Physical Activity and Cognition: A Mediating Role of Efficient Sleep

Figures & data

Table 1 Age Differences in Mean (SD) or Frequency (%) for Demographic and Health Characteristics, Physical Activity, Sleep, and Cognitive Performance

	Young	Older	Difference t(110)	p
N	59	53
Age	23.05 (2.42)	62.68 (6.08)	46.17	< 0.001
Education	16.09 (1.65)	15.22 (3.05)	1.90	0.06
N Female	38 (64.4%)	36 (67.9%)	0.38	0.689
N African American/Black	7 (11.9%)	14 (26.4%)
N Asian	3 (5.1%)	0
N Caucasian/White	48 (81.4%)	39 (73.6%)
N Pacific Islander	1 (1.7%)	0
MMSE	29.58 (0.70)	28.89 (1.03)	4.18	< 0.001
Geriatric Mood Scale	2.04 (2.29)	1.50 (2.25)	1.19	0.237
BMI	24.91 (6.07)	29.07 (5.85)	3.68	< 0.001
N Smoker	4 (6.8%)	14 (26.4%)	2.91	0.004
Self-report sleep apnea	0	8 (15%)	3.44	0.001
METs	1.87 (0.34)	1.51 (0.32)	5.65	< 0.001
Sleep Efficiency	0.83 (0.07)	0.82 (0.09)	0.47	0.643
Total sleep time (mins)	382.51 (59.80)	355.83 (67.76)	2.21	0.029
Working Memory	0.12 (0.45)	–0.13 (0.57)	2.60	0.010
Switching	0.29 (0.60)	–0.32 (0.628)	5.32	< 0.001
Inhibition	0.12 (0.49)	–0.12 (0.47)	2.65	0.009
Verbal Ability & Fluency	0.20 (0.63)	–0.22 (0.77)	3.13	0.002
Memory Recall	0.36 (0.86)	–0.40 (1.00)	4.26	< 0.001
Processing Speed	0.50 (0.55)	–0.56 (0.74)	8.71	< 0.001

METs were limited to minutes awake. MMSE reflects score using the backwards spelling of the word world.

Figure 1 Set of hypothesized (a) and alternative (b & c) mediation models: (a) hypothesized model whereby sleep efficiency is mediator in the relationship between physical activity and executive control; (b) total sleep time as a mediator in the relationship between physical activity and executive control; (c) age a moderator of the mediating role of sleep efficiency in the relationship between physical activity and executive control.

Table 2 Associations Among METs, Sleep Variables, and Cognitive Variables

	Zero-order correlations with METs (r)	p	Fully adjusted regression (β)	p
Sleep Efficiency	0.15	0.114	0.23	0.037
Total Sleep Time	0.13	0.170	0.08	0.452
Working Memory	0.20	0.038	0.13	0.251
Switching	0.15	0.108	–0.08	0.449
Inhibition	0.22	0.021	0.08	0.436
Verbal Ability & Fluency	0.15	0.112	–0.01	0.908
Recall	0.19	0.042	0.04	0.670
Processing Speed	0.43	< 0.001	0.13	0.131

Fully adjusted regression model includes age, sex, and education as covariates. Significant associations are highlighted in bold font.

Figure 2 Beta values for associations between METs, sleep efficiency, and each cognitive domain accounting for age, sex, and education. †p < 0.1, *p < 0.05, **p < 0.01, ***p < 0.001. Line thickness represents the strength of the association. Nonsignificant relationships are represented by dotted lines. Exact p values for regressions between sleep efficiency and performance are presented in the supplementary materials section. Other p values are presented where results are reported.

Table 3 Indirect Mediating Role of Sleep Efficiency on the Relationship Between Mets and Cognition

Domain	Effect (Boot SE)	Lower: Upper 95% Confidence Interval
Working Memory	0.08 (0.06)	0.001: 0.28
Switching	0.14 (0.08)	0.023: 0.36
Inhibition	0.05 (0.04)	–0.002: 0.15
Verbal Ability & Fluency	0.15 (0.09)	0.02: 0.41
Recall	0.13 (0.08)	0.01: 0.35
Processing Speed	0.08 (0.06)	–0.0004: 0.26

Significant mediation is highlighted in bold font.

Table 4 Indirect Mediating Role of Total Sleep Time in the Relationship Between Mets and Cognition

Domain	Effect (Boot SE)	Lower: Upper 95% Confidence Interval
Working Memory	0.02 (0.04)	–0.03: 0.17
Switching	0.03 (0.05)	–0.03: 0.18
Inhibition	0.01 (0.02)	–0.01: 0.10
Verbal Ability & Fluency	0.02 (0.04)	–0.02: 0.20
Recall	0.02 (0.04)	–0.03: 0.17
Processing Speed	0.02 (0.03)	–0.02: 0.14