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Introduction The effects of daylight saving time clock changes on health are the subject of intense debate, but evidence from England is scarce. We aimed to explore the effects of the daylight saving time clock changes on mental and physical health events in primary and secondary care in England.Methods We used CPRD Gold primary care records linked to hospital admissions and A&E visits. Patients were included if they had a code for acute cardiovascular disease, depression, road traffic injury, anxiety, self-harm, eating disorder or sleep disorder in their primary or secondary care record, or a code for a psychiatric condition in A&E, in the 8-week period surrounding the clock changes (2008-2019). Negative binomial regressions, adjusted for day of the week and region (and Easter weekend in Spring), compared event rates in the week after the clock changes to the control period (4 weeks before transitions and weeks 2-4 after).Results In total, 683,809 patients and 1,564,532 events were included in the study. In the week after the Autumn clock change five health conditions had fewer events ( figure 1), including: anxiety (IRR 0.97, 95% CI 0.95 to 0.98), acute CVD (IRR 0.98, 95% CI 0.96 to 0.999), depression (IRR 0.96, 95% CI 0.95 to 0.97), psychiatric conditions (IRR: 0.94, 95% CI 0.90 to 0.98) and sleep disorders (IRR 0.92, 95% CI 0.87 to 0.97). There was little evidence of reductions in eating disorder diagnoses, road traffic injuries or self-harm.Discussion There was a reduction in rates of CVD, sleep disorders and mental health disorders after the Autumn clock change (when the clocks go back an hour and people gain sleep), but little evidence that the Spring clock change (when the clocks go forward an hour and people lose sleep) affected health.Abstract P12 Figure 1Adjusted rate ratios of the number of health events in the week after the Autumn clock changes compared to the control period (England, 2008-2019)