Subjective socioeconomic position, gender and cortisol responses to waking in an elderly population
Introduction
The inverse relationship between socioeconomic position and health is well established. Lower socioeconomic status (SES) has been associated with biological and behavioural risk factors, all cause mortality and a wide range of diseases, in particular coronary heart disease (Adler and Ostrove, 1999, Marmot and Bartley, 2002). However, the mechanisms through which these health inequalities influence risk factors and disease incidence are still poorly understood. Lifestyle factors contribute, but the gradient in cardiovascular mortality and biological risk persists after smoking, lack of physical exercise, alcohol consumption and other health behaviours are taken into account (Lantz et al., 2001, Steenland et al., 2002). A psychobiological pathway, whereby low SES elicits sustained activation of neuroendocrine and other biological responses that in turn promote the development of physical pathology, has been proposed (McEwen and Seeman, 1999, Steptoe and Marmot, 2002).
Two methods are commonly used to investigate health-related psychobiological pathways: laboratory-based studies assessing acute physiological response to stressful stimuli, and naturalistic monitoring of neuroendocrine functioning in everyday life. Naturalistic studies allow the influence of everyday experiences on neuroendocrine and cardiovascular processes to be assessed. Cortisol may be an important indicator, since it is implicated in metabolic syndrome, type 2 diabetes, abdominal adiposity, depression and other conditions related to SES differences, and has also been described as a marker of chronic allostatic load (Brown et al., 2004, McEwen and Seeman, 1999).
The cortisol awakening response (CAR) has been recognised in recent years as a phenomenon that is distinct from the profile of cortisol change over the day itself (Pruessner et al., 1997). The CAR is the change in cortisol that typically takes place over 20–45 min after waking up in the morning. The CAR is sensitive to situational factors such as weekday or weekend (Kunz-Ebrecht et al., 2004a, Scholtz et al., 2004), but is also increased in people reporting high levels of general stress or work stress (Schulz et al., 1998; Wüst et al., 2000; Pruessner et al., 2003). A reduced CAR has been observed in burnout, chronic fatigue and in people reporting health problems (Pruessner et al., 1999, Kudielka and Kirschbaum, 2003, Roberts et al., 2004). The use of the CAR to study SES inequalities in biological regulation has been relatively limited thus far. An early study demonstrated that cortisol samples between 7.00 and 8.00 a.m. were positively associated with SES (Brandtstädter et al., 1991). In contrast, an investigation of salivary cortisol in children aged 6–10 years found an inverse association with SES and cortisol levels early in the day (Lupien et al., 2000). However, neither of these studies assessed the CAR itself. In an earlier study from this laboratory, no association between the CAR on a working day and grade of employment was observed in middle-aged adults (Steptoe et al., 2003). In a subsequent analysis involving both working and weekend days, it was found that lower SES was associated with a greater CAR (Kunz-Ebrecht et al., 2004a).
A difficulty with studying people of working age is that lower SES individuals typically experience greater work stress than more privileged groups, so that it is not clear which factor is related to a heightened CAR. In the present study, we therefore assessed the relationship between SES and the CAR in an older retired population that was not part of the work force. With an increasing proportion of the population of retirement age, it is important to examine whether SES differences are present in old age.
The measurement of SES in old age is complicated since conventional markers such as current occupation are not applicable. Income does not reflect lifetime differentials, while education is usually completed early in life, so may be less predictive in later years (Davey Smith et al., 1998). Additionally, Wilkinson (1999) has argued that it is not absolute level of SES that is important, but rather perceptions of status based on relative inequality. An alternative approach is to use subjective social status as an indicator. Adler et al. (2000) devised a simple, one-item measure for assessing people's perceptions of their position within the social hierarchy. In a study of healthy women, it was found that subjective social status was more consistently related to factors such as self-rated health, body fat distribution and cortisol habituation to repeated stress than was objective SES. Singh-Manoux et al. (2003) measured subjective social status in the Whitehall II cohort, and found that only 49% of the variance was accounted for by objective indicators such as employment grade, education, material deprivation and household income. Subjective social status was inversely associated cross-sectionally with the presence of angina, diabetes, respiratory illness and self-rated health.
In the present study, we assessed salivary cortisol five times in the hour after waking in elderly individuals who were classified according to the subjective social status scale. We hypothesised that the CAR would be heightened in people of lower SES. Smoking, time of waking and body mass index can influence cortisol so these factors were included as covariates (Clow et al., 2004). Additionally, we adjusted statistically for the presence of chronic illness and prescription of chronic medication, since Kudielka and Kirschbaum (2003) reported that the CAR was smaller in people with physical illnesses.
Another issue that was explored in this study was gender differences in the CAR. These have been inconsistent in younger samples, with some studies showing greater or more sustained CAR in women than men (Pruessner et al., 1997, Pruessner et al., 1999; Kunz-Ebrecht et al., 2004b), while others have reported no differences (Edwards et al., 2001, Kudielka and Kirschbaum, 2003). A recent meta-analysis of cortisol responses to challenge has shown greater age-related increases in response in women than men, suggesting that gender differences might be accentuated in older age (Otte et al., 2005).
Non-compliance with the sampling schedule is a potential confounding factor that needs to be taken into account. Saliva sampling is non-invasive and easy to apply to naturalistic studies, but it is difficult to control sample adherence and timing. In a recent study, it was demonstrated using electronic timing devices that a measurable proportion of individuals did not take samples as required (Kudielka et al., 2003). Our group has previously demonstrated that participants who delay more than 10 min between waking and taking the ‘waking’ sample show almost no CAR on average (Kunz-Ebrecht et al., 2004a). Failure of adherence to timing therefore has serious implications for analyses of the cortisol samples, and may lead to a false blunting of the CAR. In the present study we asked participants to keep a diary record of each sample in order to determine if delay in collection had occurred. As a result we hypothesised that individuals who reported delays of more than 10 min between waking and taking the first sample would have higher ‘waking’ values and a smaller CAR than would compliant participants.
Section snippets
Participants
One hundred and thirty nine men and women aged 65–80 years were recruited by letter from two general practices in the London area for a study of ageing and health. Patient databases were searched for individuals who were dwelling in the community, and had no record of coronary heart disease, tachycardia, aortic valve regurgitation, dementia, psychosis, and no cancer evident in the last 5 years. One hundred and thirty three individuals completed a clinical assessment session described elsewhere (
Characteristics of higher and lower social status groups
Details of the higher and lower social status groups are provided in Table 1. The proportion of men and women in the two groups did not differ, nor were there differences in age, marital status, or in number of chronic illnesses or medications prescribed. There was no difference in men and women's subjective social status scores (P=.41) which averaged 5.88±1.7 and 5.60±1.3, respectively. Higher social status participants had left school at an older age on average (F(1,77)=9.66, P=0.003), and
Discussion
The present study was based on the hypothesis that higher SES individuals would display smaller CARs than less privileged groups, and that this might indicate the operation of more health-protective psychobiological processes in this group. The CAR can be influenced by non-compliance with sample timing, resulting in inaccurate cortisol profiles. We, therefore, hypothesised that non-compliant participants would have a higher waking cortisol level and a smaller CAR.
Although participants in the
Acknowledgements
The study was supported by the Medical Research Council. We are grateful to Sabine Kunz-Ebrecht, Pamela J. Feldman, Elizabeth Cort, Lindsey Emmerson, and Marlous Knol for their involvement with data collection, to the staff and patients of the Lonsdale and the Simpson House Medical Centres, and to Clemens Kirschbaum for analyses of cortisol samples.
References (44)
- et al.
Self-rated oral health as an independent predictor of self-rated general health, self-esteem and life satisfaction
Soc. Sci. Med.
(2004) - et al.
Developmental and personality correlates of adrenocortical activity as indexed by salivary cortisol: observations in the age range of 35 to 65 years
J. Psychosom. Res.
(1991) - et al.
Association of depression with medical illness: does cortisol play a role?
Biol. Psychiatry
(2004) - et al.
Association between time of awakening and diurnal cortisol secretory activity
Psychoneuroendocrinology
(2001) - et al.
Awakening cortisol responses are influenced by health status and awakening time but not by menstrual cycle phase
Psychoneuroendocrinology
(2003) - et al.
Differences in cortisol awakening response on work days and weekends in women and men from the Whitehall II cohort
Psychoneuroendocrinology
(2004) - et al.
Work stress, socioeconomic status and neuroendocrine activation over the working day
Soc. Sci. Med.
(2004) - et al.
Socioeconomic disparities in health change in a longitudinal study of US adults: the role of health behaviours
Soc. Sci. Med.
(2001) - et al.
Child's stress hormone levels correlate with mother's socioeconomic status and depressive state
Biol. Psychiatry
(2000) - et al.
Health inequalities among British civil servants: the Whitehall II study
Lancet
(1991)
A meta-analysis of cortisol response to challenge in human aging: importance of gender
Psychoneuroendocrinology
Free cortisol levels after awakening: a reliable biological marker for the assessment of adrenocortical activity
Life Sci.
Cumulative biological risk and socio-economic differences in mortality: MacArthur studies of successful aging
Soc. Sci. Med.
Subjective social status: it determinants and its association with measures of ill health in the Whitehall II study
Soc. Sci. Med.
Individual differences in the diurnal cycle of salivary free cortisol: a replication of flattened cycles for some individuals
Psychoneuroendocrinology
The impact of time of waking and concurrent subjective stress on the cortisol response to awakening
Psychoneuroendocrinology
Socioeconomic status and health: what we know and what we don't
Ann. NY Acad. Sci.
Relationship of subjective and objective social status with psychological and physiological functioning: preliminary data in healthy white women
Health Psychol.
Women, men, work, and family. An expansionist theory
Am. Psychol.
Increase in concentration of waking salivary cortisol in recovered patients with depression
Am. J. Psychiatry
The awakening cortisol response: methodological issues and significance
Stress
Education and occupational social class: which is the more important indicator of mortality risk?
J. Epidemiol. Community Health
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