RESEARCH ARTICLE
Trends in urinary tract infection
hospitalization in older adults in Spain from
2000-2015
Jesu´s Redondo-Sa´nchez1,2☯, Isabel del Cura-Gonza´lez2,3,4☯, Laura Dı´ez-Izquierdo5,
Ricardo Rodrı´guez-BarrientosID3,4,6*, Francisco Rodrı´guez-CabreraID7, Elena Polentinos-
Castro3,4, Miguel Lo´pez-Miguel8, Lucas Marina-Ono9, Laura Llamosas-Falco´n10, A´ ngel Gil-
de Miguel2
1 Ramon y Cajal Health Care Center, Alcorco´n, Primary Care Management, Madrid Health Service, Madrid,
Spain, 2 Department of Medical Specialties and Public Health, University Rey Juan Carlos, Alcorco´n, Madrid,
Spain, 3 Research Unit, Primary Care Management, Madrid Health Service, Madrid, Spain, 4 Health
Services Research on Chronic Patients Network (REDISSEC) ISCIII, Madrid, Spain, 5 Infanta Sofı´a
University Hospital, San Sebastia´n de los Reyes, Madrid, Spain, 6 Biosanitary Research and Innovation
Foundation of Primary Care (FIIBAP), Madrid, Spain, 7 National School of Health, Instituto de Salud Carlos
III, Madrid, Spain, 8 Ciudades Health Care Center, Getafe, South Family and Community Care Teaching
Unit, Madrid, Spain, 9 Getafe University Hospital, Madrid, Spain, 10 Preventive Medicine and Public Health,
12 de Octubre University Hospital, Madrid, Spain
☯ These authors contributed equally to this work.
* ricardo.rodriguez@salud.madrid.org
Abstract
Objective
To analyze trends in urinary tract infection hospitalization (cystitis, pyelonephritis, prostatitis
and non-specified UTI) among patients over 65 years in Spain from 2000–2015.
Methods
We conducted a retrospective observational study using the Spanish Hospitalization Mini-
mum Data Set (CMBD), with codifications by the International Classification of Diseases
(ICD-9). We collected data on sex, age, type of discharge, main diagnosis, comorbid diag-
nosis, length of stay, and global cost. All the hospitalizations were grouped by age into three
categories: 65–74 years old, 75–84 years old, and 85 years old and above. In the descriptive
statistical analysis, crude rates were defined as hospitalizations per 1,000 inhabitants aged
�65. To identify trends over time, we performed a Joinpoint regression.
Results
From 2000–2015, we found 387,010 hospitalizations coded as UTIs (54,427 pyelonephritis,
15,869 prostatitis, 2643 cystitis and 314,071 non-specified UTI). The crude rate of hospitali-
zation for UTIs between 2000 and 2015 ranged from 2.09 in 2000 to 4.33 in 2015 Rates of
hospitalization were higher in men than in women, except with pyelonephritis. By age group,
higher rates were observed in patients aged 85 years or older, barring prostatitis-related
hospitalizations. Joinpoint analyses showed an average annual percentage increase
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OPEN ACCESS
Citation: Redondo-Sa´nchez J, del Cura-Gonza´lez I,
Dı´ez-Izquierdo L, Rodrı´guez-Barrientos R,
Rodrı´guez-Cabrera F, Polentinos-Castro E, et al.
(2021) Trends in urinary tract infection
hospitalization in older adults in Spain from 2000-
2015. PLoS ONE 16(9): e0257546. https://doi.org/
10.1371/journal.pone.0257546
Editor: Justyna Gołębiewska, Medical University of
Gdansk, POLAND
Received: February 3, 2021
Accepted: September 5, 2021
Published: September 29, 2021
Peer Review History: PLOS recognizes the
benefits of transparency in the peer review
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editorial history of this article is available here:
https://doi.org/10.1371/journal.pone.0257546
Copyright: © 2021 Redondo-Sa´nchez et al. This is
an open access article distributed under the terms
of the Creative Commons Attribution License,
which permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: Ethics Committee of
the Hospital Universitario Fundacio´n Alcorco´n has
approved this research, including any potential data
(AAPC) in incidence rates of 4.9% (95% CI 3.2;6.1) in UTI hospitalizations. We observed
two joinpoints, in 2010 and 2013, that found trends of 5.5% between 2000 and 2010 (95%
CI 4.7;6.4), 1.5% between 2010 and 2013 (95% CI -6.0;9.6) and 6.8% between 2013 and
2015 (95% CI -0.3;14.4).
Conclusions
The urinary infection-related hospitalization rate in Spain doubled during the period 2000–
2015. The highest hospitalization rates occurred in men, in the�85 years old age group,
and in non-specified UTIs. There were increases in all types of urinary tract infection, with
non-specified UTIs having the greatest growth. Understanding these changing trends can
be useful for health planning.
Introduction
Urinary tract infections (UTIs) are one of the most frequent community-acquired bacterial
infections [1, 2]. They account for between 10 and 15% of hospitalizations for infectious causes
[3, 4] and up to 6% of infection-related deaths [4].
In recent years, hospital admissions due to UTIs have increased by up to 50% [5–7]. These
hospitalizations have a high economic impact, primarily associated with the length of the hos-
pital stay [8]. The risk factors associated with community-acquired UTIs that require hospitali-
zation include male sex [9], high prevalence of comorbidities such as dementia, stroke or
urinary incontinence [10] instrumentation of the urinary tract, polypharmacy and highly resis-
tant pathogens associated with treatment failure [11, 12].
As well as these conditioning factors, age is a risk factor for hospitalization [13] and the best
predictor of admission-related mortality [14, 15]. Previous community-level population stud-
ies have revealed an increasing trend of UTIs with age [16], reporting a higher risk of bacter-
emia and death by all causes in male patients and patients above 85 years, especially in
depressed areas [17].
There are no studies on hospitalization incidence due to UTIs in Spain. From an epidemio-
logical standpoint, studying these data requires not only a global approach but also stratifica-
tion by sex and age categories, as these entail distinctive features that impact the outcome [6].
It is important to understand the data on UTI incidence at the hospital and community levels
when planning and implementing policies for antibiotic use [18].
Considering the aging population, our primary hypothesis was that there would be an
increase in the number of hospital admissions in total UTIs and in each type of UTI over the
study period.The objective of this study was to analyze trends in hospitalizations related to uri-
nary infections in patients above 65 years of age, over a period of 16 years, according to their
diagnoses of cystitis, pyelonephritis, acute prostatitis, and non-specified UTIs.
Methods
We conducted a retrospective observational study using the Spanish Hospitalization Mini-
mum Data Set (CMBD). The Reporting of Studies Conducted using Observational Routinely-
collected Health Data (RECORD checklist) is available as supporting information; see S1 File.
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sharing. The CMBD data belong to the Ministry of
Health and are partially accessible to the public. For
data series on hospitalization, like the data
presented in this article, specific selections of
anonymized microdata from CMBD records can be
requested from the Ministry. The application form
is at https://www.mscbs.gob.es/estadEstudios/
estadisticas/estadisticas/estMinisterio/
SolicitudCMBD.htm.
Funding: This study has been funded by Instituto
de Salud Carlos III through the project “PI19/
01700”, as part of the Plan Estatal de I+D+I 2017-
2020 co-funded by European Regional
Development Fund (ERDF) “A way of shaping
Europe”. In addition, the principal investigator JRS
received support to increase his research activities
and to publish this manuscript from the 2020
funding program of the Fundacio´n de Investigacio´n
e Innovacio´n Biosanitaria en Atencio´n Primaria
(FIIBAP), Community of Madrid.
Competing interests: The authors have declared
that no competing interests exist.
Participants and data source
Our study includes hospitalizations from 2000 to 2015, as during this time span, codifications
remained homogeneous nationally, following the International Classification of Diseases,
ninth version (ICD-9). Currently, approximately 99% of the population in Spain has National
Health Service (SNHS) public coverage. The CMBD is a registry for all hospitals in Spain that
contains data for up to 97.7% of discharges from public hospitals during all periods, and from
2005, the CMBD had gradual coverage from private hospitals, reaching a total coverage from
all hospitals of 92% in 2014. The CMBD defines hospitalization as admission to the emergency
department for over 24 hours and/or scheduled admission. Admissions that occur within 30
days of discharge are considered to be readmissions. The CMBD has proven its usefulness in
previous epidemiological studies [19, 20].
From the CMBD database, we selected hospitalizations in which their main diagnosis was
urinary tract infection. We considered UTI as the diagnosis codes for pyelonephritis (590.10-
11-3-80-81-9), acute (601.0) and chronic (601.1) prostatitis, cystitis (595.0-89-9), and non-
specified UTI (599.0). Among hospitalizations with the main diagnosis of non-specified UTI,
those who had a secondary diagnosis of pyelonephritis, acute or chronic prostatitis, cystitis, or
bacteriuria were reclassified as such to maximize the chances of identifying specific diagnosis
of UTI.
For each hospitalization, we collected data on patients’ demographics (sex, age), type of dis-
charge, dates of admission and discharge, main diagnosis, comorbid diagnosis, length of stay,
and global cost. All the hospitalizations were grouped by age into three categories: 65–74 years
old, 75–84 years old and older people (85 years old and above). We excluded readmissions,
defined as admissions during the first 30 days after discharge in the same hospital.
Statistical methods
Quantitative data are described with averages and standard deviations or medians with IQRs
(interquartile ranges), and categorical data are expressed with frequencies (absolutes and per-
centages). Crude rates were defined as hospitalizations per 1,000 inhabitants aged 65 or older,
according to population data on each July 1st, provided by the National Statistics Institute of
Spain. These data were also used to obtain age-sex standardization rates of both global and spe-
cific UTI conditions, which were calculated using the 2015 Spanish population.
To identify possible varying trends over time, we performed a Joinpoint regression [21]
using age-adjusted UTI rates, with the 2015 population as the reference population. This
widely used approach fits a linear model when Joinpoints (i.e., change points) are not known a
priori and are to be estimated from the data. Two measures are provided: an estimation of the
annual percent change (APC) in each linear segment and the average annual percent change
(AAPC), computed as a weighted average of the APCs from the model. In case no Joinpoints
were obtained, the AAPC exactly reflected the APC.
Statistical analysis was performed using Stata 14 and Joinpoint Regression Program, version
4.5.0.1 (National Cancer Institute).
Ethics statement
The study was approved by the Hospital Fundacio´n Alcorcon Ethics Research Committee (20/
125) favorably evaluated by the Central Research Commission of the Primary Healthcare Man-
agement of Madrid (57/20). The need for consent was waived by the Ethics Committee (20/
125). The CMBD data were fully anonymized by the Ministry of Health before investigators
accessed to them.
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Results
During the 2000–2015 period, there were 387,010 hospitalizations among patients over 65
years; 81.15% were diagnosed with non-specified UTI, 0.68% with cystitis, 14.06% with pyelo-
nephritis and 4.10% with prostatitis. The results were adjusted by reviewing non-specified UTI
hospitalizations and considering secondary diagnosis. “Fig 1” shows the flow diagram for the
hospitalizations.
Socio-demographic characteristics and clinical features of urinary tract
infection-related hospitalizations
Out of 387,010 registered hospitalizations during the study period, 42.41% of them corresponded
to the 75–84 years old age group. Relative to the sex category, 56.54% of the total were female. The
most frequent comorbidity was diabetes (32.01%), with dementia as the second most common
comorbidity (15.50%). The median length of stay was 6 days (IQR: 3–10). The median cost was
3,061 euros (IQR: 2,253–4,079), with non-specified UTIs and cystitis having the highest cost. The
overall lethality rate was 5.39%. Conditions with the highest lethality rate were non-specified UTIs
(6.19%), followed by pyelonephritis (2.36%) and cystitis (2.31%). Upon discharge from the hospi-
tal, 89% of patients returned home and 4% were transferred to another hospital or social health
center, where the proportion for patients with non-specified UTIs was higher than for other UTIs
(2.05% to 3.3%). All pathologies except for COPD were more prevalent in patients with non-spec-
ified UTIs. “Table 1” presents patients’ characteristics globally and by different conditions.
Hospitalization rates by sex and age category and UTI type
The crude rates of UTI hospitalizations during the 2000–2015 period varied from 2.04 in 2000
to 4.33 in 2015. The rate of non-specified UTIs doubled from 1.56 in 2000 to 3.63 in 2015 and
the rate of prostatitis, from 0.20 in 2000 to 0.48 in 2015, while the rates of cystitis and pyelone-
phritis remained more stable. See Tables 2 and 3.
When analyzing hospitalizations by age group, higher rates were observed in patients aged
85 years or older, with a five-fold increase between 2000 and 2015 (Table 2). This trend was
seen in all UTI types (Figs 3–5) except for prostatitis-related hospitalizations, in which the hos-
pitalization rate was higher among the 65–74 years old age group; see S2 File (and Fig 6).
Fig 1. Flow chart. Flow diagram for hospitalizations.
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During that period, UTI hospitalization rates were superior among male vs female patients
in all age categories but started to overlap in patients aged>85 years from 2013 (Fig 2); see S2
File. This was seen in all UTI types except for pyelonephritis, which was more common in
women; see S2 File (and Fig 5).
Analysis of trends (joinpoint) globally and by UTI type, sex, and age group
1. Global. Joinpoint analysis of UTI-related hospitalizations showed a 4.9% (95% CI 3.2;
6.5) annual increasing trend, with a 5.5% (95% CI 4.7; 6.4) annual percentage change (APC)
from 2000 to 2010 (see S3 File).
2. By UTI type. Changes in trends by type of infection were not observed regarding non-
specified UTI “Fig 3”and pyelonephritis-related hospitalizations “Fig 5” during the study
period, however, the other two conditions showed changes in trends: one in cystitis-related
hospitalization “Fig 4” rates in 2002 and one in prostatitis-related hospitalizations in 2008 “Fig
6”. The APCs for cystitis-related hospitalizations were -12.3% (95%CI -36.6; 21.3) from 2000–
2002 and 5.1% (95% CI 3.6; 6.6) from 2002–2015. The APCs for prostatitis-related
Table 1. Characteristics of urinary tract infection (globally and by different pathologies).
Total Non-specified UTI Cystitis Pyelonephritis Prostatitis
n = 387 010 n = 314 071 n = 2 643 n = 54 427 n = 15 869
Age groups�
65–74 years 97 726 (25.25) 64 088 (20.41) 815 (30.84) 23 709 (43.56) 9114 (57.43)
75–84 years 163 376 (42.41) 134 333 (42.77) 1 155 (43.70) 22 452 (41.25) 5436 (34.26)
�85 years 125 908 (32.53) 115 650 (36.82) 673 (25.46) 8 266 (15.19) 1319 (8.31)
Sex�
Male 168 193 (43.46) 133 819 (42.61) 1 283 (48.54) 17 222 (31.64) 15 869 (100)
Female 218 804 (56.54) 180 242 (57.39) 1 360 (51.46) 37 202 (68.35) -
Type of admission�
Urgent 371 536 (96.00) 301 564 (96.02) 1 935 (73.21) 52 657 (96.75) 15 380 (96.92)
Programmed 15 388 (3.89) 12 432 (3.96) 707 (26.75) 1 761 (3.24) 488 (3.08)
Comorbidities�
Diabetes mellitus 123 901 (32.01) 102 949 (32.78) 785 (29.70) 16 134 (29.64) 4 033 (25.41)
Dementia 59 990 (15.50) 57 047 (18.16) 251 (9.52) 2 329 (4.28) 363 (2.29)
Malignant neoplasia 44 027 (11.38) 37 781 (12.03) 283 (10.71) 4 818 (8.85) 1 145 (7.22)
COPD 33 568 (8.67) 27 481 (8.75) 245 (9.27) 3 554 (6.53) 2 288 (14.42)
Renal failure 29 844 (7.71) 26 140 (8.32) 187 (7.08) 2 810 (5.16) 707 (4.46)
Liver disease 5 674 (1.47) 4 564 (1.45) 24 (0.91) 915 (1.68) 171 (1.08)
Length of stay �� 6 (3–10) 6 (4–10) 4 (2–8) 5 (3–9) 4 (3–6)
Length of stay�
0–3 days 98 112 (25.35) 76 481 (24.35) 1 092 (41.32) 14 265 (26.21) 6 274 (39.54)
4–7 days 147 430 (38.09) 117 104 (37.29) 816 (30.87) 22 572 (41.47) 6 938 (43.72)
8–11 days 72 251 (18.67) 61 024 (19.43) 336 (12.71) 9 187 (16.68) 1 704 (10.74)
�12 days 69 217 (17.89) 59 462 (18.93) 339 (15.10) 8 403 (15.44) 953 (6.01)
Cost (€)�� 3 061 (2 253–4 079) 3 129 (2 398–4 079) 2 890 (2 333–3 518) 2 540 (2 017–3 257) 2 231 (1 787–2 351)
Type of discharge�
Home 344 884 (89.12) 276 344 (87.99) 2 477 (93.72) 50 783 (93.30) 15 280 (96.29)
Transfer 17 160 (4.43) 14 932 (4.75) 88 (3.33) 1 815 (3.33) 325 (2.05)
Others/unknown 4 112 (1.06) 3 345 (1.07) 17 (0.64) 547 (1.01) 203 (1.28)
Lethality rate� 20 854 (5.39) 19 450 (6.19) 61 (2.31) 1 282 (2.36) 61 (0.38)
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hospitalizations were 4.9% (95% CI 4.0; 5.7) from 2000–2008 and 9.0% (95% CI 8.2; 9.8) from
2008–2015; see S3 File.
During the study period, two types of infection showed changes in trends: prostatitis-
related hospitalizations in 2008 “Fig 6” and cystitis-related hospitalization in 2002 “Fig 4”; see
S3 File. The APCs for prostatitis-related hospitalizations were 4.9% (95% CI 4.0; 5.7) annual
from 2000–2008 and 9.0% (95% CI 8.2; 9.8) annual from 2008–2015. The APCs for cystitis-
related hospitalizations were 5.1% (95% CI 3.6; 6.6) annual from 2002–2015. However,
changes were not observed regarding pyelonephritis-related hospitalizations “Fig 5” see S3
File.
Table 2. Hospitalization rates from 2000 to 2015 globally and by age group.
Rates by age group
Year Total 65–74 years old 75–84 years old >85 years old
2000 2.04 1.25 2.67 4.99
2001 2.23 1.29 2.80 5.61
2002 2.17 1.27 2.69 5.39
2003 2.43 1.33 3.00 6.35
2004 2.50 1.43 3.03 6.17
2005 2.60 1.43 3.11 6.60
2006 2.87 1.48 3.45 7.39
2007 2.92 1.49 3.42 7.43
2008 3.19 1.54 3.67 8.42
2009 3.36 1.58 3.81 8.87
2010 3.52 1.64 3.98 9.10
2011 3.68 1.65 4.13 9.59
2012 3.73 1.67 4.18 9.51
2013 3.86 1.78 4.41 9.42
2014 4.01 1.84 4.48 10.08
2015 4.33 1.91 4.81 11.12
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Table 3. Hospitalization rates from 2000 to 2015, by UTI category per year.
Non-specified UTI Cystitis Pyelonephritis Prostatitis
2000 1.56 0.02 0.42 0.20
2001 1.71 0.02 0.42 0.20
2002 1.64 0.01 0.43 0.20
2003 1.90 0.01 0.42 0.22
2004 1.93 0.02 0.46 0.22
2005 2.03 0.02 0.45 0.24
2006 2.29 0.02 0.45 0.25
2007 2.35 0.02 0.44 0.27
2008 2.64 0.02 0.42 0.27
2009 2.78 0.02 0.44 0.29
2010 2.92 0.02 0.44 0.32
2011 3.06 0.03 0.45 0.35
2012 3.10 0.03 0.43 0.38
2013 3.21 0.02 0.45 0.41
2014 3.33 0.03 0.46 0.44
2015 3.63 0.03 0.47 0.48
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3. Temporal analysis by sex. In the Joinpoint analysis by age groups of UTI hospitaliza-
tion rates by sex, a statistically significant increasing trend was observed in both sex categories
and was superior in the case of female patients vs male patients regarding UTI hospitalization.
The AAPC between 2000–2015 in men was 3.8 (95% CI 2.4;5.2) annual, and in women was 4.5
(95% CI 4.1; 4.9) annual “Fig 2”; see S3 File.
The AAPCs from 2000–2015 were 3.9 (95% CI 2.4; 5.5) annual in men and 5.4 (95% CI 4.5;
6.2) annual in women in Non-Specified UTI “Fig 3”; see S3 File.
Regarding cystitis-related hospitalizations, the increasing trend was only statistically signifi-
cant in male patients, with an AAPC of 3.9 (95% CI 1.7; 6.0) annually (Fig 4); see S3 File.
Concerning pyelonephritis-related hospitalizations from 2000–2015, a decreasing trend
annual was observed among male patients, AAPCs from 2000–2015–0.6 (95% CI -1.1; 0.0)
while an annual 0.6% (95% CI 0.2;1.0) increasing trend was observed among female patients.
There were no changes in trend in either sex during this period (Fig 5); see S3 File.
There was a statistically significant increase, with an AAPC of 6.8 (95% CI 6.2; 7.3) annu-
ally, in the incidence rate of prostatitis from 2000–2015 (Fig 6), where the increase was higher
after 2008 (AAPC 4.9 [95% CI 4.0; 5.7] versus AAPC 9.0 [95% CI 8.2; 9.8]).
4. Temporal analysis by age category. During the study period, the 85 years old and
older age group had the highest increasing trend annual relative to UTI hospitalizations APPC
Fig 3. Non-specified UTIs. Non-specified UTIs hospitalization rates by sex and group of age (2000–2015).
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Fig 2. UTIs total. UTIs hospitalization rates by sex and group of age (2000–2015).
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5.4% (95% CI 3.5; 7.4), while the 65–74 years old and 75–84 years old age groups had 2.79
(95% CI 2.6; 3.0) and 4.1 (95% CI 3.8; 4.3) increases, respectively; see S4 File.
Non-specified UTI-related hospitalizations trends annual by age category were AAPC 3.4
(95% CI 1.4; 5.0), 65–74 years old, AAPC 4.5 (95% CI 4.2; 4.9) 75–84 years old; and AAPC 5.8
(95% CI 3.6; 7.9)>85 years old age analyses; see S4 File.
Cystitis-related hospitalization trends annual by age, the AAPC from 2000–2015 were 3.2
(95% CI 1.4; 5.0) 65–74 years old, 3.9 (95% CI 2.1; 5.6) 75–84 years old and 4.8 (95% CI 2.3;
7.4) in >85 years old age analyses. There were no changes in the trend; see S4 File.
Trends annual by age category regarding pyelonephritis-related hospitalizations only were
statistically significant increase in 75–84 years old age AAPC 0.6 (95% CI 0.2; 0.9).
The annual prostatitis-related hospitalization trends during the study period were less pro-
nounced in the 65–74 years old age group, with an AAPC of 5.5 (95% CI 3.8; 7.2) versus an
AAPC of 7.7 (95% CI 6.8; 8.7) in the 75–84 years old age group and an AAPC of 7.2 (95% CI
3.0; 11.6) in the>85 years old age group. The changes in trend were more pronounced in the
last few years, from 2003–2004, with an AAPC of 7 (95% CI 6.1; 7.8) annually in the 65–74
years age group and an AAPC of 11.5 (95% CI 9.2; 13.8) annually in the >85 years age group;
see S4 File.
Fig 5. Pyelonephritis. Pyelonephritis hospitalization rates by sex and group of age (2000–2015).
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Fig 4. Cystitis. Cystitis hospitalization rates by sex and group of age(2000–2015).
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Discussion
Our study has analyzed the changes in hospital admissions due to UTIs in Spain over 16 years
(2000–2016), confirming the trends in incidence and related factors.
The rates of hospitalization due to UTIs increased with age, particularly in those over 85
years old, and were higher in men than in women for all age groups, tending to equalize in
those over 85 years old. Our study included a higher percentage of women, as in other studies
[6, 10, 11, 13, 22], but after standardizing by population and sex, the hospitalization rate was
higher in men.
More than 80% of the UTI admissions in our study were for non-specified UTIs, with
higher rates in men in all age groups throughout the entire study period. Over the period ana-
lyzed, hospitalization rates for non-specified UTIs doubled, increasing in all age groups and
particularly in those over 85 years old and in both sexes, with a greater annual rate increase in
women.
These non-specified UTIs required longer hospital stays, with a higher associated cost and
greater lethality. A larger proportion of cases was referred to other hospitals and/or social
health centers than for other UTIs. The data showing worse prognosis can be explained by the
fact that they are associated with older people with more comorbidities (diabetes, dementia,
kidney or liver disease, neoplasia) than other UTIs. One exception is COPD, which was more
common among patients admitted with prostatitis, justified by this pathology being associated
with male sex.
The higher percentage of non-specified UTIs can be justified by the difficulty of reaching a
specific diagnosis in older patients. This group of patients has more non-specific symptoms
and a high prevalence of asymptomatic bacteriuria in both patients with community-acquired
disease and, in particular, institutionalized patients, patients with urinary catheters, and
patients with cognitive deficits, all of which make it more difficult to reach a correct diagnosis
[23, 24].
In our study, 14% of admissions were for pyelonephritis. Unlike non-specified UTIs, pyelo-
nephritis was more common in women and was homogeneously distributed over the study
period. Hospitalization rates were highest in women aged over 75 years and men aged over 85
years. The associated mortality was 2.3%. In other studies, age was the best predictor of mortal-
ity for cases of pyelonephritis that required hospital admission, with mortality rates of 0.7% in
women and 1.6% in men [25]. Other factors that affect mortality due to pyelonephritis are
immune suppression and the onset of septic shock [26].
Fig 6. Prostatitis. Prostatitis hospitalization rates by group of age (2000–2015).
https://doi.org/10.1371/journal.pone.0257546.g006
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PLOS ONE | https://doi.org/10.1371/journal.pone.0257546 September 29, 2021 9 / 13
In our study, 4% of all UTI admissions were for prostatitis (9.4% of infections in men).
Unlike non-specified UTIs, the rate was lower in those aged over 85 years. The rates doubled
over the study period, increasing in those over 75 years old. A greater increase (11.4%)
occurred from 2004 in those over 85 years old. The global burden of this disease remains
unknown. Acute prostatitis affects approximately 1% of males throughout their life, with hos-
pital care sometimes required to prevent adverse outcomes due to sepsis [27]. Age-incidence is
bimodal, with a peak at approximately 20–40 years and a second peak after 60 years [28, 29].
In a study of patients treated for prostatitis in hospital emergency departments, admissions
were associated with age over 75 years (like in our study’s results), a history of urinary tract
interventions, neoplasia, prescription of antibiotics in the last three months and the develop-
ment of bacterial resistance [27].
One possible explanation for the increase in hospitalizations due to UTIs is the increasing
antibiotic resistance of community-acquired infections, which reduces the efficacy of current
options for outpatient treatment [5, 6]. In this regard, fluoroquinolones are an important fac-
tor due to their high resistance rate in all age groups over 50 years old [9, 12]. Overtreatment
and incorrect use of antibiotics at the community [30] and hospital level [31] and deficiencies
in the social care networks required for community support [32] have also been indicated.
One factor that is directly related to the increase in admissions is age [6, 10]. In patients over
85 years old with multiple comorbidities, referral from long-term care facilities [13], delayed
administration or delays in starting antibiotic treatment [17, 33] also explain why the course of
disease is worse in this age group.
The limitations of the study are related to the limitations of the CMBD. Firstly, this database
does not contain any information on the microbiology of the organisms causing UTIs, the
associated antibiotic treatment, or the risk factors known to be associated with UTIs. Secondly,
it cannot be used to identify subsequent admissions of a specific patient, except those that
occur within 30 days of discharge (which were not included in this study).
The results obtained in this study provide an accurate assessment of the changes in the
national incidence of hospitalizations due to UTIs over 16 years and allow us to estimate the
real burden of UTIs in older patients and their impact on our health system.
Further research is needed on the incidence of UTIs at the community level and on patterns
of antibiotic use, which would help to improve the control of resistance and optimize clinical
management, establishing clinical pathways for managing this type of infection in older
patients. We also need to understand the factors associated with hospitalization in higher-risk
patients, such as those with comorbidities or catheters, so we can establish preventive strategies
that would reduce admissions and have a favorable impact on patient health and on the health
system.
Supporting information
S1 File. RECORD checklist (REporting of studies Conducted using Observational Rou-
tinely-collected Data).
(DOCX)
S2 File. Incidence rates by year, condition, age category, and sex.
(DOCX)
S3 File. Trend analysis (Joinpoint) by condition adjusted by age category.
(DOCX)
S4 File. Trend analysis (Joinpoint) by condition adjusted by sex category.
(DOCX)
PLOS ONE Trends in urinary tract infection hospitalization in older adults in Spain from 2000-2015
PLOS ONE | https://doi.org/10.1371/journal.pone.0257546 September 29, 2021 10 / 13
Acknowledgments
To our colleagues from the Research Unit for their support: Marcial Caboblanco-Muñoz, Juan
Carlos Gil-Moreno, Jaime Barrio-Corte´s.
To Dr. Marı´a del Canto de Hoyos for her comprehensive revision of the final draft.
Author Contributions
Conceptualization: Jesu´s Redondo-Sa´nchez, Isabel del Cura-Gonza´lez, A´ngel Gil-de Miguel.
Data curation: Laura Dı´ez-Izquierdo, Francisco Rodrı´guez-Cabrera.
Formal analysis: Isabel del Cura-Gonza´lez, Laura Dı´ez-Izquierdo, Ricardo Rodrı´guez-Bar-
rientos, Francisco Rodrı´guez-Cabrera.
Funding acquisition: Jesu´s Redondo-Sa´nchez.
Methodology: Isabel del Cura-Gonza´lez, Laura Dı´ez-Izquierdo, Ricardo Rodrı´guez-Barrien-
tos, Francisco Rodrı´guez-Cabrera, Elena Polentinos-Castro.
Resources: Jesu´s Redondo-Sa´nchez.
Supervision: Jesu´s Redondo-Sa´nchez, Isabel del Cura-Gonza´lez.
Validation: Jesu´s Redondo-Sa´nchez, Isabel del Cura-Gonza´lez, Laura Dı´ez-Izquierdo, Miguel
Lo´pez-Miguel, Lucas Marina-Ono.
Writing – original draft: Jesu´s Redondo-Sa´nchez, Isabel del Cura-Gonza´lez, Ricardo Rodrı´-
guez-Barrientos, Elena Polentinos-Castro.
Writing – review & editing: Jesu´s Redondo-Sa´nchez, Isabel del Cura-Gonza´lez, Laura Dı´ez-
Izquierdo, Ricardo Rodrı´guez-Barrientos, Francisco Rodrı´guez-Cabrera, Elena Polentinos-
Castro, Miguel Lo´pez-Miguel, Lucas Marina-Ono, Laura Llamosas-Falco´n, A´ngel Gil-de
Miguel.
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