Background: Both obesity and depression have been associated with significant increases in health care costs. Previous research has not examined whether cost increases associated with obesity could be explained by confounding effects of depression.
Objective: Examine whether the association between obesity and health care costs is explained by co-occurring depression.
Design: Cross-sectional study including telephone survey and linkage to health plan records.
Participants: 4462 women aged 40 to 65 enrolled in prepaid health plan in the Pacific Northwest.
Main measures: The telephone survey included self-report of height and weight and measurement of depression by the Patient Health Questionnaire (PHQ9). Survey data were linked to health plan cost accounting records.
Key results: Compared to women with BMI less than 25, proportional increases in health care costs were 65% (95% CI 41% to 93%) for women with BMI 30 to 35 and 157% (95% CI 91% to 246%) for women with BMI of 35 or more. Adjustment for co-occurring symptoms of depression reduced these proportional differences to 40% (95% CI 18% to 66%) and 87% (95% CI 42% to 147%), respectively. Cost increases associated with obesity were spread across all major categories of health services (primary care visits, outpatient prescriptions, inpatient medical services, and specialty mental health care).
Conclusions: Among middle-aged women, both obesity and depression are independently associated with substantially higher health care costs. These cost increases are spread across the full range of outpatient and inpatient health services. Given the high prevalence of obesity, cost increases of this magnitude have major policy and public health importance.