Impact of Socioeconomic Status on Cardiovascular Disease and Mortality in 24,947 Individuals With Type 1 Diabetes
araz.
.
Received 20 January 2015 and accepted 28
March 2015.
This article contains Supplementary Data online
at http://care.diabetesjournals.org/lookup/
suppl/doi:10.2337/dc15
Impact of Socioeconomic Status on Cardiovascular Disease and Morta lity in 24,947 Individua ls With Type 1 Diabetes
0 Araz Rawshani
Socioeconomic status (SES) is a powerful predictor of cardiovascular disease (CVD) and death. We examined the association in a large cohort of patients with type 1 diabetes. RESEARCH DESIGN AND METHODS Clinical data from the Swedish National Diabetes Register were linked to national registers, whereby information on income, education, marital status, country of birth, comorbidities, and events was obtained. Patients were followed until a first incident event, death, or end of follow-up. The association between socioeconomic variables and the outcomes was modeled using Cox regression, with rigorous covariate adjustment.
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We included 24,947 patients. Mean (SD) age and follow-up was 39.1 (13.9) and 6.0
(1.0) years. Death and fatal/nonfatal CVD occurred in 926 and 1378 individuals.
Compared with being single, being married was associated with 50% lower risk of
death, cardiovascular (CV) death, and diabetes-related death. Individuals in the
two lowest quintiles had twice as great a risk of fatal/nonfatal CVD, coronary heart
disease, and stroke and roughly three times as great a risk of death,
diabetesrelated death, and CV death as individuals in the highest income quintile.
Compared with having £9 years of education, individuals with a college/university
degree had 33% lower risk of fatal/nonfatal stroke. Immigrants had 19%, 33%,
and 45% lower risk of fatal/nonfatal CVD, all-cause death, and diabetes-related
death, respectively, compared with Swedes. Men had 44%, 63%, and 29% greater
risk of all-cause death, CV death, and diabetes-related death.
CONCLUSIONS
Low SES increases the risk of CVD and death by a factor of 2–3 in type 1 diabetes.
Socioeconomic status (SES) is a complex construct, often conceptualized as the
social standing or class of an individual. It is commonly measured as a combination
of education, income, and occupation but may include age, sex, ethnicity, and
marital status (1). SES may profoundly affect health. It is a powerful predictor of
cardiovascular disease (CVD) and death (2–5).
The impact of SES on CVD and mortality in type 2 diabetes has been examined (6),
but studies in type 1 diabetes are scarce. Available data, which are hampered by
small samples and inadequate
adjustment for confounders, suggest either a
modest effect or no significant effect of
SES on death and CVD (7–9).
Consequently, no reliable studies relating SES
to CVD and mortality in type 1 diabetes
have been conducted. This might explain
why socioeconomic variables have not
been considered in recent risk prediction
models for type 1 diabetes (10,11).
We used the Swedish National
Diabetes Register (NDR), which provides
almost complete national coverage of
type 1 diabetes, to investigate how
income, education, marital status,
immigrant status, and sex relate to CVD and
death (12,13). It is important to examine
this relationship, as it may reveal easily
accessible risk markers.
RESEARCH DESIGN AND METHODS
The NDR was initiated in 1996 as a
caregiver tool for local quality assurance and
as a feedback tool in diabetes care.
Roughly 95% of all individuals age 18
years and older with type 1 diabetes in
Sweden are included (12). Data
provided by nurses and physicians trained
in register procedures are obtained at
visits in outpatient clinics of hospitals
and primary health care centers
nationwide. Clinical information and various
measurements are updated at least
once a year.
The study was approved by the
regional ethics review board at the
University of Gothenburg. All patients give
their informed consent before being
included in the NDR.
Study Cohort
We included 24,947 individuals (220,281
appointments) with type 1 diabetes
who had at least one listing in the
NDR between 1 January 2006 and 31
December 2008. This excluded 2,186
individuals with a history of CVD (as
defined below), who were listed in the
NDR during the same period. Type 1
diabetes was defined on the basis of
epidemiologic data: treatment with
insulin and a diagnosis at the age of 30 years
or younger. This definition has been
validated as accurate in 97% of the cases
listed in the register (14).
Socioeconomic Data
Data on annual income in Swedish
kronor, highest educational level, country
of birth, marital status, and occupation
were obtained from Statistics Sweden.
Education was stratified into lower (#9
years, the length of compulsory
education in Sweden), intermediate (10–12
years, upper secondary) and higher
(col
lege/university). Income was stratified
into quintiles (Q1 [lowest] to Q5
[highest]). Immigrant status was defined as
immigrant or native Swede depending
on country of birth. Marital categories
were single (defined as never married
and (...truncated)