Kustaa Piha

Does survey non-response bias the association between occupational social class and health?

Aims: A non-response rate of 20—40%is typical in questionnaire studies. The authors evaluate non-response bias and its impact on analyses of social class inequalities in health. Methods: Set in the context of a health survey carried out among the employees of the City of Helsinki (non-response 33%) in 2000—02. Survey response and non-response records were linked with a personnel register to provide information on occupational social class and long sickness absence spells as an indicator of health status. Results: Women and employees in higher occupational social classes were more likely to respond. Non-respondents had about 20—30% higher sickness absence rates. Relative social class differences in sickness absence in the total population were similar to those among either respondents or non-respondents. Conclusions: In working populations survey non-response does not seriously bias analyses of social class inequalities in sickness absence and possibly health inequalities more generally.

Cohort Profile: The Helsinki Health Study

The Helsinki Health Study cohort was set up to enable longitudinal studies on the social and work related determinants of health and well-being, making use of self-reported as well as objective register data. The target population is the staff of the City of Helsinki, Finland. Baseline data for the cohort were derived from questionnaire surveys conducted in 2000, 2001 and 2002 among employees reaching 40, 45, 50, 55 or 60 years of age in each year. The number of responders at baseline was 8960 (80% women, response rate 67%). Additional age-based health examination data were available. A follow up survey was conducted in 2007 yielding 7332 responders (response rate 83%). Measures of health include health behaviours, self-rated health, common mental disorders, functioning, pain, sleep problems, angina symptoms and major diseases. Social determinants include socio-demographics, socio-economic circumstances, working conditions, social support, and work-family interface. Further register linkages include sickness absence, hospital discharge, prescribed drugs, and retirement updated at the end of 2010. The cohort allows comparisons with the Whitehall II study, London, UK, and the Japanese Civil Servants Study from western Japan. The cohort data are available for collaborative research at Hjelt Institute, Department of Public Health, University of Helsinki, Finland.

Health-related behaviours and sickness absence from work

Objectives: To compare associations of health-related behaviours with self-certified and medically confirmed sickness absence, and to examine whether these associations can be explained by psychosocial and physical working conditions and occupational social class. Methods: The study included 5470 female and 1464 male employees of the City of Helsinki surveyed in 2000–2002. These data were linked to sickness absence records until the end of 2005, providing a mean follow-up time of 3.9 years. Poisson regression analysis was used to examine associations of smoking, alcohol use, physical activity, dietary habits and relative weight (body mass index) with self-certified (1–3 days) and medically confirmed (⩾4 days) absence spells. Population attributable fractions (PAFs) were calculated to quantify the sickness absence burden related to the behaviours. Results: Smoking and high relative weight were most strongly associated with sickness absence, while the associations of other studied health-related behaviours were weaker. The associations were stronger for medically confirmed sickness absence spells for which heavy smoking and obesity more than doubled the risk of sickness absence in men and nearly doubled it in women. Adjusting for psychosocial working conditions had little or no effect on the associations. Physical working conditions and social class somewhat attenuated the associations, especially for smoking and relative weight. In self-certified sickness absence the PAF for smoking (16.4 in men, 10.3 in women) was largest, while in medically confirmed absence relative weight had the largest PAF (23.5 in men, 15.0 in women). Conclusions: Health-related behaviours, smoking and high relative weight in particular, were associated with subsequent sickness absence independently of psychosocial and physical working conditions and social class. Decreasing smoking and relative weight is likely to provide important gains in work ability and reduce sickness absence.

Interrelationships between education, occupational class, income and sickness absence

BACKGROUND Socio-economic position measures, such as education, occupational class and income, are well-known determinants of health. However, previous studies have not paid attention to mutual interrelationships between these socio-economic position measures and medically confirmed sickness absence. METHODS The study is a register-based study. The participants were municipal employees of the City of Helsinki aged 25-59 years in 2003. There were 21,599 women and 5841 men participants. Three socio-economic position measures were used, namely three-level education, four-level occupational class and gross individual income quartiles. Main outcome measure was medically confirmed sickness absence spells of 4 days or longer. Inequality indices were calculated using Poisson regression analysis. RESULTS High education, occupational class and individual income were all consistently associated with lower sickness absence rates among both women and men. After mutual adjustment, education and occupational class remained independent determinants of sickness absence. The association of individual income with sickness absence was practically explained by temporally preceding education and occupational class. CONCLUSIONS Our results indicate that education and occupational class-rather than income-are strong determinants of sickness absence. Education, occupational class and income are complementary socio-economic position measures. To better inform sickness absence policy, future studies should aim to establish whether the observed socio-economic differences reflect broader differences in ill-health, lifestyle and working conditions.

Explaining occupational class differences in sickness absence: results from middle-aged municipal employees

Objectives Low socioeconomic position is consistently associated with higher rates of sickness absence. We aimed to examine whether working conditions, health-related behaviours and family-related factors explain occupational class differences in medically certified sickness absence. Methods The study included 5470 women and 1464 men employees of the City of Helsinki, surveyed in 2000–2002. These data were prospectively linked to sickness absence records until the end of 2005, providing a mean follow-up time of 3.9 years. Poisson regression was used to examine the occurrence of medically certified sickness absence episodes lasting 4 days or more. Results Medically certified sickness absence was roughly three times more common among manual workers than among managers and professionals in both women and men. Physical working conditions were the strongest explanatory factors for occupational class differences in sickness absence, followed by smoking and relative weight. Work arrangements and family-related factors had very small effects only. The effects of psychosocial working conditions were heterogeneous: job control narrowed occupational class differences in sickness absence while mental strain and job demands tended to widened them. Overall, the findings were quite similar in women and men. Conclusions Physical working conditions provided strongest explanations for occupational class differences in sickness absence. Smoking and relative weight, which are well-known determinants of health, also explained part of the excess sickness absence in lower occupational classes. Applying tailored work arrangements to employees on sick leave, reducing physically heavy working conditions and promoting healthy behaviours provide potential routes to narrow occupational class differences in sickness absence.

Relative Weight and Sickness Absence

Objectives: To examine whether high relative weight increases the risk of future sickness absence and to what extent any differences in short and long absence periods can be explained by specific obesity‐related disorders, general health, and working conditions.

Socio-economic and occupational determinants of work injury absence.

BACKGROUND Measures of socio-economic position, such as education, occupational class and income, are well-known determinants of ill-health, injury and sickness absence. The aim was to analyse socio-economic and occupational determinants of work injury absence and their contribution to overall socio-economic inequalities in all-cause sickness absence. METHODS A register-based follow-up study included municipal employees of the City of Helsinki aged 25-59 years in 2004. The number of participants was 16,471 women and 5033 men. The mean follow-up time was 3.0 years. Education, occupational class and individual income were used as measures of socio-economic position. The main outcome was medically confirmed work injury and all-cause sickness absence of ≥4 days. Inequality indices were calculated using Poisson regression analysis. RESULTS High education, occupational class and individual income were consistently associated with lower work injury absence among both women and men. The inequalities in work injury absence were larger than in all-cause sickness absence, especially among men, but the contribution to overall socio-economic inequalities was limited. Among women, bus drivers, cooks and hospital attendants had the highest rates of work injuries. Among men, youth mentors, firemen and janitors had the highest rates. CONCLUSIONS Our results indicate that relative socio-economic inequalities in work injury absence are larger than in all-cause sickness absence. Prevention of work injuries provides a source of reducing socio-economic inequalities in health, but their effect is not very large. Prevention of work injuries should be targeted to lower white-collar and manual workers and vulnerable occupations.

Socioeconomic differences in health check-ups and medically certified sickness absence: a 10-year follow-up among middle-aged municipal employees in Finland

Background There is contradictory evidence on the association between health check-ups and future morbidity. Among the general population, those with high socioeconomic position participate more often in health check-ups. The main aims of this study were to analyse if attendance to health check-ups are socioeconomically patterned and affect sickness absence over a 10-year follow-up. Methods This register-based follow-up study included municipal employees of the City of Helsinki. 13 037 employees were invited to age-based health check-up during 2000–2002, with a 62% attendance rate. Education, occupational class and individual income were used to measure socioeconomic position. Medically certified sickness absence of 4 days or more was measured and controlled for at the baseline and used as an outcome over follow-up. The mean follow-up time was 7.5 years. Poisson regression was used. Results Men and employees with lower socioeconomic position participated more actively in health check-ups. Among women, non-attendance to health check-up predicted higher sickness absence during follow-up (relative risk =1.26, 95% CI 1.17 to 1.37) in the fully adjusted model. Health check-ups were not effective in reducing socioeconomic differences in sickness absence. Conclusions Age-based health check-ups reduced subsequent sickness absence and should be promoted. Attendance to health check-ups should be as high as possible. Contextual factors need to be taken into account when applying the results in interventions in other settings.