Physical activity does not alter prolactin levels in post-menopausal women: results from a dose-response randomized controlled trial

Table 2 Stratified analyses of changes in prolactin between high volume and moderate volume exercise groups in BETA, 2010–2013 (n = 386)

Stratification variables	Prescribed exercise duration	n	6 months percent change from baseline	12 months percent change from baseline	Treatment effect^a		Between-group P^b
Stratification variables	Prescribed exercise duration	n	6 months percent change from baseline	12 months percent change from baseline	Ratio of HIGH:MOD	95% CI	Between-group P^b
Time at high intensity^c
<60% prescribed	MODERATE	17	−2.0	−6.4	1.06	0.93 – 1.21	0.40
	HIGH	44	8.0	−0.3
≥60% prescribed	MODERATE	41	−5.1	−1.5	1.01	0.88 – 1.17	0.85
	HIGH	36	0.5	−1.2			0.85
BMI^d
< 30	MODERATE	116	15.1	16.0	0.98	0.91, 1.06	0.59
	HIGH	121	−4.7	−4.7
≥ 30	MODERATE	75	11.3	3.6	1.05	0.95, 1.15	0.36
	HIGH	74	7.7	−1.6			0.36
VO_2max level^e
< 27.2 ml/kg min	MODERATE	93	12.7	2.5	1.04	0.96, 1.13	0.38
	HIGH	98	3.7	−2.2
≥ 27.2 ml/kg min	MODERATE	98	14.4	19.8	0.98	0.90, 1.06	0.57
	HIGH	97	−3.9	−5.0			0.57
Total body fat^f
< 29.7 kg	MODERATE	94	9.1	8.9	0.98	0.90, 1.07	0.61
	HIGH	99	−4.7	−3.8
≥ 29.7 kg	MODERATE	97	18.1	13.0	1.03	0.95, 1.12	0.48
	HIGH	96	4.7	−3.3			0.48

^aHIGH:MODERATE ratio of geometric means for prolactin levels over 12 months adjusted for prolactin level at baseline. A ratio <1.0 indicates lower prolactin concentrations in the HIGH exercise group at 6 and 12 months; a ratio >1.0 indicates lower prolactin concentrations in the MODERATE exercise group; a ratio equal to 1.0 indicates no difference in prolactin concentrations between the HIGH and MODERATE exercise groups
^bP for testing the HIGH-MODERATE group difference over 12 months from the linear mixed model, adjusted for prolactin level at baseline
^cIncluded n = 138 women for whom, across weeks 13–52 (at full prescription), average adherence in the exercise logs was 90–100% in the MODERATE group (135–150 min/week; n = 58) or ≥90% in the HIGH group (≥270 min/week; n = 80). Time at high intensity was defined as time exercising at an intensity of 60–80% heart rate reserve averaged for each participant over 52 weeks. Cut points for the stratified analysis were 60% of the prescribed durations, i.e., 90 min/week in the MODERATE group and 180 min/week in the HIGH group
^dBody mass index at baseline
^eCut point of the baseline VO_2max level for the stratified analysis were the median value for all study participants (MODERATE and HIGH group)
^fCut point of the baseline total body fat level for the stratified analysis were the median value for all study participants (MODERATE and HIGH group)

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