The digital public defence will take place on Zoom at 12:15, March 4, 2021. The defence will follow regular procedure as far as possible, hence it will be open to the public and the audience can ask ex auditorio questions when invited to do so.

Read about how to participate in the public defence at uio.no.

Adjudication committee

• First opponent: Associate Professor Katarina Steen Carlsson, Lund University, Sweden
• Second opponent: Professor Kim Rose Olsen, University of Southern Denmark
• Third member and chair of the evaluation committee: Professor Magne Nylenna, University of Oslo

Chair of the Defence

Professor Per Nafstad, University of Oslo

Principal Supervisor

 Associate Professor Jonas Minet Kinge, University of Oslo

Summary

Several studies have found that the economic ramifications of obesity are large. This thesis investigates statistical associations between body mass index (BMI) and economic outcomes in a Norwegian setting.

The main objectives have been to study the effect of BMI on healthcare use, healthcare costs, and income. These objectives were achieved by applying methods that overcome some of the most important limitations of previous studies.

The effect of BMI on healthcare use was studied using data from the National Health and Living Surveys. Healthcare use was estimated from a lifetime perspective, which allowed us to take BMI-specific mortality into account. Considering BMI-specific mortality reduced healthcare use by up to 17% for males, and up to 16% for females, but this did not offset the effect of BMI on healthcare use.

The effect of BMI on healthcare costs and income was investigated using data from Helseundersøkelsen I Nord Trøndelag (The HUNT studies) combined with registry data. We used instrumental variable (IV) models with genetic variants associated with BMI as instruments for BMI, to try to deal with endogeneity bias.

Elevated BMI was positively associated with general practitioner (GP) costs, and specialist costs. The effect was significant for GP-costs, but not for specialist costs. For both GP and specialist costs, the IV-based effect estimates were smaller than the effects estimated from traditional models.

The effect of BMI on income was sex-specific. For females, increased BMI was associated with a smaller and non-significant likelihood of having an income, and a significantly smaller log income. For males, there was no clear association between BMI and income.

If our methods are reliable, these findings suggest that studies that have not adequately considered the complexity of the relationship between BMI and economic outcomes may have drawn incorrect conclusions.

The trial lecture “A health economist view on causality, environmental factors and genetics” will take place on Zoom at 10:15, March 4, 2021.

The trial lecture will follow regular procedure as far as possible, hence it will be open to the public and the audience can ask ex auditorio questions when invited to do so.

Read about how to participate in the trail lecture at uio.no.