© International Epidemiological Association 1999
International Journal of Epidemiology 1999;28:756–763
Printed in Great Britain
Mortality statistics in immigrant research:
method for adjusting underestimation
of mortality
Gunilla Ringbäck Weitoft,a,b Anders Gullberg,a Anders Hjerna,c and Måns Roséna,b
Background It is difficult to carry out fair comparisons of the mortality of different ethnic groups
in a population in register-based studies because sizeable numbers of immigrants
who subsequently leave their new homeland fail to register this fact with the national registration authorities. In this article we present a method which attempts
to address these problems.
Methods
Age-standardized mortality rates for native Swedes and immigrants in the age
group 20–64 years were calculated for all individuals who either were included
in the Swedish Population Censuses for 1985 or 1990, or who moved to Sweden
during the period November 1990–1994. In order to define the population under
scrutiny different sources of income are used as indicators of residence in the
country.
Results
When an analysis is made of all nationally registered individuals, significantly reduced death rates are found among immigrants outside the north-east of Europe
compared to those for Swedish-born people. Extremely low death rates are found
for those born in Turkey, Southern Europe, Latin America, Asia, and Africa and
for those who are younger and without any income. When the income criterion
is introduced, there is a change so that the earlier significantly reduced relative
death risks for immigrants born outside the north-east of Europe for some subgroups are no longer significantly lowered.
Conclusion
This study has important implications for the interpretation of every study of mortality among immigrants based on official mortality statistics. Using information
about income as an indicator of residence in the country appears to be a method
which can be pursued further in order to achieve a more accurate understanding
of mortality among immigrant groups.
Keywords
Sweden, mortality, immigration, mis-registration, income, social benefits
Accepted
13 January 1999
In recent decades, with the settlement of hundreds of thousands
of refugees and immigrant workers, Sweden has become a
multi-ethnic society. After the second world war, when there
was a labour shortage in Sweden, many people were actively
recruited into industry, especially from Finland and Southern
a Centre for Epidemiology, National Board of Health and Welfare, Stockholm,
Sweden.
b Department of Epidemiology and Public Health, Umeå University, Umeå,
Sweden.
c Department of Clinical Sciences, Huddinge University Hospital, Karolinska
Institutet, Stockholm, Sweden.
Reprint requests to: Gunilla Ringbäck Weitoft, Centre for Epidemiology,
Swedish National Board of Health and Welfare, 106 30 Stockholm, Sweden.
E-mail: [email protected]
Europe. Since the 1970s immigration has mainly been made up
of refugees and relatives of immigrants already settled in the
country.
No extensive survey of mortality and causes of death among
immigrants has been carried out in the Nordic countries.1 Considering the lower socioeconomic status as well as the stress
and trauma connected with the migration process, it has been
suggested that the mortality of many immigrant groups should
be higher than that of the native, Swedish-born population,
whose mortality rate is, in fact, among the lowest in the world.
This suggestion is based on the fact that morbidity is higher
among those born outside Sweden, irrespective of whether
it is measured as the number of days on sickness benefit, the
number of visits to health centres, the percentage of people with
disability pensions or the reported self-perceived state of health.2
756
MORTALITY STATISTICS IN IMMIGRANT RESEARCH
Immigrants from Southern Europe have a morbidity rate that
is three times higher than that of the Swedish-born population.1
Diseases of the musculoskeletal system and psychological
problems are the main reasons for sickness absence among
the women in this group. Individuals born in Greece, former
Yugoslavia and Turkey, who can primarily be described as labour
force immigrants, have a high frequency of retirement on disability pensions. Males and females born in Finland, Southern
Europe or in non-western countries have high rates of severe
long-term illness when factors such as education, material possessions, financial resources and social network are taken into
account.3 Several studies have confirmed that Finns (those living
in Sweden as well as those in Finland) are exposed to what are
traditionally regarded as risk indicators for coronary heart disease, and that they also have a relatively high risk of developing
the disease.4–6
An argument often used against this assumption of higher
mortality rates among immigrants is that generally, as far as health
status is concerned, they represent positive selection from a
population.7 Experiences from Europe, however, indicate that
immigration from neighbouring countries, for example Finnish
immigrants in Sweden and Irish immigrants in England, suggest
a negative selection regarding health.
Immigrants to Sweden born outside the Nordic area have
repeatedly been shown to have a strikingly low mortality risk.
Yet these results have not gained general recognition. Instead
they have been used to highlight and even calculate shortcomings in the Swedish population register.8–9 Immigrants tend to
be much more mobile than other segments of the population
and therefore pose new challenges to any morbidity and mortality statistics based on the Swedish national registries. It is
likely that a considerable number of those who emigrate to
Sweden and subsequently leave the country fail to inform the
national registration authorities when they do so. They are consequently not struck off from the Swedish population registers,
which results in overestimation of the immigrant population.
Thus when deaths are not reported to the Swedish registries,
the mortality figures for immigrants in Sweden will be underestimated. This problem may apply to all epidemiological studies
of ethnic groups.
There are incentives for people to remain registered in Sweden
while living elsewhere. Being struck off from the Swedish population registers means losing permanent residence status which
might make re-immigration more difficult. Some benefits are
also connected to national registration, for instance child benefit
and, until 1993, retirement pension. Being registered also ensures access to the Swedish health care system and dental
services. Sometimes it might be difficult to determine whether
a person has moved from the country or whether the situation
should be defined as double settlement.
Ekberg9 has suggested a list of indicators of overrepresentation in the population-registries:
• Strikingly low registered death rates in an immigrant group.
• Low employment levels for well-established immigrant
groups.
• Only a small percentage with social allowance or unemployment benefit despite low employment levels.
• A relatively large proportion of the individuals with no
disposable income.
757
According to Ekberg9 low mortality rates were found
especially among Greek immigrants. Greek-born males in
Sweden had a death rate which was 54% of that for Swedishborn males, and for Greek-born women the death rate was 46%
of that for Swedish-born women.
Of the Greek-born immigrants 8% had no disposable income,
compared to 0.4% of native-born Swedes.
The problem of overrepresentation in population registries
may be so great that any conclusions about differences between
Swedes and others with regard to mortality, morbidity, income,
fertility and receipt of social benefits, etc. run the risk of being
distorted. However, these circumstances do not apply to the
same extent to individuals who move between the Nordic
countries. The national registration systems in these countries
have been co-ordinated since 1969, which means that anyone
returning to a Nordic country of origin is routinely reported to
the country he or she has left.
Aim
The aim of the present study has been to analyse mortality
differences between people born in Sweden and those who
have immigrated into Sweden. For this purpose we have used a
specific method for addressing the suspected underreporting
of deaths of people born outside the Nordic countries. This
method, specially developed and used for this purpose, focuses
on information about income and social benefits as indicators of
residence in the country.
Material and Method
The population studied was generated from people who either
were included in the Swedish population censuses (FoB) of 1985
or 1990, or those who moved to Sweden during 1990–1994,
giving a total of 9 856 240.
Information about income and social benefits was obtained
from the Total Enumeration Income Survey held by Statistics
Sweden. Data on mortality were collected from the Cause of
Death register at the National Board of Health and Welfare.
The Total Enumeration Income Survey comprises annual
information on taxes and incomes of the entire population. We
had access to the annual sums in Swedish crowns (SEK) for the
years 1986–1994.
To be able to use information about income and social benefits as an indicator of residence in the country when mortality
among immigrants was analysed, the individuals were grouped
according to whether they fulfilled certain income criteria or
not. These criteria are as follows:
• At least part of an individual’s income should derive from
either work, a daily allowance, cash labour market assistance,
social security benefits or sick pay. Because of the obligation
either to have a job or to be in contact with the social welfare
office or employment office to receive money, these are sources
of income which should ensure that the person in question is
in the country. This means, for example, that people whose
sole source of income was a disability pension did not fulfil
the criteria. Any annual sum exceeding 0 SEK in a calendar
year was considered to be fulfilling the criteria.
• Those who did not fulfil the criteria above but had received
disability pension or temporary disability pension. While
758
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
the regulations about sick pay do not distinguish between
Swedish-born and others, there are special regulations regarding disability pension and temporary disability pension making
it more difficult for immigrants to qualify for this compensation, at least during the first years after immigration. The
rules also distinguish between different nationalities. Since
1993 the main part of the pension for EU-members has also
been available to individuals living abroad.
• Remaining individuals, i.e. those who do not fulfil any of the
criteria above (but are still nationally registered).
• As a comparison all nationally registered people were also
analysed. Individuals who have a residence permit and intend
to stay in Sweden for at least one year are nationally registered. Refugees and other asylum seekers who have not got
a residence permit are by definition not included in the
Swedish population and consequently not a part of this study.
The population was divided into groups according to country of
birth. The criteria for placing countries in the same group are:
(1) presumed similarities regarding systems for reporting causes
of death; (2) similarities of incentives for individuals to remain
registered in Sweden although not living here and; (3) similarities regarding the kind of migration from the country (refugee
or labour migration). The groups were as follows:
• Swedish-born.
• Born in other Nordic countries—i.e. Norway, Finland,
Denmark and Iceland.
• Eastern Europe—i.e. Estonia, Latvia, Lithuania, Albania,
Bulgaria, Romania, Czechoslovakia, former East Germany,
Poland, Hungary and the rest of the former Soviet Union.
• Southern Europe—i.e. Greece, Italy, Spain, Portugal, the
Vatican, Monaco, Malta and San Marino, former Yugoslavia,
Turkey, Latin America, Africa and Asia.
• The rest of Europe (European countries not defined above),
USA, Canada and Oceania.
Number of person-years, deaths, mean age for 1994 and mean
disposable income for 1994 are shown in Table 1 for the groups
defined above.
Mortality in the age group 20–64 years was followed up by
matching with the National Cause of Death register for the
years 1987–1994.
For an individual to contribute one person-year to the number of person-years at risk as well as to be followed up in the
National Cause of Death register, both the year before and the
actual calendar year that generated person-years and deaths,
were controlled with regard to income. For either of them the
criteria had to be fulfilled. One reason for not only checking
the actual year was to avoid eliminating people who had died
at the beginning of a calendar year and had not had enough
time to fulfil the required income criteria. Individuals might
therefore be at risk in different subgroups during different parts
of the study period. The follow-up continued until age 64 or
death. The year of death was counted as half a year for that
specific calendar year.
Age-specific mortality rates (number of deaths/number of
person-years at risk) were calculated in 5-year age intervals separately for those born in Sweden and for those born elsewhere,
and standardized mortality rates were arrived at as weighted
means of the stratum-specific mortality rates (direct age standardization weighted in accordance with the proportion of
person-years for the whole population under risk by the various
age groups, men and women separately10).
Information about country of birth, age and sex was obtained
from either the Census of 1985 or 1990 or from the income
files. As a first step, mortality according to birth country groups
was analysed for all those (1) who were nationally registered
and (2) divided into subgroups in accordance with sources of
income which in different ways can be regarded as evidence
of residence in the country. As a second step mortality was
compared between the Swedish-born and those born outside
Sweden. To do this, information from previous income analyses
was used in the generation of the study population. The hypothesis for an external validation of the suggested method is that,
when income criteria are fulfilled, the mortality pattern among
immigrants from non-Nordic countries should change more
dramatically than for native Swedes and Nordic immigrants.
Results
During the study period 1987–1994, a total of 106 465 deaths
were registered in the age group 20–64 years and 40 004 180
person-years were generated, when the whole nationally registered population was studied. The distribution of individuals
grouped according to country of birth and income criteria as
well as mean age and mean disposable income (total income
and benefits after tax) in 1994 of those at risk is seen in Table 1.
For Swedish-born males 96.3% of the person-years accumulated for all nationally registered native Swedes fulfil the income
criteria. For females the corresponding figure is 93.8%. The
lowest percentages in this group are found among those born
in Southern Europe, etc., with 83.1% and 78.5%, respectively,
for males and females. Those with no income constitute 0.9%
for Swedish-born males and 2.6% for females. For all other
country groups these percentages are higher. For people from
Southern Europe, etc., 13.3% of the nationally registered males
and 16.1% of the females lack incomes according to our criteria.
This group also has the lowest mean disposable income (1994).
At the same time, those born in Sweden with no income have
the highest mean disposable income, even higher than those
who fulfil the income criteria.
In Table 2, column 1 shows the traditional way of comparing
the total mortality between native Swedes and those born
outside Sweden where all nationally registered individuals are
taken into account. Individuals born outside the north and east
of Europe have a significantly reduced risk of dying. However,
for men born in the other Nordic countries there is a 50% excess death risk. Nordic women also have a significantly elevated
risk, which is also true for males from Eastern Europe.
Considering the shortcomings of the national registry we
felt it was necessary to go further and compare mortality for
different nationalities in accordance with the above-defined
income criteria used as indicators of residence in the country.
Age-standardized death rates with 95% confidence intervals are
shown for men (Figure 1) and women (Figure 2) for all those in
the national registry; those who either have an income from work,
a daily allowance, cash labour market assistance, social security
benefits or sick pay; those with disability pensions instead of the
income types mentioned; and finally those remaining who do
Female
293 126 (100)
Female
803 041 (100)
Female
234 850 (100)
Female
532
876
773
1879
565
1010
2892
44.3
43.0
36.4
37.6
41.9
43.9
44.9
44.2
40.8
40.6
a Mean disposable income 1994 in 1000 US$ on 1 January 1998.
263 781 (100)
Male
The rest of Europe,
USA, etc.
1 012 970 (100)
Male
Southern Europe,
Latin America, etc.
220 131 (100)
Male
Eastern Europe
932 330 (100)
1 107 062 (100)
Male
5335
17 252 786 (100) 33 049
Female
Other Nordic
countries
17 844 103 (100) 59 554
Male
Sweden
Country of birth
12.3
16.0
10.5
11.3
12.9
15.4
14.3
16.0
191 498 (81.5)
226 723 (86.0)
630 385 (78.5)
841 903 (83.1)
248 282 (84.7)
194 183 (88.2)
974 401 (88.0)
831 303 (89.2)
357
688
517
1400
384
732
1883
3921
14.6 16 187 119 (93.8) 23 486
18.3 17 175 913 (96.3) 46 732
44.2
42.8
35.3
36.2
40.4
42.0
42.6
42.6
38.2
38.3
13.9
14.2
12.2
11.8
13.5
13.6
14.6
14.2
14.1
15.0
11 848 (5.0)
6758 (2.6)
43 454 (5.4)
36 787 (3.6)
15 496 (5.3)
10 891 (4.9)
80 242 (7.2)
55 806 (6.9)
619 229 (3.6)
146
156
211
420
150
255
891
1335
8078
515 223 (2.9) 12 163
58.3
57.2
52.2
54.1
55.4
55.9
55.8
55.8
54.4
54.3
12.0
15.6
12.1
12.9
12.6
13.8
12.0
13.6
11.9
14.7
31 503 (13.4)
30 300 (11.5)
129 201 (16.1)
134 280 (13.3)
29 348 (10.0)
15 056 (6.8)
52 418 (4.7)
45 220 (4.9)
446 438 (2.6)
152 966 (0.9)
Others
29
32
45
59
31
23
118
79
1485
659
42.7
42.1
35.3
37.5
41.6
44.1
44.3
43.3
41.7
41.0
11.3
16.9
7.3
10.3
12.1
17.6
13.4
15.1
15.2
20.8
Mean Mean
Mean Mean
Mean Mean
Person-years (%) Deaths
age
inc a Person-years (%) Deaths
age inc a Person-years (%) Deaths
age
inc a
Mean Mean
Person-years (%) Deaths
age
inc a
Disability pension
Fulfils income criteria
All nationally registered
Table 1 The distribution of individuals grouped according to country of birth and criteria of income, number of person-years, deaths 1987–1994, mean-age 1994 and mean-income 1994, for
males and females respectively
MORTALITY STATISTICS IN IMMIGRANT RESEARCH
759
760
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
Table 2 Risk of death among individuals born outside Sweden compared to Swedish-born 1987–1994 in the age group 20–64 years. Agestandardized relative risks (SRR) with 95% confidence intervals (CI), men and women. All nationally registered, those who fulfil the income
criteria including those with disability pension, and the same group but without disability pensioners
All nationally registered
Fulfil income criteria
including those with
disability pension
No. of deaths
SRR
No. of deaths
SRR
Male
59 554
1.00
58 895
Female
33 049
1.00
31 564
Male
5335
1.55
1.51–1.60
5256
1.58
Female
2892
1.18
1.14–1.23
2774
1.19
1010
1.10
1.03–1.18
987
565
0.99
0.91–1.07
534
1105
0.89
0.84–0.95
414
0.80
0.72–0.88
Male
876
0.86
Female
532
0.86
Country of birth
95% CI
Only those who fulfil
income criteria
95% CI
No. of deaths
SRR
95% CI
1.00
46 732
1.00
1.00
23 486
1,00
1.54–1.63
3921
1.58
1.53–1.64
1.14–1.23
1883
1.17
1.12–1.23
1.13
1.06–1.20
732
1.12
1.04–1.21
1.01
0.93–1.10
384
1.04
0.93–1.15
1075
0.95
0.89–1.01
714
0.95
0.87–1.03
391
0.86
0.78–0.95
223
0.85
0.73–0.99
0.80–0.92
844
0.89
0.83–0.95
688
0.91
0.85–0.99
0.78–0.94
503
0.89
0.81–0.98
357
0.91
0.81–1.01
Sweden
Other Nordic countries
Eastern Europe
Male
Female
Southern Europe,
ex-Yugoslavia, Turkey
Male
Female
The rest of Europe, USA,
Canada, Oceania
Latin America
Male
161
0.67
0.56–0.81
154
0.73
0.60–0.88
142
0.79
0.64–0.95
91
0.65
0.52–0.81
85
0.69
0.55–0.87
77
0.81
0.63–1.04
Male
613
0.70
0.64–0.78
591
0.78
0.71–0.87
544
0.86
0.77–0.96
Female
268
0.75
0.65–0.86
252
0.86
0.75–1.00
217
0.91
0.78–1.06
Female
Africa and Asia
Fulfils
criteria of
income
Figure 1 Age-standardized death rates with 95% confidence intervals for all nationally registered and according to income
criteria in groups of birth countries: males
MORTALITY STATISTICS IN IMMIGRANT RESEARCH
761
Figure 2 Age-standardized death rates with 95% confidence intervals for all nationally registered and according to income
criteria in groups of birth countries: females
not fit into any of the other groups. Looking at the first diagram
bar in the groups of birth countries, in other words the one
representing all those nationally registered, we can see the
pattern from Table 2, column 1, in which there are significantly
lowered death rates among those born in Southern and Western
Europe and countries outside Europe in comparison to those
born in Sweden.
A reduction of death rates is evident, both for men (Figure 1)
and women (Figure 2), if only those who fulfil the income criteria are included. This applies to a lesser extent for individuals
from Southern and Western Europe and from outside Europe.
Not surprisingly the most evident excess of death rates is
found among individuals with a disability pension (third bar
in the diagram), although this varies with country of birth. For
men a pattern of significantly lowered death rates among
groups born in Eastern and Southern Europe, etc., is shown,
compared to those born in Nordic countries. The same applies
to women born in Southern Europe, etc. Women with disability
pensions have a lower mortality rate than men overall.
Finally the fourth bar—for our purposes perhaps the most
interesting one representing those individuals who neither have
an income from work nor from the social security system—is
remarkably low, except for the native Swedes in this group.
For Swedish-born men the death rate is significantly higher for
those with no income than for both nationally registered individuals and those who fulfil the income criteria. When the groups
of Southern Europeans, etc., are analysed, a completely different pattern emerges. Both men and women with no income
have significantly lower death rates compared to those who
have an income and also compared to the group comprising all
nationally registered individuals.
Making comparisons in this group between the countries, for
males born in Southern Europe, etc., the mortality rate is 17%
of the rate for Swedish-born males. For women the
corresponding figure is 32%. All male nationality groups with
no incomes have a significantly lower death risk compared to
the Swedish-born males, and this even applies to those born in
the other Nordic countries. For women those born outside the
Nordic countries have significantly lower death rates, while those
born in other Nordic countries have almost the same mortality
risk as native Swedes.
Table 3 shows the age-standardized risks for the different
country groups relative to those born in Sweden in the age
ranges 20–44 and 45–64 years. Men and women are looked at
separately and the figures apply only to those with no income
in accordance with our definition.
A pattern of consistently lower relative mortality risks emerges
for the younger age range, although less often deviating significantly from those for the older groups.
Finally, as a last step a comparison is made between groups
born outside Sweden and inside Sweden. Before the comparison is made, however, these groups are excluded from among
those nationally registered: (1) those who do not fulfil any of
the stated income criteria (Table 2, column 2); (2) those who do
not fulfil the income criteria and those with disability pensions
as the only source of income (Table 2, column 3).
In this analysis the relative death rates for individuals born
outside the north-east of Europe are increased considerably. For
males born in Southern Europe, former Yugoslavia and Turkey
as well as for Asian and African women the previously significantly reduced relative risk compared to native Swedes is no
longer apparent. This could be interpreted as if the groups have
762
INTERNATIONAL JOURNAL OF EPIDEMIOLOGY
Table 3 Risk of death 1987–1994 among groups of individuals born outside Sweden compared to Swedish-born in the age-groups 20–44 and
45–64 years. Age-standardized relative risks (SRR) with 95% confidence intervals (CI), men and women; those who do not fulfil income criteria
Country of birth
Age (years)
No. of deaths
SRR
95% CI
Male
20–44
45–64
185
474
1.00
1.00
Female
20–44
45–64
114
1371
1.00
1.00
Male
20–44
45–64
25
54
0.40
0.82
0.26–0.62
0.61–1.09
Female
20–44
45–64
15
103
0.77
1.04
0.45–1.33
0.83–1.31
Male
20–44
45–64
6
17
0.25
0.71
0.11–0.56
0.43–1.15
Female
20–44
45–64
7
24
0.41
0.73
0.19–0.89
0.48–1.10
Male
20–44
45–64
34
25
0.14
0.20
0.10–0.21
0.13–0.30
Female
20–44
45–64
15
30
0.21
0.35
0.12–0.38
0.24–0.51
Male
20–44
45–64
8
24
0.18
0.72
0.08–0.37
0.47–1.09
Female
20–44
45–64
3
26
0.21
0.63
0.06–0.70
0.41–0.95
Sweden
Other Nordic countries
Eastern Europe
Southern Europe, ex-Yugoslavia, Turkey, Latin America,
Asia and Africa
The rest of Europe, USA, Canada, Oceania
been made more equal with regard to representation in the
population registries.
Discussion
The present study has important implications for the
interpretation of every study of mortality among immigrants
in Northern and Western Europe in the last few decades. When
immigrants have an incentive to remain on the population
registries, even when they are in fact living in their home
countries which do not report deaths adequately to the national
registries in question, mortality rates easily become misleading.
The method used in this study demonstrates that there is an
underestimation of mortality, especially for individuals born in
Southern Europe, Latin America, Asia and Africa. The magnitude
of underestimation, however, is difficult to assess.
We used information about income and social benefits in
order to define groups with presumably dissimilar patterns of
residence in the country, and we based our methodology on
earlier findings of suggested indicators of overrepresentation in
the population registries.9 The basic idea was to sort out those
individuals for whom the information about income indicated
non-residence in the country. This was done in order to define
more carefully the denominator, and then to facilitate a better
comparison between different immigrant groups as well as
between immigrant groups and native-born Swedes.
Since it is necessary to either be employed or to be in personal
contact with authorities to receive money, an income (anything
above 0 SEK) from work, social allowance, cash labour market
assistance, social security benefits or sick pay would indicate
residence in the country at least for a short time in a calendar
year. This is, of course, quite a crude indicator, and the income
limit could always be discussed. In separate analyses (not shown
here) we used a special level of income (e.g. a disposable income
of more than 1, 2 or 3 base-rates respectively) as our income
criteria, and the results indicated that with increasing incomes
there was also an increase in the figures for the relative mortality of non-Nordic individuals compared to those born in
Sweden. The disadvantage was that it resulted in a substantial
decline in the number of people included in the study, especially those of non-Nordic origin. Furthermore, one could not
prevent presumably worse-off Swedes being excluded, which of
course could also be a problem in the present analysis, but to a
smaller extent. On the other hand, the group of Swedish-born
individuals who were excluded in this way have the highest
mean disposable incomes in 1994, probably as a result of a mixture of extremely poor individuals and very rich people having
high incomes from interest and other dividends. No unambiguous picture of a possible selection is given. Though, there are
reasons to believe that our income limit is far too low. Costs of
living in Sweden are relatively high, and living with little or no
disposable income is rare among native Swedes.
A recent study of suicide deaths among immigrants in Sweden reported surprisingly low rates for immigrants from Southern Europe, Africa, Asia and Latin America.11 For Yugoslavian
immigrants comparisons were also made with the suicide rate in
their country of birth and was found to be significantly reduced.
Recent studies of Turkish immigrants in Germany found that
the immigrant population experience an overall mortality
half that of the indigenous German population.12 This also
MORTALITY STATISTICS IN IMMIGRANT RESEARCH
applies to deaths from cardiovascular diseases.13 Given the
relatively low socioeconomic status of Turkish immigrants, this
is puzzling and the authors seek part of the explanation in a
‘healthy migrant effect’ and an ‘unhealthy re-migration effect’.
These results to some extent may be taken into consideration in
discussion of the present study, with consideration of the possible impact on the strikingly reduced mortality risks of the shortcomings in the population registries. This is especially true when
it comes to suicide-related mortality, since this is a cause of death
most common in younger age groups, and our results indicate
that the problem with overrepresentation in the registries seems
to be more widespread among younger individuals.
The Total Enumeration Income Survey, comprising information
on all declared taxes and incomes of all nationally registered
people in Sweden, is the best available source of information
for our purpose. Though incomes from the ‘black sector’ are not
possible to assess, the question is whether it is possible to live in
the country without having any kind of legal income at all during a calendar year. Housewives supported by their husbands,
with no connection to the labour market, might incorrectly
be excluded. A former income from work forms the basis of
national insurance (except for part of the disability pension),
but it is not used for cash labour market assistance and social
benefit. Therefore the suggested method is perhaps more applicable to males.
Since a disability pension does not necessarily indicate
residence in the country, we chose to analyse individuals with
such a pension as their only source of income separately. All
this is the result of inconsistent regulations about time periods
and different conventions in different countries. The mortality
pattern might indicate that this group is overrepresented in the
population registries for some nationalities. For those born in
Eastern and Southern Europe, etc., the mortality rates are significantly lower than for Swedish-born disability pensioners.
Considering that Southern Europeans, in particular, are mainly
older labour force immigrants with a history of undertaking
heavy work and thus with more reports of musculoskeletal
diseases and psychological problems than other groups, this
relatively low mortality rate might reflect that they suffer from
fewer fatal diseases than Swedish-born disability pensioners.
Conclusion
Our results indicate that Swedish mortality statistics are misleading for immigrants, particularly for those born in Southern
Europe, Turkey, Latin America, Africa and Asia.
When the income criterion is introduced in comparisons
between immigrant groups and native Swedes only modest
changes in relative mortality emerge with a slightly reduced risk
for immigrant groups. The income limit used here is the lowest
possible, discriminating only those with no income at all of
the kind we presumed indicated residence in the country. Using
763
stricter criteria with higher levels might make the groups even
more equal in terms of representation in the population
registries.
The methods that have been applied here—using information
about income as an indicator of the degree of continuing residence in Sweden and links with the country and also as an
indication of the extent of overregistration which may occur—
appear to be ones which can be pursued further, in order to
obtain a more accurate understanding of mortality among
immigrant groups.
References
1 Hjern A. Migrationsmedicinsk forskning—en översikt (Research in
migration medicine—a literature review), MFR-rapport 1, Medicinska
forskningsrådet och Socialvetenskapliga forskningsrådet. Stockholm:
Swedish Medical Research Council and the Swedish Council for
Social Research, 1995.
2 Kindlund H-L. Invandrarna i socialförsäkringen (Immigrants in the
social insurance system). Riksförsäkringsverket (The National Social
Insurance Board), 1996:11.
3 Sundquist J, Johansson S-E. Long-term illness among indigenous and
foreign-born people in Sweden. Soc Sci Med 1997;44:189–98.
4 Alfredsson L, Ahlbom A, Theorell T. Incidence of myocardial
infarction among male Finnish immigrants in relation to length of
stay in Sweden. Int J Epidemiol 1982;11:225–28.
5 Tomson Y, Åberg H. Risk factors for cardiovascular disease—a com-
parison between Swedes and immigrants. Scand J Prim Health Care
1991;12:147–54.
6 Theorell T, Vigborg A, Kallner A, Dahlen G, Walinder O. A comparison
between Finnish immigrants and native Swedes in the greater Stockholm region—social and medical risk indicators of ischemic heart
disease. Scand J Soc Med 1980;8:105–15.
7 Marmot MG, Adelstein A. M., Bulusu L. Lessons from the study of
immigrant mortality. Lancet 1984;i:1455–57.
8 Nilsson Å. Brister i folkbokföringen (Deficiencies of the national
registration). Statistiska Centralbyrån, Statistics Sweden 1994:4. (PM
1994–10–04, Dnr 2574/94)
9 Ekberg J, Andersson L. Invandring, sysselsättning och ekonomisk effekter
(Immigration, employment and economic effects). Ds 1995:68. ESO.
Stockholm, 36–50.
10 Ahlbom A. Biostatistics for Epidemiologists. Boca Raton: Lewis, 1993.
11 Johansson L. M, Sundquist J, Johansson S-E, Bergman B, Qvist J,
Träskman-Bendz L. Suicide among foreign-born minorities and native
Swedes: an epidemiological follow-up study of a defined population.
Soc Sci Med 1997;44:181–87.
12 Razum O, Zeeb H, Akgün H. S, Yilmaz S. Low overall mortality of
Turkish residents in Germany persists and extends into a second generation: merely a healthy migrant effect? Trop Med Int Health 1998;
Apr 3(4):297–303.
13 Razum O, Zeeb H, Gerhardus A. Cardiovascular mortality of Turkish
nationals residing in West Germany. Ann Epidemiol 1998;Jul 8(5):
334–41.