Table 2.

Assessment of heterogeneity among reports of the association between physical activity and global DNA methylation

Subgroup	Estimates (n)	SMD (95% CI); P	I²	Meta-regression P
Study demographics
Mean age
<50	4	−0.10 (−0.51–0.31); P = 0.50	84.9%	0.25
50–<60	6	0.37 (−0.04–0.78); P = 0.08	88.4%
60+	4	0.21 (−0.15–0.57); = 0.25	87.2%
% Female
<60	5	0.36 (0.02–0.70); P = 0.04	86.1%	0.07
60+	7	0.00 (−0.12–0.12); P = 0.99	24.6%
Country
North American	8	0.26 (−0.03–0.55); P = 0.08	85.9%	0.73
Other	6	0.09 (−0.28–0.46); P = 0.64	87.4%
Physical activity measure
Study design
Intervention	6	0.25 (−0.27–0.77); P = 0.34	92.2%	0.66
Observational	8	0.12 (−0.06–0.31); P = 0.19	73.4%
Measurement type
Self-reported	6	0.16 (−0.07–0.39); P = 0.17	80.7%	0.99
Other^a	8	0.19 (−0.21–0.59); P = 0.34	89.4%
Duration of physical activity^b
Long-term	10	0.29 (0.04–0.54); P = 0.02	87.8%	0.11
Acute	4	−0.12 (−0.59–0.36); P = 0.63	83.7%
DNA methylation assessment
Genomic context
Global	2	−0.09 (−0.29–0.12); P = 0.42	0.00%	0.61
Repetitive elements	9	0.25 (0.00–0.49); P = 0.048	85.4%
LUMA	3	0.15 (−0.84–1.14); P = 0.77	94.2%
Assay type
Non-LUMA	11	0.18 (−0.02–0.39); P = 0.08	82.9%	0.92
LUMA	3	0.15 (−0.84–1.14); P = 0.77	94.2%
Tissue
Blood	13	0.25 (0.05–0.45); P = 0.02	84.2%	0.01
Muscle	1	−0.90 (−1.38 to −0.42); P < 0.01	—

↵^aOther includes intervention studies and observational studies with objective assessments via accelerometry.
↵^bLong-term physical activity exposure was defined as a physical activity intervention that lasted 6 or more months in duration or an observational study employing self-reported physical activity levels reflective of typical levels in the past year. Acute physical activity exposure was defined as a physical activity intervention lasting less than 6 months or an observational study that assessed levels of physical activity over periods shorter than 2 months using objective measures.