Evidence for daily and weekly rhythmicity but not lunar or seasonal rhythmicity of physical activity in a large cohort of individuals from five different countries

Figures & data

Table I. Participant characteristics (means ± standard deviations).

	Ghana	South Africa	Jamaica	Seychelles	United States
Men
Sample size	207	236	249	230	245
Age (years)	34.6 ± 6.7	33.7 ± 5.6	34.0 ± 5.9	36.5 ± 5.1	35.6 ± 6.2
BMI (kg/m^2)	22.2 ± 2.7	22.4 ± 4.3	23.6 ± 4.5	26.5 ± 4.9	29.7 ± 7.5
Education (y)	9.2 ± 3.8	9.5 ± 2.6	10.6 ± 2.1	13.1 ± 2.4	12.7 ± 1.6
Employed (%)	98.6	91.4	90.8	97.8	85.2
Manual laborer (%)	60.9	90.4	61.8	54.4	67.1
Women
Sample size	293	268	251	270	257
Age (years)	34.0 ± 6.6	33.1 ± 6.0	34.7 ± 6.2	35.8 ± 6.0	35.0 ± 6.3
BMI (kg/m^2)	25.5 ± 5.2	31.9 ± 8.2	29.5 ± 6.7	27.6 ± 6.2	34.1 ± 8.8
Education (y)	7.5 ± 4.1	10.0 ± 2.1	10.7 ± 2.0	13.0 ± 2.5	13.8 ± 2.6
Employed (%)	89.4	81.7	72.1	95.6	83.7
Manual laborer (%)	90.4	89.3	68.8	26.4	28.9

Table II. The time intervals used for the four cycles.

	Cycle
Time of day	1: night (00.00 to 05.59)
	2: morning (06.00 to 11.59)
	3: afternoon (12.00 to 17.59)
	4: evening (18.00 to 23.59)
Day of the week	1: Monday, Tuesday
	2: Wednesday, Thursday
	3: Friday
	4: Saturday, Sunday
Moon phase	1: New moon
	2: Quarter moon
	3: Full moon
	4: Three-quarter moon
Month of the year	1: Jan, Feb, Mar
	2: Apr, May, Jun
	3: Jul, Aug, Sep
	4: Oct, Nov, Dec

Figure 1. Results of the unbiased analysis. The bars represent mean values (± SEM) of physical activity (in counts per hour ×1,000) for the four time intervals of each of the four cycles in each of the five countries. Codes for the time intervals are listed in Table II. The results of two-way ANOVAs are shown in Table III. Asterisks indicate probabilities associated with the F statistics obtained in post hoc one-way ANOVAs for each panel: ***P < 0.0001, *P < 0.05. Absence of asterisks indicates P > 0.10. When the main effect is significant, significance of multiple comparisons by Tukey’s test is indicated by lower-case letters: bars with different letters are significantly different from each other.

Table III. Results of two-way ANOVAs for the primary (unbiased) analysis.

Rhythmicity effect	F statistic	P	ω^2
Daily rhythmicity
Country	F(4, 2304) = 12.655	<0.0001	0.015
Time of day	F(3, 2304) = 242.579	<0.0001	0.228
Interaction	F(12, 2304) = 7.599	<0.001	0.025
Weekly rhythmicity
Country	F(4, 2304) = 19.389	<0.0001	0.030
Day of the week	F(3, 2304) = 6.664	<0.001	0.007
Interaction	F(12, 2304) = 1.468	>0.800	0.002
Lunar rhythmicity
Country	F(4, 2304) = 21.056	<0.0001	0.033
Moon phase	F(3, 2304) = 4.088	=0.056	0.004
Interaction	F(12, 2304) = 1.326	>0.800	0.002
Seasonal rhythmicity (by calendar)
Country	F(4, 2304) = 19.944	<0.0001	0.030
Season	F(3, 2304) = 3.174	=0.184	0.003
Interaction	F(12, 2304) = 1.754	=0.400	0.004
Seasonal rhythmicity
Country	F(4, 2304) = 18.944	<0.0001	0.030
Season	F(3, 2304) = 1.879	>0.800	0.001
Interaction	F(12, 2304) = 2.078	=0.128	0.005

Figure 2. Results of the secondary analysis for the combined data set of men and women from the five countries. The bars represent mean values (± SEM) of physical activity (in counts per hour ×1,000). Asterisks indicate probabilities (corrected for multiple testing) associated with the F statistics obtained in one-way ANOVAs for each panel: ***P < 0.0001. Absence of asterisks indicates P > 0.10. When the main effect is significant, significance of multiple comparisons by Tukey’s test is indicated by lower-case letters: bars with different letters are significantly different from each other.