Document 6563525

European Heart Journal (1997) 18, 1019-1023
Blood pressure and mortality in an older population
A 5-year follow-up of the Helsinki Ageing Study
S.-M. Hakala, R. S. Tilvis, and T. E. Strandberg
Division of Geriatrics, Department of Medicine, University of Helsinki, Helsinki, Finland
Objective Hypertension is an established risk factor of
cardiovascular diseases, and in clinical studies its treatment
has reduced cardiovascular complications in subjects up to
80 years of age. In the older age groups, prognostic data on
blood pressure is sparse. We evaluated the prognostic
significance of different blood pressure levels and the
history of elevated blood pressure in an older population.
Conclusion At the population level, among subjects aged
75 years and over, favourable 5-year survival is indicated by
a high, but not a low, blood pressure.
(Eur Heart J 1997; 18: 1019-1023)
Results At 5 years, 240 subjects (40%) had died, 50% of
them of cardiovascular disease. In crude analyses, an inverse relationship between both systolic and diastolic blood
Key Words: Blood pressure, survival prognosis, elderly,
hypertension.
Introduction
As the proportion of individuals over that age
(and with a high prevalence of hypertension) is rapidly
increasing in Western societies, it is important to elucidate the role of hypertension in this age group. There is
evidence both from Finland'4' and in the United States'5'
that older people with high blood pressure have a
favourable survival prognosis. The purpose of our study
was to extend these previous studies by investigating
the prognostic value of blood pressure in those aged
between 75 and 85 years at the population level.
Recent reviews of several randomized trials have convincingly shown that older people benefit from treatment for elevated blood pressure'1>2'. Antihypertensive
treatment has been shown to reduce the incidence of
cardiovascular accidents, particularly strokes. In addition, the treatment of isolated systolic hypertension —
considered earlier to be an innocuous phenomenon in
the elderly — was shown to prevent cardiovascular complications in one study'3'. However, the studies have
been selective, including mostly healthy elderly, and
consequently, the results may not apply to the elderly at
large. Furthermore, the trial evidence was mostly only
up to 79 years.
Revision submitted 2 July 1996, and accepted 8 July 1996.
Correspondence: Professor Reijo S. Tilvis, MD, Division of
Geriatrics, Department of Medicine, University of Helsinki,
FIN-00290 Helsinki, Finland.
0195-668X/97/061019+05 $18.00/0
Methods
Subjects
The Helsinki Ageing Study is a population-based joint
study of general and special health care in the City of
Helsinki, Finland. It was planned to evaluate the prognostic significance of different clinical findings in the
1997 The European Society of Cardiology
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Design In the Helsinki Ageing Study random individuals
75, 80, and 85 years of age (n = 521) were evaluated at
baseline using postal questionnaires, structured interviews,
clinical examinations, laboratory investigations, and blood
pressure measurements (supine, seated, standing). Date
of death during a 5-year follow-up was verified using
computerized registers, and thus the follow-up was 100%
complete. The data were analysed using life-table analyses
and Cox proportional hazards models.
pressure and mortality was observed in all groups combined
(P<001), and separately in the 80 and 85-year-old groups.
However, a J-shaped link between diastolic blood pressure
and mortality was found in the 75-year-old group. After
controlling for age, gender and the presence of clinically
significant diseases (in 72% of subjects) baseline blood
pressure was associated with favourable 5-year survival.
The risk ratios of systolic (per lOmmHg) and diastolic
blood pressure (per 5 mmHg) were 0-90 (95% CI 0-85-0-96)
and 0-92 (95% CI 0-86-0-99), respectively. Neither isolated
systolic hypertension nor a history of hypertension treatment were associated with 5-year survival.
1020 S.-M. Hakala et al.
Table 1
Helsinki Ageing Study population by gender and living conditions
Age group (years)
Gender
Women
Men
Living conditions
Home
Nursing home
Hospital
85
80
75
Random
sample
Studied
clinically
This
study
Random
sample
Studied
clinically
This
study
Random
sample
Studied
clinically
This
study
190
84
168
71
143
58
192
74
155
57
126
48
201
54
156
44
115
31
248
20
6
216
17
6
186
11
4
217
39
10
172
30
10
153
16
5
169
64
22
126
52
22
107
29
10
Clinical evaluations and follow-up
The cohorts were re-examined three times (in 1991, 1993
and 1994). The examinations included a postal questionnaire, a structured interview conducted by public-health
nurses, a review of all available patient records, a
thorough clinical structured examination carried out by
general practitioners, comprehensive laboratory investigations, and echocardiogaphic examinations at entry161.
The census status was examined annually until 31
December 1994 (5 years).
overnight, but they had taken their regular medications.
Blood pressure and heart rate were first measured while
seated, followed by an electrocardiogram recording.
After lying down for 5 min, the supine blood pressure,
and after 1 min quiet standing, the standing blood
pressure were measured. Seated blood pressure values
were also registered by physicians.
The group of healthy elderly
Of the subjects, 126 were assigned to a group of healthy
elderly, if their subjective health was good or moderate
(scale: good, moderate, bad, very bad), if they had
normal exercise tolerance according to the examining
physicians (NYHA I)[9], and if they were free from
diabetes, dementia, cancer, emphysema, and if they
had no symptoms of cardiovascular (except high blood
pressure) or cerebrovascular disorders.
Statistical evaluation
Data were analysed with Biomedical Data Processing
(BMDP 1988) system"01. Life-table analyses and Cox
proportional hazards regression models were used for
survival analyses.
Clinical criteria
Hypertension was denned as a past diagnosis of hypertension with medication, or current blood pressure over
160/95 mmHg. Isolated systolic hypertension was defined
as supine systolic blood pressure over 160 mmHg and
diastolic less than 90 mmHg (with or without treatment).
Clinical criteria for dementia and major depression were
those of DSM-IH-R17'. Angina pectoris was diagnosed
according to the criteria of Rose'81. The presence of other
diseases was based either on data from hospital patients'
records or the present clinical examination.
Blood pressure measurements
These were performed by specially trained nurses
between 0800h and lOOOh. The subjects had fasted
Eur Heart J, Vol. 18, June 1997
Results
At 5 years, 240 subjects (40%) had died, 50% of them
from cardiovascular diseases. Life-table analyses of all
age groups showed an inverse relationship between total
mortality and both systolic (/><0001) and diastolic
blood pressure (/><0-001). Separate analyses of different
age groups are shown in Fig. 1. In general, the associations were inverse between blood pressure and 5-year
mortality. However, in the 75-year-old group, the association between diastolic blood pressure and mortality
was J-shaped.
After controlling for age, gender and the presence of clinically significant diseases (in 72% of subjects),
baseline blood pressure was associated with beneficial
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older population at large. From the Helsinki Census
Register, random cohorts of individuals alive in July
1988 and born in 1904, 1909 and 1914 (300 in each
group, 11 -2% of total population of 8035) were invited
to join the study in September 1989. Of these cohorts,
795 were still alive and living in the City of Helsinki.
Altogether 144 (181%) refused to participate leaving
651 (81 -9%) people to be examined clinically until April
1990. The gender distribution of the study population
equalled that of the total population. Three measurements of blood pressure were completed in 521 subjects
(80%) (Table 1). Seventy-one of the study participants
were in homes for the elderly.
Blood pressure and mortality
<120
Syst
121-140
°Hc blood
141-160
161-180
1021
>180
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Figure 1 Percentage 5-year survival of three birth cohorts using baseline blood
pressure levels from the population-based Helsinki Ageing Study. (There were no
subjects in the 80-year-old group with diastolic blood pressure > 100 mmHg).
5-year survival (Table 2). The results were similar irrespective of whether the sample had been taken with the
subjects supine, standing or seated. Neither the presence of isolated systolic hypertension at baseline, nor a
history of hypertension treatment was significantly
associated with 5-year survival. Exclusion of early
deaths (during first 2 years) did not materially alter the
results either.
Eur Heart J, Vol. 18, June 1997
1022 S.-M. Hakala et al.
Table 2 Adjusted risk ratios for five- year mortality of
different blood pressure measurements
Measurement
Systolic, per lOmmHg
supine
standing
sitting
mean
Diastolic, per 5 mmHg
supine
standing
sitting
mean
Risk ratio
95% confidence
interval
0-92
0-93
0-90
0-90
0-87-O-97
0-89-0-98
0-85-0-95
0-85-0-96
0-93
0-94
0-94
0-92
0-88-0-99
0-89-0-99
0-89-1 00
0-86-0-99
The risk ratios were calculated using the Cox regression model, in
which age, gender and presence of diseases (yes/no) were forced in.
Discussion
Eur Heart J, Vol. 18, June 1997
This study was supported by the Ragnar Ekberg Foundation.
References
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In the extensive field of hypertension and its treatment,
the present study makes an important contribution for
three reasons. First, the Helsinki Ageing Study was
initially planned to evaluate the risk of different clinical
conditions in the elderly. Therefore, special emphasis
has been paid to the representativeness of the population sample. A second important feature — which also
differentiates the study from most other studies in the
elderly — is the age (birth) cohort approach. Consequently, it is possible to recognize possible differences
inside the elderly population. This approach was useful
in the present study where associations between blood
pressure and mortality were not consistent until 80 years
onwards. Third, our data can be seen to be reliable,
as different methods of blood pressure measurement
gave consistent results. The number of deaths was also
sufficiently large to draw reliable conclusions.
The inverse association between blood pressure
and mortality seems to be at odds with well-known
adverse effects of hypertension in young and middleaged populations'"1. The earlier finding in many studies
in the elderly has been a J-shaped or U-shaped relationship between blood pressure and mortality. However,
several former studies have found an inverse relationship, both in persons over 85 years'41 and around 78
years'51. This and the J-shape have usually been attributed to the effect of co-morbidity. The individuals with
serious diseases have also low (or recently lowered)
blood pressure and increased risk of death. Indeed, the
recent study of Glynn et a/.'121 showed that after adjustment for serious diseases and exclusion of deaths during
the first 3 years of follow-up, lower blood pressure did
predict better survival. The age of their population,
however, started from 65 years with the mean age less
than 75 years. In the present study, the relationship
tended to be inverse after 75 years, thus pinpointing the
transition of high blood pressure from 'bad' to 'good' at
80 years of age. The statistical control for diseases,
or exclusion of early deaths did not alter the major
relationship. However, we do not believe that these
procedures are sufficient to totally exclude recidual
confounding by diseases associated with ageing. Thus,
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'senile devitalization' preceding death. Also the lack of
effect of antihypertensive treatment tends to support
this.
Recent reviews have shown that generally the
treatment of hypertension benefits the elderly up to 80
years'121. Studies in persons over 80 years are sparse, but
the Swedish STOP-hypertension study suggested benefit
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blood pressure > 180/90 mmHg'131. However, no reports
describe the benefit, specifically in the group over 80
years, which only constituted 16% of the study population. In general, participants in trials are very selective.
For example, our cohorts were screened in order to find
participants for the SYST-EUR trial of isolated hypertension, only 4% were found eligible. Not a single
participant was eligible for the Hypertension in the Very
Elderly Trial (HYVET, [14]).
Overall, previous data and the present results
suggest that starting antihypertensive medication after
80 years is problematic. Those with the lowest blood
pressure are at increased risk of death, and as compared
to them, those with highest values are not. Thus, at the
individual level the finding of very old persons at true
risk due to their hypertension is difficult, and the start of
medication requires very individual assessments of benefits and risks. On the other hand, in contrast to some
other studies'15il6], we found no association between
antihypertensive drug use and subsequent mortality in
our study.
Blood pressure and mortality
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Eur Heart J, Vol. 18, June 1997