Objective. Although those age 75 and older are the fastest growing age group in the U.S., few studies focus on the course and treatment of depression in this age group. This study examines the differences between the young-old (age 60 to 74) and the old-old (age 75 and older) in regards to their response to a collaborative care model for depression in primary care. We hypothesized that old-old participants would have more severe depression and have a lower rate of treatment response compared to young-old participants.

Methods. The sample consisted of 906 participants (n = 606 young-old; n = 300 old-old) who were randomized to receive the intervention with a depression care manager in the IMPACT trial. This study compared young-old and old-old patients on process of care and outcome variables to identify potential differences between the two age groups. Process of care was determined by the type of treatment and level of stepped care received. Clinical outcomes included SCL-20 depression scores, treatment response (defined as a ≥50% decrease in SCL-20 score from baseline) and complete remission (defined as a SCL-20 score <0.5) at 3-, 6-, and 12-months follow-up.

Results. The process of care variables did not differ between the two age groups. SCL-20 depression scores did not significantly differ between the two age groups at all follow-up intervals. Treatment response was significantly different between young-old and old-old participants at 6- and 12-months. Complete remission rates were significantly different between the two age-groups at 12-months follow-up.

Conclusions. Young-old and old-old patients have a similar clinical response to initial collaborative depression care in a primary care setting, but old-old patients may have lower rates long-term treatment response and complete remission. These findings will help guide future clinical and public health approaches to treat old-old patients with depression.