THE LSH STUDY

The Life Conditions, Stress, and Health study (LSH)

The LSH study investigates the link between socioeconomic position, psychosocial factors, and biomarkers of stress, inflammation and plaque vulnerability, in order to elucidate the psychobiological mechanisms that can link “stress” to coronary heart disease (CHD), and ultimately, explain socioeconomic differences in CHD. Socioeconomic differences persist in Sweden and their causes are still not clear. As lifestyle factors and material wealth have shown to not suffice in explaining these differences, there is also evidence for a psychosocial impact on CHD as a complementary factor in this association. However, the mechanisms for these effects are not yet known. This is where the LSH study aims to contribute to the research field.

Many studies have focused on a single or just a few determinants. We have (apart from traditional risk factors for CHD such as lifestyle choices) also included several validated psychometric instruments on psychosocial strain, ranging from work-related factors (poor balance of demand/control or effort/reward) to social factors such as low social integration or social support. However, our main focus is on individual psychosocial resources and risks, such as coping, perceived control, sense of coherence, hopelessness, cynicism, depression, and vital exhaustion. These measures of psychosocial strain are tested in relation to different measures of socioeconomic position (education, occupation, subjective social status) and psychobiological indicators of stress, inflammation and plaque vulnerability. Outcomes are CHD and stroke but also musculoskeletal disorders and self-reported measures of health and mental well-being.

The study is now in its third phase, where data from 8 000 participants will be collected from 30 primary health care units in a region in the southeast of Sweden. We believe that the prospective design of the study will generate knowledge that can help broaden our understanding of underlying mechanisms in the socioeconomic position – health chain. Through this, it can help reveal effects of different psychosocial factors and different social positions within a society, and therefore help in assisting interventions on both individual and structural levels.

Research questions

We aim to test the associations of coronary heart disease (CHD) with socioeconomic status (SES), psychosocial strain, and biological markers of stress, inflammation and plaque vulnerability. The specific objectives are to examine:

• to what extent different measures of SES predict CHD in a normal, middle-aged Swedish population. (SES measures comprise education, occupation, income, unemployment, and subjective social status)

• to what extent different measures /combinations of psychosocial strain predict CHD.

• to what extent SES differences in CHD can be explained by psychosocial strain,

• to what extent established and emerging biological markers of stress (diurnal cortisol deviation), inflammation (C-reactive protein, interleukin -6 and -10) and plaque vulnerability (matrix metalloproteinase-9) predict CHD.

• to what extent observed effects of psychosocial strain on SES differences inCHD are mediated by biological markers of stress, inflammation and plaque vulnerability.

Design

The first phase of the LSH study consisted of a baseline data collection in 2003-2004, including 1007 men and women aged 45-69 who were randomly selected from the catchment areas of 10 primary health care centres in southeast Sweden. The response rate was 62 % and the participants were representative for their respective catchment areas in terms of education, occupational and immigrant status. Participants collected saliva samples at home (three times a day) and they also completed an extensive questionnaire on life conditions, lifestyle choices, self-rated health measures, previous diagnoses, and psychosocial factors. They also visited their local PHC for anthropometrics and a blood test.

The second phase of the LSH study was a follow-up study carried out in 2005-2006 with an 80 % response rate. All participants received a new questionnaire and a third of the group were invited to another set of tests at their PHC. The cross-sectional analyses and stability calculations from the initial phases of the LSH study provided experiences of feasibility and relevance of a large-scale prospective study design which is currently underway.

The study is now in its third phase, where data from 8 000 participants will be collected from 30 primary health care units in a region in the southeast of Sweden. So far, the study has generated around a dozen publications and two dissertations (see “Publikationer” to the left).

Results

Stability of risk factors over 2 years were assessed for lifestyle factors, psychosocial factors, MMP-9 and cortisol in a follow-up study carried out in 2005-2006 (80 % response rate). For physical activity (PA), 65 % of the participants remained in the same category over 2 years, indicating a potential risk of misclassification and attenuation bias if using only one time point of measurement. For psychosocial factors, stability over two years tended to be lower for all instruments among low SEP groups (Lundberg 2008, manuscript), supporting the need of repeated exposure measuring. Preliminary analyses on MMP-9 reveal a correlation between the two time points of about r=0.6 which is reasonable in terms of stability of a proposed predictor for CHD. Changes in MMP-9 follow changes in PA where reported increase of PA at the second time point was associated with lower MMP-9.

Further results revealed that in a middle-aged group, the prevalence of metabolic syndrome (MS) was 12 %, and this was mainly driven by overweight (Hollman et al 2008a). Also, addressing the broad spectrum of psychosocial factors at hand, we found that women with MS had a more unfavourable social situation compared to women without MS. Both men and women with MS had poorer social and physical well-being compared to those without MS. In contrast, we found no relation between MS and psychological strain, stress or poor mental health. The major part of observed effects in MS was dependent on lifestyle, mainly low physical activity (Hollman et al 2008a).

Further, poor scores on psychosocial instruments were associated with new cardiac events. Adjusting for age and sex, new events were associated with higher scores on two depression scales (p=0.002 and 0.022, respectively), vital exhaustion (p=0.001) and hopelessness (p=0.015). Accordingly, new events were associated with lower score on scales on coping (p<0.001) and self esteem (p=0.009), and close to significant associations were found with low social integration (p=0.062). Regarding potential mediators, it has been demonstrated that plasma levels of MMP-9 are associated with psychosocial factors in the LSH study. Analyses on cortisol are not complete yet, but preliminary analyses reveal an association between two depression scales and high evening values of cortisol (p=0.020 and p=0.040). In addition, high evening levels of cortisol are associated with high levels of MMP-9 (18). Taken together, these data support the hypothesis that cortisol and MMP-9 are plausible mediators in the association between psychosocial factors and new cardiac events.

The questionnaire used in the LSH study has been evaluated from several perspectives, both including qualitative and quantitative analyses and we therefore intend to keep this for the planned cohort study. Qualitative analyses have investigated respondent motivation and satisfaction (Wenemark, conference abstract 2007) and these results will be weighed in to enhance clarity of design and adjustment of single items that were perceived as vague or hard to understand. 

Page responsible: kajsa.bendtsen@liu.se
Last updated: 2011-06-14