key: cord-0967528-9nicryzs authors: Takagi, H.; Kuno, T.; Yokoyama, Y.; Ueyama, H.; Matsushiro, T.; Hari, Y.; Ando, T. title: Higher Air Temperature, Pressure, and Ultraviolet Are Associated with Less Covid-19 Incidence date: 2020-05-13 journal: nan DOI: 10.1101/2020.05.09.20096321 sha: 5c2d04e14830f2ac4461cf31e45889679df675cb doc_id: 967528 cord_uid: 9nicryzs A recent study from China suggests that high temperature and ultraviolet (UV) radiation cannot decrease the epidemics of Coronavirus disease 2019 (Covid-19). To determine whether COVID-19 incidence is modulated by meteorological factors, meta-regression of Japanese prefectural data was herein conducted. We extracted 1) cumulative numbers of confirmed Covid-19 patients in each Japanese prefecture from January to April 2020; 2) populations per 1-km2 inhabitable area in each prefecture in 2020; and 3) meteorological factors at each prefectural capital city from January to April 2020. Meteorological factors included monthly mean air temperature (degree Celsius), wind speed (m/s), sea level air pressure (hPa), relative humidity (%), and percentage of possible sunshine (%); monthly total of sunshine duration (h) and precipitation (mm); and monthly mean daily maximum ultraviolet (UV) index. To adjust for prefectural population density, we defined the incidence of Covid-19 as the cumulative number of Covid-19 patients divided by the population per 100-km2 inhabitable area. Random-effects meta-regression was performed, and its graph depicted Covid-19 incidence (plotted as the logarithm transformed incidence on the y-axis) as a function of a given meteorological factor (plotted on the x-axis). A slope of the meta-regression line was significantly negative as a function of the mean air temperature (coefficient, -0.127; P = 0.023), the mean sea level air pressure (coefficient, -0.351; P < 0.001), and the mean daily maximum UV index (coefficient, -0.001; P = 0.012) which indicated that Covid-19 incidence decreased significantly as air temperature, air pressure, and UV increased. In conclusion, higher air temperature, air pressure, and UV may be associated with less Covid-19 incidence. In Northern Europe, low air temperature and ultraviolet (UV) index have been reported as the most important meteorological predictors for the transmission of influenza virus. 1 Whereas, a recent study from China suggests that high temperature and UV radiation cannot decrease the epidemics of Coronavirus disease 2019 . 2 To determine whether COVID-19 incidence is modulated by meteorological factors, meta-regression of Japanese prefectural data was herein conducted. We extracted 1) cumulative numbers of confirmed Covid-19 patients in each Japanese prefecture from January to April 2020 (Ministry of Health, Labour and Welfare; https://www.mhlw.go.jp/content/10906000/000627448.pdf); 2) populations per 1-km 2 inhabitable area in each prefecture in 2020 (Statistics of Japan; https://www.estat.go.jp/en/statsearch/files?page=1&layout=datalist&toukei=00200502&tstat=000001137306&cycle= 0&year=20200&month=0&tclass1=000001137307); and 3) meteorological factors at each prefectural capital city from January to April 2020 (Japan Meteorological Agency; https://www.data.jma.go.jp/obd/stats/data/en/smp/index.html, https://www.data.jma.go.jp/gmd/env/uvhp/link_uvindex_month54.html) (Supplementary Table 1) . Meteorological factors included monthly mean air temperature (°C), wind speed (m/s), sea level air pressure (hPa), relative humidity (%), and percentage of possible sunshine (%); monthly total of sunshine duration (h) and precipitation (mm); and monthly mean daily maximum ultraviolet (UV) index. To adjust for prefectural population density, we defined the incidence of Covid-19 as the All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. incidence on the y-axis) as a function of a given meteorological factor (plotted on the xaxis). A slope of the meta-regression line ( Fig. 1) was significantly negative as a function of the mean air temperature (coefficient, -0.127; P = 0.023), the mean sea level air pressure (coefficient, -0.351; P < 0.001), and the mean daily maximum UV index (coefficient, -0.001; P = 0.012) which indicated that Covid-19 incidence decreased significantly as air temperature, air pressure, and UV increased. The present meta-regression suggests that air temperature, air pressure, and UV may be negatively associated with COVID-19 incidence. A recent Chinese study has reported no association of COVID-19 epidemics with temperature and UV radiation, 2 which, however, may be denied by the present findings of the negative association of air temperature, air pressure, and UV with COVID-19 incidence in Japan. In conclusion, higher air temperature, air pressure, and UV may be associated with less Covid-19 incidence, which should be confirmed by further epidemiological investigations taking other risk and protective factors of Covid-19 into account. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 13, 2020. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. Mean daily maximum UV Index log Log Proportion Log Covid-19 incidence Log Covid-19 incidence All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 13, 2020. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 13, 2020. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted May 13, 2020. . https://doi.org/10.1101/2020.05.09.20096321 doi: medRxiv preprint Low Temperature and Low UV Indexes