. 2016 Feb 26;11(2):e0150099. doi: 10.1371/journal.pone.0150099

Table 5. Polynomial regression results of measured parameters as function of overwintering time.

Parameter	Gender	Regression equation	Equation order	R	R²	p-value
Time in bed (min)	Both	= 448.860 − (0.241 * x)	1^st	0.0159	0.0002	0.685
		= 415.991 + (6.557 * x) − (0.268 * x²)	2^nd	0.1118	0.0125	0.042
Time in bed (min)	Male	= 441.772 − (0.799 * x)	1^st	0.0514	0.0026	0.270
		= 417.884 + (4.218 * x) − (0.200 * x²)	2^nd	0.0960	0.0092	0.144
Time in bed (min)	Female	= 470.603 + (0.629 * x)	1^st	0.0484	0.0023	0.500
		= 410.006 + (12.724 * x) − (0.466 * x²)	2^nd	0.2280	0.0520	0.022
Sleep time (min)	Both	= 369.208 − (1.049 * x)	1^st	0.0816	0.0066	0.036
		= 361.123 + (0.625 * x) − (0.0660 * x²)	2^nd	0.0877	0.0077	0.112
Sleep time (min)	Male	= 360.751 − (1.165 * x)	1^st	0.0876	0.0077	0.060
		= 360.636 − (1.141 * x) − (0.000965 * x²)	2^nd	0.0876	0.0077	0.184
Sleep time (min)	Female	= 392.848 − (1.081 * x)	1^st	0.0989	0.0098	0.167
		= 363.209 + (4.834 * x) − (0.228 * x²)	2^nd	0.1628	0.0265	0.106
Sleep efficiency (%)	Both	= 82.825 − (0.196 * x)	1^st	0.1183	0.0140	0.002
		= 86.696 − (0.997 * x) + (0.0316 * x²)	2^nd	0.1685	0.0284	0.002
Sleep efficiency (%)	Male	= 82.286 − (0.134 * x)	1^st	0.0819	0.0067	0.079
		= 86.523 − (1.025 * x) + (0.0355 * x²)	2^nd	0.1591	0.0253	0.015
Sleep efficiency (%)	Female	= 84.055 − (0.333 * x)	1^st	0.1967	0.0387	0.006
		= 87.412 − (1.004 * x) + (0.0258 * x²)	2^nd	0.2184	0.0477	0.029
Arousals (n/night)	Both	= 8.900 + (0.0825 * x)	1^st	0.0987	0.0097	0.010
		= 8.811 + (0.101 * x) − (0.000725 * x²)	2^nd	0.0988	0.0098	0.069
Arousals (n/night)	Male	= 8.996 + (0.0523 * x)	1^st	0.0642	0.0041	0.165
		= 8.371 + (0.184 * x) − (0.00524 * x²)	2^nd	0.0758	0.0057	0.246
Arousals (n/night)	Female	= 8.763 + (0.143 * x)	1^st	0.1634	0.0267	0.020
		= 9.878 − (0.0800 * x) + (0.00861 * x²)	2^nd	0.1741	0.0303	0.078
Sleep latency (min)	Both	= 11.420 + (0.0182 * x)	1^st	0.0094	0.0001	0.804
		= 8.779 + (0.564 * x) − (0.0216 * x²)	2^nd	0.0714	0.0051	0.067
Sleep latency (min)	Male	= 12.395 − (0.108 * x)	1^st	0.0656	0.0043	0.155
		= 9.809 + (0.435 * x) − (0.0216 * x²)	2^nd	0.0824	0.0068	0.106
Sleep latency (min)	Female	= 9.278 + (0.290 * x)	1^st	0.1220	0.0149	0.830
		= 5.674 + (1.009 * x) − (0.0278 * x²)	2^nd	0.1414	0.0200	0.154
Sleep onset (min)	Both	= 1465.842 + (0.624 * x)	1^st	0.0400	0.0016	0.294
		= 1425.390 + (8.994 * x) − (0.331 * x²)	2^nd	0.1404	0.0197	0.010
Sleep onset (min)	Male	= 1471.424 + (0.958 * x)	1^st	0.0583	0.0034	0.206
		= 1428.491 + (9.975 * x) − (0.359 * x²)	2^nd	0.1500	0.0225	0.021
Sleep onset (min)	Female	= 1449.069 + (0.171 * x)	1^st	0.0141	0.0002	0.842
		= 1416.457 + (6.686 * x) − (0.252 * x²)	2^nd	0.1292	0.0167	0.195
Sleep offset (min)	Both	= 436.322 + (0.260 * x)	1^st	0.0200	0.0004	0.609
		= 378.321 + (12.257 * x) − (0.474 * x²)	2^nd	0.2256	0.0509	<0.001
Sleep offset (min)	Male	= 434.479 + (0.246 * x)	1^st	0.0173	0.0003	0.706
		= 377.585 + (12.194 * x) − (0.476 * x²)	2^nd	0.2138	0.0457	<0.001
Sleep offset (min)	Female	= 441.502 + (0.222 * x)	1^st	0.0200	0.0004	0.773
		= 380.090 + (12.481 * x) − (0.473 * x²)	2^nd	0.2692	0.0725	0.006
Physical activity level (MET)	Both	= 1.799 − (0.00711 * x)	1^st	0.1308	0.0171	<0.001
		= 1.896 − (0.0272 * x) + (0.000792 * x²)	2^nd	0.1594	0.0254	0.003
Physical activity level (MET)	Male	= 1.838 − (0.00776 * x)	1^st	0.1375	0.0189	0.003
		= 1.925 − (0.0260 * x) + (0.000727 * x²)	2^nd	0.1597	0.0255	0.014
Physical activity level (MET)	Female	= 1.691 − (0.00452 * x)	1^st	0.0959	0.0092	0.174
		= 1.810 − (0.0283 * x) + (0.000920 * x²)	2^nd	0.1536	0.0236	0.122

Comparison of polynomial regression results; x denotes the time of measurement based on two-week time increments; bold-typed results denote significant results. Analyses regarding sleep onset and offset are reported as number of minutes.