Sickness absence with psychiatric diagnoses: Individual and contextual predictors of permanent disability

Abstract

Sickness absence due to psychiatric problems is on the increase. Many sickness absentees do not recover and end up on a permanent disability pension (DP). A prospective cohort study of 12,283 women and 7099 men with a spell of sickness absence longer than 8 weeks, certified with a psychiatric diagnosis, was carried out. Diagnoses and socioeconomic data for each case were obtained from a national insurance research database. Socio-demographic data characterising each of Norway's 19 counties were obtained from Statistics Norway, and a deprivation index was constructed. Cox regression models with county-level variables only and combinations of variables at individual and county level were estimated separately for each gender as predictors of DP. Men had the highest risk of disability. Several individual-level variables predicted permanent disability. Contextual factors had a marginal effect among women also, after adjustment for individual-level variables. No such effect was present among the men.

Introduction

Long-term sickness absence due to mental health problems or disorders is probably increasing in Western Europe (Moncrieff and Pomerleau, 2000; Knapp, 2003; Jarvisalo et al., 2005; Henderson et al., 2005; Hensing et al., 2006). However, sickness absence benefit schemes vary, and comparison between countries may be difficult. Sickness absence is an indicator of the functional consequences of diseases (Marmot et al., 1995; Norman and Bambra, 2007), and such data can supplement self-reported data from classic epidemiological surveys of the prevalence of mental health disorders (Broadhead et al., 1990; Judd et al., 1996; Kessler and Frank, 1997; Kringlen et al., 2001). In the Nordic countries, tax-based social insurance is universal, covering all vocationally active inhabitants, and therefore population-based studies using social insurance data are feasible.

The literature on sickness absence and disability pension (DP) due to mental health problems has recently been reviewed (Hensing and Wahlstrom, 2004). A female/male prevalence gradient of approximately 2:1 is observed in most studies. This corresponds to the gender differences in the incidence of common mental disorders (Piccinelli and Wilkinson, 2000; Kringlen et al., 2001; Stordal et al., 2001; Angst et al., 2002; Bijl et al., 2002). However, studies from Sweden (Hensing et al., 1996) and Norway (Hensing et al., 2000) have shown that spells of sick leave with psychiatric diagnoses tend to be longer among men. The risk of permanent occupational disability after psychiatric sickness absence is probably also higher for men than women, compared to men with other diagnoses (Gjesdal and Bratberg, 2003; Gjesdal et al., 2004, Gjesdal et al., 2008). A higher threshold among men for reporting mental health problems and for taking sick leave has been suggested, but this is controversial (Roness et al., 2005). A higher incidence of serious mental illness and alcohol dependence among men is another possible explanation.

Socioeconomic deprivation predicts major psychiatric disorders at individual level (Muntaner et al., 2004; Kivimaki et al., 2007), whereas the findings for “common mental disorders” are more mixed (Weich and Lewis, 1998a, Weich and Lewis, 1998b; Lahelma et al., 2006; Skapinakis, 2007).

A growing literature has also analysed how contextual and geographic factors influence mental health. Several contextual levels have been examined: households (Weich et al., 2003, Weich et al., 2005; Sundquist and Ahlen, 2006), neighbourhoods (Sundquist and Ahlen, 2006), electoral wards (Croudace et al., 2000; Weich et al., 2003, Weich et al., 2005; Fone et al., 2007a, Fone et al., 2007b), and other small areas (Sytema, 1991; Fone et al., 2007c). Similar investigations have also been carried out in larger areas like local authority districts (Skapinakis et al., 2005) or regions of the UK (Lewis and Booth, 1992; Weich et al., 2001), or states in the US (Kennedy et al., 1998; Edlund et al., 2006). In these studies outcome measures have also varied: rates of psychiatric admissions (Sytema, 1991; Croudace et al., 2000; Edlund et al., 2006; Sundquist and Ahlen, 2006), incidence of psychoses (Croudace et al., 2000), and prevalence of “common mental disorders” (Weich et al., 2003; Skapinakis et al., 2005; Fone et al., 2007a, Fone et al., 2007b, Fone et al., 2007c). Overall, most studies have found that geographical variations are marginal when fully adjusted for individual factors. However, people living in urban areas might have a higher prevalence of mental health problems, compared to those living in more rural areas (Paykel et al., 2003; Weich et al., 2006). A recent study from Norway found that the prevalence of DP with mental health diagnoses was highest in semi-rural areas (Andersson et al., 2006).

In the UK several indices have been constructed to measure deprivation on a contextual level (Jarman, 1984; Carstairs and Morris, 1991; Townsend et al., 1988), and in addition similar indices have been constructed to specifically predict the need for mental health services in geographic areas (Croudace et al., 2000; Fone et al., 2007a, Fone et al., 2007c).

Despite the fact that the Nordic countries have universal schemes for sickness absence benefits and DP (Box 1), there are unexplained geographical variations in sickness absence rates and numbers of DP recipients (Knutsson and Goine, 1998; Norwegian Social Insurance Services, 2000). In the 19 Norwegian counties, the mean number of sick days compensated by the Norwegian Social Insurance Services (NIS) in 1997 varied between 7.2 and 11.2 days. In the same year, the proportion of disability pensioners among the population aged 16–66 varied between 6% and 11.1% (Norwegian Social Insurance Services, 1998).

Contextual explanations for a higher consumption of social insurance benefits might include factors such as level of unemployment, economic prosperity, population health status, and availability of health services. Finally, compositional effects of individual factors, such as age, education, earnings, or morbidity figures, may also cause variations among geographical and administrative entities like counties. Plant downsizing in Norway has been found to increase the sickness absence entry rate of workers in affected plants (Rege et al., 2008), and decreased demand for low-skilled labour seems to increase disability entrance in the US (Autor and Duggan, 2003). Furthermore, a high use of social insurance benefits at baseline might predict higher consumption in the future, reflecting differing attitudes in the population and/or different practices of local departments of social insurance services. A recent study found that DP risk was affected by the DP entry rate in the neighbourhood (Rege et al., 2007), and a previous Norwegian study has shown that deprived municipalities have higher rates of disability pensioning, after adjustment for individual predictors (Krokstad et al., 2004). In the UK, too, levels of incapacity benefits in local government districts probably have a strong relationship with all-cause mortality and census measures of morbidity (Bambra and Norman, 2006) as well as with the mental health status of the population (Fone et al., 2007b).

The aims of the current study were (1) to assess the cumulative incidence of long-term sickness absence with psychiatric diagnoses in Norwegian counties in 1997 and (2) to identify contextual and individual predictors of the further transition to permanent DP status using a multi-level statistical approach.