Open Access Highly Accessed Research article

Body mass index and overweight in relation to residence distance and population density: experience from the Northern Finland birth cohort 1966

Simo Näyhä123*, Tiina Lankila14, Arja Rautio5, Markku Koiranen1, Tuija H Tammelin6, Anja Taanila17, Jarmo Rusanen4 and Jaana Laitinen3

Author Affiliations

1 Institute of Health Sciences, University of Oulu, PO Box 5000, FI-90014 Oulu, Finland

2 Center for Environmental and Respiratory Health Research, University of Oulu, PO Box 5000, FI-90014 Oulu, Finland

3 Finnish Institute of Occupational Health, Aapistie 1, FI-90220 Oulu, Finland

4 Department of Geography, University of Oulu, PO Box 8000, FI-90014, Finland

5 Centre for Arctic Medicine, Thule Institute, University of Oulu, PO Box 7300, FI-90014 Oulu, Finland

6 LIKES – Research Centre for Sport and Health Sciences, Viitaniementie 15a, FI-40720 Jyväskylä, Finland

7 Primary Health Care Unit, Oulu University Hospital, PO Box 5000, FI-90014 Oulu, Finland

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BMC Public Health 2013, 13:938  doi:10.1186/1471-2458-13-938

Published: 8 October 2013

Abstract

Background

The effect of urban sprawl on body weight in Finland is not well known. To provide more information, we examined whether body mass index (BMI) and the prevalence of overweight are associated with an individual’s distance to the local community centre and population density in his/her resident area.

Methods

The sample consisted of 5363 men and women, members of the Northern Finland Birth Cohort 1966 (NFBC), who filled in a postal questionnaire and attended a medical checkup in 1997, at the age of 31 years. Body mass index (BMI; kg/m2) and the prevalence of overweight (BMI ≥ 25.0 kg/m2) were regressed on each subject’s road distance to the resident commune’s centre and on population density in the 1 km2 geographical grid in which he/she resided, using a generalized additive model. Adjustments were made for sex, marital status, occupational class, education, leisure-time and occupational physical activity, alcohol consumption and smoking.

Results

The mean BMI among the subjects was 24.7 kg/m2, but it increased by increasing road distance (by 1.3 kg/m2 from 5–10 to 20–184 km) and by decreasing population density (by 1.7 kg/m2 from 1000–19,192 to 1–5 inhabitants/km2). The respective increases in overweight (overall prevalence 41%) were 13 per cent units for distance and 14 per cent units for population density. Adjusted regressions based on continuous explanatory variables showed an inverse L-shaped pattern with a mean BMI of 24.6 kg/m2 at distances shorter than 5 km and a rise of 2.6 kg/m2 at longer distances, and an increase of 2.5 kg/m2 from highest to lowest population density. The associations with road distance were stronger for women than men, while the sex difference in association with population density remained indeterminate.

Conclusions

We conclude that young adults in Northern Finland who live far away from local centres or in the most sparsely populated areas are fatter than those who live close to local centres or in densely populated areas. The likely explanations include variations in everyday physical activity in different residential environments, although causality of the associations remains to be confirmed.

Keywords:
Body mass index; Overweight; Medical geography; Urban/rural; Population density; Finland