Table 3 The association of WBGT and heart rate variability (HRV) indicators in a 5-min resolution in (a) non-sleeping periods (excluding raining periods) (n = 24,786), (b) working hours considering clothing conditions excluding long sleeves and long pants (n = 9752), and (c) working hours considering clothing conditions excluding short sleeves and short pants (n = 9752).

WBGT

−1.13***

−1.05***

0.625***

−2.14***

−2.44***

−1.43***

−1.69***

0.647***

Age ≥40

−22.3*

−33.3**

5.92

−52.8**

−55.4*

−35.6

−42.5*

−2.95

Male

−2.80

−19.3

59.5**

−23.1

−51.9*

7.91

−12.8

−1.44

Overweight/obese

−10.8

−9.01

−13.4

−26.8

−15.6

−20.7

−20.5

1.34

PM_2.5

−0.141

−0.185

0.340*

−0.138

−0.480

−0.309

−0.290

0.0374

(b)

SDNN

RMSSD

LF/HF

LF

HF

VLF

TP

HR

(Adj R² = 0.097)

(Adj R² = 0.127)

(Adj R² = 0.122)

(Adj R² = 0.162)

(Adj R² = 0.119)

(Adj R² = 0.081)

(Adj R² = 0.114)

(Adj R² = 0.341)

WBGT

−0.742***

−0.849***

−0.413

−1.73***

−1.40***

−0.843**

−0.964***

0.612***

Short sleeves

3.49

2.69

3.22

14.0**

9.94

5.92

9.47*

−1.49*

Short pants (skirts)

7.12

2.68

12.0

1.74

−8.56

10.2

5.56

−5.19**

Gloves

−8.68***

−10.8**

3.52

−18.5**

−21.2**

−15.4**

−15.6**

0.995

Mask

−9.12***

1.70

−11.4**

−4.87

6.04

−23.3***

−12.9*

1.82

Waterproof shoes

−0.192

−2.33

−5.62

−6.31

1.19

1.79

0.763

3.01***

Bamboo hat

1.73

−0.859

−1.66

−1.90

−0.899

5.89

1.87

0.447

Age ≥40

−22.1*

−31.8*

−9.54

−56.8**

−52.2*

−34.2*

−41.8*

−2.58

Male

−15.2

−36.8*

75.6**

−50.4*

−71.5**

−12.9

−36.0

1.09

Overweight/obese

−3.63

−0.535

−15.7

−16.1

−1.19

−7.91

−8.26

−1.55

PM_2.5

0.0316

−0.00863

0.0629

0.113

0.00188

0.0522

0.0863

−0.00184

(c)

SDNN

RMSSD

LF/HF

LF

HF

VLF

TP

HR

(Adj R² = 0.096)

(Adj R² = 0.121)

(Adj R² = 0.120)

(Adj R² = 0.152)

(Adj R² = 0.105)

(Adj R² = 0.081)

(Adj R² = 0.109)

(Adj R² = 0.338)

WBGT

−0.763***

−0.862***

−0.436*

−1.78***

−1.45***

−0.883**

−1.01***

0.614***

Long sleeves

−4.36*

−5.05*

−1.46

−19.5***

−18.1***

−5.85

−11.8***

1.27

Long pants (skirts)

−5.44

−2.66

−9.07*

−3.94

5.31

−8.96

−5.92

3.95**

Gloves

−8.67**

−10.7**

3.51

−18.4**

−21.1**

−15.4**

−15.5**

0.849

Mask

−8.80***

2.07

−11.2**

−3.58

7.17

−22.9***

−12.2*

1.62

Waterproof shoes

0.263

−2.07

−5.13

−5.23

1.98

2.73

1.80

2.96***

Bamboo hat

2.56

0.0927

−1.40

1.97

2.74

7.11

4.23

0.268

Age ≥40

−21.0*

−30.9*

−8.86

−54.7**

−50.3

−33.1*

−40.1*

−3.10

Male

−15.0

−36.9*

76.7**

−50.6*

−71.8**

−12.7

−36.0

0.723

Overweight/obese

−4.24

−1.14

−16.1

−17.9

−2.99

−8.63

−9.47

−1.33

PM_2.5

0.0239

−0.0114

0.0510

0.0988

−0.00343

0.0377

0.0711

−0.0007