Reported frequency of physical activity in a large epidemiological study: relationship to specific activities and repeatability over time

Table 3 Agreement of reported physical activity, by time between completing identical questionnaires

	Number of women	Agreement	Kappa (95% CI) with quadratic weighting
Time between completing identical questions on the frequency of strenuous activity (average time between the two)
≤ 6 months (0.3 years)	238	64%	0.71 (0.59 - 0.83)
> 6 months - 1 year (0.9 years)	1,224	59%	0.61 (0.55 - 0.67)
> 1 - 2 years (1.5 years)	7,002	54%	0.55 (0.53 - 0.57)
> 2 years (2.6 years)	9,153	52%	0.51 (0.49 - 0.53)
P for trend			0.03
Time between completing identical questions on the frequency of any activity (average time between the two)
≤ 6 months (0.2 years)	221	57%	0.67 (0.53 - 0.81)
> 6 months - 1 year (0.9 years)	1,171	53%	0.67 (0.61 - 0.73)
> 1 - 2 years (1.5 years)	6,044	48%	0.60 (0.58 - 0.62)
> 2 years (2.6 years)	5,312	47%	0.58 (0.56 - 0.60)
P for trend			0.05

P-values for trend in kappa were estimated by weighted least squares regression using the inverse of the variances of the kappa coefficients

ISSN: 1471-2288