Relationship Between Physical Exercise and Cognitive Impairment Among Older Adults with Type 2 Diabetes: Chain Mediating Roles of Sleep Quality and Depression

Figures & data

Figure 1 A model of chain mediating effects of sleep quality and depression between physical exercise and cognitive impairment.

Table 1 Descriptive Analysis of Sample Characteristics (n = 2646)

	M ± SD	Range	n	%
Age (years)	69.7 ± 6.2	60–100
Cognitive impairment	2.8 ± 4.2	0–30
Depression	3.2 ± 4.4	0–24
Number of years with T2DM	8.7 ± 6.5	0–41
Self-reported health status	2.9 ± 1.0	1–5
Physical exercise
No			1375	52.0
Yes			1271	48.0
Sleep quality
Poor			91	3.4
General			1449	54.8
Good			1106	41.8
Sex
Male			1071	40.5
Female			1575	59.5
Marital status
Married			2239	84.6
Other			407	15.4
Educational level
Primary school or below			1474	55.7
Junior high school			835	31.6
Senior high school or above			337	12.7
Job status
Employed/retire			1220	46.1
Unemployed			1426	53.9
Annual household income (RMB)
< 20,000			1560	59.0
20,000–50,000			712	26.9
50,000–100,000			322	12.2
> 100,000			52	2.0
Self-reported T2DM control effects
Very good			393	14.9
Relatively stable			1703	64.4
Mediocre			522	19.7
Little			28	1.1

Abbreviations: M, mean; SD, standard deviation; T2DM, type 2 diabetes mellitus.

Table 2 Correlation Analysis of Variables

	1	2	3	4	5	6	7	8	9	10	11	12	13
1. Physical exercise	—
2. Cognitive impairment	−0.186**	—
3. Sleep quality	0.322**	−0.185**	—
4. Depression	−0.176**	0.443**	−0.224**	—
5. Age	0.000	0.210**	−0.036	0.150**	—
6. Sex	−0.041*	0.111**	−0.102**	0.072**	0.015	—
7. Marital status	−0.053**	0.130**	−0.042*	0.100**	0.269**	0.102**	—
8. Educational level	0.073**	−0.191**	0.043*	−0.071**	−0.212**	−0.278**	−0.142**	—
9. Job status	0.036	0.071**	−0.008	0.030	0.108**	0.167**	0.094**	−0.337**	—
10. Annual household income	−0.021	−0.074**	−0.042*	−0.012	−0.088**	−0.124**	−0.114**	0.397**	−0.384**	—
11. Self-reported health status	−0.206**	0.282**	−0.264**	0.406**	0.140**	0.061**	0.108**	−0.058**	−0.005	0.008	—
12. Number of years with type 2 diabetes mellitus (T2DM)	0.004	0.006	−0.042*	0.082**	0.114**	−0.007	0.022	0.066**	−0.037	0.114**	0.051**	—
13. Self-reported T2DM control effect	−0.167**	0.093**	−0.178**	0.139**	−0.009	0.030	0.004	0.000	0.000	0.010	0.265**	0.062**	—

Notes: *p < 0.05, **p < 0.01.

Table 3 Regression Analysis of Physical Exercise, Sleep Quality, and Depression on Cognitive Impairment

Independent Variable	Sleep Quality (M1)			Depression (M2)			Cognitive Impairment (Y)
		Coeff.	t		Coeff.	t		Coeff.	t
Physical exercise (X)	a1	0.2968***	14.5143	a2	−0.5326***	−3.6248	c’	−0.6858***	−4.4804
Sleep quality (M1)				d	−0.7036***	−5.2226	b1	−0.3397*	−2.4143
Depression (M2)							b2	0.3866***	19.0965
Fit index
R	0.4003***			0.4447***			0.5081***
R^2	0.1602			0.1977			0.2582
F	50.2668			59.0109			76.3619

Notes: *p < 0.05, ***p < 0.001.

Table 4 Analysis of Chain Mediating Effects

	Effect	Boot SE	95% Confidence Interval		Proportion
			Lower	Upper
Total effect	−1.0732	0.1475	−1.3652	−0.7862
Direct effect of physical exercise	−0.6858	0.1461	−0.9702	−0.3974	63.90%
Indirect effect	−0.3875	0.0724	−0.5369	−0.2521	36.11%
Physical exercise → sleep quality → MMSE	−0.1008	0.0441	−0.1889	−0.0166	9.39%
Physical exercise → depression → MMSE	−0.2059	0.0618	−0.3359	−0.0943	19.19%
Physical exercise → sleep quality → depression → MMSE	−0.0807	0.0181	−0.1171	−0.0469	7.52%

Abbreviations: MMSE, cognitive impairment. 95% confidence intervals were based on BC‐bootstraps with 10,000 resamples. Proportion, ratio to total effect.

Data Sharing Statement

The data used to support the conclusions of this study can be obtained from the corresponding authors upon reasonable request.