Background Depression, osteoarthritis, and type 2 diabetes are a significant cause of reductions in the years patients spend without illness and its impacts (so called ‘disability free life expectancy’). The UK National Institute for Health and Care Excellence guidelines are a key source of decision support for general practitioners in managing these conditions. As well as providing clinically effective care, a key goal of primary care is to ensure equitable outcomes. We explored what interventions work to narrow the gap in disability-free life expectancy between different socio-economic groups, using these three exemplar conditions.

Methods For each condition, we searched the guidelines to identify recommended interventions: July 2008 (depression); January 2016 (osteoarthritis); and July 2012 (type 2 diabetes). We examined evidence cited in support of these interventions to identify any variation in outcomes by socioeconomic status. Where we found no data on outcomes by socioeconomic status in the evidence, we extended our search to identify observational studies, and to update guideline searches for randomised controlled trials. Between 2008 and 2022, approximately 8,636 studies were published reporting evaluations of these guidance-recommended interventions for depression (2,744 reviews), osteoarthritis (5,137 primary studies) and type 2 diabetes (755 reviews). Of these studies, just 19 (0.22%) considered the outcomes of the intervention by socioeconomic status in depression (7 reviews) and osteoarthritis (12 primary studies).

Results Research evidence underpinning guidance recommendations for intervening in all three conditions offered no robust information on how outcomes may vary with social disadvantage. In our wider searches, we found limited evidence for social patterning in outcomes of interventions for two of the exemplar conditions (depression and osteoarthritis), and no evidence for type 2 diabetes. The limited evidence of social patterning was heterogeneous (in study design, populations, comparable measures of socio-economic status, outcomes) and tended to show better outcomes for less disadvantaged people.

Conclusion This study identified an important gap in the evidence needed to inform policy on improving the gap in disability-free life expectancy between rich and poor. There is a dearth of research on how the impacts of long-term conditions interventions vary for people living in different socioeconomic circumstances. A lack of consideration of socio-economic status within the evidence base generates uncertainty about the impact of the recommended interventions for disadvantaged populations. Routine inclusion of measures of socioeconomic status/social disadvantage in intervention studies could be considered to develop the evidence base at minimal cost and inconvenience.