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Response to Rozzini and Colleagues' Letter to the Editor

Division of Geriatrics University of California at San Francisco and Department of Veterans Affairs Medical Center San Francisco California

To the Editor:

We thank Dr. Rozzini and colleagues for their interest in our study (1), and for sharing their results. Similar to our study, they demonstrate that depressive symptoms are associated with mortality, as has been shown in other studies (2). Interestingly, however, they found that depressive symptoms did not increase the risk for mortality in participants with cognitive decline, while we found the mortality risks associated with depressive symptoms and poor cognitive function were additive.

Although we cannot determine precisely why these findings differ, we can speculate on several possibilities. First, the spectrum of cognitive impairment may differ between the 2 studies. Rozzini's cohort included participants with more-severe cognitive impairment than our study, and we agree it is possible that, in participants with severe cognitive impairment, the impact of depressive symptoms may differ. It is also notable that instruments used to assess cognitive impairment and depressive symptoms differed in the 2 studies, and the prognostic impact of these risk factors may differ depending on the measurement tools used. Finally, the responses to questions about depressive symptoms may in part depend on cultural factors.

These issues highlight the need for additional research on the impact of depressive symptoms and cognitive impairment on health outcomes. Future studies would benefit from more data collection points in order to assess the impact of changes in cognitive function and depressive symptoms on health outcomes. Similarly, future studies with multiple data collection time points could clarify any potential interactions between depressive symptoms, cognitive impairment and health outcomes.

Acknowledgments

Address correspondence to Kala Mehta, DSc, Division of Geriatrics, UCSF, 4150 Clement Street, Box 181G, San Francisco CA 94121. E-mail: kala{at}itsa.ucsf.edu

References

1. Mehta KM, Yaffe K, Langa KM, Sands L, Whooley MA, Covinsky KE. Additive effects of cognitive function and depressive symptoms on mortality in elderly community-living adults. J Gerontol Med Sci.. 2003;58A:461-467.
2. Blazer DG. Depression in late life: review and commentary. J Gerontol Med Sci.. 2003;58A:249-265.

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