Relationship between body mass index and depression in women: A 7-year prospective cohort study. The APNA study

Abstract Background The association between body mass index (BMI) and depression is complex and controversial. The present study examined the relationship between BMI and new-onset depression during 7 years of follow-up in 20,212 adult women attending Primary Health Care Centres in Navarra, Spain. Methods The Atención Primaria de Navarra (APNA) study is a dynamic prospective cohort study. A total of 20,212 women aged 18–99 years (mean age: 50.7 ± 18.5 years) without depression at baseline were selected from 2004 to 2011. We estimated the incidence of depression. We used the Kaplan-Meier analysis to predict the survival curve. The risk of depression onset according to different measures of BMI at baseline was assessed using Cox regression analyses. Results During the 7 years of follow-up, depression appeared in 8.9% (95% CI 8.5–9.3). The highest rates of depression incidence at follow-up occurred in underweight and obese women (9.8% [95% CI 7.3–12.9] and 10.3% [95% CI 9.5–11.1] respectively). The distribution of depression incidence by weight category was U-shaped. The risk of depression increased over time with an observed Kaplan-Meier estimation of 6.67. After adjusting for age, underweight and obese women at baseline have increased risk of depression onset during the follow-up period compared with normal weight women (HR = 1.48, 95% CI = 1.09–2.00 and HR = 1.14, 95% CI = 1.01–1.29 respectively). Conclusions In this 7-year prospective study in the APNA women population, depression emerged in 8.9%. Being underweight or obese (not overweight) at baseline is significantly associated with future onset of depression.