Baseline characteristics of the study population
Cross-sectional data were available for 1519 subjects (59.0% females, 57.9±13.3 years old). The demographic and clinical characteristics of the study population are summarized in Table 2. Males had a higher average HGS (40.2 kg) than females (25.0 kg) (p<0.01); compared with females, males also had better pulmonary function (p<0.01).
Table 2. General characteristics of the study population
|
Males (n=623)
|
Females (n=896)
|
Total
|
Age, years
|
57.9±13.5
|
58.0±13.2
|
57.9±13.3
|
Handgrip strength, kg
|
40.2±8.2
|
25.0±5.7*
|
31.5±10.2
|
Height, cm
|
170.9±9.1
|
159.5±5.1
|
164.4±9.1
|
Weight, kg
|
73.0±12.6
|
61.4±10.4*
|
66.4±12.9
|
BMI, kg/m2
|
24.8±4.0
|
24.1±4.2
|
24.4±4.2
|
Waist circumference, cm
|
91.4±9.1
|
82.9±11.7
|
86.6±11.4
|
Hip circumference, cm
|
99.8±7.5
|
97.9±7.3
|
98.7±7.4
|
Pulse pressure, mmHg
|
50.9±10.1
|
53.0±11.2*
|
52.1±10.8
|
Hb, g/L
|
151.9±12.3
|
133.9±11.4
|
141.5±14.7
|
Plasma glucose, mmol/L
|
5.6±1.7
|
5.4±1.4
|
5.5±1.5
|
Albumin, g/L
|
45.9±5.0
|
45.8±4.5
|
45.8±4.8
|
Alanine aminotransferase, U/L
|
24.4±17.6
|
19.0±15.9
|
21.3±16.8
|
Creatinine, μmol/L
|
83.2±15.0
|
65.5±11.5*
|
73.1±15.8
|
TC, mg/mL
|
4.6±0.9
|
4.8±1.0
|
4.7±1.0
|
HDL, mg/mL
|
1.3±0.3
|
1.5±0.4
|
1.4±0.4
|
Education, n (%)
|
|
|
|
≤High school
|
60.4
|
62.9
|
61.9
|
≥College
|
39.6
|
37.1
|
38.1
|
Regular exercise, n (%)
|
44.3
|
47.5
|
46.2
|
Drinking, n (%)
|
51.2
|
25.7*
|
36.1
|
Cigarette smoking, n (%)
|
32.6
|
5.7*
|
16.7
|
Pulmonary function index
|
|
|
|
FEV 1 (L)
|
2.9±0.7
|
2.2±0.5*
|
2.5±0.7
|
FEV 2 (L)
|
3.3±0.7
|
2.4±0.5*
|
2.8±0.8
|
FVC (L)
|
3.3±0.7
|
2.5±0.5*
|
2.8±0.8
|
FEV 0.5 (L)
|
2.3±0.6
|
1.7±0.4*
|
2.0±0.5
|
MEF 25 (L/s)
|
1.3±0.6
|
1.1±0.5*
|
1.2±0.6
|
FEV 3 (L)
|
3.4±0.8
|
2.5±0.5*
|
2.8±0.8
|
VC max (L)
|
3.6±0.7
|
2.6±0.5*
|
3.1±0.8
|
VC IN (L)
|
3.5±0.8
|
2.6±0.6*
|
3.0±0.8
|
MEF 50 (L/s)
|
3.7±1.4
|
3.0±1.0*
|
3.3±1.2
|
VC EX (L)
|
3.4±0.8
|
2.5±0.6*
|
2.9±0.8
|
MEF 75 (L/s)
|
6.0±1.8
|
4.7±1.2*
|
5.2±1.6
|
MVV (L/min)
|
80.3±27.8
|
65.7±20.3*
|
71.9±24.9
|
*p<0.01 for comparison with males. BMI: body mass index, Hb: haemoglobin, TC: total cholesterol, HDL: high-density lipoprotein, FEV 0.5/1/2/3: forced expiratory volume in 0.5/1/2/3 second, FVC: forced vital capacity, VC IN: inspiratory vital capacity, VC EX: expiratory vital capacity, VC max: maximum value of vital capacity, MEF 25/50/75: maximum expiratory flow rate at 25%/50%/75% vital capacity, MVV: maximum ventilation volume
Handgrip strength and pulmonary function were negatively associated with age
The average HGS was significantly higher in the younger group (33.3 kg) than in the older group (27.6 kg) (p<0.01). Pulmonary function was also significantly better in the younger group (p<0.01).
In the linear correlation analysis, we found that HGS was significantly correlated with age (r=-0.30, p<0.01), and the parameters of pulmonary function were strongly negatively correlated with age, especially FEV 1 (r=-0.55, p<0.01), FEV 2 (r=-0.53, p<0.01), FVC (r=-0.50, p<0.01), FEV 0.5 (r=-0.53, p<0.01), and MEF 25 (r=-0.60, p<0.01).
Table 3. Comparison of handgrip strength and pulmonary function in different age groups and their coefficients of correlation with age
|
Younger group
(<60 years, n=725)
|
Older group
(≥60 years, n=794)
|
r
|
Handgrip strength
|
33.3±16.4
|
27.6±9.4*
|
-0.30
|
FEV 1 (L)
|
2.8±0.6
|
2.2±0.6*
|
-0.55
|
FEV 2 (L)
|
3.1±0.8
|
2.5±0.7*
|
-0.53
|
FVC (L)
|
3.1±0.8
|
2.6±0.7*
|
-0.50
|
FEV 0.5 (L)
|
2.2±0.5
|
1.7±0.4*
|
-0.53
|
MEF 25 (L/s)
|
1.3±0.6
|
1.1±0.5*
|
-0.60
|
FEV 3 (L)
|
3.2±0.8
|
2.6±0.7*
|
-0.47
|
VC max (L)
|
3.4±0.8
|
2.7±0.7*
|
-0.46
|
VC IN (L)
|
3.2±0.8
|
2.7±0.8*
|
-0.44
|
MEF 50 (L/s)
|
3.8±1.1
|
2.8±1.1*
|
-0.50
|
VC EX (L)
|
3.1±0.8
|
2.6±0.7*
|
-0.41
|
MEF 75 (L/s)
|
5.7±1.5
|
4.8±1.5*
|
-0.39
|
MVV (L/min)
|
79.6±24.1
|
64.6±23.4*
|
-0.38
|
*p<0.01 for comparison with the younger group;
r is the correlation coefficient between parameters and age; all correlation coefficients listed are significant at the 0.01 level.
Relationship between pulmonary function and handgrip strength
Pearson correlation analysis showed that VC max had the strongest significant correlation (r=0.72, p<0.001) with HGS for all participants, followed by VC IN, FEV 3 and FVC (r=0.71; 0.70 and 0.69, respectively) (Table 4). As both VC max and VC IN are parameters of the vital capacity, we selected VC max, FEV 3 and FVC as representatives of lung function to analyze their associations with HGS.
Table 4. Correlation coefficients between handgrip strength and parameters of pulmonary function stratified by sex
Parameters of
Pulmonary Function
|
Males
(n=623)
|
Females
(n=896)
|
Total
(n=1519)
|
VC max
|
0.48*
|
0.51*
|
0.72*
|
VC IN
|
0.47*
|
0.50*
|
0.71*
|
FEV 3
|
0.48*
|
0.50*
|
0.70*
|
FVC
|
0.49*
|
0.50*
|
0.69*
|
FEV 2
|
0.48*
|
0.52*
|
0.69*
|
FEV 1
|
0.48*
|
0.46*
|
0.65*
|
VC EX
|
0.42*
|
0.43*
|
0.65*
|
FEV 0.5
|
0.45*
|
0.43*
|
0.62*
|
MEF 75
|
0.34*
|
0.35*
|
0.52*
|
MVV
|
0.33*
|
0.35*
|
0.41*
|
MEF 50
|
0.34*
|
0.30*
|
0.40*
|
MEF 25
|
0.30*
|
0.31*
|
0.30*
|
FEV 0.5/1/2/3: forced expiratory volume in 0.5/1/2/3 second, FVC: forced vital capacity, VC IN: inspiratory vital capacity, VC EX: expiratory vital capacity, VC max: maximum value of vital capacity, MEF 25/50/75: maximum expiratory flow rate at 25%/50%/75% vital capacity, MVV: maximum ventilation volume. * p<0.001 for the correlation coefficients listed.
To identify mixed factors in the relationship between pulmonary function and HGS, we conducted a Pearson correlation analysis between other parameters and pulmonary function (VC max, FEV3 and FVC) (Table 5). HGS, age, height, SBP and PP were significantly correlated with pulmonary function (ǀrǀ≥0.30, p<0.01).
Table 5. Correlation coefficients (r) of variables with pulmonary function in males and females
Variables
|
VC max
|
FEV3
|
FVC
|
Males
|
Females
|
Males
|
Females
|
Males
|
Females
|
Handgrip strength
|
0.507
|
0.481
|
0.504
|
0.476
|
0.497
|
0.486
|
Age
|
-0.573
|
-0.604
|
-0.59
|
-0.605
|
-0.611
|
-0.614
|
Height
|
0.304
|
0.518
|
0.192
|
0.508
|
0.281
|
0.504
|
Weight
|
0.226
|
0.125
|
0.186
|
0.161
|
0.216
|
0.128
|
BMI
|
0.053
|
-0.065
|
0.083
|
-0.053
|
0.062
|
-0.055
|
Waist circumference
|
-0.017
|
-0.156
|
0.02
|
-0.185
|
-0.013
|
-0.155
|
Hip circumference
|
0.116
|
0.027
|
0.15
|
0.006
|
0.115
|
0.028
|
SBP
|
-0.182
|
-0.332
|
-0.118
|
-0.278
|
-0.186
|
-0.334
|
DBP
|
-0.044
|
-0.146
|
0.063
|
-0.117
|
-0.04
|
-0.136
|
PP
|
-0.294
|
-0.38
|
-0.231
|
0.325
|
-0.303
|
-0.385
|
Hb
|
0.240
|
0.017
|
0.303
|
0.03
|
0.263
|
0.016
|
Plasma glucose
|
-0.172
|
-0.265
|
-0.146
|
-0.356
|
-0.186
|
-0.261
|
Albumin, g/L
|
0.125
|
0.087
|
0.144
|
0.089
|
0.148
|
0.114
|
Alanine aminotransferase
|
0.162
|
-0.101
|
0.197
|
-0.102
|
0.183
|
-0.079
|
Creatinine
|
-0.066
|
-0.104
|
0.009
|
0.019
|
-0.085
|
-0.114
|
TC
|
-0.014
|
-0.067
|
0.059
|
0.003
|
0.004
|
-0.043
|
HDL
|
-0.15
|
-0.005
|
-0.202
|
-0.016
|
-0.154
|
-0.015
|
The data shown in bold are variables with values of ǀrǀ> 0.30 and p< 0.01.
VC max: maximum value of vital capacity, FVC: forced vital capacity, FEV3: forced expiratory volume in 3 second;BMI: body mass index, SBP: systolic pressure, DBP: diastolic blood pressure, PP: pulse pressure, Hb: haemoglobin, TC: triglycerides, HDL: high-density lipoprotein
We conducted a series of multivariate linear regression analyses to explore the relationships between pulmonary function (VC max, FVC and FEV3) and four independent variables (HGS, age, height, SBP and PP) (Table 6). The results showed that height and HGS had positive coefficients in multivariate linear regression models, and age and PP had negative coefficients, while SBP was excluded. In male, FVC, VC max and FEV3 increased by 0.02L, 0.023L and 0.03L in per 1 kg increase in HGS, respectively. The average annual decrease in FVC, VC max and FEV3 in male was 0.024L, 0.022L and 0.028L, respectively. Compared with male, the effect of age and HGS on pulmonary function was smaller in female, while the effect of height was greater.
Table 6. The coefficients of variables in multivariate linear regression models assessing the associations between pulmonary parameters and HGS
Gender
|
Independent
Variables
|
Unstandardized coefficients
|
Standardized coefficients (95% CI)
|
age
|
HGS
|
height
|
PP
|
age
|
HGS
|
height
|
PP
|
Male
|
FVC
|
-0.024
|
0.020
|
0.012
|
-0.010
|
-0.449 (-0.524, -0.374)
|
0.225 (0.158, 0.293)
|
0.148 (0.086, 0.210)
|
-0.130 (-0.182, -0.065)
|
|
VC max
|
-0.022
|
0.023
|
0.014
|
-0.010
|
-0.396 (-0.468, -0.324)
|
0.254 (0.177, 0.320)
|
0.168 (0.096, 0.228)
|
-0.134 (-0.201, -0.067)
|
|
FEV3
|
-0.028
|
0.030
|
/
|
/
|
-0.464 (-0.580, -0.348)
|
0.303 (0.182, 0.424)
|
/
|
/
|
Female
|
FVC
|
-0.017
|
0.018
|
0.034
|
-0.005
|
-0.407 (-0.479, -0.359)
|
0.182 (0.121, 0.233)
|
0.319 (0.272, 0.375)
|
-0.097 (-0.155, -0.039)
|
|
VC max
|
-0.016
|
0.017
|
0.036
|
-0.005
|
-0.393 (-0.467, -0.344)
|
0.175 (0.124, 0.226)
|
0.337 (0.290, 0.393)
|
-0.101 (-0.162, -0.040)
|
|
FEV3
|
-0.021
|
0.019
|
0.035
|
/
|
-0.447 (-0.532, -0.362)
|
0.194 (0.102, 0.286)
|
0.324 (0.231, 0.407)
|
/
|
HGS: handgrip strength, PP: pulse pressure, FVC: forced vital capacity, VC max: maximum value of vital capacity, FEV3: forced expiratory volume in 3 second, VC IN: inspiratory vital capacity. All coefficients listed are with p< 0.01.