The Effects of Age on Cognitive Deficits in Schizophrenia: Page 2 of 2
The Effects of Age on Cognitive Deficits in Schizophrenia: Page 2 of 2
In a longitudinal study of older ambulatory patients, Heaton et al. (2001) found no evidence of change over an average of 60 months on a comprehensive neuropsychological battery. However, only 22 of the 142 patients were over age 65 at entry into the study. Another longitudinal study reported that older patients had selectively greater impairments in abstraction abilities than younger patients, with no increased age-related differences in other aspects of cognitive functioning (Fucetola et al., 2000). Further, Granholm et al. (2000) reported that older patients had a reduced ability to process complex information, as shown by increased utilization of information-processing resources while performing an attentional task. There is some evidence of age-related changes in the ability to perform complex and resource-demanding tasks even in ambulatory patients.
In a study of hospitalized patients with chronic schizophrenia (age>65) with MMSE scores >17, 30% declined over a 30-month period (Harvey et al., 1999b). The best two predictors of cognitive decline were lower education and greater severity of positive symptoms at baseline. A follow-up study of geriatric patients with schizophrenia who entered the study while hospitalized and who were reassessed after they were discharged to nursing homes also demonstrated cognitive decline over an average of 2.5 years (Harvey et al., 1999a).
Additional support for age-related cognitive decline comes from a study of chronically institutionalized patients ranging in age from 25 to 85 who were followed for six years and compared to healthy individuals and patients with AD (Friedman et al., 2001). This study found that the patients with schizophrenia had an age-associated risk of cognitive decline not found in the patients with AD or the healthy controls. The oldest patients with schizophrenia (ages 75 to 80 at baseline) dropped by six MMSE points in six years, while those under the age of 65 did not change in their functioning over the follow-up period. Furthermore, patients with AD declined by 12 or more MMSE points, regardless of age at entry into the study. This suggests that chronicity alone is not a sufficient determinant of cognitive decline until patients cross a certain age threshold. Later studies have indicated that newly incident medical conditions predict risk for cognitive decline (Friedman et al., 2002) and have sug-gested more recently that declines in cognitive functioning over time in poor-outcome patients predict the course of functional decline as well (Harvey and Davidson, 2002).
While a number of studies on cognition in older patients with schizophrenia have been published in the past decade, the specific effect of aging remains unclear. It appears that cognitive decline with aging in schizophrenia is multi-determined. While the decline does not appear to occur at all in younger patients, even those with a chronic course of illness, it is also not likely to be a pattern found in all older individuals with schizophrenia.
It appears that certain risk factors-possibly a chronic course of illness, less education, higher levels of positive symptoms and poor baseline cognitive functioning-are associated with the age-related cognitive decline observed in some patients. Ambulatory patients may also decline in late life on particularly complex tasks. However, the timing and severity of the decline may differ from poor-outcome patients.
Complicating the identification of those at risk for cognitive decline are the different research designs employed by various groups of researchers. This leads to the difficulty of parsing out the effects on cognition of life-long institutionalization, chronic psychosis, long-term antipsychotic medication administration and other factors. The Figure illustrates that longitudinal studies of chronically ill patients universally find global cognitive decline, while the only cross-sectional studies that failed to find age-related differences in cognition assessed only one specific domain and excluded low-functioning patients. In addition, a longitudinal study that failed to observe cognitive decline was of somewhat younger ambulatory patients. Since expected declines in cognition for healthy individuals only become substantial after age 65, it stands to reason that examination of patients with schizophrenia who are younger than 65 may be insufficient to detect decline.
Future longitudinal studies will assist in determining why cognitive decline occurs in late life for some patients with schizophrenia, but not for others. Consequently, treatment strategies for those at highest risk for decline may be developed in the near future. In turn, functional outcome, by way of improving or at least preserving cognitive functions, may be improved for the large number of elderly patients with schizophrenia.
1. Arnold SE, Gur RE, Shapiro RM et al. (1995), Prospective clinicopathologic studies of schizophrenia: accrual and assessment of patients. Am J Psychiatry 152(5):731-737.
2. Auslander LA, Lindamer LL, Delapena J et al. (2001), A comparison of community-dwelling olderschizophrenia patients by residential status.Acta Psychiatr Scand 103(5):380-386.
3. Bartels SJ, Mueser KT, Miles KM (1997), A comparative study of elderly patients with schizophrenia and bipolar disorder in nursing homes and the community. Schizophr Res 27(2-3):181-190.
4. Bilder RM, Goldman RS, Robinson D et al. (2000), Neuropsychology of first-episode schizophrenia: initial characterization and clinical correlates. Am J Psychiatry 157(4):549-559.
5. Bowie CR, Harvey PD, Moriarty PJ et al. (2002), Cognitive assessment of geriatric schizophrenic patients with severe impairment. Arch Clin Neuropsychol 17(7):611-623.
6. Cornblatt B, Obuchowski M, Roberts S et al. (1999), Cognitive and behavioral precursors of schizophrenia. Dev Psychopathol 11(3):487-508.
7. Davidson M, Harvey PD, Powchik P et al. (1995), Severity of symptoms in chronically institutionalized geriatric schizophrenic patients. Am J Psychiatry 152(2):197-207.
8. Davidson M, Reichenberg A, Rabinowitz J et al.(1999), Behavioral and intellectual markers for schizophrenia in apparently healthy male adolescents. Am J Psychiatry 156(9):1328-1335 [see comments].
9. Evans JD, Negron AE, Palmer BW et al. (1999), Cognitive deficits and psychopathology in institutionalized versus community-dwelling elderly schizophrenia patients. J Geriatr Psychiatry Neurol 12(1):11-15.
10. Eyler Zorrilla LT, Heaton RK, McAdams LA et al. (2000), Cross-sectional study of older outpatients with schizophrenia and healthy comparison subjects: no differences in age-related cognitive decline. Am J Psychiatry 157(8):1324-1326.
11. Friedman JI, Harvey PD, Coleman T et al. (2001), Six-year follow-up study of cognitive and functional status across the lifespan in schizophrenia: a comparison with Alzheimer's disease and normal aging. Am J Psychiatry 158(9):1441-1448.
12. Friedman JI, Harvey PD, McGurk SR et al. (2002), Correlates of change in functional status of institutionalized geriatric schizophrenic patients: focus on medical comorbidity. Am J Psychiatry 159(8):1388-1394.
13. Fucetola R, Seidman LJ, Kremen WS et al. (2000), Age and neuropsychologic function in schizophrenia: a decline in executive abilities beyond that observed in healthy volunteers. Biol Psychiatry 48(2):137-146.
14. Granholm E, Morris S, Asarnow RF et al. (2000), Accelerated age-related decline in processing resources in schizophrenia: evidence from pupillary responses recorded during the span of apprehension task. J Int Neuropsychol Soc 6(1):30-43.
15. Green MF (1996), What are the functional consequences of neurocognitive deficits in schizophrenia? Am J Psychiatry 153(3):321-330 [see comment].
16. Green MF, Kern RS, Braff DL, Mintz J (2000), Neurocognitive deficits and functional outcome in schizophrenia: are we measuring the "right stuff"? Schizophr Bull 26(1):119-136.
17. Harvey PD, Davidson M (2002), Schizophrenia: course over the lifetime. In: Neuropsychopharmacology: Fifth Generation of Progress, Davis KL, Charney D, Coyle JT, Nemeroff C, eds. Philadelphia: Lippincott Williams & Wilkins.
18. Harvey PD, Docherty N, Serper MR, Rasmussen M (1990), Cognitive deficits and thought disorder: II. An 8-month follow-up study. Schizophr Bull 16(1):147-156.
19. Harvey PD, Howanitz E, Parrella M et al. (1998), Symptoms, cognitive functioning, and adaptive skills in geriatric patients with lifelong schizophrenia: a comparison across treatment sites. Am J Psychiatry 155(8):1080-1086.
20. Harvey PD, Leff J, Trieman N et al. (1997a), Cognitive impairment in geriatric chronic schizophrenic patients: a cross-national study in New York and London. Int J Ger Psychiatry 12(10):1001-1007.
21. Harvey PD, Lombardi J, Leibman M et al. (1997b), Verbal fluency deficits in geriatric and nongeriatric chronic schizophrenic patients. J Neuropsychiatry Clin Neurosci 9(4):584-590.
22. Harvey PD, Parrella M, White L et al. (1999a), Convergence of cognitive and adaptive decline in late-life schizophrenia. Schizophr Res 35(1):77-84.
23. Harvey PD, Silverman JM, Mohs RC et al. (1999b), Cognitive decline in late-life schizophrenia: a longitudinal study of geriatric chronically hospitalized patients. Biol Psychiatry 45(1):32-40.
24. Heaton RK, Gladsjo JA, Palmer BW et al. (2001), Stability and course of neuropsychological deficits in schizophrenia. Arch Gen Psychiatry 58(1):24-32.
25. Heaton RK, Paulsen JS, McAdams LA et al. (1994), Neuropsychological deficits in schizophrenics. Relationship to age, chronicity, and dementia. Arch Gen Psychiatry 51(6):469-476.
26. Putnam KM, Harvey PD (1999), Memory performance of geriatric and nongeriatric chronic schizophrenic patients: a cross-sectional study. J Int Neuropsychol Soc 5(6):494-501.
27. Rund BR (1998), A review of longitudinal studies of cognitive functions in schizophrenia patients. Schizophr Bull 24(3):425-435.
28. Saykin AJ, Shtasel DL, Gur RE et al. (1994), Neuropsychological deficits in neuroleptic naive patients with first-episode schizophrenia. ArchGen Psychiatry 51(2):124-131.
29. Seno H, Shibata M, Fujimoto A et al. (1998), Evaluation of Mini Mental State Examination and Brief Psychiatric Rating Scale on aged schizophrenic patients. Psychiatry Clin Neurosci 52(6):567-570.