Age-specific association between body mass index and depression: The Korea National Health and Nutrition Examination Survey 2014

Background/Objectives: Decades of research have investigated the association between body mass index (BMI) and depression. Although it has been suggested that obesity lowers the risk of depression in elderly adults, the association of overweight and obesity with depression across age groups remains controversial. Thus, we aimed to investigate how the odds of depression vary between BMI groups in the general population. Subjects/Methods: In this study, data were collected from the sixth Korea National Health and Nutrition Examination Survey of 2014 (KNHANES VI; n =7550), and 4932 adults were included in the study sample. We investigated the adjusted association between depression, which was measured by the Patient Health Questionnaire 9 (PHQ-9), and BMI groups (underweight, normal weight, overweight, obese class I, obese classes II and III). Results: In all adults, after adjusting for sex, age, income and presence of chronic illnesses, overweight had lower odds of depression than normal weight (OR, 0.811; 95% CI, 0.661–0.995), whereas underweight had higher odds of depression than normal-weight subjects (OR, 1.776; 95% CI, 1.241–2.540). Overweight elderly adults had lower odds of depression than normal-weight elderly adults (OR, 0.522, 95% CI, 0.367–0.743), and obese class I elderly adults also had lower odds of depression than normal-weight elderly adults in both men (OR, 0.482, 95% CI, 0.251–0.924) and women (OR, 0.637, 95% CI, 0.418–0.970). Furthermore, in the normal-weight-to-obese class I elderly adults group, we found that an increase of 1 kg m −2 BMI was significantly associated with a decreased prevalence of depression in both men (OR, 0.898, 95% CI, 0.808–0.997) and women (OR, 0.911, 95% CI, 0.844–0.982). Conclusions: We found that overweight and mild obesity significantly lowered the risk of depression in elderly adults. These findings suggest that mild increases in BMI beyond the normal range may be a protective factor for depression in elderly Korean adults.