Health forecasting and COPD.

In cold weather Grandma used to say ‘‘wrap up warm.’’ But was she right? Exposure to extremes of both hot and cold weather is associated with excess mortality due to myocardial infarction, pneumonia and COPD. The hypothesis has therefore been formulated that if one can predict the advent of a cold snap, then COPD exacerbations and hospitalisation, and ultimately mortality, can be prevented. By sending high-risk patients a recorded phone message, they can be warned of the impending cold spell and be given advice about what they should do in order to promote self-management. The message sent is a reminder to have available a full course of medication, to contact their doctor or nurse if symptoms become worse, to make sure that their bedand living rooms are kept warm, and to keep active. The matter is not simple, however, and what little evidence there is seems to challenge this initially intuitive hypothesis. Interestingly, increased mortality associated with cold exposure is well described and may be related to physiological changes in the immune system, blood viscosity, blood pressure and the airway. Respiratory symptoms in the cold are also twice as common in smokers. However, to complicate matters, despite identical mean winter temperatures in London and Northern Italy, mortality from cardiorespiratoy disease is nearly three times higher in London. It is likely that factors other than a fall in temperature are interacting. Acclimatization to the cold, staying active, smoking, air quality, and rate of change in environmental or indoor temperature to name a few. Exacerbations of COPD are commonly caused by viruses, especially influenza. As such viruses are particularly common in winter months and spread by person-to-person contact, staying indoors might reduce exacerbations as a result of isolation alone. Vaccination against influenza is particularly effective in reducing admission to hospital as a consequence of COPD exacerbation. To confound matters further, will a patient heed the advice given? The treatment of COPD requires patients to take treatment on a daily basis and use an anticipatory care plan. The evidence suggests that, using didactic advice, about a half do not adhere to the treatment plan advised. The study described by Diar-Bakerly et al therefore is of interest. Many commissioners are implementing Health Forecasting for COPD, with little other than the premise ‘that it seems reasonable’. Now we are beginning to gather evidence concerning its use – and are coming up with what are perhaps surprising results. The paper describes the use of weather forecasts in anticipatory care for patients with mild and moderate COPD, and reports that it did not reduce admission rates to hospital, or reduce overall costs of healthcare. Similar results have been reported from Sheffield, where patients were found to like the service, but there was little evidence for any change in management. Where does this leave us? The hypothesis that exposure to cold is associated with an increase in mortality is sound, albeit complicated. Advice to patients about this seems reasonable; however, we need to consider how this should be done. Should it form part of a self-management or anticipatory care plan? If so, how should the plan be implemented and used? The evidence shows that simply giving advice does not change patient behaviour. We should use other techniques linked with the advice. If we wish to see, in response to a cold weather warning, a change in patient behaviour then we should engage patients in the decision making process. 8 This is clearly an important area and unfortunately we have little in the way of clear-cut evidence. The paucity of evidence means that we require more