While handgrip strength is associated with osteoporosis in the older population and muscle weakness is related to a reduction in bone mineral density, no study has yet assessed the association between relative hand grip strength (RHGS) and osteoporosis in the older Korean population. This study assessed the associations between RHGS and osteoporosis in Korean older women aged over 60 years.
We used data of 4,179 older women from the Korea National Health and Nutrition Examination Survey (KNHANES) from 2014 to 2018. We applied binomial logistic regression to identify an association between RHGS and osteoporosis while controlling for other covariates such as age; socioeconomic status; smoking behavior; alcohol consumption, laboratory test results; and the prevalence of hypertension, diabetes mellitus, thyroid disease, and obesity.
RHGS was significantly associated with osteoporosis of the left hand in older Korean women. RHGS levels 2 and 4 of the left hand showed an inverse association with the prevalence of osteoporosis in female participants aged 60–69 years (odds ratio [OR]=0.637; 95% confidence interval [CI], 0.452–0.898; p=0.010; and OR=0.496; 95% CI, 0.258–0.956; p=0.036, respectively) but not in those aged over 70 years and in the right hand.
osteoporosis was significantly associated with left-hand RHGS in 60–69-year-old women, and the osteoporosis risks decreased by approximately 36.3% and 50.4% in women with RHGS levels 2 and 4, respectively. RHGS may be used to predict osteoporosis in pre-clinical settings such as public health care institutes.
Osteoporosis is a musculoskeletal disease characterized by decreasing bone mineral density (BMD) and mass that can result in damaged bone structure. BMD can be decreased by losing too much bone or generating too little bone. The consequent reduction in bone strength is clinically evidenced by bone fractures. Aging, genetics, nutrition, vitamin and mineral deficiencies, lifestyle choices, smoking history, hormonal production, and medications reportedly contribute to skeletal fragility. An imbalance in bone metabolism is a cause of osteoporosis.
Osteoporosis often leads to musculoskeletal disorders that cause hip, spine, and wrist fractures that decrease the quality of life of patients. Moreover, it can increase the risk of mortality.
Moreover, the International Osteoporosis Foundation reported that over 30% of women older than 50 years experienced osteoporotic fractures.
Osteoporosis is more common in postmenopausal women owing to estrogen, which plays a critical role in bone remodeling by controlling osteoclastogenesis
Postmenopausal osteoporosis occurs because the ovarian functions stop and the interactions with bone materials do not occur naturally because of a decrease in estrogen secretion. Osteoporotic bones are reportedly susceptible to breaks owing to their porosity and sparsity. In particular, the older population experiences frequent falls due to muscle weakness, senescence of vascular functions, and other critical conditions such as visual impairment or Parkinson disease, for which patients have a very high risk of osteoporotic fractures
Handgrip strength (HGS) is a common assessment tool used to evaluate physical function, such as the maximum voluntary force of both hands, which is measured in a seated or a standing position to reflect muscle strengths of the upper limbs or lower limbs and core muscles, respectively.
Guidelines including the European Working Group on Sarcopenia in Older People, have accepted HGS as a recommended tool in the diagnostic algorithm for sarcopenia.
Lee et al.
However, no study has assessed the association between RHGS (HGS divided by the BMI) and osteoporosis in the older Korean population. Hence, this cross-sectional study investigated the association between RHGS and osteoporosis in older Korean adults aged 60–69 and 70+ years.
This study was conducted using data from the Korea National Health and Nutrition Examination Survey (KNHANES) from 2014 to 2018. This survey has been performed since 1998 by the Korea Center for Disease Control and Prevention (KCDC). The KNHANES involves a multistage stratified cluster sampling of 4,600 households and 10,000–12,000 individuals annually. Details of the survey design and data source are described elsewhere.
The dataset in the present study included survey results on health conditions obtained from general health examinations and nutritional assessments. This study included participants aged 60 years or older who completed assessments for osteoporosis and underwent HGS tests of both hands. We divided the participants into two groups based on age (60–69 years and 70+ years).
Dual-energy X-ray absorptiometry (DXA, QDR 4500A; Hologic Inc., Waltham, MA, USA) was used to measure bone mineral content and BMD in the KNHANES. The manufacturer (DEX) provided the criteria for the diagnosis of osteoporosis
HGS was measured in each hand three times using a digital grip strength dynamometer (Model T.K.K 5401; Takei Scientific Instruments Co., Tokyo, Japan). The participants were instructed to hold the dynamometer with the second proximal interphalangeal joint of the hand flexed at 90° to the handle and squeeze the handle as hard as they could in the standing position (elbow extension status). After each measurement, the participants rested for at least 30 seconds.
A recent study suggested the use of BMI for adjusting HGS as a muscle quality index.
We categorized RHGS in women into four levels according to the quartiles as previously described:
The covariates included in this study were identified by referring to previously reported factors associated with decreased HGS.
This study included the following baseline sociodemographic characteristics: age (60–69 and ≥70 years), income level (in quartiles), and education status (below elementary school, middle school graduate, high school graduate, and college graduate or above). There were also several variables related to health-related behaviors, including alcohol consumption classified into six categories (none, <1/month, about 1/month, 2–4/month, 2–3/week or ≥4/week); smoking behavior classified into four categories (never, past smoking, smoking sometimes, or smoking daily); walking exercise indicated by three categories (never, 1–6 days/week, or daily); muscle exercise divided into three categories (never, 1–4 days/week or ≥5 days/week); aerobic activity classified into two categories (yes or no); DM prevalence (yes or no); family medical history of hypertension (HTN) in the father, mother, brother, or sister (yes or no); and results of laboratory tests such as those of systolic blood pressure (SBP), diastolic blood pressure (DBP), and fasting blood sugar (FBS), cholesterol, triglyceride (TG), aspartate aminotransferase (AST), and alanine aminotransferase (ALT).
The KNHANES is a complex, stratified, multistage, probability-cluster survey of a representative sample of the non-institutionalized civilian population in Korea.
The results are presented as numbers and percentages for the general characteristics of the participants. Chi-square tests were used to compare percentages to describe the general characteristics of the participants. Independent t-tests were used to assess differences in clinical variables. We performed multiple logistic regression analysis to identify associations between RHGS and osteoporosis in older participants by controlling for other covariates and determining the odds ratios (ORs) and 95% confidence intervals (CIs). The significance level was set at p<0.05. We performed these analyses using IBM SPSS Statistics for Windows, version 22.0 (IBM Corp, Armonk, NY, USA).
The mean age of the 4,179 older women included in this study using KNHANES 2014–2018 data was 70.0±6.6 years. This study included 490 (23.5%) participants with osteoporosis and 1,596 (76.5%) participants without osteoporosis in the 60–69-year group and 758 (35.8%) and 1,357 (64.2%) participants, respectively, in the 70+-year group (
We observed a significant association between right and left RHGS in the two age groups (p<0.05). The dominant hand was not significantly associated between the two groups (94.8% and 94.3% of subjects had right-hand dominance in the 60–69- and 70+-year groups, respectively). There was no association between the groups with respect to income levels. Education levels showed a significant association in both groups (p<0.05). We observed significant associations between alcohol consumption (p<0.05) and smoking behavior (p<0.05) in both groups. The prevalence of HTN, DM, and thyroid diseases showed significant associations in both groups (p<0.05) (
We observed significant differences between participants with and without osteoporosis in the 60–69-year group (p<0.05) but not in the 70+-year group (
The OR of the prevalence of osteoporosis in the 60–69-year group was 0.696 (95% CI, 0.500–0.970; p<0.05) in only RHGS level 2 of the left hand; however, we observed no significant association between the prevalence of osteoporosis and RHGS in other levels of the right hand (
After controlling for covariates such as socioeconomic status; smoking behavior; alcohol consumption; laboratory test results; and prevalence of HTN, DM, and thyroid disease, the prevalence of osteoporosis was significantly associated with RHGS level 2 (OR=0.637; 95% CI, 0.452–0.898; p=0.010) and level 4 (OR=0.496; 95% CI, 0.258–0.956; p=0.036) of the left hand in the 60–69-year group (
In this study, RHGS was significantly associated with osteoporosis in the left hand of older Korean women. RHGS levels 2 and 4 of the left hand were inversely associated with the prevalence of osteoporosis in female participants aged 60–69 years but not in those aged 70+ years and in the right hand.
Our finding of an association between RHGS and osteoporosis was similar to that of four previous studies. Karkkainen et al.
In addition, previous studies have reported an association between HGS and several chronic diseases. Ilich et al.
In this study, only RHGS of the left hand was significantly associated with the prevalence of osteoporosis in female subjects aged 60–69 years. This study included an analysis based on the dominant hand in using RHGS to predict osteoporosis diagnosis. Recent studies have reported that left key-pinch strength is less than the right key-pinch strength in right-hand-dominant subjects.
In our study, RHGS was not significantly associated with the prevalence of osteoporosis in female subjects aged 70 years or older. Recently, Kwak et al.
It is challenging to compare this study to previous studies on osteoporosis because few have reported the association between osteoporosis and HGS; while several studies showed the relationship between osteoporotic fracture and HGS,
Several limitations should be considered when interpreting the results of this study. First, the cross-sectional nature of our study prevented us in demonstrating any causal relationships between RHGS and osteoporosis prevalence. Second, we could not determine whether the participants received treatment for osteoporosis. Finally, we did not consider surgical or natural menopause. In the future, a more comprehensive study to overcome these limitations is needed. Moreover, additional studies are needed to identify causes for the differences in results between the 60–69-year and 70+-year groups as the present study did not document the causality-making differences among those results. RHGS has been reported as a significant predictor of frailty, metabolic syndrome, DM, and other musculoskeletal diseases. Moreover, it is a particularly good and quick tool to assess muscle strength.
In this study, the prevalence of osteoporosis was significantly associated with left-hand RHGS in women aged 60–69 years after adjusting for sociodemographic characteristics, lifestyle behaviors, and other health-related variables in the KNHANES data from 2014 to 2018. Furthermore, the osteoporosis risks were decreased by approximately 36.3% and 50.4% in levels 2 and 4, respectively. In contrast, RHGS was not significantly associated with osteoporosis in women aged >70 years and in the right hand.
The researchers claim no conflicts of interest.
Conceptualization, KHA, MR; Methodology, YL; Software, SL, HG; Validation, HG; Formal Analysis, SL, HG; Investigation, DYK; Writing–Original Draft Preparation, KHA; Writing–Review & Editing, YL, TYS; Supervision, MR; Project Administration, SL.
Characteristics of the subjects included in this study according to age group
Characteristic | 60–69 years | 70+ years | p-value |
---|---|---|---|
Osteoporosis | <0.001 |
||
No | 1,596 (76.5) | 1,357 (64.2) | |
Yes | 490 (23.5) | 758 (35.8) | |
Right RHGS | <0.001 |
||
Level 1 | 666 (34.6) | 1,203 (64.7) | |
Level 2 | 633 (32.9) | 461 (24.8) | |
Level 3 | 444 (23.1) | 155 (8.3) | |
Level 4 | 182 (9.5) | 41 (2.2) | |
Left RHGS | <0.001 |
||
Level 1 | 675 (34.9) | 1,227 (65.6) | |
Level 2 | 619 (32.0) | 432 (23.1) | |
Level 3 | 453 (23.4) | 163 (8.7) | |
Level 4 | 186 (9.6) | 49 (2.6) | |
Dominant hand | 0.261 | ||
Right | 1,978 (94.8) | 1,995 (94.3) | |
Left | 108 (5.2) | 120 (5.7) | |
Income level | 0.873 | ||
1st | 520 (25.0) | 521 (24.8) | |
2nd | 515 (24.8) | 534 (25.4) | |
3rd | 506 (24.3) | 522 (24.9) | |
4th | 538 (25.9) | 523 (24.9) | |
Education level | <0.001 |
||
Elementary | 1,015 (48.9) | 1,664 (80.1) | |
Middle school | 464 (22.3) | 183 (8.8) | |
High school | 398 (19.2) | 161 (7.8) | |
University | 200 (9.6) | 69 (3.3) | |
Alcohol consumption | <0.001 |
||
None | 975 (47.0) | 1,419 (68.3) | |
<1/month | 524 (25.2) | 356 (17.1) | |
About 1/month | 196 (9.4) | 95 (4.6) | |
2–4/month | 241 (11.6) | 119 (5.7) | |
2–3/week | 105 (5.1) | 51 (2.5) | |
>4/week | 35 (1.7) | 38 (1.8) | |
Smoking | 0.038 |
||
Never | 1,944 (93.7) | 1,949 (93.9) | |
Past | 66 (3.2) | 80 (3.9) | |
Sometimes | 11 (0.5) | 2 (0.1) | |
Daily | 53 (2.6) | 44 (2.1) | |
Hypertension | <0.001 |
||
No | 1,274 (61.1) | 793 (37.5) | |
Yes | 812 (38.9) | 1,322 (62.5) | |
Diabetes mellitus | <0.001 |
||
No | 1,801 (86.3) | 1,613 (76.3) | |
Yes | 285 (13.7) | 502 (23.7) | |
Thyroid disease | <0.001 |
||
No | 1,973 (94.6) | 2,054 (97.2) | |
Yes | 112 (5.4) | 60 (2.8) |
Values are presented as number (%).
RHGS, relative hand grip strength.
p<0.05,
p<0.01.
Comparisons of clinical outcomes with respect to the presence of osteoporosis according to age groups
Item | 60–69 years |
70+ years |
||||
---|---|---|---|---|---|---|
Without osteoporosis | With osteoporosis | p-value | Without osteoporosis | With osteoporosis | p-value | |
Age (y) | 64.0±2.9 | 65.1±2.8 | <0.001 |
75.8±3.5 | 75.5±3.5 | 0.092 |
BMI (kg/m2) | 24.6±3.4 | 24.2±3.2 | 0.015 |
24.7±3.4 | 24.1±3.3 | <0.001 |
SBP (mmHg) | 126.0±17.1 | 124.0±15.9 | 0.027 |
132.4±18.4 | 129.7±18.1 | 0.001 |
DBP (mmHg) | 75.7±9.4 | 74.9±8.6 | 0.090 | 71.2±10.1 | 71.3±9.7 | 0.839 |
Cholesterol (mg/dL) | 104.4±24.0 | 104.5±26.1 | 0.893 | 108.7±26.8 | 105.5±25.5 | 0.009 |
FBS (mg/dL) | 199.3±39.6 | 194.5±38.7 | 0.021 |
187.6±40.1 | 186.9±37.6 | 0.716 |
TG (mg/dL) | 134.7±82.5 | 127.2±67.7 | 0.072 | 135.2±76.7 | 135.4±101.7 | 0.978 |
AST (U/L) | 23.8±9.1 | 23.9±10.7 | 0.817 | 24.1±9.8 | 24.0±9.7 | 0.859 |
ALT (U/L) | 21.3±13.8 | 20.9±13.2 | 0.523 | 19.2±11.4 | 18.7±11.3 | 0.362 |
BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; FBS, fasting blood sugar; TG, triglyceride; AST, aspartate aminotransferase; ALT, alanine aminotransferase.
p<0.05,
p<0.01.
Associations between RHGS and osteoporosis according to age groups: unadjusted model
RHGS | 60–69 years |
70+ years |
||||||
---|---|---|---|---|---|---|---|---|
OR | 95% CI |
p-value | OR | 95% CI |
p-value | |||
LL | UL | LL | UL | |||||
Right RHGS | ||||||||
Level 1 | 1.000 | 0.680 | 1.000 | 0.821 | ||||
Level 2 | 1.042 | 0.751 | 1.446 | 0.806 | 0.934 | 0.703 | 1.241 | 0.639 |
Level 3 | 0.867 | 0.558 | 1.348 | 0.527 | 0.820 | 0.496 | 1.356 | 0.439 |
Level 4 | 1.079 | 0.588 | 1.979 | 0.807 | 0.670 | 0.262 | 1.715 | 0.404 |
Left RHGS | ||||||||
Level 1 | 1.000 | 0.073 | 1.000 | 0.509 | ||||
Level 2 | 0.696 | 0.500 | 0.970 | 0.032 |
1.057 | 0.792 | 1.410 | 0.707 |
Level 3 | 0.869 | 0.567 | 1.330 | 0.517 | 1.370 | 0.848 | 2.211 | 0.198 |
Level 4 | 0.597 | 0.319 | 1.119 | 0.107 | 1.756 | 0.726 | 4.245 | 0.211 |
OR, odds ratio, CI, confidence interval; RHGS, relative handgrip strength; LL, lower limit; UL, upper limit.
p<0.05.
Associations between RHGS and osteoporosis according to age groups: adjusted model
RHGS | 60–69 years | 70+ years | ||||||
---|---|---|---|---|---|---|---|---|
OR | 95% CI | p-value | OR | 95% CI | p-value | |||
LL | UL | LL | UL | |||||
Right RHGS | ||||||||
Level 1 | 1.000 | 0.789 | 1.000 | 0.800 | ||||
Level 2 | 0.947 | 0.673 | 1.331 | 0.753 | 0.892 | 0.656 | 1.212 | 0.464 |
Level 3 | 0.803 | 0.505 | 1.276 | 0.352 | 0.816 | 0.474 | 1.403 | 0.462 |
Level 4 | 0.898 | 0.477 | 1.694 | 0.741 | 0.667 | 0.251 | 1.775 | 0.418 |
Left RHGS | ||||||||
Level 1 | 1.000 | 0.022 |
1.000 | 0.664 | ||||
Level 2 | 0.637 | 0.452 | 0.898 | 0.010 |
0.953 | 0.698 | 1.302 | 0.763 |
Level 3 | 0.790 | 0.506 | 1.232 | 0.298 | 1.272 | 0.757 | 2.136 | 0.363 |
Level 4 | 0.496 | 0.258 | 0.956 | 0.036 |
1.390 | 0.535 | 3.613 | 0.500 |
OR, odds ratio, CI, confidence interval; RHGS, relative handgrip strength; LL, lower limit; UL, upper limit.
p<0.05.