Seasonal variation in the onset of acute pancreatitis

Table 1 Monthly distribution of acute pancreatitis by gender and risk factors

Month	Total (n = 549)	Males (n = 285)	Females (n = 264)	Biliary tract disease (n = 286, 52.1%)	No bil. tract disease (n = 263, 48.9%)	Alcoholism (n = 48, 8.7%)	Fatal cases (n = 18, 3.2%)
January	34	18	16	17	17	1	3
February	46	19	27	22	24	2	2
March	62	35	27	28	34	8	1
April	61	33	28	31	30	7	0
May	56	32	24	35	21	5	0
June	44	23	21	19	25	3	0
July	40	20	20	23	17	2	1
August	45	25	20	30	15	4	1
September	39	20	19	22	17	4	1
October	40	20	20	19	21	2	2
November	46	25	21	22	24	6	3
December	36	15	21	17	19	3	4

Table 2 Seasonal distribution of acute pancreatitis (χ² test for goodness of fit)

	n (%)	December-February n (%)	March-May n (%)	June-August n (%)	September-November n (%)	χ2	P
Total	549	116 (21.1)	179 (32.6)	129 (23.5)	125 (22.8)	17.5	0.001
Males	285 (51.9)	52 (18.2)	100 (35.1)	68 (23.9)	65 (22.8)	17.05	0.001
Females	264 (48.1)	64 (24.2)	79 (29.9)	61 (23.1)	60 (22.7)	3.55	0.316
Biliary tract disease	286 (52.1)	56 (19.5)	94 (32.8)	73 (25.4)	64 (22.3)	11.02	0.011
No bil. tract disease	263 (47.9)	60 (22.9)	85 (32.4)	56 (21.4)	61 (23.3)	7.93	0.049
Chronic alcoholism	48 (8.7)	6 (12.5)	20 (41.7)	10 (20.8)	12 (25)	8.67	0.035
Fatal cases	18 (3.2)	9 (50)	1 (5.6)	2 (11.1)	6 (33.3)	9.11	0.029

Table 3 Seasonal variation of acute pancreatitis (chronobiologic parameters by Fourier analysis)

	n	Period (h)	PR (%)	MESOR	Amplitude	Peak	95%CL	P
Total	549	8766	51.1			March	February-April	0.006
		4383	33.7			September	August-October	0.017
		Overall	84.8	45.68	3.28	March	February-April	0.005
Males	285	8766	42.6			March	February-April	0.030
		4383	32.7			September	NS	0.052
		Overall	75.4	23.71	9.06	March	February-April	0.027
Females	264	8766	50.9			March	February-April	0.024
		4383	22.3			September	NS	0.121
		Overall	73.3	21.97	4.52	March	February-April	0.035
Biliary tract disease	286	8766	42.2			March	NS	0.074
		4383	19.5			August	NS	0.234
		Overall	61.8	23.72	7.60	March	NS	0.108
No bil. tract disease	263	8766	44.8			March	February-April	0.041
		4383	25.1			October	NS	0.119
		Overall	69.9	21.96	7.66	March	NS	0.052
Chronic alcoholism	48	8766	13.2			March	NS	0.415
		4383	40.7			September	NS	0.109
		Overall	53.9	3.91	2.51	March	NS	0.192
Fatal cases	18	8766	86.2			November	November-December	< 0.001
		4383	10.9			June	May-July	0.004
		Overall	97.1	1.50	1.90	November	November-December	< 0.001

PR = percentage of rhythm (percentage of overall variability of data about arithmetic mean attributable to the rhythmic fitted function MESOR = midline estimated statistics of rhythm, the rhythm-adjusted mean over the time period analysed amplitude: half the distance between the absolute maximum and minimum of the function of the best-fitting curve 95%CL = 95% confidence limits NS = not significant, (when acrophase did not reach the significance level, 95%CL could not be given).