Social Inequalities in Obesity Persist in the Nordic Region Despite Its Relative Affluence and Equity

There are no nationally representative objective data on prevalence of obesity in Swedish adults, but all available data point to a large increase in prevalence in the latter part of the twentieth century. High prevalence of obesity in socioeconomically disadvantaged groups in Sweden has also been observed consistently during this period.

An early example is from the 1968/9 baseline examination of the Population Study of Women in Gothenburg, where 38 and 50-year old women with more education were far less likely to be overweight or obese than those with middle and lower educational status [12]. This pattern has persisted to the present time (Fig. 1).

In a nationally representative sample surveyed by Statistics Sweden in 2004–5, only self-reported weight and height data are available. In this study, age-standardized mean BMI in both women and men was lower in those with at least 12 years of education compared to groups with less education, by circa 0.75 BMI units [13]. Around the same time, measured anthropometric data from the InterGene population-based survey in Western Sweden indicated that the prevalence odds ratio for obesity in the lower education category was 1.89 (1.37–2.60), or 8.1 % in university educated subjects compared to 14.4 % in the rest [14•].

The current social gradient in Swedish children seems to be consistent with that observed in adults. The only nationally representative and objectively measured survey of obesity in Swedish children is part of the WHO-COSI survey of 7–9 year olds. Using data on educational attainment on the area level, OWOB respectively were approximately 2 and 3 times more prevalent in areas with lower compared to higher area-level education areas [15]. An urban-rural gradient was also observed, which was to a large extent explained by lower educational attainment in the rural areas. Using individual level data from parents of the same children, the education gradient for obesity was confirmed, with a somewhat larger effect of paternal then maternal education (OR 6.6 for fathers and 4.8 for mothers with low education, relative to more than 12 years of education [16]. In the IDEFICS western Sweden study of 2–8 year children, other socioeconomic indicators showed stronger associations than parental education: specifically, high household income and parental occupational position were both highly protective for OWOB [17].

There are also a few studies investigating whether the inverse socioeconomic gradient as described above has been widening or narrowing in recent decades. As illustrated in Fig. 1 the gradient has been relatively stable in middle-aged western Swedish women over the past few decades, with no evidence of a significant shift over time. At baseline (1968/69) as well as at the latest examination point (2004/05) women with more education were far less likely to be overweight or obese than those with middle and lower educational status. There was no interaction between time and education in relation to overweight, suggesting that the slope of the gradient did not change significantly between 1968 and 2005. In contrast to this local study of women, a nationally representative comparison of Statistics Sweden’s questionnaire surveys conducted in the early 1980s and the late 1990s gave some indication of a narrowing of the education gradient for overweight in younger adults aged 25–44 years, but a stable inverse gradient at ages 45–64 [18]. However, a population based cohort of elderly residents in western Sweden indicated that the gradient was getting steeper between 1971–2000, with greatest obesity prevalence increases observed in 70 year olds with basic education only [19]. Studies in 10 year old children have also given inconsistent answers to the question whether the gradient was increasing. In female cohorts from Stockholm and Gothenburg, studied in 1994–5 and 1999–2000, there was no evidence that the inverse gradient was changing in girls [20, 21]. Interestingly, there was a trend towards lower BMIs during this period in girls from all social groups. In boys, the picture was less consistent, with those from lower income areas in Stockholm showing the greatest prevalence increases, i.e. steeper gradient, but this was not the case in Gothenburg [20‐22].

Studies document that already in the early 2000s almost 1 in 5 of all Danish adults aged 30–60 years were obese, compared to less than 1 in 10 just 20 years earlier [23]. However, there are trends suggesting increase as well as decrease among sub-segments of the population. Measured heights and weights among adults aged 20 + years, from the greater Copenhagen County, showed that while the overall Danish trend for obesity prevalence markedly increased from the beginning of 1960, the trends over the following 40 years were different among men and women and for different age- and birth-cohorts. Indeed, there was only little indication of an increasing trend in obesity prevalence for premenopausal, whereas among postmenopausal women and men of all ages, the prevalence of obesity was increasing [24]. These data suggested stable or even declining obesity prevalence among the premenopausal Danish women. The Danish trends from mid-1960s to mid-1990s were paralleled by similar findings for women in the other Nordic countries, suggesting common conditions operating, i.e. the rate of entrance into the paid labor force, which took place much earlier and at a higher rate than among women from most other countries. Marked differences in obesity occurrence still exist between employed and unemployed women [25], as well as between those with longer and shorter education (Fig. 2a) [26]. Another Danish study showed that young men with shorter education (7–9 years) were more overweight than those with high school degrees [27]. Finally, another study including subjects selected at random from the civil registration system concluded that education was the dimension most consistently associated with BMI and obesity, particularly for women, indicating the importance of cultural capital for weight status [28].

Danish children from lower SEP groups run a greater risk of developing overweight and obesity. This has been the conclusion from several studies including a recent one, from among a total of 1656 children followed between 1996 and 2003, and selected to be a representative sub-sample of children from the two major cities of Denmark: Copenhagen and Aarhus. The study used measures of height and weight, taken at the school health examination as the children were in 9th grade, in 23 municipalities. The study found a higher prevalence of obesity among those children that came from low SEP families, and the inverse social gradient in overweight became steeper with age for girls while it emerged for boys in late adolescence [29]. Another study among 8694 children, also measured during the 9th grade school health examinations in 2007–2009, found higher obesity prevalence among children from more disadvantaged areas. In this study, municipalities characterized as being overall high or low socioeconomic status areas, based on factors such as number of unemployed, uneducated and low income families, had more overweight children than municipalities with high socioeconomic status, prevalence varying between 15.3 and 33.5 % [30]. Finally, health check-ups among almost 1800 3-year olds living in the city of Aalborg in 2002, showed that already at this young age, children from low SEP families (one or more parents being unskilled workers or unemployed/disabled pensioners/students) were more overweight and obese [31].

Not much data is available that can document the more recent development in obesity rates as a function of SEP. However, data following trends among adults until 2006 suggests a diverging development for men and women. In fact, among overweight women, those with some education (professional education, high school or more) seem to have experienced some recent decline in prevalence, while this has not been observed for women with primary school only. Among men, those with some education seem to have experienced a levelling off in prevalence of OWOB since 2000, while a significant decline was seen for those with low education (Fig. 2b) [26]. The results suggest that whether the gradient is getting steeper or flatter among Danes depends on both socioeconomic position and gender.

Mean BMI and prevalence of OWOB increased in Finland since the 1970s in men, whereas women actually became slimmer during the 1970s and started gaining weight thereafter [32‐34]. In 2007, 22 % of the working-aged men and 20 % of the working-aged women were obese [34]. According to the most recent information, the prevalence of OWOB among Finnish adults may have been plateauing during the past 10 years (2002–2012) [35].

Higher BMI and OWOB in the Finnish population are more common in the lower SEP groups (Fig. 3a and b). An inverse gradient in mean BMI according to education was already evident in women in the first available survey in 1972, whereas in men the gradient emerged during the next 5 years [32]. Mean BMI or OWOB also differed by occupational status [33], employment status [36], and income [36, 37••], especially in women. The typical educational gradient was observed also among the older population [38]. BMI and OWOB were more common in rural than urban areas across Finland [39, 40].

The prevalence of OWOB has increased also among Finnish adolescents [41, 42]. The only study with comparative information in OWOB in younger Finnish children found no increase in the prevalence of OWOB in pre-school children from the 1970s to the 2000s [42]. In 2007–2009, approximately 15 % of pre-school girls and 10 % of boys were overweight or obese (IOTF criteria), while the respective proportions for school-aged children and adolescent were 20 % in girls and 21 % in boys [43].

Regarding adolescents, an inverse association between SEP and prevalence of OWOB has been observed in both genders, according to several indicators representing family SEP (parental education, occupational status, and employment status), the adolescent’s own social position (school achievement, school attendance) or the family’s material affluence [41, 44]. Data on associations between SEP and OWOB among children (younger than adolescents) are scarce. A similar rural-urban difference as in adults has been observed in children and adolescents [41, 42].

Three large population-based studies in working-aged adults ([32‐34, 37••, 45] one in older people [38], and one in adolescents [41] have examined the associations between SEP and BMI or OWOB across time in Finland. Results from the Mini-Finland survey and the comparative Health 2000 Survey [45] suggest that the educational gradient in obesity diminished during the 1980s and 1990s especially in men, because of a prominent increase in the prevalence of obesity in men with the highest education. The same was not observed in the FINRISK study, where the educational gradient in BMI was observed to have widened during the 1970s and 1980s [32, 33], but stayed stable during the 1990s or 2000s [33, 34] (Fig. 3). Regarding occupation, the trends in BMI were similar in all occupational groups in women, while the increase was greatest among retired and unemployed men between 1982 and 1997 [33]. The Finnish adult health behavior survey did not show any overall change in the educational or income-related differences in BMI either, between 1978 and 2002 [37••]. However, education and income interacted with each other in men, such that the most prominent increase in BMI across the study period took place in high income men with low education and in low income men with high education [37••]. Among the older people, the educational differences in obesity stayed at approximately constant level, even if a slight decrease in the disparity was observed in women [38]. Among adolescents, there were some fluctuations in the SEP gradient in OWOB between subsequent surveys (the Adolescent Health and Lifestyle Survey, repeated biennially in 1979–2005), but in general the gradient remained rather stable, regardless of whether the SEP was measured by familial or adolescent’s own socioeconomic position, or by the urbanization level of the place of residence [41].

Studies from different parts of Norway have shown an increase in obesity in all age groups from the late 1960s, more so in men compared to women [46‐49]. In women a decline in obesity (BMI ≥ 30) was actually seen from the 1960s until the late 1970s before it again increased [46]. In the HUNT study, Nord-Trøndelag county, including 90,000 adults 20 years and older, obesity measured in 1984–86, 1995–97 and 2006–08 increased from 7.7 % to 14.4 % and 22.1 % in men and from 13.3 % to 18.3 % and 23.1 % in women [48]. The increase in weight has been observed at all social levels, but a higher prevalence of obesity has constantly been found in the more socioeconomically disadvantaged groups at all time points [46, 49, 50••, 51]. Some studies have reported larger educational inequalities in BMI in women compared to men [51], others not. In the most recent HUNT survey (2006–2008) the prevalence ratio in educational inequalities (low to high) of obesity was 1.9 in men and 1.6 in women [50••]. Educational inequalities have mostly been focused on, but differences in obesity prevalence have also been observed between people living on the east or west side of the capital city, Oslo and between cities and rural districts [52, 53].

Overweight and obesity has increased since the 1970s also among children and adolescents from 4 to 19 years of age [54‐60]. The growth study in Oslo (2012) found 3.6 % of 8 years old children to be obese [52], while the Young-HUNT3 Survey (2006–08) found 4 % of girls and 5.6 % of boys aged 13–16 years and 5 % of girls and 7.5 % of boys aged 17–19 years to be classified as obese using the IOTF recommended cut-points for age and gender [60]. The same social gradient of obesity as in adults is also reported in children and adolescents [52, 61‐66]. Lower parental education level has clearly been associated with higher prevalence of obesity in studies both from the larger cities, Oslo and Bergen [61, 62, 66] and also more rural areas [57, 63‐65]. In the Bergen Growth Study and the Young-HUNT Study higher parental education was found to be associated with a less obesogenic lifestyle [66, 67]. Obesity in adolescence has been associated with plans for lower education. A higher prevalence of obesity is observed in rural areas compared to more densely populated cities and residential area in Oslo. Differences in education and economy may partly explain this [68].

In three waves (1974–78, 1977–83 and 1985–88) The Norwegian Counties Study including 48,000 middle aged men and women in three counties, also focused on trends in educational inequalities in cardiovascular risk factors [51]. For BMI there was a tendency to a decrease in inequality for men while for women an increase. The same tendency was not verified studying differences in obesity in 40–42 aged men and women in eight counties between 1994–96 and 1997–99 [49]. The HUNT Study compared the three waves of 1984–86, 1995–97 and 2006–08 regarding changes in socioeconomic differences in obesity in 30–69 years old men and women including over 40,000 people in each wave [50••]. In this study relative socioeconomic inequalities in obesity measured by level of education did not show a clear trend (men: 1.9, 1.7, and 1.9; women: 1.8, 1.8, and 1.6). However, the absolute prevalence differences in obesity between people with primary and tertiary education increased from 4.5 to 14 % among men and from 6.2 to 10 % among women in 1984–86 compared to 2006–08 (Fig. 4a and b). Similar studies of trend in gradients are not found for children or adolescents.

The prevalence of obesity has increased in Iceland since the 1980s [69] and is by the Nordic Monitoring report considered to be higher than in any other Nordic country (Table 1) [10]. In 1990, less than 10 % of 18–80 years were obese, which has increased to about 1 in 5 in 2007 [69]. According to the most recent National Nutrition Survey [70] the prevalence of overweight was 38 % and obesity 21 % or total of 59 % in the age group 18–80 years. The National Nutrition Survey (self-reported by telephone) also confirms that obesity is more common among men (22.7 %) than women (19.3 %). Comparison with data from the Reykjavik study by the Icelandic Heart Association (repeated objective measurements within the capital area) could indicate underreporting as obesity for men was 27.5 % and 23 % for women in 2007 [69]. A population-based study of 15,000 women 18–45 years old in 2003–2004 [71] revealed that living outside the capital area and not having university education was associated with increased risk of obesity (OR of being obese living outside capital area 1.66, 95 % CI 1.50–1.83, and having less than university education 1.53, 95 % CI 1.36–1.71). The proportion of obese women was more than double within the group who had finished elementary school compared to the group with a university education. According to the same study, the prevalence of obesity for women 18–45 years old was 13 % within the capital area compared to 21 % outside the capital area. The difference between weight status within and outside the capital area could not be explained by different education between the areas. In the two most recent National Nutrition Surveys [70, 72] the urban-rural gradient has been found, however only for women and for total OWOB.

According to the Nordic Monitoring report [10] the prevalence of overweight in children 7–12 years was 15.1 % and of obesity 3.5 %, and did not significantly differ from the other Nordic countries. Regular objective measurements of 9-year-old school children by the Primary Health Care of the Capital Area indicate that the increase in childhood OWOB seen in the last decades has now halted [73]. Inverse associations have been found between OWOB in young adults, and parents’ education [74••]. According to the Nordic monitoring report [10] the number of children in normal weight increased with increased educational level of the parent. This trend was significant in Iceland. The urban-rural gradient has also been found for adolescents, in a study based on self-reported data from two cross-sectional population-based samples of 14- and 15-year-old pupils in 2000 and 2009, from the “Youth in Iceland” surveys [75]. Overweight and obesity increased for both boys and girls between the study years. Mean BMI and prevalence rates of OWOB were higher in rural areas than urban areas in both study years. An unpublished undergraduate thesis (Randversdottir LB. 2011. Are children and adolescents getting heavier? In Icelandic) has studied the urban-rural gradient in OWOB with similar conclusions as the studies on adults: The prevalence of OWOB was higher outside the capital area than within it and this gap was persistent between the survey years 2006 and 2010.

Eidsdóttir and colleagues [74••] have analyzed data from repeated population-based, cross-sectional surveys from cohorts of 16 to 20 year olds in 1992, 2004, 2007 and 2010 within the national survey Youth in Iceland. According to self-reported data on height and weight, the prevalence of OWOB increased across three subgroups of parental education level. The probability of OWOB across all years was consistently highest for youths with parents in the low-education category. The inverse SEP gradient in OWOB trends between parental education backgrounds became steeper over time with an exception for boys in association with fathers’ education, where the net increase in OWOB was nearly similar in all education subgroups (Fig. 5a and b).