Seasonal bias may alter how EPP patients recall their symptoms

Seasonal recall bias — when a person’s memory of a previous time of year is distorted by the way they feel in the present — may lead erythropoietic protoporphyria (EPP) patients to remember their summer symptoms as more severe and their treatments as less effective when they are describing them in the winter, a study from Denmark found.

The findings suggest that doctors should consider scheduling follow-up visits during the summer, when EPP symptoms are most active, to get a more accurate picture of patients’ experiences.

The study, “Seasonal variations in erythropoietic protoporphyria patients’ responses about sun behaviour, symptoms, and treatment effect,” was published as a short communication in Photodiagnosis and Photodynamic Therapy.

Like other types of porphyria, EPP causes extreme sensitivity to sunlight. EPP patients have an unusually high amount of a substance called protoporphyrin IX (PpIX). When PpIX is released into the skin, it absorbs sunlight and becomes chemically active. This can cause pain and other porphyria symptoms even without a visible sunburn.

Northern Europe provides example

Patients often have to change their daily activities to cope with their symptoms. They may spend less time outdoors, avoid direct sunlight, wear protective clothing, and limit travel to sunny places. In Northern European regions like Denmark, symptoms may be less noticeable during winter because sunlight is weaker and winter clothes cover more skin.

The researchers wanted to understand whether seasonal differences affected how patients with EPP described their symptoms and response to treatment. They also wanted to see whether these experiences were related to the amount of PpIX. Nineteen patients answered the same questions in the middle of summer and again in the following winter.

“During the winter months, the weather in Denmark requires no treatment or protection measures due to low light intensity and wearing winter clothes,” the researchers wrote, so ” it is to be expected that patients with EPP may have a different perception of symptoms, behaviour in the sun, and treatment.”

However, the patients reported similar sun-related behavior in both seasons. There were no differences in the number of hours they spent outdoors each week, how long they could stay in sunlight before symptoms began, travel to sunny destinations, or the use of sun protection.

Despite this, patients reported their symptoms as worse when questioned in winter. Their EPP Dermatology Life Quality Index (DLQI) score was 20% higher in winter. The DLQI is a questionnaire that measures how EPP affects daily life, with higher scores indicating worse quality of life. Their estimate of maximum pain was also 40% higher in winter, although the number of painful episodes was about the same.

Patients reported greater improvement in their symptoms when answering during the summer. When they answered the same question in winter, they recalled 27% less improvement in response to treatment. This could be partly due to recall bias: Being symptom-free in the winter could skew patients’ recall of the severity of their summer symptoms and the effectiveness of their treatment.

In contrast, the reported improvement in overall quality of life from treatment was the same in summer and winter. This suggests that although patients may remember symptoms differently depending on the season, their broader view of how treatment benefits their lives may be more stable.

Sixteen patients were taking oral cimetidine, an over-the-counter medication normally used to treat heartburn, and a supplement of zinc sulfate. Among these patients, erythrocyte PpIX levels were 23% lower in the summer than in the following winter, and 6.1% lower than in the previous winter.

Overall, the findings suggest that the season can affect how patients remember and report their symptoms and response to treatment, which may help doctors decide when to schedule follow-up visits.

“Annual follow-up consultations should be performed in the season where disease-related symptoms are most pronounced,” the researchers wrote.