Feeling the Portuguese pulse: unveiling the hospitalisation-leading cardiac arrhythmias.

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Oct 30, 2013 (3 years and 9 months ago)

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1

Feeling the Portuguese pulse: unveiling the hospitalisation
-
leading cardiac
arrhythmias.


ALBERTO, M.
1
;
ANDRADE, T;
1

CARDOSO, S.
1
; CORREIA, C.
1
; MAGALHÃES, D.
1
; MEDEIROS,
N.
1
;

NEVES, A.
1
;
SANTOS, J.
1
;

TELES, A.
1
; VIEIRA, B.
1
; SANTOS, J.V.
2
; FREITAS, J.
2


1
Class 22, Introdução à Medicina I
I
, Faculdade de Medicina da Universidade do Porto

2
Advisers, Introdução à Medicina I
I
, Faculdade de Me
dicina da Universidade do Porto


ABSTRACT


This article intends to find out whether there is or not an asymmetrical
distribution in
hospitalisations due to cardiac arrhythmias in Portugal, and to provide a possible explanation for
those findings.

Methods:

113 631 mainland Portuguese individuals, hospitalised from 2000 to 2008 in
mainland Portuguese health facilities, wh
ose principal diagnoses were

“426” or “427” ICD9
-
CM
codes, were divided according to NUT II region classification.
Total population
and ageing index data
was obtained from external sources. Hospitalisation frequencies per a hundred thousand inhabitants
wer
e crossed with established arrhythmia
-
leading factors (age,
hypertension, diabetes mellitus
-

DM,
h
yperthyroidism,
o
besity
, chronic kidney d
isease

-

CKD

and
h
yperlipidemia
), and conclusions were
withdrawn from there.

Results:

G
ender

and
age

distribution

were very similar across all NUT II regions
;
North

constantly
showed lower hospitalisation frequencies than the other
four
regions;
North is the
youngest region;
W
hen adjusting the
number of hospitalisations (NOH)

for age groups, significant
differences are still found for
North and Lisbon from the age of 40 onwards; North presents higher
values of NOH with Obesity, Hyperlipidemia, CKD and DM per a 100 000 hospitalisations due to
arrhythmias than Lisbon;
Obesity a
nd Hyperlipidemia increase the odds of being hospitalised due to
arrhythmias (AOR = 1,17 and AOR = 1,14)
and are higher in North;

Hypertension (AOR = 1,30) and
Hyperthyroidism (AOR = 3,45) are both more frequent in Lisbon and are more relevant (higher AOR)

than Obesity and Hyperlipidemia.


Conclusions:

A
ge is
a risk

factor in the emergence of cardiac arrhythmias
;
Hypertension’s and
hyperthyroidism’s prevalence are the most relevant influencers in

the number of hospitalisations;
CKD as a protective effect in the appearance of cardiac arrhythmias; North population has a lower
2

risk of being hospi
talised than Lisbon population;

Centre, Algarve and Alentejo were similar in terms
of number of hospitalisations.


Key words
:

Cardiac
arrhythmias
; Portugal
; Hospitalisation; Aging;
Hypertension; Diabetes Mellitus;
Hyperthyroidism; Obesity;

Chronic Kidney Disease; Hyperlipidemia;

Epidemiologic studies


BACKGROUND


C
ardiac arrhythmias are
a
large group

of
conditions
in which
t
h
ere

i
s

not

a

normal sinus
rhythm
and

normal atrioventricular (AV) conduction.
[1]

Quan H
et al

(2005) updated the definition

(
originally
by Elixhauser
et al

(1998))

of
a selection of ICD
-
9
-
CM codes

for
several comorbidities
,

including
“cardiac arrhythmia”
.
[
2]

Atrioventricular (AV) block, atrial (APB) or ventricular premature
beats (VPB), sinus bradycardia and atrial fibrillation (AF) stand amongst the most common
arrhythmias.
[1]

A
ge is a decisive influencer in the appearance
of arrhythmias
.

Atrial fibrillation

(AF)
, which
affects approximately 0
,
4% of the global population
,
[3
]

doubles its prevalence every ten years
beyond
th
e
50

year

benchmark
.
[
4
]

In the USA,
roughly
70% of individuals with AF are between 65 and 85
years of age
.
[5
]

Various other studies support

this relation
.
[6
]

Several studies have demonstrated that ch
anges
of the
thyroid function
are
associated to
greater

levels
of
cardiovascular morbidity
, including

angina
, myocardial infar
ction
and arrhythmias.
[
7
]

The thyroid hormones play

a key
role

in controlling lipid metabolism.
If the condition called
hyperthyroidism is present, there is an inc
rease of cholesterol synthesis
, possibly leading to the
aforementioned pathologi
es
.
[
7
]


Fatal arrhythmias
are
pointed as
the most frequent cause of death

among obese patients,
[
8
]

w
h
ich means that obesity is a significant cause of cardiac arrhythmias. Obesity is
a

status
in which
body weight

is grossly above th
e acceptable or desirable weight, and whose

standards may vary with
age, sex, genetic or cultural
background.

A
n individual with
BMI
(Body Mass I
ndex)
greater than 30,
0
kg/m
2

is considered obese, and with a

BMI greater than 40,
0 kg/m
2

is considered morbidly
obese
.
[
9
]

In Portugal
, a study developed in 2006 for the 10th Portuguese Congress of Obesity in Oporto
found
some differences in
the
prevalence of obesity
by

NUT II
region
s:
North

(13,1%) is the least obese
region, in contrast wit
h Alentejo (16,4%), the most obese
.

Algarve

(13
,2%)
,
Centre

(14,2%)
and
Lisbon

(15,8%)

are in
the midterm.
[
10
]

Hypertension is one of the most important risk factors for cardiovascular disease.
[11
]
Hypertension facilitates development and progression of cardiac diseases such as left ventricular
hypertrophy (LVH), coronary artery disease (CAD)
, arrhythmia and heart failure.
[
12
]

A 2007
3

Portuguese stud
y (subjects aged 18 to 90 years old)
pointed

North

as the region with the lowest
prevalence
of hypertension
(33,4%), and Alentejo with the highest
(49,5%).
[13
]

Chronic kidney disease (CKD) affects up to 10% of adults

[14]

and carries a high risk for
cardiovascular disease, inc
luding atrial fibrillation (AF).
[15]

Diabetes Mellitus

(DM)
increases the in
cidence of cardiac
arrhythmias.
[
16
]

Individuals with
DM

had one third greater risk of incident AF compared with those without diabetes after adjustment with
no evidence of interactions with
race or gender.
[17
]

Dyslipidemia, an important risk factor for cardiovascular disease, may be associa
ted with atrial
fibrillation (AF).
[18
]

There has been an increase in

the
prevalence
of arrhythmias
in industrialised countries

for
more than 50 years

now
.
[
19
-
21
]

AF
followed this general trend
.
[6
]

Concerning Portugal,
Bonhorst D

et
al.

(2010) concluded
that
the prevalence of AF is higher than in other countries
where similar data is
available,
when focusing on the population aged 40 and onwards
.
[22
]

With
a growing number of patients with cardiac arrhythmias, swiftly managing them
is

becom
ing

more of a

challenge.
The first step towards a solution is to study and understand their
common background.
However, answers might ha
ve to be regionally tailor
-
made
rather than global.


Hence,
our main goal is
to find out whether there is or not an asymmetrical
distribution in
hospitalisations due to cardiac arrhythmias in Portugal, and to provide a possible explanation for
those findings
.

Specifically,
we will
:



Analys
e Portuguese
arrhythmia
-
caused
hospitalisations from 2000 to 2008
, dividing it
by NUT II regions

and age groups
;



Recourse

to population age,
Hypertension, Diabetes Mellitus, H
yperthyroidism
,
O
besity
,
Chronic Kidney Disease

and
Hyperlipidemia

to try and explain our
findings
;



Study the
evolution of the
arrhythmias

and associated factor
s.


PARTICIPANTS
AND METHODS


Participants

This study focuses

on

hospitalisations
in mainland Portug
uese public acute care hospitals with
discharges,
between 2000 and 2008.

All patients with a principal diagnosis
codified in I
CD
-
9
-
CM
as

426
-

Conduction disorders
”,


427
-

Cardiac dysrhythmias

,

or a subheading of these classifications
,

and resident in mainland Portugal,

were included
.

4

11
3

6
31

i
mpatient episodes
were

taken into account. 5
8

839

(51,
8%)
of the
episodes
referred

to male

individuals
,
and 5
4

792

(48,
2%)
to
female

individuals
.

P
atients’

age ranged from 0 to 108
years

(
M
ean =
69,
7
; SD

= 15,
6
).


Study design

This is an epidemiologic
, cross
-
sectional

study
[
23
]

that

covers a nine
-
year period,

2000 to 2008.
E
ach episode was

analysed
only
onc
e

(there is no follow
-
up period)
,

and readmissions were
considered

independent e
pisode
s
.


Data collection methods

Hospitalisations’ d
ata
was
provided

by
Department of Health Information and Decision
Sciences, Faculty of Medicine, University of Porto.

Supporting evidence was withdrawn from studies
relating
cardiac arrhythmias with
individual factor
s

such as age, gender, demographic
or geographic
data
, hyperthyroidism, obesity
,
hypertension
,
chronic kidney disease, diabetes mellitus

and
hyperlipidemia
.

The main data collection method

was on
-
line research on Pubmed
.

ICD
-
9
-
CM arrhythmia diagnose
s codes were
first selected

acco
rding to Quan H. et al (2005).
[2
]

Of

th
ose
, this article

only consider
s

diagnoses wh
ich fall on the categories “426
-

Conduction
disorders
” or “
427

-

Cardiac dysrhythmias


of ICD
-
9
-
CM
.


Variables description

P
rincipal diagnosis
: ICD
-
9
-
CM 426
.xx

or

427
.xx

codes
.

Secondary diagnose
s
were chosen
based on
frequency
(
ten

most frequent)
:
Congestive H
eart
F
ailure

(428.0, 398.91)
, Syncope
and Collapse

(780.2)
, Atrial Fibrillation
(427.31)
and Chronic
Isquemic Heart D
isease
(414.x)
are heart
-
related diseases, and therefore were excluded from the
analysis
;

Hypertension (401
.xx
)

appeared twice
,

but frequencies were merged
;

Obesity

(
278
.0x
)
,
Hyperlipidemia

(
272.0, 272.1, 272.2, 272.3, 272.4
)
, C
hronic Kidney Disease (C
KD
;
585
.x
)
and

Diabetes Mellitus

(DM;
250.00, 648.8x
)

completed top ten.

Hyperthyroidism
(
242.xx, 775.3
) was also
included.

Demographic variables
us
ed were
patients’ age group
,
gender,
patients’ residence by NUT II
regions
(
mainland

Po
rtugal is currently divided in

five NUT II regions:
North
,
Central Region
-

from
here onwards referred as “
Centre

-
,
Lisbon
, Alentejo and Algarve
)
[24
]
,
Portuguese population data
(
INE estimates
yearly

the population of each NUT II region; in 2001 the national Census took place,
determining more accurate figures for that specific year
)

and A
geing Index
, whose data was obtained
from INE
.

Ageing Index: quotient between the number of people of 65 years
-
old or more and the
NUT 3

5

number of those of 14 or less years
-
old
;

It is expressed in number of elders by 100
youths
.

Discharg
e
date (years) was also analy
sed.


Statistical analysis

S
tatistic
s

were

performed using IBM SPSS Statistics v20
®

and
Microsoft Office Excel

2010
®
.

Table 1: Characteristics of the patients
,
taken

from database.

Supplementary table I
:
Population by NUT II region
is available

on INE
(National Institute

of
Statistics)
website
[24
]
.

Number of hospitalisations (NOH)
was
withdrawn

from our database.

Table
2

and
C
hart 1:
Built based on
Supplementary table I

by
dividing the NOH of each region
for its total population
,

times a
hundred
thousand
.

Table 3
: U
npaired, two
-
tail t
-
tests were performed to compare each region
with the other four,
concerning NOH per a hundred thousand inhabitants.

Significance level set at
p <
0,05.

Table 4:

Ageing Index by NUT II region is available on INE website.
[24
]

A
Welch
test was
ran to
compare all regions.

Significance level set at p < 0,05.

Chart 2:

Chart 1 was corrected for

age group,
i.e.
, age influence was eliminated by dividing
the
NOH of each region for its total population by age group
. An average was used for NOH
and
population figures.

Supplementary table I
I
:
shows
all chart 2 values and 95% CI

(confidence intervals)
.

CI
’s

were
calculated using the formula


(

)







(



)








(



)



, where
p

is the NOH (
per capit
a)
and
n

is the absolute population within that age group in a certain region.

Values for 95% CI were
adjusted
to

100 000 inhabitants.

Chart 3:
frequencies were obtained through the SPSS

Frequencies

tool applied to all
secondary diagnoses

in

the provided database.

Table
5
:

N
OH

with Hypertension, Obesity, Hyperlipidemia, CKD
, H
yperthyroidism
or
DM

as
secondary diagnoses, per a hundred thousand hospitalisations due to cardiac arrhythmias and per
NUT II region
, were withdrawn from the provided database
.

Table
6
:
Logistic regression

including all hospitalisations in mainland Portugal from 2000 to
2008
. Dependent variable

-

principal diagnosis
for hospitalisation
: cardiac arrhythmia or other.

Independent f
actors
: secondary diagnoses (
hypertension
,
diabetes mellitus
,
hyperlipidemia
,
obesity
,
hyperthyroidism
, CKD
,
c
ongestive
h
eart
fa
ilure
, syncope and collapse, atrial fibrillation, chronic
isquemic heart d
isease
) and demographic var
iables (
patients’ residence by NUT II region,
age
)
.

It
was m
ade using
the
Forward
Stepwise Method

through

SPSS v20.




NUT 3

NUT 3

6

RESULTS


CHARACTERISTICS

NORTH

CENTRE

LISBON

ALENTEJO

ALGARVE

N

28
545

29606

38944

11287

5249

Sex
-

%







Mal e

50,9

54,5

49,3

53,9

55,8


Femal e

49,1

45,6

50,7

46,1

44,2

Age


year






M
ean
±SD

69,25
±15,82

70,20
±15,42

69,54
±15,64

70,37
±
15,16

69,27
±
16,10


Table 1


Characteristics of the patients

hospitalised due to cardiac arrhythmias, from 2000 to 2008, in mainland
Portugal
.

Note:

R
eadmissions were considered independent episodes.


Gender
and age
distribution

were very similar across all NUT II regions
, as expected
.

In
particular,
all five regions registered their

greatest number of hospitalisations
in patients within the 75
-
79 years old range.


YEAR

NORTH

CENTRE

LISBON

ALENTEJO

ALGARVE

2000

71,0

109,
1

143,7

131,
8

126,5

2001

74,3

118,
3

151,
1

141,5

105,5

2002

74,2

122,
2

153,2

143,
9

129,0

2003

79,1

1
30,0

161,
5

142,
3

121,6

2004

88,8

145,3

165,
7

1
69,0

156,
8

2005

91,0

143,4

171,1

181,3

149,
5

2006

97,7

157,4

160,
1

182,5

146,
9

2007

93,5

151,6

155,5

192,5

175,9

2008

98
,
0

172,0

156,8

189,
7

163,
5


Table
2



Number of Hospitalisations (NOH) per a hundred thousand inhabitants, by year and NUT II region.

Note: Results were obtained by dividing the NOH of each region for its total population, times a
hundred thousand.


Chart
1

provides an easie
r overview of the values described above.

7


Chart
1



Nu
mber of Hospitalisations (NOH) per

a
hundred
thousand

inhabitants, by year and NUT II region.

Note: Results were obtained by dividing the NOH of each region for its total population, times a
hundred
thousand.




Tab
le
3



p
-
values
*

for

comparisons

between
the

NOH

per a hundred thousand inhabitants, by year and NUT II
region

(see
table 2
)
.

Note:
*
Obtained through
t
-
test
s.


There
was

a general trend of increasing hospitalisations per year
.
Lisbon

is the
sole
exception,
showing an inversion
to
negative evolution
between 2005 and 2006.

Reasons for this are proposed in
the
d
iscussion

part
.

Regarding
NOH

per a hundred thousand inhabitants
,
North

stands
clearly apart from all other
regions.
Moreover
,
significant differences
(p<0,
001
)
were found between
North

and

Centre
,
Lisbon
,
Alentejo and Algarve,
in contrast with those found between these four last regi
ons

(see table 3
).


YEAR

NORTH

CENTRE

LISBON

ALENTEJO

ALGARVE

p
*

2000

80
,0

130,9

110
,0

173,4

127,3


2001

82,2

132,3

110,5

166,6

128,4


2002

84,2

135,3

110,7

179,8

128,2


2003

86,2

135,8

106,6

169,1

127,4


2004

88,6

138,2

105,6

170,4

127,4

< 0,001

2005

90,9

140,1

105,9

170,8

126,2


2006

93,3

142,3

106,3

171,6

125,2


2007

96,4

144,8

107,0

172,7

124,1


50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
2000
2001
2002
2003
2004
2005
2006
2007
2008
Number of hospitalisations per a
hundred thousand inhabitants

Year

NORTH
CENTRE
LISBON
ALENTEJO
ALGARVE

NORTH

CENTRE

LISBON

ALENTEJO

ALGARVE

NORTH

---

<

0,001

<

0,001

<

0,001

<

0,001

CENTRE

< 0,001

---

0,349

0,060

1,000

LISBON

< 0,001

0,349

---

1,000

0,717

ALENTEJO

< 0,001

0,060

1,000

---

0,141

ALGARVE

< 0,001

1,000

0,717

0,141

---

8

2008

99,3

147,2

108,1

172,9

123,5



Table
4



Ageing Index (AgIdx) by NUT II regions, from 2000 to 2008.

Notes: Ageing Index: quotient between the
number of people of 65 years
-
ol
d or more and the number of those of 14 or
less years
-
old. It is expressed in numb
er of elders by 100 youngsters; *Obtained through
Welch

test.


Over these nine years

the

Agein
g

Index

rose steadily
in
North

and
Centre
, while
it
hover
ed
around the same values in the remaining regions.

North

is
,

concerning general population,

by far
the
younge
st

region, in contrast with Alentejo.

T
his fact (
North

and
Lisbon
,
the second youngest region,
are

on average
separated by 18,84 points
)

m
ight

explain the
shape

of chart 1.



Chart
2



Nu
mber of Hospitalisations (NOH) per

a
hundred thousand

inhabitants, by

age group

and NUT II region.

Note
s
: Results were obtained by dividing the NOH of each region for its total population

by
age group
, times a
hundred
thousand.

A nine year average was used for values of NOH and population by age group
; see
Supplementary

Table I

for
all
these values

and

all
95% C.I.


However, when adjusting
the
NOH for age groups

(see chart 2), significant differences (see
Supplementary

table

I
I
) are still found for
North

and
Lisbon

from the age of 40 onwards.
Centre
,
Alentejo and Algarve
present

close curves,
while
North

continues to have
the
lowest

ratios

and
Lisbon

stands out with the
worst
scenario
. In the most relevant age

group, 75 to 7
9
, there is a
difference of
406,81 NOH per 100 000 inhab
itants b
etween
Lisbon

and
North

(1010,06


603,25
; see
Supplementary Table I
).

Therefore, other factors must
b
e taken into
account

to explain chart 1
,
c
o
-
morbidities
being an obvious one. Co
-
morbidities where

studied

with
bas
is

on the registered
secondary diagnoses at time of admission
.


0
200
400
600
800
1000
1200
1400
Number of hospitalisations per a
hundred thousand inhabitants

Age group

NORTH
CENTRE
LISBON
ALENTEJO
ALGARVE
9


Chart
3



M
ost frequent secondary diagnoses
registered
on
patients

at time of admission
.


Congestive Heart Failure, Syncope and Collapse, Atrial F
ibrillation

and Chronic Isquemic
Heart D
isease are heart
-
related diseases, and
therefore
were excluded from th
e analysis
.

However,
they were included in the logistic regression (table

6)
for adjustment purposes.
Hypertension was the
most recorded diseas
e, having being diagnosed to 29,
1% of patients.

Hyperthyroidism, despite not
appearing in this chart, is a well
-
known arrhythmia
-
potentiating
factor, so was included for
analysis
.



HYPERTENSION

OBESITY

HYPERLIPIDEMIA

CKD

HYPERTHYROIDISM

DM

NORTH

28667

4505

10618

313
9

43
8

893
7

CENTRE

22664

2391

434
4

222
6

39
9

7424

LISBON

33035

295
6

7395

2945

70
4

849
7

ALENTEJO

34624

3907

4988

317
2

84
2

981
7

ALGARVE

26500

54
30

731
6

316
3

97
2

10192


Table
5



Number of hospitalisations

with Hypertension, Obesity, Hyperlipidemia, Chronic Kidney Disease (CKD)
,
Hyperthyroidism

or Diabetes Mellitus (DM)

as
secondary diagnoses
,

per a hundred thousand
hospitalisations

due to cardiac arrhythmias

and
per
NUT
II region.


FACTORS

N (%)
*†

(= 8 634 005)

UNADJUSTED ODDS

RATIO (95% CI)

ADJUSTED ODDS

RATIO (95% CI)

Secondary Diagnoses




Hypertension

1 133 475 (13,1)

2,77 (2,73
-
2,80)

1,30

(1,2
9
-
1,32
)

Diabetes Mellitus

411 762 (4,8)

1,89 (1,85
-
1,93)

0,9
7

(0,9
5
-
0,9
9
)

Atrial Fibrillation

322 997 (3,7)

1,61 (1,57
-
1,65)

0,53 (0,51
-
0,54)

Hyper
lipidemia

299 103 (3,5)

2,18 (2,13
-
2,23)

1,14 (1,12
-
1,17)

Chronic Isquemic Heart
Disease

238 259 (2,8)

3,75 (3,67
-
3,82)

1,57 (1,54
-
1,61)

Congestive Heart F
ailure

212 731 (2,5)

4,95 (4,86
-
5,05)

2,43 (2,38
-
2,48)

Obesity

172 980 (2,0)

1,74 (1,69
-
1,80)

1,17 (1,13
-
1,21)

0
5
10
15
20
25
30
35
Hypertension
Diabetes mellitus
Hyperlipidemia
Congestive heart failure
Syncope and colapse
Chronic kidney disease
Atrial fibrillation
Chronic ischemic heart disease
Obesity
Frequency (%)

10

Chroni c Ki dney Di sease

133 459 (1,5)

1,88 (1,82
-
1,95)

0,87 (0,84
-
0,90)

Syncope and Col l apse

22 408 (0,3)

39,69 (38,57
-
40,83)

24,73 (23,99
-
25,49)

Hyperthyroi di sm

10 310 (0,1)

5,18 (4,79
-
5,60)

3,
45

(
3,18
-
3,
74
)

Demographic Variables




North

3 042 889 (35,2)

1

**

1

**

Centre

2 268 053 (26,3)

1,40 (1,37
-
1,42)

1,19 (1,17
-
1,21)

Lisbon

2 319 759 (26,9)

1,80 (1,78
-
1,83)

1,56 (1,54
-
1,59)

Alentejo

655 611 (7,6)

1,85
(1,81
-
1,89)

1,49 (1,46
-
1,52)

Algarve

347 693 (4,0)

1,62 (1,57
-
1,67)

1,60 (1,55
-
1,65)

Age

-

1,04 (1,04
-
1,04)

1,04 (1,04
-
1,04)


Table
6



Odds ratio for secondary diagnoses and demographic variables

on the
hospitalisations motivated by
cardiac
arrhythmias.

Note
s
:
All hospitalisations in mainland Portugal from 2000 to 2008 were
included in this logistic regression. The
dependent
variable

was the principal diagnosis leading to the hospitalisation: 1


cardiac arrhythmia; 0


other.

*

For secondary

diagnoses: number of hospitalisations featuring that disease as secondary diagnosis.



For demographic variables: number of hospitalisations
in that region.

**

Base category for odds ratio determination
.


DISCUSSION


A
ge is
a risk

factor in the emergence of cardiac arrhythmias

(AOR = 1,04
), which
is consistent
with studies on this subject, which state that
beyond the
45
-
50 year
s

benchmark the prevalence
rises
dramatically
.


All co
-
morbidities (secondary diagnoses

excluding heart
-
related diseases
), bar
CKD and DM
,
obtained significant adjusted odds ratio
(AOR) values
above 1

for hospitalisations due to arrhythmias.
These roles of
arrhythmia
-
potentiating factors

go along with the scientific literature.
DM is largely

irrelevant when looking to the 95% CI.

CKD

turned out being a protective factor, in contrast with what
is described
.

Hyperthyroidism deserves
a
special attention, since it is the most important factor for
the emergence of cardiac arrhythmias
:
individ
uals
with hyperthyroidism are 3,45

times
likelier
to
develop arrhythmias than those
without

this condition.


There is no significant difference between
Centre
, Alentejo and Algarve regarding NOH per a
100 000 inhabitants (chart 1), nor when eliminating the fact
or age (chart 2). This proved to be
strange, because
Centre

features a
lower NOH
with
any
associated
co
-
morbidities (
table 5
) than
Alentejo or Algarve

and a lower AOR (table 6)
. A counterbalance between
co
-
morbidities and
age
influence
could explain chart
1, but age was shown to be irrelevant for comparing these three regions
(chart 2)
.

11


Chart 1 brings all attention to
North
, which registered the
lowest
NOH per a 100 000
inhabitants.
Lisbon

does not stand apart from
Centre
, Alentejo and Algarve.
Lisbon
’s ne
gative
evolution between 2005 and 2006 can be explained by some changes on the classification of NUT II
Portuguese regions:

in 2002 the NUT

II

Lisbon

e Vale do Tejo


(which consisted in 5

N
ut

III) was
abolished and its territory was distributed by several other Nut II regions: one of
those
Nut III regions
was delivered to Alentejo, two were delivered to
Centre

and the other two went on to form the new
Nut II region:
Lisbon
.

This revamp only to
ok practical effect in 2005.


However, when
the
age
groups are

include
d
,
age’s influence is eliminated and
significant
differences are found for both
North

and
Lisbon

in comparison with the other
three

regions
and
between themselves
(chart 2), but
while
No
rth

still h
a
s

the
lowest

ratios,

Lisbon

holds
the worst
scenario
. Since
North

and
Lisbon

are the youngest regions, some

conclusions can be withdrawn:
r
egarding
North
, a young population means more protection, but other factors also contribute to a low
NOH per a 100 000 inhabitants; concerning
Lisbon
, age influence is offsetting co
-
morbidities,
resulting in an outcome (NOH/100 000 inhab; chart 1) on the level of
Centre
, Alentejo and Algarve.
Without age’s protective effect, hospitalisations
in Lisbon
rose sharply (see chart 2 and
supplementary

table
I
I).

In fact, when accounting all the factors, Lisbon has a AOR of 1,56
in

compari
son

with North.


North

presents higher values of NOH with Obesity, Hyperlipidemia, CKD and DM per a 100
000 hospitalisat
ions due to arrhythmias (table 5
) than
Lisbon
. CKD
as a protective effect and DM is
mostly irrelevant
. Obesity and Hyperlipidemia increase the odds of being h
ospitalised due to
arrhythmias (
AOR = 1,17 and AOR = 1,14
) and are higher in
North
, which seems to be a
contradiction. H
owever, Hypertension (AOR = 1,30
)

and Hyperthyroidism (AOR = 3,45
) are both
more frequent in
Lisbon

and are more relevant (higher AOR) t
han obesity and hyperlipidemia. As
such, we suppose that hypertension and hyperthyroidism are at the root of the differences found in
chart 2. Nonetheless, we believe they are not the unique reasons for such glaring disparities
displayed in
chart 2

between

North and Lisbon.


Conclusions

Age distribution is a major contributor in
assessing

the susceptibility of a population to
hospitalisation
-
leading cardiac arrhythmias. With this factor eliminated, hypertension’s and
hyperthyroidism’s prevalence are the most relevant influencers in the number of hospitalisations.

12

North population has a low
er risk of being hospitalised than Lisbon population.
This may be
due
t
o
the North’
relative
you
th

and
to a
greater prevalence of hyperthyroidism and hypertension in
Lisbon.
Nonetheless,
we suspect there
ar
e other underlying reasons
contributing to these
results.

Centre, Algarve and Alentejo
were similar in terms of number of hospitalisations.

However,
this

was

an

unpredictable result
,
reveal
ing

the high degree of complexity
on the epidemiology of cardiac
arrhythmias. Therefore, further studies
on this issue
are encouraged
.


Limitations

As in all studies we
were confronted with

several limitations. Some important information is not
routinely collected, for example information related to secondary diagnos
e
s. The high prevalence of
cardiac arrhythmias as principal diagnosis
might
be explained
in part
by the

increase in repeated
hospitalis
ations, since readmissions were considered as independent events.

This could also
int
roduce some bias on the results regar
ding co
-
morbidities.


ACKNOWLEDGEMENTS


We would like to
express thanks
to

Prof.
Dr.
Altamiro
da Costa
Pereir
a,
for his

constructive
criticisms and
sharp
suggestions to improve
our work and to

Dr.
Fernando

Lopes
, for

his
decisive
orientation on a critical
step of our wor
k.



13

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EFERENCES


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on obesity

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[Internet].
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NL, Dries DL, Bazzano L, M
ohler ER, Wright JT, Feldman HI.
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K,
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L,
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16

APPENDIX


Population and number of hospitalisations by NUT II regions


YEAR

NORTH

CENTRE

LISBON

ALENTEJO

ALGARVE


P
OP
[24
]

NOH

P
OP
[24
]

NOH

P
OP
[24
]

NOH

P
OP
[24
]

NOH

P
OP
[24
]

NOH

2000

3 643 795

2588

2 325 186

2536

2 608 117

3749

765

742

1009

383 399

485

2001

3

687

293

2741

2

348

397

2778

2 661 850

4021

776 585

1099

395

218

417

2002

3 691
922

2741

2 354
552

2877

2 714
614

4159

767
983

1105

398
370

514

2003

3 711
797

2935

2 366
691

3076

2 740
237

4425

767
549

1092

405
380

493

2004

3 727
310

3308

2 376
609

3452

2 760
697

4574

767
679

1297

411
468

645

2005

3 737
791

3402

2 382
448

3417

2 779
097

4755

765
971

1389

416
847

623

2006

3 744
341

3658

2 385
891

3756

2 794
226

4472

764
285

1395

421
528

619

2007

3

745

236

3502

2

385

911

3616

2

808

414

4368

760

933

1465

426

386

750

2008

3

745

439

3670

2

383

284

4098

2

819

433

4421

757

069

1436

430

084

703


Supplementary
Table
I

-

Population (POP) and Number o
f H
ospitalisations (NOH)
from 2000 to 2008, by NUT II
regions.

Note:

O
nly the values of the population referring to the year of 2001 are real values. All the others are
official
estimates

provided by INE.
[ 24
]


Chart 2 figures

and
95% Confidence Intervals


AGE GROUP

NORTH

CENTRE

LISBON


NOH

95% CI

NOH

95% CI

NOH

95% CI

0
-
4

8,2

4,1
-

1
2
,
3

15,4

8,0

-

2,
3

9,1

4,
3
-

1
4
,
0

5
-
9

2,5

0,3

-

4,6

4,4

0,5

-

8,4

5,8

1,7
-

9,9

10
-
14

4,2

1,4

-

7,0

10,1

4,
3
-

1
6
,
0

10,4

4,9
-

1
6
,
0

15
-
19

6,1

2,8
-

9,
3

10,6

5,0
-

1
6
,
3

14,7

8,3

-

2
1
,
2

20
-
24

8,6

5,0

-

1
2
,
2

13,4

7,5
-

1
9
,2

18,2

1
1
,
7

-

2
4
,
6

25
-
29

11,3

7,4
-

1
5
,
3

14,9

9,1
-

2
0
,8

20,1

1
4
,
0

-

2
6
,
1

30
-
34

12,1

8,
1
-

1
6
,
1

20,0

13,2
-

2
6
,8

21,5

1
5
,
3

-

2
7
,
7

35
-
39

15,8

11,2
-

2
0
,5

25,0

1
7
,
3
-

3
2
,7

26,3

1
9
,
2

-

3
3
,
5

40
-
44

25,3

1
9
,
3

-

3
1
,2

33,6

24,7
-

4
2
,4

43,6

3
4
,
1

-

5
3
,
0

45
-
49

35,0

27,7
-

4
2
,2

50,6

39,5
-

6
1
,8

63,4

5
1
,
7

-

7
5
,
0

50
-
54

54,6

45,0
-

64,1

79,5

6
5
,0

-

9
4
,
0

90,9

7
6
,
9
-

1
04,8

55
-
59

82,3

69,8
-

9
4
,8

126,8

107,7
-

145,8

143,1

125,4
-

160,8

60
-
64

141,9

124,0
-

159,8

192,8

168,5
-

217,0

225,6

201,9

-

249,3

65
-
69

226,9

2
0
3,6
-

2
50
,3

291,5

261,8
-

321,2

354,3

322,7
-

385,9

70
-
74

311,3

2
8
2,5
-

3
40
,1

430,2

393,2
-

467,1

568,1

524,9
-

611,3

75
-
79

603,3

557,7
-

648,8

743,3

689,7
-

797,0

1010,1

943,9
-

1076,3

80
-
84

602,0

5
45
,2
-

658,7

702,9

639,5
-

766,3

1059,5

973,7
-

1145,2

85 +

651,5

577,9
-

7
25
,2

750,8

671,1
-

830,4

1203,1

1090,7
-

1315,4


AGE GROUP

ALENTEJO

ALGARVE

17


NOH

95% CI

NOH

95% CI

0
-
4

8,8

-
1,
4

-

1
8
,
9

4,0

-
4,5

-

12
,
5

5
-
9

6,0

-
2,
5

-

1
4
,
4

3,9

-
5,1

-

12
,
9

10
-
14

8,5

-
1,3

-

1
8
,
3

30,4

5,
6

-

55
,
1

15
-
19

22,0

7,3

-

3
6
,
7

10,2

-
3,4

-

23
,
8

20
-
24

18,5

6,
2

-

3
0
,
7

10,9

-
2,
1

-

2
3
,
8

25
-
29

16,7

5,
6

-

2
7
,
8

15,0

0,9

-

29
,
1

30
-
34

24,7

1
1
,
0

-

3
8
,
4

22,2

5,3

-

3
9
,
1

35
-
39

27,1

1
2
,
6

-

4
1
,
6

23,4

5,9

-

4
1
,
0

40
-
44

51,0

31,4
-

70,7

38,0

1
5
,
6

-

60,
5

45
-
49

64,6

4
2
,
1

-

8
7
,
1

55,6

2
7
,
8

-

8
3
,
4

50
-
54

98,1

6
9
,
5

-

1
2
6,7

102,5

6
3
,
5

-

1
4
1,5

55
-
59

133,1

9
8
,
8

-

1
67
,5

159,3

108,7
-

209,8

60
-
64

192,2

150,5
-

233,8

188,3

131,0
-

245,5

65
-
69

299,4

249,4
-

349,4

303,7

229,7
-

377,7

70
-
74

460,2

397,6
-

522,8

465,2

369,5

-

561,0

75
-
79

784,9

694,5
-

875,3

746,7

611,5
-

881,9

80
-
84

809,8

692,1
-

927,4

710,1

550,1
-

870,0

85 +

762,5

628,2
-

896,7

850,2

639,2
-

1061,2


Supplementary table
I
I



NOH per a hundred thousand inhabitants, by age group and NUT II region

(
C
hart 2) and
95% confidence i
ntervals

(
adjusted to 100 000 inhabitants)
.