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Of the original CHARLS participants, 4,802 males (46.7%) and 5,478 females (53.3%) accepted follow-up interviews. The age of participants at baseline ranged from 45 to 96 years old, and the median number of years of follow-up was seven years. Baseline characteristics are summarized in Table 1. The quartiles of grip strength at baseline were 30, 37, and 44 kg for males and 20, 25, and 30 kg for females. The majority of participants (male, 3,618, 75.3%; female, 4,348, 79.4%) were of agricultural hukou. Before the follow-up, 1,106 death events had occurred, and these comprised 1,787 heart disease cases, 317 for stroke, and 1,591 for chronic lung diseases. For behavioral risk factors, 1,210 (25.2%) males and 4,796 (87.6%) females reported current tobacco use, and 2,243 (46.7%) males and 4,796 (87.6%) females reported currently drinking alcohol. For metabolic risk factors, 3,667 (21.4%) participants reported hypertension and 903 (5.3%) reported diabetes.
Baseline
characteristics
(N = 10,280)Male (n = 4,802) Female (n = 5,478) P SMD < 30 kg
(n = 1,201)30– kg
(n = 1,200)37– kg
(n = 1,219)> 44 kg
(n = 1,182)< 20 kg
(n = 1,455)20– kg
(1,401)25– kg
(n = 1,448)> 30 kg
(n = 1,174)Age, mean (SD) 66.84
(9.45)61.87
(8.83)58.24
(8.23)54.59
(7.28)65.08
(10.44)60.43
(9.04)57.47
(8.50)54.87
(7.79)< 0.001 1.006 Education level, n (%) < 0.001 0.322 No formal education 579
(48.2)442
(36.8)338
(27.8)227
(19.2)1,079
(74.2)884
(63.1)804
(55.5)548
(46.7)Primary school 342
(28.5)336
(28.0)372
(30.5)283
(23.9)200
(13.8)253
(18.1)269
(18.6)239
(20.4)Middle or high school 256
(21.3)391
(32.6)476
(39.1)612
(51.8)167
(11.5)254
(18.1)356
(24.6)370
(31.5)College or above 23
(1.9)31
(2.6)32
(2.6)60
(5.1)8
(0.6)10
(0.7)19
(1.3)17
(1.4)Married, n (%) < 0.001 0.408 Yes 1,010
(84.1)1,065
(88.8)1,135
(93.1)1,124
(95.1)1,039
(71.4)1,164
(83.1)1,277
(88.2)1,047
(89.2)No 191
(15.9)135
(11.2)84
(6.9)58
(4.9)416
(28.6)237
(16.9)171
(11.8)127
(10.8)Hukou, n (%) < 0.001 0.105 Agricultural 962
(81.7)918
(77.4)907
(75.4)831
(72.3)1,206
(84.0)1,097
(79.9)1,119
(78.9)926
(79.9)Non-agricultural 216
(18.3)268
(22.6)296
(24.6)319
(27.7)230
(16.0)276
(20.1)299
(21.1)233
(20.1)Smoking, n (%) < 0.001 0.367 Never 632
(52.7)665
(55.4)707
(58.0)691
(58.5)112
(7.7)107
(7.6)81
(5.6)59
(5.0)Formal 246
(20.5)226
(18.8)216
(17.7)207
(17.5)47
(3.2)32
(2.3)38
(2.6)31
(2.6)Current 322
(26.8)309
(25.8)295
(24.2)284
(24.0)1,295
(89.1)1,262
(90.1)1,328
(91.8)1,084
(92.3)Drinking, n (%) 0.068 0.078 Never 373
(31.1)504
(42.0)586
(48.1)596
(50.4)96
(6.6)102
(7.3)96
(6.6)95
(8.1)Formal 122
(10.2)115
(9.6)122
(10.0)140
(11.8)60
(4.1)84
(6.0)69
(4.8)79
(6.7)Current 705
(58.8)581
(48.4)511
(41.9)446
(37.7)1,298
(89.3)1,215
(86.7)1,283
(88.6)1,000
(85.2)ADL, mean (SD) 13.1
(6.3)10.5
(4.6)9.6
(4.0)8.6
(3.8)13.5
(5.6)11.5
(4.3)10.9
(3.8)10.1
(3.6)< 0.001 0.627 Physical function,
mean (SD)13.7
(5.7)11.12
(4.5)10.0
(3.6)9.1
(3.0)14.9
(5.6)12.8
(4.8)11.7
(4.2)10.9
(4.0)< 0.001 0.673 Sleep, mean (SD) 6.3
(2.1)6.3
(1.8)6.4
(1.8)6.6
(1.6)5.8
(2.2)6.0
(2.0)6.1
(1.8)6.4
(1.8)0.031 0.066 Nap, mean (SD) 40.8
(47.3)40.1
(43.9)37.8
(44.9)39.0
(41.9)27.9
(40.1)28.3
(41.1)27.4
(40.1)30.4
(42.1)< 0.001 0.114 ABSI, mean (SD) 8.4
(3.2)8.2
(2.5)8.3
(3.5)8.2
(3.4)8.6
(3.4)8.5
(3.7)8.2
(1.1)8.1
(0.8)0.004 0.095 BMI, mean (SD) 22.1
(3.8)22.8
(3.6)23.6
(3.4)24.8
(3.5)23.4
(4.1)24.0
(4.0)24.7
(4.0)25.4
(3.6)< 0.001 0.438 Fall down, n (%) 0.263 0.627 Yes 238
(20.2)220
(18.5)196
(16.2)144
(12.2)383
(27.0)314
(22.6)261
(18.2)188
(16.1)No 938
(79.8)970
(81.5)1,012
(83.8)1,034
(87.8)1,037
(73.0)1,073
(77.4)1,176
(81.8)982 (83.9) Hip fraction, n (%) 0.327 0.034 Yes 31
(2.6)18
(1.5)23
(1.9)15
(1.3)32
(2.3)28
(2.0)25
(1.7)17
(1.5)No 1,145
(97.4)1,172
(98.5)1,184
(98.1)1,164
(98.7)1,389
(97.7)1,357
(98.0)1,413
(98.3)1,153
(98.5)History of comorbidities, n (%) Hypertension 439
(36.6)394
(32.8)385
(31.6)407
(34.4)607
(41.7)494
(35.3)518
(35.8)423
(36.0)< 0.001 0.187 Cancer 7
(1.0)9
(1.3)10
(1.4)3
(0.4)6
(0.7)9
(1.1)17
(2.0)6
(0.9)0.463 0.041 Chronic lung diseases 293
(24.4)238
(19.8)211
(17.3)157
(13.3)236
(16.2)178
(12.7)171
(11.8)107
(9.1)< 0.001 0.278 Heart disease 215
(17.9)189
(15.8)170
(13.9)151
(12.8)301
(20.7)276
(19.7)252
(17.4)233
(19.8)0.018 0.075 Diabetes 109
(9.1)88
(7.3)98
(8.0)85
(7.2)147
(10.1)135
(9.6)134
(9.3)107
(9.1)< 0.001 0.098 Stroke 77
(6.4)41
(3.4)31
(2.5)28
(2.4)61
(4.2)42
(3.0)37
(2.6)19
(1.6)< 0.001 0.075 Note. P-values are based on χ2 or analysis of variance or Mann-Whitney U test. Calculated as weight in kilograms divided by height in meters squared. Measured in the sub-population of 10,280 participants. Grip strength grouped by quartiles. SMD, SD mean difference. Missing data instances: four for age, three for educational level, four for smoking, two for drinking, 177 for hukou, 114 for fall down, 114 for hip fraction, 260 for sleep hour, and 185 for nap. SD, standard deviation. Table 1. Baseline characteristics of 10,280 participants according to gender
Table 2 shows the association between grip strength and mortality hazard. After adjusting for confounders, with category 1 as the reference group, the adjusted HRs were 0.58 (0.42–0.79) in males and 0.70 (0.48–1.00) in females (category 4). A linear association was also found between the grip strength values and all-cause death risk (males, P = 274; females, P = 0.883) by using restricted spline regression. Here, we selected the median grip strength as the reference point, for males with a grip strength < 37 kg and female with a grip strength < 30 kg, grip strength and death were negatively associated (Figures 2–3). Similar patterns were found in models of quantile values of grip strength (Table 2).
Sex Outcomes death of all causes HR (95% CI) Grip strength
values (kg)Cases,
NoIncidence rate,
per 1,000
person-yearsModel 1 Model 2 Model 3 Model 4 Male (n = 4,802) < 30 335 12.3 1 [Reference] 1 [Reference] 1 [Reference] 1 [Reference] 30– 160 5.9 0.60 (0.50–0.73)* 0.64 (0.52–0.77)* 0.64 (0.52–0.77)* 0.75 (0.61–0.91)* 37– 118 4.3 0.51 (0.40–0.64)* 0.55 (0.44–0.70)* 0.55 (0.44–0.70)* 0.68 (0.54–0.87)* > 44 62 2.3 0.38(0.28–0.51)* 0.44(0.30–0.60)* 0.45 (0.33–0.60)* 0.58 (0.42–0.79)* Female (n = 5,478) < 20 240 7.4 1 [Reference] 1 [Reference] 1 [Reference] 1 [Reference] 20– 93 2.9 0.60 (0.47–0.77)* 0.61 (0.48–0.78)* 0.62 (0.48–0.79)* 0.71 (0.55–0.91)* 25– 58 1.8 0.48 (0.35–0.64)* 0.51 (0.38–0.69)* 0.52 (0.38–0.70)* 0.62 (0.45–0.84)* > 30 40 1.2 0.53 (0.37–0.76)* 0.57 (0.39–0.81)* 0.58 (0.40–0.83)* 0.70 (0.48–0.99) Note. Model 1 was adjusted for age. Model 2 was adjusted as model 1 plus BMI, ABSI, educational level, marriage, and hukou. Model 3 was adjusted as model 2 plus smoking, and drinking. All 20 items were entered simultaneously in model 4. HR, hazard ratio. Table 2. Incidence of mortality hazard according to grip strength
Figure 2. Adjusted hazard ratios (HRs) for mortality hazard according to grip strength in males. RCS, restricted cubic spline.
Figure 3. Adjusted hazard ratios (HRs) for mortality hazard according to grip strength in females. RCS, restricted cubic spline.
We compare the socioeconomic factors of participants before and after deleting those without chronic diseases. According to Table 3, the deleted 3,577 participants not responding to grip strength were significantly younger (P < 0.001), more likely not to be married (P < 0.001), had a non-agricultural hukou (P < 0.001), and had a higher educational level (P < 0.001) than those performing grip strength examination.
Variables Level No response, n (%)
n = 3,577Response, n (%)
n = 10,280P* Gender, n (%) Males 1,693 (47.4) 4,795 (46.7) 0.469 Females 1,879 (52.6) 5,478 (53.3) Age [mean (SD)] 58.16 (11.57) 60.02 (9.72) < 0.001 hukou, n (%) Agriculture 2,290 (67.5) 7,966 (79.4) < 0.001 Non-agriculture 1,104 (32.5) 2,073 (20.6) Education, n (%) No formal education 1,422 (39.9) 4,901 (47.7) < 0.001 Primary school 717 (20.1) 2,294 (22.3) Middle or high school 1,244 (34.9) 2,882 (28.0) College or above 185 (5.2) 200 (1.9) Marriage, n (%) Yes 2,700 (86.0) 8,402 (94.8) < 0.001 No 438 (14.0) 459 (5.2) Note. *P is used for comparison of dichotomous variables. Table 3. Socioeconomic factor comparison between the population that responded to and did not respond to grip strength examination
The figures show HRs for death of all causes adjusted for age, hukou, marital status, education, smoking, drinking, history of diabetes, hypertension, heart disease, stroke, chronic lung disease, cancer, history of falls, hip fraction, ADL, physical function, BMI, ABSI, and sleep/nap duration. Data were fitted by a restricted spline Cox proportional hazard regression model. The reference values were the medians: 37 kg for males (P < 0.001) and 30 kg for females (P = 0.008).
Figure 4 shows the association between grip strength and mortality hazard stratified by gender. There was no interaction effect between handgrip strength and mortality hazard (P > 0.05) for either gender. Specifically, between-group differences were statistically insignificant for any covariate. The HRs were insignificant or close to 1 in all subgroups. Additionally, the sensitivity analysis results did not significantly change in category 4 [males, 0.62 (0.44–0.86), P = 0.004; females, 0.53 (0.35–0.80), P = 0.002].
Figure 4. Gender-specific association between grip strength values and mortality hazard stratified by different factors
The figure show hazard ratios (HRs) and 95% CIs for mortality hazard adjusted for age, hukou, marital status, education, smoking, drinking, history of diabetes, hypertension, chronic lung disease, heart disease, stroke, cancer, history of falls, hip fraction, ADL, physical function, BMI, ABSI, and sleep/nap duration.
Low Grip Strength and Increased Mortality Hazard among Middle-Aged and Older Chinese Adults with Chronic Diseases
doi: 10.3967/bes2023.013
- Received Date: 2022-06-29
- Accepted Date: 2022-09-20
-
Key words:
- Grip strength /
- Death /
- Chronic disease
Abstract:
Citation: | XIE Kai Hong, HAN Xiao, ZHENG Wei Jun, ZHUANG Su Fang. Low Grip Strength and Increased Mortality Hazard among Middle-Aged and Older Chinese Adults with Chronic Diseases[J]. Biomedical and Environmental Sciences, 2023, 36(3): 213-221. doi: 10.3967/bes2023.013 |