Baseline characteristics of participants
In the present study, all data collected from 86,930 men were analyzed. The average age was 46.39 years, the average BMI was 25.01 kg / m2, the average PSA level was 0.65 ng / mL, the average PV was 18.43 mL, the average PSA density level was 0.04 mg, the average BV level was 2.97 L, and the average PSA mass level was 1.91 mg, respectively. The minimum and maximum values of these variables were also presented. The demographics of the study population are listed in Table 1.
Table 1 Characteristics of the study population
|
n
|
Minimum
|
Maximum
|
Mean
|
SD
|
Age (years)
|
86, 930
|
18
|
475
|
46.39
|
12.22
|
Height (cm)
|
103.00
|
202.00
|
166.67
|
6.29
|
Weight (kg)
|
40
|
171
|
69.53
|
9.72
|
BMI (kg/m2)
|
18.5
|
63.0
|
25.01
|
3.00
|
PSA (ng/ml)
|
0
|
33
|
0.65
|
0.74
|
PV (ml)
|
0.137
|
189.82
|
18.43
|
6.73
|
PSA density (μg)
|
0
|
9
|
0.04
|
0.05
|
BV (L)
|
2
|
5
|
2.97
|
0.23
|
PSA mass (μg)
|
0
|
95
|
1.91
|
2.10
|
Notes: BMI, body mass index; PSA, prostate specific antigen; PV, prostate volume; BV, blood volume; SD, standard deviation.
Correlation among BMI, BV, PV and PSA levels
Spearman rank test results showed that BMI (P < 0.001) and BV (P < 0.001) were negatively associated with PSA, but PV (P < 0.001) was positively associated with PSA after adjustment for age (Table 2), indicating that PSA levels was affected by BV, PV and BMI. Furthermore, BV (P < 0.001) and PV (P < 0.001) were positively associated with BMI after adjustment for age, indicating that a higher BMI might have a larger PV and BV. Particularly, BV and PV most likely showed the positive association with BMI and PSA, respectively.
Table 2 Pairwise correlation among the variables after adjustment for age
|
BMI
|
BV
|
PV
|
BMI
|
-
|
-
|
-
|
BV
|
0.651﹡
|
-
|
-
|
PV
|
0.061﹡
|
0.115﹡
|
-
|
PSA
|
-0.057﹡
|
-0.041﹡
|
0.227﹡
|
Notes: BMI, body mass index; PV, prostate volume; BV, blood volume; PSA, prostate specific antigen; ﹡means P < 0.05
Correlation among BMI and PSA-related parameters
Table 3 showed the relationship between BMI and PSA, PSA density and PSA mass in different BMI categories. BMI was negatively associated with PSA (all sample: correlation coefficient = -0.057, P-value < 0.001; Normal weight: correlation coefficient = -0.026, P-value < 0.001; Overweight: correlation coefficient = -0.031, P-value < 0.001; Obese: correlation coefficient = -0.057, P-value < 0.001) and PSA density (all sample: correlation coefficient = -0.095, P-value < 0.001; Normal weight: correlation coefficient = -0.019, P-value < 0.001; Overweight: correlation coefficient = -0.022, P-value < 0.001; Obese: correlation coefficient = -0.036, P-value < 0.001) in all categories (Table 3). However, no significant association between BMI and PSA mass was detected in all categories (all sample: correlation coefficient = 0.001, P-value = 0.763; Normal weight: correlation coefficient = 0.008, P-value = 0.145; Overweight: correlation coefficient = -0.003, P-value = 0.497; Obese: correlation coefficient = -0.005, P-value = 0.554) (Table 3).
Table 3 Partial Spearman correlation among the variables after adjustment for age
BMI category
|
PSA
|
|
PSA density
|
|
PSA mass
|
|
Coefficient
|
p
|
Coefficient
|
p
|
Coefficient
|
p
|
All sample
(n = 86930)
|
-0.057
|
<0.001
|
|
-0.060
|
<0.001
|
|
0.001
|
0.763
|
|
Normal
(n = 32321)
|
-0.026
|
<0.001
|
|
-0.019
|
0.001
|
|
0.008
|
0.145
|
|
Overweight
(n = 40779)
|
-0.024
|
<0.001
|
|
-0.022
|
<0.001
|
|
-0.003
|
0.497
|
|
Obese
(n = 13830)
|
-0.031
|
<0.001
|
|
-0.036
|
<0.001
|
|
-0.005
|
0.554
|
|
Notes: BMI, body mass index; PSA, prostate specific antigen;