Smartphone Use and Inflammation at 2-Year Follow-Up in College Students: The Mediating Role of Physical Activity

Figures & data

Table 1 Descriptive Statistics of the Study Samples (n=210)

Variables	Baseline	2-Year Follow-Up
Age (years, M±SD)	18.7±1.0
Males (n, %)	82 (39.0)
Residence
Rural (n,%)	182 (86.7)
Urban (n,%)	28 (13.3)
Health status
Good (n,%)	118 (56.2)
Medium (n,%)	88 (41.9)
Poor (n,%)	4 (1.9)
SES scores (M±SD)	8.27±2.14
BMI (kg/m^2, M±SD)	21.00±2.51
Duration of smartphone use (hours, M±SD)	3.07±0.80	2.22±1.19
Total scores of smartphone dependence (M±SD)	23.91±8.30	21.95±8.95
Smartphone dependence (n,%)	64 (30.5)	45 (21.4)
Total PA levels (MET-min/w, M±SD)	3.34±0.37	3.29±0.45
Physical activity levels
High group (n,%)	79 (37.6)	82 (39.0)
Medium group (n,%)	116 (55.2)	91 (43.3)
Low group (n,%)	15 (7.1)	37 (17.6)
TNF-α (M±SD)	0.83±0.21	0.37±0.21
IL-6 (M±SD)	0.76±0.35	−0.40±0.75
IL-1β (M±SD)	0.41±0.28	0.34±0.22
CRP (M±SD)	−0.39±0.58	−0.06±0.36

Notes: Total PA levels, TNF-α, IL-6, IL-1β and CRP were all log-transformed.

Abbreviations: M, mean; SD, standard deviation; SES, socioeconomic status; BMI, body mass index; PA, physical activity; TNF-α, tumor necrosis factor-α; IL-6, interleukin-6; IL-1β, interleukin-1β; CRP, C-reactive protein.

Table 2 Bivariate Correlations Between Smartphone Use, Physical Activity and Inflammation

Variables	1	2	3	4	5	6
1. Duration of smartphone use^a
2. Total scores of smartphone dependence^a	0.33**
3. Total PA levels (MET-min/w) ^b	−0.11	−0.18**
4. TNF-α^b	−0.12	−0.09	0.21**
5. IL-6^b	0.08	0.03	−0.26**	0.04
6. IL-1β^b	−0.12	−0.06	0.08	0.47**	0.36**
7. CRP^b	0.01	0.07	0.06	0.13	−0.16*	−0.01

Notes: *P<0.05, **P<0.01; Total PA levels, TNF-α, IL-6, IL-1β and CRP were all log-transformed. ^aBaseline; ^bFollow-up.

Abbreviations: PA, physical activity; TNF-α, tumor necrosis factor-α; IL-6, interleukin-6; IL-1β, interleukin-1β; CRP, C-reactive protein.

Figure 1 Comparison of the inflammation levels in different groups of smartphone dependence.

Notes: TNF-α, IL-6, IL-1β and CRP were all log-transformed.

Abbreviations: TNF-α, tumor necrosis factor-α; IL-6, interleukin-6; IL-1β, interleukin-1β; CRP, C-reactive protein; SD, smartphone dependence; Non-SD, non-smartphone dependence.

Figure 2 Comparison of the inflammation levels in different groups of physical activity.

Notes: TNF-α, IL-6, IL-1β and CRP were all log-transformed. *P<0.05; ** P<0.01; *** P<0.001.

Abbreviations: TNF-α, tumor necrosis factor-α; IL-6, interleukin-6; IL-1β, interleukin-1β; CRP, C-reactive protein; H-PA, high physical activity group; M-PA, medium physical activity group; L-PA, low physical activity group.

Table 3 The Mediating Effect of Physical Activity on the Associations Between Smartphone Use and Inflammation Among College Students

	Estimate (S.E.)				Indirect (S.E.)
	a	b	c′	c	ab	95% CI
Duration of smartphone use
TNF-α	−0.177 (0.064)**	0.154 (0.048)**	−0.016 (0.030)	−0.043 (0.028)	−0.027 (0.012)*	−0.052, −0.007
IL-6	−0.177 (0.064)**	−0.115 (0.059)	−0.040 (0.072)	−0.020 (0.071)	0.020 (0.012)	0.001, 0.046
IL-1β	−0.177 (0.064)**	0.014 (0.021)	−0.047 (0.024)	−0.049 (0.023)*	−0.002 (0.004)	−0.011, 0.004
CRP	−0.177 (0.064)**	−0.213 (0.081)**	−0.028 (0.039)	0.010 (0.044)	0.038 (0.021)	0.004, 0.086
Smartphone dependence
TNF-α	−0.898 (0.354)*	0.155 (0.047)**	−0.075 (0.163)	−0.214 (0.167)	−0.139 (0.070)	−0.288, −0.017
IL-6	−0.898 (0.354)*	−0.107 (0.061)	−0.044 (0.393)	0.053 (0.383)	0.096 (0.075)	−0.004, 0.289
IL-1β	−0.898 (0.354)*	0.021 (0.021)	−0.076 (0.115)	−0.095 (0.115)	−0.019 (0.021)	−0.068, 0.013
CRP	−0.898 (0.354)*	−0.229 (0.084)**	−0.565 (0.247)*	−0.359 (0.238)	0.206 (0.109)	0.020, 0.421

Notes: Total PA levels, TNF-α, IL-6, IL-1β and CRP were all log-transformed. *P<0.05, **P<0.01; ab=indirect effect; c′=direct effect; c=total effect.

Abbreviations: TNF-α, tumor necrosis factor-α; IL-6, interleukin-6; IL-1β, interleukin-1β; CRP, C-reactive protein; CI, confidence interval; S.E., standard error.