GRIP STRENGTH DIFFERENCES BETWEEN RACIAL GROUPS AND CORRELATIONS WITH DAILY DIETARY INTAKE OF ENERGY AND PROTEIN IN THE UNITED STATES

RESULTS FROM NHANES 2011-2012

Stephanie Kuo

NTR 555: Nutrition in Epidemiology December 8, 2015

BACKGROUND AND RATIONALE

• Muscle function is an important indicator of health and nutrition status; predictive of morbidity and hospital outcomes.1,2

• Muscle biopsies of malnourished populations (anorexia, starvation) have shown evidence of structural changes and muscle atrophy.1

• Grip strength is a simple, non-invasive tool to measure muscle strength as a surrogate for atrophy.

• Grip strength itself can sensitively assess nutrition status and is predictive of disability and mortality.1,3

• NHANES data has been used to investigate differences in grip strength between age, gender, and chronic disease, but not between race and not in association with diet.4,5,6

RESEARCH QUESTION What are the differences in grip strength between racial groups in the United States, and are these differences correlated with daily energy and protein intake?

OBJECTIVES 1.  To determine the differences in grip strength

between racial groups.

2.  To determine the association between grip strength and daily dietary intake of energy and protein.

METHODS

Study Sample

• 2011-2012 cycle of NHANES

•  Individuals who completed the grip strength test on both hands while in a standing position and who reliably completed two 24-hour diet recalls

• Only includes adults aged 20+ years

Outcome Variables • Demographics: age, gender, race, poverty to income ratio,

education, marital status • Anthropometrics: BMI, weight, height, upper arm length, arm

circumference • Grip Strength Assessment: Combined grip strength

•  Handgrip dynamometer (Takei Digital Grip Strength Dynamometer, Model T.K.K.5401)

• Dietary Assessment: Energy (kcal), protein (g) •  Two 24-hour recalls •  USDA’s Food and Nutrient Database for Dietary Studies (based on

USDA’s National Nutrient Database for Standard Reference) •  Average energy and protein intake = (diet recall 1 + recall 2) ÷ 2 •  Energy and protein per kg body weight = Average energy and protein

intake ÷ body weight (kg)

Data Analysis • SPSS Statistics version 22 (IBM, Chicago, IL).

• Most continuous variables were non-normally distributed, so they were described using median (25th percentile, 75th percentile).

• Categorical variables were described using frequency [n, (%)].

• Kruskal Wallis: differences in grip strength and energy/protein intake between races. • Mann Whitney U tests for post-hoc analyses.

• Bonferonni correction: p < 0.005

• Spearman’s Rho: correlations between grip strength and dietary intake and other continuous variables

RESULTS

Table 1. Demographic Characteristics

Variable Total (n=3804)

Caucasian (n=1502)

African American (n=997)

Hispanic (n=712)

Asian (n=482)

Other (n=111)

Gender, n (%) Female 1917 (50.4) 752 (50.1) 528 (53.0) 353 (49.6) 237 (49.2) 47 (42.3)

Age (yrs) 48 (33, 62) 50 (35, 66) 49 (32, 61) 47 (32, 60) 41.5 (30, 55) 38 (28, 54)

Age, n (%) 20-29 yrs 30-39 yrs 40-49 yrs 50-59 yrs 60-69 yrs 70-79 yrs 80+ yrs

710 (18.7) 654 (17.2) 634 (16.7) 668 (17.6) 627 (16.5) 334 (8.8) 177 (4.7)

221 (14.7) 266 (17.7) 249 (16.6) 233 (15.5) 210 (14.0) 187 (12.5) 136 (9.1)

206 (20.7) 125 (12.5) 168 (16.9) 199 (20.0) 207 (20.8) 74 (7.4) 18 (1.8)

135 (19.0) 135 (19.0) 111 (15.6) 133 (18.7) 142 (19.9) 45 (6.3) 11 (1.5)

117 (24.3) 102 (21.2) 86 (17.8) 86 (17.8) 59 (12.2) 23 (4.8) 9 (1.9)

31 (27.9) 26 (23.4) 20 (18.0) 17 (15.3) 9 (8.1) 5 (4.5) 3 (2.7)

Table 1. Demographic characteristics of NHANES 2011-2012 participants with grip strength and diet recall data, stratified by race (n=3804)1

Variable Total (n=3804)

Caucasian (n=1502)

African American (n=997)

Hispanic (n=712)

Asian (n=482)

Other (n=111)

Ratio of Family Income to Poverty

2.0 (1.1, 4.2) 2.2 (1.1, 4.6) 1.8 (1.0, 3.9) 1.6 (0.8, 3.0) 3.5 (1.6, 5.0) 1.7 (1.0, 3.6)

Education, n (%) Some HS HS grad Some college College grad

772 (20.3) 790 (20.8) 1193 (31.4) 1049 (27.6)

223 (14.8) 310 (20.6) 520 (34.6) 449 (29.9)

188 (18.9) 247 (24.8) 357 (35.8) 205 (20.6)

295 (41.4) 156 (21.9) 169 (23.7) 92 (12.9)

53 (11.0) 57 (11.8) 99 (20.5) 273 (56.6)

13 (11.7) 20 (18.0) 48 (43.2) 30 (27.0)

BMI (kg/m2) 27.8 (24.1, 32.4)

27.7 (24.2, 32.0)

29.8 (25.4, 34.6)

29.0 (25.7, 33.1)

23.9 (21.7, 26.8)

27.3 (23.8, 31.5)

BMI, n (%) Underweight Normal Overweight Obese Class I Class II Class III

67 (1.8) 1091 (28.7) 1239 (32.6) 1388 (36.5) 782 (20.6) 344 (9.0) 262 (6.9)

25 (1.7) 435 (29.0) 516 (34.4) 529 (34.6) 291 (19.4) 132 (8.8) 96 (6.4)

14 (1.4) 203 (20.4) 290 (29.1) 484 (48.5) 253 (25.4) 118 (11.8) 113 (11.3)

6 (0.8) 138 (19.4) 262 (36.8) 302 (42.4) 182 (25.6) 81 (11.4) 39 (5.5)

19 (3.9) 275 (57.1) 135 (28.0) 51 (10.6) 40 (8.3) 6 (1.2) 5 (1.0)

3 (2.7) 40 (36.0) 36 (32.4) 32 (28.8) 16 (14.4) 7 (6.3) 9 (8.1)

Table 1. Demographics cont.

Table 1. Demographics cont.

Variable Total (n=3804)

Caucasian (n=1502)

African American (n=997)

Hispanic (n=712)

Asian (n=482)

Other (n=111)

Weight (kg) 78.9 (66.6, 92.7)

80.8 (68.0, 94.1)

84.9 (72.9, 100.6)

77.9 (67.3, 90.1)

64.9 (56.3, 74.5)

79.1 (65.4, 93.2)

Height (cm) 167.6 (160.4, 174.6)

169.6 (162.2, 176.7)

168.8 (162.5, 175.9)

163.5 (155.9, 170.4)

163.5 (157.0, 171.2)

169.7 (163.2, 175.9)

Upper arm length (cm)

37.1 (35.2, 39.2)

37.5 (35.7, 39.6)

38.0 (36.3, 39.8)

36.2 (34.4, 38.2)

35.2 (33.4, 37.0)

38.0 (35.5, 40.0)

Arm circum. (cm)

32.8 (29.6, 36.2)

32.6 (29.5, 36.0)

34.7 (31.3, 38.1)

33.1 (30.3, 36.2)

29.6 (27.0, 32.3)

33.5 (29.0, 36.5)

1 Values are given as median (IQR: 25th percentile, 75th percentile) unless otherwise noted

Table 2. Grip Strength and Dietary Intake

Variable Total (n=3804)

Caucasian (n=1502)

African American (n=997)

Hispanic (n=712)

Asian (n=482)

Other (n=111)

Grip Strength (kg)

67.5 (54.2, 87.0)

66.7 (54.1, 87.8)ab

71.8 (58.4, 91.3)c

64.8 (52.0, 85.4)ad

62.8 (51.6, 80.5)d

71.6 (58.1, 92.2)bc

Calories (kcal) Avg/day 1939 (1509,

2504) 1976 (1558, 2537)

1936 (1474, 2486)

1944 (1493, 2580)

1826 (1435, 2301)a

1986 (1632, 2574)

Calories (kcal/kg)

24.7 (18.3, 32.8)

24.7 (18.7, 32.5)a

22.4 (16.4, 29.8)b

24.7 (18.3, 33.8)ac

28.3 (21.7, 36.1)d

26.1 (19.4, 33.9)abcd

Protein (g) Avg/day 76.1 (56.8,

98.7) 75.0 (56.1, 98.4)a

74.2 (55.2, 95.7)a

80.9 (39.6, 105.0)b

77.0 (59.6, 98.0)ab

77.5 (59.3, 104.7)ab

Protein (g/kg) 0.96 (0.70, 1.28)

0.93 (0.69, 1.22)a

0.85 (0.64, 1.14)b

1.03 (0.74, 1.38)ac

1.21 (0.89, 1.54)d

0.94 (0.73, 1.33)abcd

Table 2. Comparison of grip strength and dietary intake of calories and protein by race in NHANES 2011-2012 participants (n=3804)1, 2, 3, 4

1 All values are given as median (IQR: 25th percentile, 75th percentile) 2 Races with different letter superscripts are significantly different from each other 3 All comparisons were completed using Mann Whitney U tests 4 After Bonferroni Correction, significance set at p < 0.005

Figure 1. Differences in Grip Strength by Race

Figure 1. Kruskal-Wallis and Mann Whitney tests with Bonferroni correction were used to make pairwise comparisons of the groups. Significant differences were found between six of the ten pairs: Blacks and Whites (p < 0.001), Blacks and Hispanics (p < 0.001), Blacks and Asians (p < 0.001), Other and Hispanic (p = 0.003), Other and Asians (p < 0.001), and Whites and Asians (p < 0.001). Races with different (letters) are significantly different from each other.

Variables Total

(n=3804) Caucasian (n=1502)

African American (n=997)

Hispanic (n=712)

Asian (n=482)

Other (n=111)

Grip Strength Age -0.296** -0.369** -0.248** -0.355** -0.178** -0.156

(p = 0.103) Ratio of family income:poverty

0.057* 0.052 (p = 0.051)

0.088** 0.089** 0.066 (p = 0.167)

0.042 (p = 0.667)

BMI 0.081** 0.088** -0.016 (p = 0.609)

-0.024 (p = 0.527)

0.196** 0.295** (p = 0.002)

Weight 0.422** 0.430** 0.309** 0.397** 0.569** 0.577** Height 0.740** 0.755** 0.711** 0.782** 0.748** 0.735** Upper arm length 0.602** 0.585** 0.549** 0.642** 0.669** 0.683**

Arm circum. 0.350** 0.346** 0.265** 0.297** 0.468** 0.504**

Table 3. Correlations with Grip Strength

1 Values are given as Spearman’s Rho. ** p < 0.01 * p < 0.05

Table 3. Correlations between combined grip strength and demographic and anthropometric variables in NHANES 2011-2012 participants, stratified by race (n=3804)1

Variables Total

(n=3804) Caucasian (n=1502)

African American (n=997)

Hispanic (n=712)

Asian (n=482)

Other (n=111)

Grip Strength Avg kcals/day 0.400** 0.434** 0.347** 0.437** 0.347** 0.443** Avg g protein/day 0.385** 0.427** 0.356** 0.413** 0.338** 0.434**

Avg kcals/kg 0.115** 0.140** 0.140** 0.212** 0.042 (p = 0.362)

0.010 (p = 0.916)

Avg g protein/kg 0.127** 0.169** 0.160** 0.210** 0.078

(p = 0.088) 0.065 (p = 0.501)

Table 3. Correlations cont.

1 Values are given as Spearman’s Rho. ** p < 0.01 * p < 0.05

Correlations between combined grip strength and demographic and anthropometric variables in NHANES 2011-2012 participants, stratified by race (n=3804)1

Figure 2a. Correlations with Grip Strength

Figure 2a. In NHANES 2011-2012 participants (n=3804), Spearman’s correlation analysis indicated statistically significant positive relationships with daily dietary intake of energy (rs = 0.400, p < 0.001) and protein (rs = 0.385, p < 0.001), indicating medium effect sizes.

Figure 2b. Correlations with Grip Strength

Figure 2b. In NHANES 2011-2012 participants (n=3804), Spearman’s correlation analysis indicated that when calorie and protein intakes described as calories per kilogram of body weight and grams of protein per kilogram of body weight, a statistically significant positive relationship was still observed, however the effect sizes became small (rs = 0.115, p < 0.001 and rs = 0.127, p < 0.001, respectively).

CONCLUSIONS •  Blacks had the highest grip strength, followed by

Other, Whites, Hispanics, and Asians.

•  Total calorie and protein intake were only moderately associated with grip strength.

•  Grip strength was more associated with measures of body stature, like height and upper arm length.

DISCUSSION

• Mixed findings regarding grip strength and energy/protein intake: • Rahi, 2015: Adequate energy intake did not protect against

functional decline, while adequate protein intake (1 g/kg) did maintain muscle strength and decreases functional decline in women.7

• Association between grip strength and height is consistent with other studies: • Ramlagan, 2014: In South African men and women (n=3840),

multivariate analyses showed that height was positively associated with grip strength [β = 0.19 (0.08 to 0.30), p < 0.001 for men; β = 0.20 (0.08 to 0.33), p < 0.01 for women].8

Limitations • Dietary intake is self-reported and relies memory

• Physical activity was not analyzed

• Nutrients analyzed included energy and protein only

Future Research • Examine physical activity and overall diet quality

• More research including Asians

•  Investigate appropriateness of grip strength reference ranges for body stature rather than gender

References 1.  Norman K, Stobäus N, Gonzalez MC, Schulzke J-, Pirlich M. Hand grip strength: Outcome predictor

and marker of nutritional status. Clin Nutr 2011;30:135-42.

2.  Cooper R, Strand BH, Hardy R, V Patel K, Kuh D. Physical capability in mid-life and survival over 13 years of follow-up: British birth cohort study. BMJ (Online) 2014;348.

3.  Singh DKA, Manaf ZA, Yusoff NAM, Muhammad NA, Phan MF, Shahar S. Correlation between nutritional status and comprehensive physical performance measures among older adults with undernourishment in residential institutions. Clin Interventions Aging 2014;9:1415-23.

4.  Mainous AG, Tanner RJ, Anton SD, Jo A. Grip Strength as a Marker of Hypertension and Diabetes in Healthy Weight Adults. Am J Prev Med 2015.

5.  Perna FM, Coa K, Troiano RP, Lawman HG, Wang CY, Li Y, Moser RP, Ciccolo JT, Comstock BA, Kraemer WJ. U.S. Population Muscular Grip-Strength Estimates from the National Health and Nutrition Examination Survey (NHANES) 2011-2012. J Strength Cond Res 2015;

6.  Araujo AB, Chiu GR, Kupelian V, Hall SA, Williams RE, Clark RV, McKinlay JB. Lean mass, muscle strength, and physical function in a diverse population of men: A population-based cross-sectional study. BMC Public Health 2010;10.

7.  Rahi B, Morais JA, Gaudreau P, Payette H, Shatenstein B. Energy and protein intakes and their association with a decline in functional capacity among diabetic older adults from the NuAge cohort. Eur J Nutr 2015.

8.  Ramlagan S, Peltzer K, Phaswana-Mafuya N. Hand grip strength and associated factors in non-institutionalised men and women 50 years and older in South Africa. BMC Res Notes 2014;7.