Will Cancer Worsen Older Adults' Cognitive Functioning?:the Moderating Role of Different Old Age Groups

Background and Purpose: Considering that 64% of cancer survivors are older adults, it is plausible that the overlap of cancer and old age may worsen older cancer survivors’ cognitive functioning. However, previous studies indicated controversial conclusions of effects of cancer history on cognition scores. Therefore, this current study aimed to test the effect of cancer history on different dimensions of cognition scores in comparison with older adults without cancer history and examine how age groups moderated the association between cancer and cognition.

Methods: A subsample of 9,197 participants drawn from the Health and Retirement Study (HRS) Wave13 were included in this cross-sectional study. Four continuous measures of cognition served as the dependent variables in this study: self-rated memory (measured on a 5-point Likert Scale); immediate recall (score range: 0-10), delayed recall (0-10), and mental status (0-15). The independent variable, cancer history, was measured by dichotomously (Yes/No). The moderator, age group, was measured categorically: younger-old (65-74), middle-old (75-84), oldest-old (85+). Gender, marital status, race, and years of school were included as covariates. Multilinear regressions were conducted with and without the interaction term (cancer history * age group) to examine moderation effects.

Results: Findings showed cancer survivors tended to be older, non-Hispanic white males with higher educational attainment. Multilinear regressions showed that, after controlling for gender, marital status, race and years of school, cancer history (B= .19, p<.01) predicted only one of the four cognition outcomes: mental status. Cancer survivors had a .19-unit higher mental status score than older adults without cancer history. The moderation effects of age groups on the association between cancer history and immediate recall (B= .34, p< .05), delayed recall (B= .33, p<.05), and mental status (B=.61, p< .01) were significant only in the 85+ group. After adjusting for other variables, cancer survivors in the 85+ age group had a .34-unit higher immediate recall score, a .33-unit higher delayed recall score, and a .61-unit higher mental status score than their counterparts without cancer. No significant differences on self-rated memory were found between cancer survivors and older adults without cancer history across all three age groups.

Conclusions and Implications: This study indicated cancer survivors in the 85+ group had significantly higher recall scores and mental status scores than counterparts. Selective survival, or “survival of the fittest”, can potentially explain the surprising result that older cancer survivors had higher cognition scores. In other words, it was high cognitive functioning that lengthened survival, but not cancer history that increased cognition. However, due to the cross-sectional design, the causal relationship cannot be identified. More future longitudinal studies are needed to further investigate the relationship between cancer history and cognitive functioning among older adults, and examine the moderation effect of age groups in this relationship.