We conducted the present study based on previous literature suggesting the relevance of low atmospheric pressure to abdominal aortic aneurysm ruptures[6, 7]. We applied a similar approach to the lymphatic system and its disorder, lymphedema, and hypothesized a relationship between climatic conditions and the occurrence of cellulitis in lymphedema, which is of relevance considering the unusual weather patterns in recent years, such as global warming. As a result, we found that cellulitis in patients with limb lymphedema is meteoropathic in nature, as in previous studies, including a systematic review[9, 10]. Accordingly, patients with limb lymphedema may need to take special care to avoid developing cellulitis in summer or in seasons with lower atmospheric pressure.
In the present study, conducted in Japan, the number of admitted patients was about two times higher in summer than in other seasons (Supplementary Fig. S2). Moreover, when the analysis was limited to patients living in Yokohama City (removing the influence of geographical environment factors), the same tendency was observed; most of the 25 patients were admitted during the months and days with higher temperature and lower atmospheric pressure. Thus, severe cellulitis may be more apt to occur in patients with limb lymphedema on days with higher temperature or lower atmospheric pressure (e.g. summer in Japan).
In addition, the average change in the temperature or atmospheric pressure around the time of admission was higher in spring and autumn than in summer, at least when considering the period from 4 days before admission to the day before admission. However, because the present study utilized 15-day CMA data, the development of cellulitis might have been influenced by climatic conditions during the prior 2 weeks.
Based on the abovementioned study results, there seems to be a seasonal occurrence of cellulitis in patients with limb lymphedema. A higher temperature or lower atmospheric pressure conceivably contributes to the development of cellulitis. Moreover, cellulitis in patients with limb lymphedema might be caused by a continuous higher temperature, rather than by daily and random changes in weather conditions.
Furthermore, if limb lymphedema is categorized as a meteoropathic disease, limb lymphedema conditions may be controlled by medication, as with migraine, rheumatoid arthritis, and bronchial asthma[11–13]. In fact, some previous studies have suggested that ketoprofen might be effective in secondary lymphedema[14–16]. Based on histopathology, the end stage of lymphedema shows fibrosis and fat deposition in the subcutaneous tissue[17–20]. Thus, lymphedema can be regarded as a type of chronic inflammatory disease that is meteoropathic in nature[14, 21].
The limitations of the present study are as follows. First, this study was a retrospective single-center study with only 25 cases. Second, this study did not include patients with cellulitis who were not admitted during the study period. Moreover, we could not evaluate cases with limb lymphedema that had not progressed to cellulitis during the study period. Third, the reasons for admission were varied; the only unanimous finding of the admitted patients was severe redness at the affected site. Thus, the evaluation criteria of admission were obscure. Fourth, data regarding the compliance of the patients in using elastic garments or bandages from the medical records was of poor quality. Given the high temperature in summer in Japan, many patients with limb lymphedema are apt to neglect the garments although they understand the importance of the garments in managing lymphedema. Furthermore, a previous study in Japan indicated that wearing garments in summer is a risk factor of cellulitis for lower limb lymphedema. Additionally, the 15-day CMAs of the temperature and atmospheric pressure might not entirely represent the climatic conditions of the 2 weeks before admission; however, 15 days was defined and hypothesized as a valid number of days by the authors. Prospective cohort and multi-institutional joint research with unified inclusion criteria for admission and consideration of the patient background, such as age, sex, and site of affected limbs, is desirable for the further elucidation of the meteoropathic nature of lymphedema.