Objective: To assess the prevalence of obesity and the association with smoking and education among young Icelandic women residing within and outside the capital area.

Materials and methods: A self-administered questionnaire was sent to 28.000 Icelandic women, 18-45 years-old, in the period November 2004 to June 2005. The sample was randomly selected from The National Registry, response rate being 54.6%. The study was part of a large Nordic population-based cross-sectional study. Logistic regression was used for assessing the odds ratio of obesity (BMI≥30) in a multivariate analysis according to smoking and education, taking also into account age and alcohol consumption. The chi-square test was used for comparing percentages.

Results: Thirteen percent of women residing in the capital area were obese compared with 21% outside the capital. In the multivariate analysis obesity was increased among women living outside the capital (OR = 1.66; 95% CI 1,50-1,83), among smokers (OR=1,13; 95% CI 1.01-1.28), and among women who did not have university education (OR=1.53; 95%CI 1.36-1.71). Daily smokers within the capital area were more likely to be obese (OR=1.27; 95%CI 1.07-1.49) but not smokers outside the capital (OR=1.0). .

Conclusions: Residence outside the capital area, daily smoking and non-university education are associated with an increased risk of obesity among young Icelandic women. The relationship beween these factors is complex and differs between women residing within and outside the capital area.

Table I. Baseline characteristics of respondents (15,025) from a random sample of 28,000 Icelandic women, according to residence

		Within the capital area   (n=9229)	Outside the capital area   (n=5796)
Response rate (%)		50.9	58.6
Average age (range)		31.6 (18-46)	32.0 (18-46)
Daily smoking (%)		17.7	19.6
Average height, cm (range)		168.0 (120-196)	167.2 (138-198)
Average weight, kg (range)		69.7 (40-184)	73.3 (37-180)
Underweight (BMI<18.5) (%)		2.8	1.9
Ideal weight (BMI 18.5-24.9) (%)		60.6	48.1
Overweight (BMI 25-29.9) (%)		23.5	28.9
Obese (BMI ≥30) (%)		13.1	21.1
Academic education (%)		37.3	21.4

 

 

Table II. Logistic regression with obesity as the dependent varable and residence, smoking and education as independent variables. Alcohol consumption and age at response are also included in the model.

	Odds ratio (OR)	95% Confidence interval (CI)
Residence outside the capital  area compared with residence within the capital area	1.66	1.50-1.83
Daily smoking compared with other smoking habits and not smoking*	1.13	1.01-1.28
Other education compared with academic education	1.53	1.36-1.71

 

* The association between obesity and smoking was modified by residence (P=0.067 for the interaction between smoking and residence).

In a stratified analysis according to residence: OR = 1.27 (95% CI 1.07-1.49) within the capital area and OR = 1.00 (95% CI 0.84-1.19) outside the capital area

Figure 1. Percentage of obese women by residence and education group.
Numbers in each category are shown.

Figure 2. Percentage of obese women by residence and age group.
Numbers in each category are shown.

Figure 3. Percentage of obese women by residence and smoking habits.
Numbers in each category are shown.