Seasonal variations in the onset of ulcerative colitis in Japan

Figure 3 Seasonal variations in the onset of ulcerative colitis. The highest seasonal onset rate was observed in the winter (57/198, 28.8%), followed by the spring (55/198, 27.8%), autumn (53/198, 26.8%), and summer (33/198, 16.7%). A seasonal pattern was also observed (χ²_{(3 df)} = 7.88, P = 0.048), as the onset rate was highest during autumn to spring (observed/expected: 53/49.36, 57/48.82, 55/49.91, respectively).