How do we keep people out of hospitals – those giant, multimillion-pound “monuments to the failure of preventive medicine”, as one director of public health recently put it?

One of the Department of Health’s sticks (sorry: “policy levers”) is to withhold payments for patients readmitted as emergencies within 28 days of a previous discharge. Estimates on the cost of the penalty range from £600m-£790m a year, money the DH expects primary care trusts to spend on reablement initiatives to reduce emergency admissions.

Perhaps it is no wonder a recent HSJ investigation found hospitals and PCTs conspiring to subvert the policy, with outrageous notions such as checking first whether it really is the hospital’s fault, before docking its pay.

Those checks are throwing up some interesting results.

One exercise at Gloucestershire Hospitals Foundation Trust audited a small sample of patient case notes to ascertain the cause of readmissions. The top three reasons were: deliberate self-harm, alcohol, and respiratory conditions, including chronic obstructive pulmonary disease.

A much bigger sample pulled together by NHS data specialists CHKS seems to partially corroborate this finding. Out of a sample of 1.2 million readmissions, the biggest single healthcare resource group was “poisoning toxic environmental and unspecified effects”, that is, “overdose”.

That prominence will be in part a function of HRG categorisation: COPD and other respiratory admissions also feature highly in the CHKS sample, but are broken down into narrower categories.

A breakdown of readmissions by primary diagnosis further confirms the significance of mental health and societal health problems. “Mental and behavioural disorders due to use of alcohol” form the 20th most common diagnosis for readmission, while “poison by non-opioid analgesic antipyretic and anti-rheumatics” is also high at 28.

No one would argue that less should be done to prevent patients requiring hospital readmissions, but the data suggests it is time at least to broaden the thinking on what constitutes good post-discharge care and which patients need more attention.

Sally Gainsbury is a news reporter for the Financial Times.