Psychosocial stress moderates the relationship of cancer history with natural killer cell activity

Data suggest that both cancer history and psychosocial stress may be associ ated with reductions in natural killer cell activity (NKA). Therefore, we t ested whether individual differences in cancer history, chronic/perceived s tress, and their interactions would be associated with decreased levels of NKA. We tested these hypotheses in 80 spouse caregivers of victims of Alzhe imer's Disease (AD) (persons known to report high levels of psychosocial st ress) and in 85 age- and sex-matched spouses of no-demented controls. Parti cipants were assessed at study entry (Time 1) and 15-18 months later (Time 2). Individuals with cancer histories 15-18 months later (Time 2). Individu als with cancer histories (N = 43) had not been treated with immune alterin g medications within the last year. At both Times 1 and 2, cross-sectional main within the last year. At both Times 1 and 2, cross-sectional main effe cts were weak or absent for cancer history, perceived stress (e.g. high has sles, low uplifts), and caregiver status; however, interactions occurred be tween cancer history and perceived stress, such that persons with cancer hi stories and high hassles/low uplifts had the lowest NKA values (p < .05). T hese results occurred even after controlling for age, gender, beta-blocker use, hormone replacement therapy, alcohol, and exercise. At Time 1, an inte raction also occurred between caregiver status and cancer history-caregiver s with cancer histories had lower NKA than did controls with cancer histori es and caregivers/controls without cancer histories (p < .05). At Time 2, t his interaction only showed a trend ( p < .08), primarily because caregiver s with cancer histories experienced increases in NKA (p < .05) from Time 1 to Time 2, whereas in the other three groups NKA did not change. Importantl y, in caregivers with cancer histories, high perceived stress at Time 1 pre dicted low NKA at Time 2 (p < .05). This research suggests that the combina tions of biological vulnerabilities and chronic/perceived stress may have i nteractive effects resulting in reduced NKA.