Impact of ambient temperature on postoperative cognitive dysfunction in elderly patients surgery: A seasonal comparison in tropical regions

Table 1 Comparison of clinical characteristics before matching between the two groups, n (%)

	Winter (n = 63)	Summer (n = 62)	Z/t/χ2	P value
Age (years, P25-P75)	70 (67-78)	70 (66.75-73.25)	-1.230	0.219
Gender
Male	34 (54)	38 (61.3)	0.686	0.408
Female	29 (46)	24 (38.7)
BMI (kg/cm2, mean ± SD)	24.05 ± 3.39	22.44 ± 3.04	2.792	0.006
Education level
> Junior high	24 (38.1)	21 (33.9)	0.242	0.623
≤ Junior high	39 (61.9)	41 (66.1)
Surgical duration
≥ 3 hours	32 (50.8)	37 (59.7)	0.997	0.318
< 3 hours	31 (49.2)	25 (40.3)
Hypertension	35 (55.6)	30 (48.4)	0.643	0.423
Diabetes	10 (15.9)	7 (11.3)	0.558	0.455
Cardiovascular disorders	8 (12.7)	5 (8.1)	0.720	0.396
Cerebrovascular disorders	5 (7.9)	7 (11.3)
Anemia	4 (6.3)	8 (12.9)	1.547	0.214
Hypoalbuminemia	7 (11.1)	16 (25.8)	4.494	0.034
Elevated creatinine	7 (11.1)	6 (9.7)	0.069	0.793
Surgical grading			2.399	0.49
I	32 (50.8)	35 (56.5)
II	15 (23.8)	18 (29)
III	10 (15.9)	6 (9.7)
IV	6 (9.5)	3 (4.8)
PPS on postoperative day 1			0.748	0.688
< 4	25	20
4-6	28	31
> 6	10	11
PPS on postoperative day 3			0.778	0.678
< 4	39	43
4-6	18	14
> 6	6	5
PPS on postoperative day 7			-	0.440
< 4	58	60
4-6	5	2
> 6	0	0

BMI: Body mass index; PPS: Postoperative pain scores.

Table 2 Comparison of clinical characteristics after matching between the two groups, n (%)

	Winter (n = 41)	Summer (n = 41)	Z/t/χ2	P value
Age (years, P25-P75)	69 (67-75)	71 (68-75.5)	-1.214	0.225
Gender
Male	24 (58.5)	24 (58.5)	< 0.001	1
Female	17 (41.5)	17 (41.5)
BMI (kg/cm2, mean ± SD)	23.17 ± 3.01	23.12 ± 3.13	0.077	0.939
Education level
> Junior high	14 (34.1)	14 (34.1)	< 0.001	1
≤ Junior high	27 (65.9)	27 (65.9)
Surgical duration
≥ 3 hours	19 (46.3)	22 (53.7)	0.439	0.508
< 3 hours	22 (53.7)	19 (46.3)
Hypertension	21 (51.2)	22 (53.7)	0.049	0.825
Diabetes	6 (14.6)	5 (12.2)	0.105	0.746
Cardiovascular disorders	2 (4.9)	4 (9.8)	-	0.675
Cerebrovascular disorders	4 (9.8)	6 (14.6)	0.456	0.500
Anemia	3 (7.3)	3 (7.3)	-	1
Hypoalbuminemia	7 (17.1)	8 (19.5)	0.082	0.775
Elevated creatinine	4 (9.8)	5 (12.2)	-	1
Surgical grading			0.847	0.838
I	21 (51.2)	25 (61.0)
II	10 (24.4)	8 (19.5)
III	7 (17.1)	6 (14.6)
IV	3 (7.3)	2 (4.9)
PPS on postoperative day 1			-	0.782
< 4	20	17
4-6	18	20
> 6	3	4
PPS on Postoperative day 3			-	0.546
< 4	30	33
4-6	10	6
> 6	1	2
PPS on postoperative day 7			-	1
< 4	39	39
4-6	2	2
> 6	0	0

BMI: Body mass index; PPS: Postoperative pain scores.

Table 3 Seasonal variation in postoperative cognitive dysfunction incidence

	P value	OR	95%CI
			Lower bound	Upper bound
Postoperative day 1	0.262	0.600	0.246	1.463
Postoperative day 3	0.820	1.109	0.454	2.710
Postoperative day 7	1	1.000	0.316	3.160

Table 4 Summer and winter cohort Mini-Mental State Examination scores over time

	Preoperative	Postoperative day 1	Postoperative day 3	Postoperative day 7
Summer	26.60 ± 2.131	25.48 ± 2.338a	25.52 ± 2.345b	26.05 ± 2.130
Winter	26.16 ± 2.049	24.79 ± 2.483c	24.63 ± 2.953d	25.48 ± 2.539

^aP = 0.003 vs Mini-Mental State Examination scores between postoperative day 1 and preoperative baseline.

^bP = 0.004 vs scores between postoperative day 3 and preoperative baseline.

^cP = 0.0002 vs Mini-Mental State Examination scores between postoperative day1 and preoperative baseline.

^dP = 0.0005 vs Mini-Mental State Examination scores between postoperative day 3 and preoperative baseline.

Table 5 Multivariable binary logistic regression analysis

	P value	OR	95%CI
Postoperative day 1
Surgical duration	0.049	2.103	1.003-4.408
Postoperative day 3
Age	0.044	1.075	1.002-1.154
Elevated creatinine	0.008	6	1.613-22.319
Hypoalbuminemia	0.042	2.864	1.037-7.914
Postoperative day 7
Hypoalbuminemia	0.015	3.777	1.300-10.972