Prevalence of overweight in 2 to 17 year-old children and adolescents whose parents live separately: a Nordic cross-sectional study
BMC Public Health
Prevalence of overweight in 2 to 17 year-old children and adolescents whose parents live separately: a Nordic cross-sectional study
Lena Hohwü 0 3
Mika Gissler 2 5
Agneta Sjöberg 1
Anna M Biehl 7
Alfgeir L Kristjansson 4 6
Carsten Obel 0 3
0 Section for General Practice, Department of Public Health, Aarhus University , Bartholins Allé 2, 8000 Aarhus C , Denmark
1 Department of Food and Nutrition, and Sport Science, University of Gothenburg , Post Box 300405 30 Gothenburg , Sweden
2 THL National Institute for Health and Welfare , PO Box 3000271 Helsinki , Finland
3 Section for General Practice, Department of Public Health, Aarhus University , Bartholins Allé 2, 8000 Aarhus C , Denmark
4 Icelandic Centre for Social Research and Analysis, Reykjavik University , Reykjavik , Iceland
5 NHV Nordic School of Public Health , Gothenburg , Sweden
6 West Virginia University, School of Public Health , PO Box 9190, Morgantown, WV 26506-9190 , USA
7 Division of Epidemiology, Norwegian Institute of Public Health , PO Box 4404Nydalen, 0403 Oslo , Norway
Background: Comparative data of parental separation and childhood overweight has not been available before across the Nordic countries. The aim of this study was to examine the within-country prevalence and association between parental cohabitation and overweight in Nordic children. Methods: A cross-sectional survey of 2-17-year-old children was conducted in 2011, titled: “NordChild”. A random sample of 3,200 parents in each of the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden were invited to participate in the study with parents of 6,609 children accepting to give answers about their children's health and welfare including information on height and weight of each child and parental cohabitation (response rate 41.5%). The group differences in prevalence and adjusted odds ratio (OR) for overweight, with corresponding 95% confidence intervals (CI) were performed in children whose parents lived separately. Additionally, a missing data analysis was performed to determine whether the adjusted estimates might result from confounding or selection bias. Results: A significant difference was observed in Iceland between children whose parents live separately compared to those who live with both parents (difference: 9.4%, 95% CI: 2.8; 15.9) but no such difference was observed in Denmark, Finland, Norway and Sweden. No significant odds of overweight were observed in children whose parents lived separately compared to children in normal weight at the time of study; Denmark: OR 1.03 (95% CI: 0.42; 2.53), Finland: OR 1.27 (95% CI: 0.74; 2.20), Iceland: OR 1.50 (95% CI: 0.79; 2.84), Norway: OR 1.46 (95% CI: 0.81; 2.62), and Sweden: 1.07 (95% CI: 0.61; 1.86). The missing data analysis indicated that the findings in Norway, Finland and Iceland were partly observed due to selection effects, whereas the adjustment in Denmark was due to confounding. The crude OR for overweight was higher in the 2-9-year-old group than in the 10-17-year-old group whose parents lived separately in Iceland, Norway and Sweden. Conclusions: No association between parental cohabitation and overweight in Nordic children was found. Our finding of greater prevalence of overweight in Icelandic children whose parents live separately may be an indication that the welfare system in Iceland is separating from the other Nordic countries.
Cohabitation; Divorce; Body mass index; Overweight; Children; Nordic
The prevalence of overweight in children and
adolescents has increased greatly in most European countries
during the last 30 years [
]. This applies also to the
Nordic countries [
], although recent evidence
suggests that the prevalence rates of overweight may be
levelling off in some of them [
]. By examining the
association of exposure of psychological stress early in
life and risk of overweight, we have earlier found that
schoolchildren born of mothers who experienced loss of
a close relative during the prenatal time period had an
increased risk of being overweight . Bereavement is a
severe, but rare, stress exposure whereas parental
separation or divorce is a broader and more common
exposure that is not as severe [
]. A larger body of literature
has showed a higher prevalence and increased risk of
overweight in children whose parents have separated
than in children whose parents are cohabiting [
However, some studies have showed that girls, but not
boys, were more likely to be overweight if living with a
single parent [
]. These studies that have been
performed in different countries have used different methods
of data collection and analyses but studies that utilize
comparative methods across countries are rare.
The populations in the Nordic countries are
comparatively homogenous, but up to this point comparative
data of family structure and children’s height and weight
has not been available across the Nordic countries. The
hypothesis of this study was that the prevalence of
overweight in children whose parents lived separately
compared to those living with both parents would be the
same within each of the Nordic countries. Thus, we
aimed to examine the prevalence of overweight and the
association between parental cohabitation and
overweight status in 2-17-year-old children and adolescents
across the five Nordic countries.
Sample and procedures
This cross-sectional study is based on the 2011 NordChild
survey. The NordChild survey (“Health and welfare
among children and young people in the Nordic
countries”) was conducted in 1984, 1996 and 2011 in the five
Nordic countries: Denmark, Finland, Iceland, Norway,
and Sweden. The survey questionnaire included questions
on the health of the children, and welfare of both the
children and the parents. In each survey, information on
changes in family structure since the birth of the child was
collected, but in 2011 information of self-reported height
and weight of each participating child was included for
the first time. A total of 16,000 randomly selected parents
of children between the ages of 2 to 17 years were invited
to participate in the study across the five Nordic countries;
one child per family was drawn from the population
registries in each country. A paper questionnaire was
mailed to the invited participants in each country;
however in Denmark a mix-mode approach of paper and
internet-based questionnaire was used including a small
nonmonetary incentive. Of the 16,000 invited participants,
55 were excluded due to reluctance to participate or
the child had turned 18 years after the original sample
was selected, and before the questionnaire was mailed
to the participants. Overall, 7,805 of 15,945 parents
responded the questionnaire, with a response rate within
each country as follows: Denmark 54.1%, Finland 48.1%,
Iceland 47.5%, Norway 49.4%, and Sweden 45.7%. Further
details of the 2011 NordChild data collection have been
described elsewhere [
]. The study was approved by the
Regional Ethical Board in Gothenburg (Dnr. 009–11, 22
In the present analyses additional 1,196 responses
(15.3%) were excluded because of inadequate or invalid
information regarding height, weight or parental
cohabitation. The study population therefore consisted of a
total of 6,609 2-17-year-old children that were born
between 1994 and 2009 and where self-reported
information of parental cohabitation and height and weight of
each child was available (response rate for the present
The information of parental cohabitation was based on
the question “Has the living situation of the parents
changed since the birth of the child”, and where the
options “No change” or “Yes, separation/divorce” were
combined with information on whether the mother and the
father of the child lived at the same address as the child at
time of the study. Children of parents who responded
“yes” to changed living situation and whose mother or
father did not live at the same address as the child
comprised the study group (Separate), whereas children to
parents who responded “no” to changed living situation
and where both parents lived at the same address as the
child comprised the comparison group (Cohabiting).
The body mass index (BMI) of the child was derived
by questions of height and weight: “How tall is the child
(measure without shoes and round up to full
centimeter)” and “What is the child’s weight (weight the child
without clothes and round up to whole kilogram)”. As
the BMI in children differs by age and gender, and
anthropometric and body composition measures change
considerably in relation to their physiological growth,
the dependent variable of overweight status including
obesity was created by dichotomizing BMI according to
the standardized age and gender-specific cut-off points
defined by the International Obesity Task Force [
Information of potential confounders and covariates
was limited in the study design. Included control variables
were; gender (boys/girls), age of the child, calendar year of
child’s birth (1994–2009), maternal and paternal
educational levels (≤9 years, 10–11 years, ≥12 years), and
maternal and paternal age (<35 years, 35–44 years, ≥45 years).
A combined Nordic figure was not derived due to
statistical interaction between countries and consequently
stratification by country was performed. No gender-based
differences were observed across the Nordic countries and
therefore no results stratified by gender are reported.
Significance of interaction between cohabitation and
gender, and between cohabitation and country was
tested using a likelihood-ratio test.
The descriptive characteristics between children of
separated and cohabiting parents are tested using a Chi-square
test. The overall prevalence of overweight, and prevalence
of overweight and difference in proportion of prevalence
between separate and cohabiting parents with
corresponding 95% confidence intervals (CI) was estimated within
each of the Nordic countries.
We used multiple logistic regression analysis to
examine the association between parental cohabitation and
overweight in the data and report crude and adjusted
odds ratios (OR) with corresponding 95% CI. We
entered the data using a stepwise approach as parental
level of education has been shown to be associated with
overweight in adolescents [
]: First we stratified only by
calendar year of birth, and gender and age of the child.
Second, by adding maternal educational level and age,
and third, we added paternal educational level and age.
Furthermore, we performed a missing data analysis to
determine whether the adjusted estimates were a result
of confounding or selection bias. The missing analysis
was based only on the number of observations available
in the last step of the stepwise approach and we used
multiple logistic regression analysis to estimate another
crude and stepwise adjusted OR. If the two estimated
crude OR differed substantially, the adjusted estimates
most likely were caused by selection effects.
A sub-analysis of OR was also performed, stratified by
age groups, to examine whether the association was
different in younger and older children. Within each of the
Nordic countries, the age was divided into two equal
sized age groups: 2-9-years and 10-17-years. Due to a
limited number of participants within each age group a
crude estimation was only performed.
A p value below 0.05 was considered statistically
A written informed consent for participation in the
study was not requested as it is not required in the Nordic
countries for this kind of study.
Data analyses were conducted with STATA version
11.0, software (StataCorp LP, College Station, TX, USA).
The descriptive characteristics of the separate and
cohabiting groups within each of the Nordic countries
are presented in Table 1. The proportion of separate
parents in our sample was 19.6% in Sweden, 16.9% in
Finland, 16.8% in Norway, 15.9% in Iceland, and 14.5%
in Denmark. The largest proportion of mothers with
low levels of education was observed in Finland
(26.4%) and Iceland (34.9%). This pattern was also
observed for low level of paternal education, although the
proportions were not as high as for the mothers (see
The overall prevalence of overweight in 2-17-years-old
children, and prevalence of overweight and difference in
prevalence proportion between the separate and
cohabiting groups are shown in Table 2. The difference in
proportion of overweight children between the separate and
cohabiting groups was only statistically significant in
Iceland where the largest difference was observed or 9.4
percentage points (95% CI: 2.8, 15.9). The overall
prevalence was similar in Finland, Norway and Sweden,
whereas the prevalence of 11.2% in Denmark and 19.0%
in Iceland differed from the other three countries.
The crude and stepwise models of adjusted ORs are
shown in Figure 1. In short, within each country, we
found no statistically significant association for
overweight in children whose parents lived separately
compared to children whose parents lived together at the
time of study in the fully adjusted models; Denmark: OR
1.03 (95% CI: 0.42; 2.53), Finland: OR 1.27 (95% CI: 0.74;
2.20), Iceland: OR1.50 (95% CI: 0.79; 2.84) Norway: OR
1.46 (95% CI: 0.81; 2.62), and Sweden: OR1.07 (95% CI:
The missing analysis of the association is shown in
Figure 2. We found that the adjusted OR in Finland
most likely was caused by selection as the two crude
ORs differed: 1.73 versus 1.59, p = 0.03 (Figure 1 versus
Figure 2). In Finland, Norway and Sweden the
adjustment may partly have been due to selection; the crude
ORs were 1.23 versus 1.31 (p = 0.23) for Finland, 1.23
versus 1.59 (p = 0.29) for Norway, and 1.43 versus 1.16
(p = 0.24) for Sweden (Figure 1 versus Figure 2). In
Denmark, we found the adjustment most likely was
due to confounding as the two crude ORs were similar;
1.09 versus 1.12, p = 0.15 (Figure 1 versus Figure 2).
Table 3 shows the crude analyses stratified by the two
age groups 2-9-years and 10-17-years. Within each
country, the crude OR for overweight was higher in the
youngest than the oldest age group. For the
2-9-yearsold children, the OR was significantly higher in Iceland
(2.11, 95% CI: 1.17; 3.82) and Norway (2.02, 95% CI:
1.04; 3.93) and, at significant level in Sweden (1.85, 95%
CI: 1.00; 3.43). Non-significant OR was observed in both
age groups in Denmark and Finland.
Across the five Nordic countries, only in Iceland was the
prevalence of overweight significantly larger in children
whose parents lived separately at time of study compared
to children who live with both parents. Referring to our
hypothesis, we would have expected a significant association
between parental cohabitation and childhood overweight
within each of the countries. Our results based on adjusted
analyses indicated that the results were most likely caused
by selection; except in Denmark, where the difference
could be ascribed to differences in parental educational
level and age. We found that the odds of being overweight
were generally largest in children under the age of 10 years
and in children whose parents lived separately.
Comparison to other studies
Our findings are not in line with other studies
specifically examining parental divorce or separation and risk of
overweight in children [
]. Three of these four
studies used objective measurement of height and
weight in children aged 3 to 5 , 5 to 14 [
8 years [
]. The fourth, a cross-sectional study, used
self-reported measurement in 16 to 20 years old
]. One of the four studies, a US study of
preschool children, found a statistically significant odds
ratio of 1.83 for children’s overweight if the parents lived
separately compared to children with cohabitating
]. Another study, based on a nationally
representative sample of 8-year-olds in Norway and parents’
marital status from population registry, found a 54%
higher prevalence for overweight (statistically significant)
and a 89% higher prevalence for abdominal obesity
(statistically significant) in children whose parents were
divorced compared to married parents [
one, conducted among US school children, had
examined timing of family disruption and found a
statistically increased risk for obesity, but not for overweight,
in the two years leading up to the disruption and until
12 years after it [
]. Our study is based on
selfreported height and weight and even though we found
high point OR estimates in Finland, Iceland and
Norway, they were not statistically significant.
Furthermore, across the Nordic countries we found the
greatest odds for being overweight in the youngest age
group of children whose parents lived separately, although
our results may be interpreted with caution as these
estimates are based on unadjusted analyses. Though, the
fourth study, of secular trends in overweight and obesity
in Icelandic adolescents aged 16–20, demonstrated a
statistically significantly increased odds of overweight and
obesity in girls (odds ratio 3.36), but not among boys
(odds ratio 1.71, N.S.), across the survey years 1992, 2004,
2007, and 2010 [
]. We did however not stratify our
analyses by gender, so comparability to our study may not be
We found the largest prevalence of overweight in
217-years-old children living in Iceland (19.0%) and the
lowest in Denmark (11.2%). This same pattern has
previously been described in a review of trends in adolescent
overweight in general between the Nordic countries
from 1939 to 2003 [
]. The study of secular trends in
overweight and obesity in Icelandic adolescents found
that the probability of overweight was highest for
adolescents of parents in the lowest educational strata [
comparing children whose parents live separately in
Denmark and Iceland in the present study, there were
fewer low-educated mothers and fathers represented in
Denmark than in Iceland.
Throughout the Nordic countries, the overall
prevalence of overweight in children and youth was more or
less the same as shown in studies examining the
prevalence of overweight in children in general [
the Nordic countries, so far only Norway and Sweden
have participated in the World Health Organization
(WHO) European Childhood Obesity Surveillance
Initiative (COSI) [
]. The pattern of difference in
prevalence of overweight in Denmark and Iceland, and almost
the same in Finland, Norway and Sweden, is also found
in the aforementioned studies.
Strengths and limitations
Strength in our study is that the data collection was
carried out at the same time throughout the Nordic
countries and the same questionnaire was used, despite a
mixed-mode data collection in Denmark. This supports
the comparability of the prevalence of overweight across
the Nordic countries. Moreover, we observed the
prevalence of overweight at two levels; overall and in children
of separated parents. Furthermore, the invited study
population is representative of the 2-17-year-old
population in each of the Nordic countries. Our study also has
some limitations. First, we cannot rule out selection bias
as 41.5% of all invited participants in the 2011
NordChild survey comprised the present study population.
The missing data analysis indicated that some of our
results may be caused by selection effects; probably a
greater proportion of high-educated parents participated.
If there was a higher proportion of divorced or separated
parents with overweight children among the
nonresponders, than we may have underestimated the
prevalence proportion. Second, the prevalence of
overweight is based on self-reported height and weight. It is
common for parents to misclassify their overweight child
as normal weight [
], but we attribute this
misclassification as non-differential in the present study which
entails a bias towards the null (equally across each
country). The fact that parents were asked to round up child’s
body weight to whole kilograms is recognized and could
lead to misclassification of weight status in some
children. However, this error is expected to be randomly
distributed and did probably not affect our findings.
Furthermore, BMI is easy to calculate and widely used, but
it also reflects a more lean body mass. The BMI only to
a certain extent reflects the negative influence of
overweight for health, mainly related to the intra-abdominal
fat, and waist circumference may probably have been a
more relevant anthropometric measure in this respect
]. Moreover, it remains unknown whether increase
in odds of obesity exists, but it was not possible to
examine due to too few cases in our sample. Third,
timing of parental separation is not taken into account even
though the questionnaire had asked for the age of the
child when the parents were separated or divorced.
Unfortunately only about 20% of the participants answered
this question rendering the response rate too low for any
meaningful analyses. Further, due to nature of the
crosssectional study design multiple-partner separations were
also not taken into account but are of course possible.
The situation of multiple divorces or separations could
especially be present for the older children. In our study
the majority of the children in the separate group were
in the oldest age groups and if a higher prevalence of
overweight children is present in multiple divorces or
separations we might have overestimated this
prevalence. Finally, lack of information of the major a priory
confounder parental BMI could be another potential
limitation of the study. Younger children’s risk of
becoming overweight increases with parental overweight
and obesity [
] and therefore we cannot rule out that
our findings may be confounded by parental overweight.
The generous social service systems in the Nordic
countries may be accounted for the non-difference between
parental cohabitation and childhood overweight. Though,
Iceland may differ from the other four Nordic countries as
the prevalence of overweight in both the parental
cohabiting and separate groups was greater in Iceland than in the
other Nordic countries. Obesity has been shown to be
associated with income inequality [
], and the ongoing
financial crisis, worldwide as well as in the Nordic
countries, may have been more dramatic in Iceland
than the other four Nordic countries. Iceland experienced
a complete collapse of its banking system in October
2008, an event that the country has not fully recovered
from to date. Currently, the public in Iceland pays more
out of pocket for health care and social services than ever
before. This may support a reflection of increase and
sudden development of inequality in Iceland.
Another possible explanation could be parental
educational level as the point estimate for OR reduced when
adjusting for parental educational level and age, especially
in Denmark and Sweden. Interestingly, comparing the
crude and fully adjusted OR models for overweight in
children whose parents lived separately, the fully adjusted OR
decreased but the point estimate was still high in Iceland.
The fully adjusted estimate increased in Norway which
partly could be explained by unmeasured confounding
impact. The results in Iceland may suggest that the paternal
level of education may impact childhood overweight if the
parents separated in an economic insecure setting; an
association found in the previous study of Icelandic adolescents
]. Though, it may be questionable whether the Icelandic
banking collapse may have caused higher rates of divorce
and/or separation as the rate of 15.9% of the Icelandic
parents lived separately was comparable to the other countries.
Finally, parental divorce and separation may be a
stressful life transition for both adults and children, and
such an episode appears to contribute to a decrease in
children’s well-being [
]. The impact of divorce or
separation is potentially complicated, as there is
multitude of potential environmental moderating factors
involved in such a process [
]. Further, there may be
variations of interactions and events that precede and
follow the divorce or separation that impact the child’s
mental and physical health; i.e. decline in contact with
one parent, unhealthy eating patterns, etc. [
factors may have been more pronounced in Iceland.
Across the Nordic countries, we found no association for
overweight in children whose parents lived separately
compared to children whose parents lived together at time
of study. Though, our finding of greater prevalence of
overweight in Icelandic children whose parents live
separately may indicate that the welfare society in Iceland is
separating from the other Nordic countries.
The authors declare that they have no competing interests.
LH carried out the collection of the Danish data, performed the statistical
analysis and drafted the manuscript. MG carried out the collection of the
Finnish data. CO participated in the design of the Danish part of the study.
All authors have commented on and contributed in the writing of the
manuscript. All authors read and approved the final manuscript.
The Danish part of NordChild 2011 survey was funded by Trygfonden (www.
trygfonden.dk) grant 7-11-00-1396. Lena Hohwü was supported by a full PhD
fellowship at Aarhus University, Denmark.
We thank Ynna Margot Nielsen, Søren Beck Morsing and Marianne Pedersen,
Aarhus University, for their effort helping Lena Hohwü gathering the Danish
data. We thank Ylva Bjereld, NHV Nordic School of Public Health, and Max
Petzold, University of Gothenburg, who gathered the Swedish data. We also
thank Heidi Lyshol, Norwegian Institute of Public Health, as project manager
for the Norwegian data collection. We also thank Jenný Ingudóttir, Jon Oskar
Gudlaugsson and Geir Gunnlaugsson at the Directorate of Health in Reykjavik
for gathering the Icelandic data, and Heljä-Marja Surcel, THL National Institute
for Health and Welfare in Oulu, Finland as project manager for the data
collection in Finland.
The funding sources had no role in study design or conduct, data collection,
data analysis, data interpretation, or in the preparation, review, approval, or
submission of the report. The corresponding author had full access to all the
data in the study. Lena Hohwü had the final responsibility for the decision to
submit for publication.
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