Epilepsy and deprivation, a data linkage study

To investigate whether the link between epilepsy and deprivation is due to factors associated with deprivation (social causation) or factors associated with a diagnosis of epilepsy (social drift).

We reviewed electronic primary health care records from 2004 to 2010, identifying prevalent and incident cases of epilepsy and recording linked deprivation scores. Logistic and Poisson regression models were used to calculate odds ratios and incidence rate ratios. The change in deprivation was measured 10 years after the initial diagnosis of epilepsy for a cohort of people.

Between 2004 and 2010, 8.1 million patient-years of records were reviewed. Epilepsy prevalence and incidence were significantly associated with deprivation. Epilepsy prevalence ranged from 1.13% (1.07-1.19%) in the most deprived decile to 0.49% (0.45-0.53%) in the least deprived decile (adjusted odds ratio 0.92, p < 0.001). Epilepsy incidence ranged from 40/100,000 per year in the most deprived decile to 19/100,000 per year in the least deprived decile (adjusted incidence rate ratio 0.94, p < 0.001). There was no statistically significant change in deprivation index decile 10 years after a new diagnosis of epilepsy (mean difference -0.04, p = 0.85).

Epilepsy prevalence and incidence are strongly associated with deprivation; the deprivation score remains unchanged 10 years after a diagnosis of epilepsy. These findings suggest that increasing rates of epilepsy in deprived areas are more likely explained by social causation than by social drift. The nature of the association between incident epilepsy and social deprivation needs further exploration.