Short telomeres drive pessimistic judgement bias in zebrafish

The role of telomerase reverse transcriptase has been widely investigated in the contexts of ageing and age-related diseases. Interestingly, decreased telomerase activities (and accelerated telomere shortening) have also been reported in patients with emotion-related disorders, opening the possibility for subjective appraisal of stressful stimuli playing a key role in stress-driven telomere shortening. In fact, patients showing a pessimistic judgement bias have shorter telomeres. However, in humans the evidence for this is correlational and the causal directionality between pessimism and telomere shortening has not been established experimentally yet. We have developed and validated a judgement bias experimental paradigm to measure subjective evaluations of ambiguous stimuli in zebrafish. This behavioural assay allows classification of individuals in an optimistic-pessimistic dimension (i.e. from individuals that consistently evaluate ambiguous stimuli as negative to others that perceive them as positive). Using this behavioural paradigm we found that telomerase-deficient zebrafish (tert-/-) were more pessimistic in response to ambiguous stimuli than wild-type zebrafish. The fact that individuals with constitutive shorter telomeres have pessimistic behaviours demonstrates for the first time in a vertebrate model a genetic basis of judgement bias.

Prognostic accuracy of patients, caregivers, and oncologists in advanced cancer

BACKGROUND

In caring for patients with advanced cancer, accurate estimation of survival is important for clinical decision making. The purpose of this study was to assess the accuracy of 2-year survival probabilities estimated by oncologists, patients, and caregivers and to identify demographic and clinical factors associated with prognostic accuracy.

METHODS

This was a secondary observational analysis of data obtained from a cluster randomized controlled trial. Participants included 38 oncologists, 263 patients with advanced nonhematologic cancer, and 193 of their caregivers from clinics in Sacramento and Western New York. Discrimination within each group (oncologists, patients, caregivers) was evaluated using the C statistic, whereas calibration was assessed by comparing observed to predicted 2-year mortality using the chi-square statistic.

RESULTS

The median survival from study entry was 18 months, and 41.8% of patients survived for 2 years. C statistics for oncologists, patients, and caregivers were 0.81 (95% CI, 0.76-0.86), 0.62 (95% CI, 0.55-0.68), and 0.72 (95% CI, 0.65-0.78), respectively; oncologists' predictions were better than the predictions of both patients (P = .001) and caregivers (P = .03). Oncologists also had superior calibration: their predictions of 2-year survival were similar to actual survival (P = .17), whereas patients' (P = .0001) and caregivers' (P = .003) predictions diverged significantly from actual survival. Although most oncologists' predictions were classified as realistic (62.0%), approximately one-half of patients' and caregivers' predictions (50.0% and 46.0%, respectively) were unduly optimistic. Among patients, nonwhite race and higher levels of social well-being predicted undue optimism (P < .05).

CONCLUSIONS

Compared with oncologists, patients and caregivers displayed inferior prognostic discrimination, and their predictions were poorly calibrated, primarily because of overoptimism.