of data and in the manuscript preparation. FL has contributed in
the analyses of the data and in the manuscript preparation. CH is responsible
for managing the patient database, retrieving the follow up information and
has contributed in the manuscript preparation. RMN has been supervising
the statistical work and has contributed to the manuscript preparation. AHR
has been supervising the ongoing research, taken part in the initiation of the
study and contributed to the manuscript preparation. All authors contributed
to the study concept and design and critical review of the manuscript. All
authors read and approved the final manuscript and agree to be accountable
for all aspect of the work.
The authors declare that they have no competing interests.
Compliance with ethical standards
The study was approved by the Norwegian Regional Comittee for Medical
and Health Research Ethics (2011/REKvest), and informed consent was signes
by the patients before entering the study. No experimental interventions
1. Ferrucci L , Balducci L . Anemia of aging: the role of chronic inflammation and cancer . Semin Hematol . 2008 ; 45 : 242 - 9 .
2. Merchant AA , Roy CN . Not so benign haematology: anaemia of the elderly . Br J Haematol . 2012 ; 156 : 173 - 85 .
3. Ble A , Fink JC , Woodman RC , et al. Renal function, erythropoietin, and anemia of older persons: the InCHIANTI study . Arch Intern Med . 2005 ; 165 : 2222 - 7 .
4. Culleton BF , Manns BJ , Zhang J , et al. Impact of anemia on hospitalization and mortality in older adults . Blood . 2006 ; 107 : 3841 - 6 .
5. Landi F , Russo A , Danese P , et al. Anemia status, hemoglobin concentration, and mortality in nursing home older residents . J Am Med Dir Assoc . 2007 ; 8 : 322 - 7 .
6. Groenveld HF , Januzzi JL , Damman K , et al. Anemia and mortality in heart failure patients a systematic review and meta-analysis . J Am Coll Cardiol S . 2008 ; 52 : 818 - 27 .
7. Hong CH , Falvey C , Harris TB , et al. Anemia and risk of dementia in older adults: findings from the Health ABC study . Neurology . 2013 ; 81 : 528 - 33 .
8. Bowling CB , Muntner P , Bradbury BD , et al. Low hemoglobin levels and recurrent falls in U.S. men and women: prospective findings from the REasons for geographic and racial differences in stroke (REGARDS) cohort . Am J Med Sci . 2013 ; 345 : 446 - 54 .
9. Chaves PH . Functional outcomes of anemia in older adults . Semin Hematol . 2008 ; 45 : 255 - 60 .
10. Makipour S , Kanapuru B , Ershler WB . Unexplained anemia in the elderly . Semin Hematol . 2008 ; 45 : 250 - 4 .
11. Artz AS , Thirman MJ . Unexplained anemia predominates despite an intensive evaluation in a racially diverse cohort of older adults from a referral anemia clinic . J Gerontol A Biol Sci Med Sci . 2011 ; 66 : 925 - 32 .
12. Ferrucci L , Guralnik JM , Bandinelli S , et al. Unexplained anaemia in older persons is characterised by low erythropoietin and low levels of proinflammatory markers . Br J Haematol . 2007 ; 136 : 849 - 55 .
13. Semba RD , Ricks MO , Ferrucci L , et al. Types of anemia and mortality among older disabled women living in the community: the Women's Health and Aging Study I . Aging Clin Exp Res . 2007 ; 19 : 259 - 64 .
14. Willems JM , den Elzen WP , Vlasveld LT , et al. No increased mortality risk in older persons with unexplained anaemia . Age Ageing . 2012 ; 41 : 501 - 6 .
15. Abrahamsen J , Haugland C , Nilsen RM et al. Three different outcomes in older community-dwelling patients receiving intermediate care in nursing home after acute hospitalization . J Nutr Health Aging . 2015 ; In press, doi:10.1007/s12603-015-0592-y.
16. Mahoney FI . Functional evaluation: the Barthel index . Md State Med J. 1965 ; 14 : 108 - 12 .
17. Strobel CEK , Engedal K. MMSE-NR . Norwegian revised mini mental status evaluation. Revised and expanded manual . Oslo, Norway: Norwegian Centre for Ageing and Health; 2008 .
18. Folstein MF , Folstein SE , McHugh PR . “ Mini-mental state”. a practical method for grading the cognitive state of patients for clinicians . J Psychiatr Res . 1975 ; 12 : 189 - 98 .
19. Yesavage JA . Geriatric Depression Scale . Psychopharmacol Bull . 1988 ; 24 : 709 - 11 .
20. Guigoz Y , Lauque S , Vellas BJ . Identifying the elderly at risk for malnutrition. The mini nutritional assessment . Clin Geriatr Med . 2002 ; 18 : 737 - 57 .
21. Levey AS , Stevens LA , Schmid CH , et al. A new equation to estimate glomerular filtration rate . Ann Intern Med . 2009 ; 150 : 604 - 12 .
22. van den Broek NR , Letsky EA , White SA , et al. Iron status in pregnant women: which measurements are valid? Br J Haematol . 1998 ; 103 : 817 - 24 .
23. Skikne BS . Serum transferrin receptor . Am J Hematol . 2008 ; 83 : 872 - 5 .
24. Alehagen U , Dahlstrom U , Rehfeld JF , et al. Pro-A-type natriuretic peptide, proadrenomedullin, and N-terminal pro-B-type natriuretic peptide used in a multimarker strategy in primary health care in risk assessment of patients with symptoms of heart failure . J Card Fail . 2013 ; 19 : 31 - 9 .
25. Scrutinio D , Mastropasqua F , Guida P , et al. Renal dysfunction and accuracy of N-terminal pro-B-type natriuretic peptide in predicting mortality for hospitalized patients with heart failure . Circ J . 2014 ; 78 : 2439 - 46 .
26. Artz AS , Xue QL , Wickrema A , et al. Unexplained anaemia in the elderly is characterised by features of low grade inflammation . Br J Haematol . 2014 ; 167 : 286 - 9 .
27. Guralnik JM , Eisenstaedt RS , Ferrucci L , et al. Prevalence of anemia in persons 65 years and older in the United States: evidence for a high rate of unexplained anemia . Blood . 2004 ; 104 : 2263 - 8 .
28. Migone De Amicis M , Poggiali E , Motta I , et al. Anemia in elderly hospitalized patients: prevalence and clinical impact . Intern Emerg Med . 2015 ; 10 : 581 - 6 .
29. Riva E , Tettamanti M , Mosconi P , et al. Association of mild anemia with hospitalization and mortality in the elderly: the health and anemia population-based study . Haematologica . 2009 ; 94 : 22 - 8 .
30. Dharmarajan TS , Avula S , Norkus EP . Anemia increases risk for falls in hospitalized older adults: an evaluation of falls in 362 hospitalized, ambulatory, long-term care, and community patients . J Am Med Dir Assoc . 2006 ; 7 : 287 - 93 .
31. Bach V , Schruckmayer G , Sam I , et al. Prevalence and possible causes of anemia in the elderly: a cross-sectional analysis of a large European university hospital cohort . Clin Interv Aging . 2014 ; 9 : 1187 - 96 .
32. Rohrig G , Klossok W , Becker I , et al. Prevalence of anemia among elderly patients in an emergency room setting . Eur Geriatr Med . 2013 ; 5 : 3 - 7 .
33. Gaskell H , Derry S , Andrew Moore R , et al. Prevalence of anaemia in older persons: systematic review . BMC Geriatr . 2008 ; 8 : 1 .
34. Juarez-Cedillo T , Basurto-Acevedo L , Vega-Garcia S , et al. Prevalence of anemia and its impact on the state of frailty in elderly people living in the community: SADEM study . Ann Hematol . 2014 ; 93 : 2057 - 62 .
35. Artz AS . Anemia and the frail elderly . Semin Hematol . 2008 ; 45 : 261 - 6 .
36. Hirani V , Naganathan V , Blyth F , et al. Cross-sectional and longitudinal associations between anemia and frailty in older Australian Men: the concord health and aging in Men project . J Am Med Dir Assoc . 2015 ; 16 : 614 - 20 .