Late night salivary cortisol, stress-resilience and Type 2 diabetes mellitus. Findings from population-based KORA Age study

Aims: We aim to understand the underlying psychoneurendocrinology mechanism of stress resilience in T2DM. We examined the association between late night salivary Cortisol levels and stress resilience in type 2 diabetes mellitus (T2DM). Methods: A cross-sectional analysis was conducted among 761 participants (men=389, women=372, age 65 - 90 years) of the population-based KORA-Age study in Southern Germany. Resilience was assessed by using the screening version of the German RS-11 scale. The association between late night salivary Cortisol (LNSC) and stress resilience in individuals with and without T2DM was modelled using linear regression. Results: Among 761 study participants, LNSC levels were significantly lower in participants with high resilience (31%, N=236) compared to individuals with low resilience (69%, N=525) with age-adjusted mean (95% CI) of 2.36 nmol/L (2.08-2.68) and 2.72 nmol/L (2.41-3.05), respectively (P for difference= 0.03). Our data demonstrated a significant interaction between resilience and T2DM in men (P= 0.03) but not in women (P=0.87). In men with T2DM, increased LNSC levels were observed in low resilience (adjusted mean, 95% CI: 2.42, 2.02-2.91 nmol/L) compared to individuals with high resilience (1.52, 1.52-1.98). After stratifying according to T2DM status, a continuous one standard deviation (SD) increase in LNSC levels were significantly associated with low compared to high resilience among men with T2DM (P=0.005) whereas no significant association in men without T2DM was found (P=0.15). No significant association between LNSC and resilience in women was found. Conclusion: Lower LNSC levels were observed in men with high resilience. Elevated LNSC levels were observed among men with low resilience and the association was attenuated in T2DM. Thus, in this aged population, a sex-dependent association between hypersecretion of LNSC levels and low stress resilience were observed in T2DM.