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Table 1 Chronobiologic analysis of seasonal distribution of multiple sclerosis relapses, and meteorological data

From: A seasonal periodicity in relapses of multiple sclerosis? A single-center, population-based, preliminary study conducted in Bologna, Italy

  N Period (hours) PR (%) MESOR ± SE Amplitude Acrophase p
Total relapses 164 8766.00 10.7     N.S.
   4383.00 64.0     0.012
   Overall 74.7 13.69 ± 0.83 6.42 -142° (May) 0.030
Females 108 8766.00 12.1     N.S.
   4383.00 29.6     N.S.
   Overall 41.7 9.01 ± 0.95 3.62 -139° N.S.
Males 56 8766.00 2.3     N.S.
   4383.00 35.1     N.S.
   Overall 37.4 4.68 ± 0.87 2.81 -144° N.S.
< 40 yrs 115 8766.00 2.7     N.S.
   4383.00 64.9     0.021
   Overall 67.6 9.60 ± 0.72 4.37 -142° (May) 0.065
≥40 yrs 49 8766.00 41.0     0.031
   4383.00 34.9     0.043
   Overall 75.8 4.09 ± 0.26 2.11 -141° (May) 0.025
Temperature (°C)   8766.00 97.4 15.4 ± 0.39 10.05 -188.8 ± 3. 2 (July) < 0.001
Humidity (%)   8766.00 81.2 61.0 ± 1.65 14.57 -3.3 ± 9.2 (January) < 0.001
Wind speed (m/sec)   8766.00 63.1 2.20 ± 0.11 0.63 -164.7 ± 14.6 (June) 0.011
Rain precipitation (mm)   8766.00 0.7 1.81 ± 0.47 0.17 -20.8 ± 227.1 N.S.
  1. Abbreviations (see text for details) derived by Cosinor analysis of the time series data: PR : percentage of rhythm - MESOR: midline estimated statistic of rhythm (the rhythm-adjusted mean over the time period analyzed, i.e., the monthly mean for a cycle of one year) - Amplitude: one-half the difference between the absolute maximum and minimum of the fitted curve - Acrophase: the absolute time of the peak expressed in degrees, with 360° = 12 months or 1 day = 0.9863, as a negative value (i.e., a delay) in reference to midnight December 31. P value derived by the F-test statistic of the null hypothesis that the amplitude of the fitted cosine approximation of a given period = 07