Background Recent studies suggest that employees in low grade and poor quality work improve in mental health and well-being upon retirement, although there is no evidence on whether this is accompanied by an improvement in biological measures associated with stress around the period of retirement. The Research Questions of the study were: 1) Does the occupational gradient in salivary cortisol, a marker of the primary stress response axis, change around retirement? 2) Is retirement associated with a reduction in adverse diurnal cortisol profiles for those at the bottom of the occupational hierarchy compared to those at the top?

Methods Data from the 7^th (2002–2004), 8^th (2006) and 9^th (2007–09) phases of the Whitehall II study were analysed. 1,143 respondents who were employed at phase 8 (mean age 59.9 years) and who had salivary cortisol measured from six samples collected across the day at phases 7 and 9 were included in the analysis. Data were analysed using multilevel growth curve models.

Results Compared to employees in highest occupational grades at phase 7, employees in the lowest grades were associated with adverse diurnal cortisol slopes (flatter decline across the day). A similar pattern was observed for those who remained in employment at phase 9, and those who had recently retired. The occupational gradient changes around retirement, with those formerly working in highest employment grades having the steeper diurnal slopes compared to their peers who remain in employment.

Discussion Occupational grade differences in a biomarker associated with stress increase around the period of retirement. Employees working in the highest employment grades appear to benefit the most from retirement in terms of steeper diurnal cortisol slopes, while there is no apparent benefit of retirement among those working in the lowest grades. These biological differences associated with transitions into retirement for different occupational groups may partly explain the pattern of widening social inequalities in health in early old age.