Hospitalization due to stroke and myocardial infarction in self-employed individuals and small business owners compared with paid employees in Sweden—a 5-year study
Hospitalization due to stroke and myocardial infarction in self-employed individuals and small business owners compared with paid employees in Sweden-a 5-year study
Susanna Toivanen 0 1 2 3 4 5
Rosane Härter Griep 0 1 2 3 4 5
Christin Mellner 0 1 2 3 4 5
Mikael Nordenmark 0 1 2 3 4 5
Stig Vinberg 0 1 2 3 4 5
Sandra Eloranta 0 1 2 3 4 5
0 R. Härter Griep Laboratory of Health and Environment Education, Oswaldo Cruz Institute , Oswaldo Cruz Foundation (Fiocruz), Rio de Janeiro , Brazil
1 S. Toivanen School of Health, Care and Social Welfare, Mälardalen University , Västerås , Sweden
2 S. Toivanen (
3 S. Eloranta Scandinavian Development Services , Stockholm , Sweden
4 M. Nordenmark
5 C. Mellner Department of Psychology, Stockholm University , Stockholm , Sweden
Analysing Swedish population register data, the aim of the present study is to investigate differences in acute cardiovascular disease (CVD) in terms of stroke and myocardial infarction incidence between selfemployed individuals and paid employees and to study whether the associations vary by gender or across industrial sectors. A cohort of nearly 4.8 million employed individuals (6.7% self-employed in 2003) is followed-up for hospitalization due to stroke and myocardial infarction (2004-2008). Self-employed individuals are defined as sole proprietors and limited liability company owners according to legal type of their enterprise. Negative binomial regression models are applied to compare hospitalization rates between the self-employed and paid employees, adjusted for socioeconomic and demographic confounders. Two- and three-way interaction are tested between occupational group, industrial sector, and gender. Limited liability company owners have significantly lower hospitalization for myocardial infarction than paid employees. Regarding two-way interaction, sole proprietors have higher myocardial infarction hospitalization in trade, transport and communication, and lower in agriculture, forestry, and fishing than paid employees. Limited liability company owners have lower hospitalization rate for myocardial infarction than employees in several industries. The results highlight the importance of enterprise legal type and industrial sector for CVD among self-employed individuals.
Self-employment; Cardiovascular disease; Hospitalization; Sweden
Labour markets are changing due to digitalization and
economic globalization, giving rise to new forms of
(Grosheide and Barenberg 2015)
. As a
consequence, self-employment is increasingly common
in many countries, and the proportion varies between 7
and 30% of the working populations in European
. Despite their large proportion of
the working populations, the self-employed are still a
neglected group in international occupational safety and
health (OSH) research
(Pedersini and Coletto 2010)
instance, at the 7th International Conference on Work
Environment and Cardiovascular Diseases organized by
(International Commission on Occupational
, only one presentation focused specifically
on self-employed workers and one focused on farmers.
Research reviews on working conditions and health
among the self-employed are scarce
general finding from previous studies comparing the
self-employed and paid employees is that the
selfemployed tend to have more job control, work longer
hours, have shorter vacations, and are not able to take
sick leave to the same extent as employees
. Thus, they are more likely to have higher
sickness presence than employees meaning that they go to
work even though their health status imply they would
need to take sick leave
(Aronsson and Gustafsson 2005;
Knani et al. 2015)
. Yet, research into health differences
between self-employed individuals and paid employees
is somewhat inconclusive due to variation of study
design and methodology. Most studies have focused
on general and mental health outcomes
1997; Vinberg et al. 2013)
. Generally, previous research
suggests that the self-employed have better health than
(Stephan and Roesler 2010; Andersson
2008; Yoon and Bernell 2013)
(Rietveld et al. 2015; Gunnarsson et al.
2007; Dolinsky and Caputo 2003)
, as well as differences
between women and men
(Nordenmark et al. 2012)
between immigrant and natives (
Sevä et al. 2016
For CVD, there are few studies on the self-employed.
In a cross-sectional study based on a national
Stephan and Roesler (2010)
blood pressure, lower prevalence rates of hypertension,
as well as higher well-being and more favorable
behavioral health indicators among entrepreneurs than
employees. Studies into mortality among the
selfemployed report 23% higher mortality from CVD
among individuals in trade, transport, and
communication compared with those in agriculture, forestry, and
(Toivanen et al. 2015)
. In general, mortality is
reported to be higher in self-employed that operate as
sole proprietors compared with those that run a limited
(Toivanen et al. 2015)
. One study
reports lower mortality from CVD among limited
liability company (LLC) owners than among paid employees
(Toivanen et al. 2016)
CVD is the leading global cause of death
, accounting for 17.5 million deaths
per year, a number that is expected to grow to
more than 23.6 million by 2030
(Mckay et al.
2005; WHO 2016b)
. Among CVD, the main
killers are stroke and ischaemic heart disease
including myocardial infarction (MI). In addition to
biological and lifestyle-related risk factors, several
social- and work-related factors confer an
increased risk of CVD, e.g. low socio-economic
position defined as low educational level, low
occupational class, or low income (Hobbs et al.
2016). This may be explained by dominance
hierarchies suggesting that dominant members of a
group have better cardiovascular health compared
to subordinate group members
The stepwise social gradient of cardiovascular
disease with higher risk among those with lower
socio-economic position compared to those with
higher position is explained partly by social
gradients in health behaviors
. Yet, three
decades of research provide evidence for a
psychosocial pathway in terms of job stress leading to
cardiovascular morbidity and mortality
Chronic stress at work in terms of long
working hours, extensive overtime work, high
psychological demands, low job control, job strain,
and unfairness are associated with increased risk
(Hobbs et al. 2016)
How chronic stress
effects cardiovascular health depends on other
simultaneous factors. For instance, the literature
on social modulation of stress response suggests
that social support and affiliation provide a
buffering effect that reduces the adverse impact
of stress on health
(DeVries et al. 2003)
. A recent
study shows that the self-employed suffer from
less work-related stress than paid employees, and
that the negative relationship between
selfemployment and work-related stress was fully
mediated by job control
(Hessels et al. 2017)
However, previous studies of social and work related
factors and risk of CVD mainly focus on paid
(Kivimäki and Kawachi 2015)
our present knowledge about CVD in general,
and stroke and myocardial infarction in particular,
among the self-employed in relation to paid
employees is limited.
Even if the self-employed are more likely to have
higher sickness presence than paid employees, yet
with regard to acute severe CVD such as stroke or
myocardial infarction, which require immediate
hospital care, there might not be differences between
the occupational groups. To our knowledge, the
question has not been thoroughly investigated.
Hospitalization and mortality data are particularly useful
when comparing health status between different
occupational groups. Differences in hospitalization
cannot be explained by differential reporting, which
is an inherent issue in studies based on self-reported
data. Therefore, based on analyses of Swedish
administrative register data, the main aim of the
present explorative study is to estimate the risk of
hospitalization due to stroke or myocardial infarction by
occupational group considering repeat hospital
episodes. Because the Swedish labour market is
segregated by gender and because mortality risk varies by
industry, we also investigate how risk of
hospitalization depend on gender and industrial sector.
2 Data and methods
Data were obtained from the Swedish Work and
Mortality Database maintained at the Centre for
Health Equity Studies, Stockholm University/
Karolinska Institutet. Ethical permission (no.
02481) was provided by the Regional Ethics
Committee in Stockholm. The database comprises several
administrative registers provided by Statistics
Sweden and the National Board of Health and Welfare,
of which the Total Population Register, Longitudinal
Database on Education, Income and Employment
(LOUISE), the Hospital Discharge Register and the
Cause of Death Register were used in the present
analyses. Record linkages were possible using an
encrypted version of 10-digit personal identity
number provided by authorities to ensure anonymity.
2.2 Study population and follow-up
The population included all self-employed persons and
paid employees as recorded in the Swedish registry
2003. After excluding persons with missing values on
central variables, the final cohort consisted of 211,464
self-employed persons registered as sole proprietors
(31% women), 109,809 self-employed persons
registered as limited liability company owners (27%
women), and 4,454,845 employees (50% women). Age
ranged between 18 and 100 years and the proportion
of individuals < 65 years of age was 89.5% among sole
proprietors, 94.8% among LLC owners, and 96.6%
among paid employees. Thus, 10.5% of the
selfemployed are older than 65 years, which is the reason
for keeping the present age-range.
The cohort was followed for recurrent
hospitalizations for stroke and myocardial infarction,
respectively, by record linkage to the Hospital Discharge
Register 2004–2008. Each participant was
considered at risk for hospitalization from the date of
inclusion to the study (1 January 2004) until the
date of death, emigration, or end of the study (31
December 2008), whichever came first.
2.3 Assessment of exposures, covariates, and outcomes
2.3.1 Occupational group
In Swedish labour statistics, a business owner is defined
as a physical person engaged in active business
(selfemployed) or a limited liability company owner having
his or her principal employment within the company
(Statistics Sweden 2007)
. In the data, a person’s
occupational group is stated as (1) employee, (2)
selfemployed as sole proprietor, or (3) limited liability
company owner (LLC). In this study, all occupational
groups were selected. Employees were used as the
reference category. Sociodemographic and health-related
differences between sole proprietors and LLC owners in
relation to employees have been reported elsewhere
(Toivanen et al. 2016; Toivanen et al. 2015)
included in Appendices 1 through 3 which are available
online. Briefly, sole proprietors and LLC company
owners are older, a smaller proportion of them have
tertiary education and their health is slightly poorer
compared with employees (Toivanen et al. 2016). While
the largest proportion of employees operate in welfare
sectors including services mainly provided by the
welfare state such as education and health care, a substantial
share of the self-employed work in trade, transport, and
2.3.2 Industrial sector
The Swedish Standard Industrial Classification
that corresponds to NACE Rev. 1.1 (EU level)
and ISIC Rev. 3 (world level) was used to classify
(European Commission and Eurostat
2013; Statistics Sweden 2004)
. The highest aggregate
level identified by an alphabetical code was used to
collapse industries into eight categories: agriculture,
forestry, and fishing (AFF); manufacturing and mining
(MM); construction (C); trade, transport, and
communication (TTC); financial intermediation, business
activities (FB); personal and cultural services, including
hotels and restaurants (PCS); sector not specified (NS);
and welfare (W). W includes services mainly provided
by the welfare state such as education, research, health
and social care, and electricity, gas, and water supply.
AFF was used as the reference category. Previous
research shows that AFF has lower mortality risk
compared to other industries as regards to all-cause
mortality, and mortality from CVD and neoplasms, but higher
mortality from suicide than other industries (Toivanen
et al. 2015).
2.3.3 Assessment of covariates
Age at entry to the study was included as a
continuous and squared variable, respectively. Sole
proprietors and LLC owners are slightly older than paid
employees, and the risk of CVD increases with age
(Toivanen et al. 2015)
. Gender was included as
women and men work largely in different industrial
sectors. Also, the incidence of stroke and myocardial
infarction, respectively, has previously been shown
to depend of gender
. The primary
regression analysis was performed adjusting for
gender as a main effect. However, effect modification
by gender was formally tested in a secondary
analysis to assess the need for a gender-stratified
analysis. Country of origin was classified as Sweden or
elsewhere. Previous research shows that
selfemployment is more common in immigrant groups
than natives in Sweden
(Joona and Wadensjö 2008)
Education was categorized into four groups:
primary, secondary, tertiary, and unknown education.
Most health outcomes including CVD have a social
gradient indicating poorer health in lower
socioeconomic positions than in higher positions and a
gradient for the intermediate positions (Kuper et al.
2007). Family structure was categorized into five
groups: living alone, lone parent, cohabiting
(married or cohabiting), cohabiting parent, unknown.
Previous results show that cohabiting is more
frequent among self-employed individuals than
(Toivanen et al. 2016)
. Cohabiting may
influence getting medical help quicker. Number of
children was grouped into small children (ages 0–6)
and older children (ages 7–17) and included as a
continuous variable. Location was categorized as
urban or rural based on place of residence as
distance to hospital may influence individuals’ access
to specialized care. Also, most self-employed
operate in urban areas. Health status before baseline may
influence the risk of hospitalization during
followup and was adjusted for in terms of the Charlson
included in the index cover a large variety of somatic
diseases, and the index was calculated from ICD-10
codes available in the data from years 1999–2003.
Enterprise size was classified as solo (one worker),
micro (2–9 workers), small or medium-sized (SME,
≥ 10 and < 250 workers), or unknown size. Previous
research shows that self-employed individuals with
employees experience more work-related stress than
those without employees because of higher job
(Hessels et al. 2017)
2.3.4 Hospitalization for stroke and myocardial infarction
Based on International Classification of Diseases
, tenth revision (IDC-10), following
primary diagnoses for hospitalization were used:
acute myocardial infarction (I21), stroke
(intracerebral haemorrhage I61, cerebral infarction I63,
undetermined pathological type I64). Transient ischaemic
attack (G45) and subarachnoid haemorrhage (I60)
were excluded in line with previous investigations
(Ellekjaer et al. 1999).
2.4 Statistical analyses
Stroke and myocardial infarction hospitalization
incidence rate ratios (IRR) and 95% confidence intervals
(CI) were estimated using negative binomial regression
models. The negative binomial model can be viewed as
a generalized version of the Poisson model that is able to
appropriately accommodate highly skewed distributions
of count outcomes, such as those arising from repeat
hospital episodes (HES), as well as different individual
tendencies for repeat hospitalizations
(Rogers et al.
2014; Rogers et al. 2012)
. All regression models
included an offset term representing time at risk for repeat
hospitalizations, thereby taking into account that the
observed follow-up time differed between individuals,
due to death and emigration.
Occupational group and industrial sector were
included in all main effects regression models, including
the crude models (Model 1). Adjustments for
prespecified potential confounding covariates were
introduced sequentially. The first series of adjustments
included gender, age at inclusion to the cohort, and
country of origin (Model 2). The second set of adjustments
included previous health status, education level, family
structure, number of children, location, and enterprise
size (Model 3).
Regression models that included a two-way
interaction term between occupational group and industrial
sector were estimated to study whether the effect of
occupational group was modified by industrial sector.
In addition, a model with three-way interaction terms
between occupational group, industrial sector, and
gender was estimated to further investigate the potential for
effect modification by gender. Likelihood ratio tests
were used to formally assess the evidence for effect
modification. For all statistical tests, the significance
level was set to 0.05.
All statistical analyses were conducted using the
Stata software 2013. Stata Statistical Software: Re
lease 13. College Station, TX: StataCorp LP.
3.1 Population characteristics and hospital episodes due
to stroke or myocardial infarction
Of all individuals included in present analyses, 93%
were paid employees, 5% sole proprietors, and 2%
LLC owners (Table 1). Sole proprietors and LLC
owners were older than the employees. The
proportion of women was 50% among employees, and
about 30% among sole proprietors and LCC owners.
In all occupational groups, about 70% of those
hospitalized for stroke had only one hospital episode
(HES) during the follow-up period. The duration of
HES due to stroke varied between 16 to 18 days.
Employees and LLC owners had the longest
duration, while sole proprietors had the shortest duration
The pattern was similar for myocardial infarction
as described above for stroke (Table 1). Yet, the
HES duration was shorter for myocardial infarction
compared with stroke (6 versus 18 days). The
majority (60%) had only one HES due to myocardial
infarction during the follow-up period. The HES
duration varied between 5 to 6 days and was longest
among sole proprietors and employees and shortest
among LLC owners.
Regarding gender differences in hospitalization due
to stroke or myocardial infarction, 0.67% of all men had
been hospitalized for stroke compared with 0.34% of
women (Table 2). For myocardial infarction, the
corresponding figure was 0.97% of men and 0.27% of
women. Men had longer HES duration due to stroke than
women (18 versus 17.5 days, Table 2), and women had
longer HES duration than men due to myocardial
infarction (5.9 versus 5.6 days).
Among men, 0.63% of employees, 1.66% of sole
proprietors, and 0.87% of LLC owners had been
hospitalized due to stroke during the follow-up period. Sole
proprietors had shorter HES duration for stroke than
LLC owners and employees. Regarding myocardial
infarction, 0.92% of employees, 1.55% of sole
proprietors, and 1.25% of LCC owners had been hospitalized.
Sole proprietors had longer HES duration than
employees and LCC owners.
Among women, 0.33% of employees, 0.59% of
sole proprietors, and 0.47% of LLC owners had
been hospitalized due to stroke. The pattern of
HES duration among women differed from that
among men. LCC owners had the shortest HES
duration due to stroke, followed by sole proprietors
and employees. For myocardial infarction, 0.28% of
employees, 0.51% of sole proprietors, and 0.35% of
LLC owners had been hospitalized. The HES
duration was longer among sole proprietors than LLC
owners (6.1 days) and employees.
3.2 Hospitalization by occupational group and industrial
Compared with paid employees, the hospitalization
i n c i d e n c e r a t e r a t i o ( I R R ) f o r s t r o k e w a s
*25th and 75th percentiles
significantly higher in sole proprietors (IRR 1.71,
95% CI 1.60–1.83) and LLC owners (IRR 1.67,
95% CI1.52–1.83) in the unadjusted negative
binomial regression model (Table 3, Model 1 for stroke).
When adjusting for gender, age, and country of
origin (Table 3, Model 2), the estimated associations
were no longer observed. No significant differences
between the occupational groups were found in the
fully adjusted Model 3. However, significant
differences were observed by industrial sectors. All
industries had higher IRRs compared to the reference
category of agriculture, forestry, and fishing. The
lowest IRR was in construction (IRR 1.17, 95% CI
1.04–1.32) and the highest in personal and cultural
services (IRR 1.49, 95% CI 1.33–1.67) compared
with the reference category.
3.2.2 Myocardial infarction
For MI, the general patterns were similar to those
observed in stroke hospitalizations (Table 3, Model
1 for myocardial infarction). Differences observed
across occupational groups were statistically
significant in the unadjusted Model 1. When adjusted for
covariates in Model 2, LLC owners had a
significantly lower hospitalization rate (IRR 0.86, 95% CI
0.80–0.93) compared with employees. This
association remained when fully adjusted in Model 3 (IRR
0.87, 95%CI 0.80–0.94) indicating that LLC owners
have a 13% lower risk for hospitalization due to
myocardial infarction than paid employees.
Furthermore, the IRRs varied by industrial sector.
Generally, the estimates were lower for MI than stroke.
Lowest hospitalization rate ratios were in trade,
transport, and communication (IRR 1.17, 95% CI
1.07–1.29) and in the not specified industry (IRR
1.17, 95% CI 1.04–1.31), and the highest in
personal and cultural services (IRR 1.25, 95% CI 1.13–
1.38) and in the welfare industry (IRR 1.20, 95% CI
1.09–1.32) compared to the reference category.
3.3 Interaction analyses
In a regression model that included a two-way
interaction term between occupational group and industrial
sector, no evidence of effect modification was
observed for stroke hospitalization (p for interaction =
0.2112, Table 4). For MI (p = 0.0111), sole proprietors
had a higher hospitalization incidence rate ratio in
trade, transport, and communication (IRR 1.19, 95%
CI 1.04–1.34) and lower in agriculture, forestry, and
fishing (IRR 0.81, 95% CI 0.68–0.96) compared with
paid employees in the same industries. LLC owners
had lower hospitalization in trade, transport, and
comm u n i c a t i o n ( I R R 0 . 8 8 , 9 5 % C I 0 . 7 7 – 1 . 0 0 ) ;
manufacturing and mining (IRR 0.84, 95% CI 0.70–
1.00); financial intermediation and business activities
(IRR 0.86, 95% CI 0.73–1.00); and personal and
cultural services (IRR 0.62, 95% CI 0.44–0.88) than
paid employees in the same industries. Three-way
interaction by occupational group, industrial sector,
and gender was not significant.
AFF, agriculture, forestry, and fishing; C, construction; FB, financial intermediation and business activities; MM, manufacturing and mining;
NS, not specified; PCS, personal and cultural services; TTC, trade, transport, and communication; W, welfare industries including education
and research, health and social care, public administration, and energy, water and waste management
1 Unadjusted model
2 Adjusted for sex, age at inclusion, country of origin
3 Further adjusted for Charlson Comorbidity Index (none/mild/severe), education level (primary/secondary/tertiary/unknown), family type
(alone/lone parent/cohabiting parent/cohabiting/unknown), number of young (0–6 years) and old (7–17 years) children, respectively,
enterprise size, and location (urban/rural)
4.1 Key findings
Based on Swedish total population register data, this
five-year follow-up study investigated differences in
hospitalization due to stroke or myocardial infarction
between sole proprietors, LLC owners, and paid
employees, and whether the associations found varied by
industrial sector and gender. LLC owners had 13%
lower hospitalization for myocardial infarction than paid
employees. No significant differences between the
occupational groups were found for hospitalization for
However, an increased risk for hospitalization for
stroke was found in several industries, for instance trade,
transport, and communication; financial intermediation
and business activities; and personal and cultural
services. Similarly, increased risks were found for
hospitalization for myocardial infarction, but these risks
were lower than those for stroke, in trade, transport, and
communication; personal and cultural services; and
Interaction analyses of occupational group and
industrial sector showed that sole proprietors had
higher hospitalization for myocardial infarction in
trade, transport, and communication and lower
hospitalization in agriculture, forestry, and fishing than
paid employees in the same industries. LLC owners
had lower hospitalization for myocardial infarction
in trade, transport, and communication;
manufacturing and mining; financial intermediation and
business activities; and personal and cultural services
compared with paid employees. The results
highlight the importance of industrial sector for
hospitalization due to acute CVD among sole proprietors
and LLC owners. Regarding gender differences, the
present study found no significant associations.
Bold items indicate significant estimates
* The reference group is paid employees
1 Adjusted for sex, age at inclusion, country of origin, Charlson Comorbidity Index (None/Mild/Severe), education level (primary/
secondary/tertiary/unknown), family type (alone/lone parent/cohabiting parent/cohabiting/unknown), number of young (0–6 years) and
old (7–17 years) children, respectively, enterprise size, and location (urban/rural)
†Welfare industries include education and research; health and social care; public administration; energy, water, and waste management
4.2 Study strengths and limitations
The study’s main strengths are that Swedish register data
provided information on the total working population, and
included thus employees and all self-employed individuals
registered as sole proprietors and LLC owners that were
active in the labour market at study baseline in 2003. The
study population was followed up for 5 years for
hospitalization for stroke or myocardial infarction by record
linkage to the hospital discharge register by an encrypted
version of the 10-digit personal identity number. Therefore,
the outcome measure is not hampered by self-report bias, a
common problem in self-reported survey data. Most of the
previous research into occupational safety and health
(OSH) in relation to CVD has been conducted among
employees. Thus, the present research provides new
findings on the leading cause of death and disability among
sole proprietors and LLC owners. The analyses focused on
stroke and myocardial infarction that are acute and severe
types of CVD and need immediate hospitalization.
Moreover, classification of industrial sectors was based on
international standards. Taken together, the results are valid
for the total working population in Sweden and are perhaps
generalizable to similar working populations. However,
total population registers do not include data on work
environment factors. We could not analyse the role of work
environment for hospitalization which could affect the
results. Moreover, this is a follow-up study with
measurement of occupational group at baseline (2003). It is
plausible that some individuals may change occupational group
during the follow-up period (2004–2008) which could
influence our findings.
4.3 Present findings in relation to previous studies
To our best knowledge, the present study is the first
focusing specifically on CVD hospitalization among sole
proprietors and LLC owners in comparison to paid
employees in same industrial sectors. The findings led to
some new insights. First, we used repeat hospitalizations
taking into account all hospitalizations during the
followup. Even if most hospitalized individuals only had one
hospital episode during the follow-up, about 30% of those
experiencing a stroke and 40% with myocardial infarction
had repeat episodes implying that they were hospitalized at
several occasions during the follow-up. If we had focused
only on the first hospital episode, which is a common
strategy in hospitalization studies, we would have lost a
fair amount of data. Previous research into mortality
among self-employed workers, defined as sole proprietors
or limited liability company (LLC) owners by the legal
form of their enterprise, has indicated higher mortality
among sole proprietors than LCC owners
et al. 2015)
. Previous findings state 16% lower mortality
from CVD among LLC owners than employees
et al. 2016)
, which is in line with the present results of 13%
lower hospitalization for myocardial infarction in LLC
owners than in paid employees.
Second, we identified industries with the highest
risk for hospitalization due to stroke or myocardial
infarction. As in previous studies
(Toivanen et al.
2016; Toivanen et al. 2015)
, trade, transport, and
communication was singled out as a troublesome
industry with increased risk for hospitalization for
both stroke and myocardial infarction. However,
interaction analyses found that this was the case
only among sole proprietors in relation to
myocardial infarction. LLC owners on the other hand had
actually lower hospitalization for myocardial
infarction in trade, transport, and communication than
employees in the same industry. Moreover, they
had had lower risk for hospitalization than
employees in manufacturing and mining; financial
intermediation and business activities; and personal
and cultural services. Thus, this finding confirms
that LLC owners are generally a healthier group
compared to employees in terms of hospitalization
due to myocardial infarction.
4.4 Possible mechanisms behind the associations
The excess risk of hospitalization for stroke or
myocardial infarction that was identified for most industrial
sectors compared to the reference category may partly
depend on industry-specific factors such as varying
market competition, working conditions, and work
environment factors. For instance, it may be that some
industries such as trade, transport, and communication
and personal and cultural services that also include
hotels and restaurants have more psychosocial stress
which has been associated with increased risk for
(Belkic et al. 2004; DeVries et al. 2003)
present results indicate that sole proprietors in trade,
transport, and communication had an increased for
hospitalization for myocardial infarction, but LLC owners
had a lower risk compared with paid employees in the
same industry. In line with the literature on social
hierarchies (Sapolsky 2005), it may be that the working
conditions of sole proprietors are more stressful than
of the other occupational groups due to more financial
insecurity, less control over work, and perhaps less
work-family balance. Regarding enterprise legal form,
it is plausible that sole proprietors experience more work
stress due to financial demands than LLC owners, as
they are personally responsible for all transactions.
Financial stress is suggested to be a major category of
(Grant and Ferris 2012; Lechat
and Torrès 2017)
Working life is changing due to global
competition, ageing working populations, and the need to
integrate refugees and other groups in a vulnerable
situation into the labour market, all of which can
lead to an increase in new forms of employment
including self-employment. Therefore, it is
important to monitor working conditions among the sole
proprietors particularly in trade, transport, and
communication because the conditions may be more
detrimental than in other industries for the health
and well-being of this occupational group.
More research is needed that considers both industry
and work environment factors in relation to CVD in the
self-employed, bearing in mind that previous
occupational safety and health research has mainly been
conducted among paid employees. Even if the present study
did not establish any gender differences, future studies
should consider gender due to segregated labour
markets and perhaps different motivation for becoming
selfemployed among women and men. The differences in
hospitalization by industrial sector found in the present
study provide information to further investigation of
working conditions and health in those industries with
higher risks for hospitalization. The results contribute to
policy strategies aimed at improving well-being among
working populations in general and self-employed
individuals in particular.
Acknowledgements The authors would like to thank the
organizers and participants at the 1st international research seminar on
the health of entrepreneurs and small business owners at
Montpellier Business School, September 2016, and a seminar at the Centre
for Health Equity Studies, Stockholm University/Karolinska
Institutet for helpful comments on an earlier version.
Funding information This study is financially supported by the
Swedish research council for health, working life and welfare
(FORTE), project number 2012-0615.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://
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