Mean power frequency, Hz	0−<20th percentile <0.001≤−<0.23	20th≤−40th percentile 0.23≤−0.24	40th≤−60th percentile 0.24≤−0.27	60th≤−80th percentile 0.27≤−0.29	80th≤−≤100th percentile 0.29≤−0.45	Total
CTS, number of cases	897	1117	1068	1941	1811	6834
Person years	936 938	1 179 089	924 313	1 258 279	1 078 308	5 376 927
IR*	9.6	9.5	11.6	15.4	16.8	12.7
IRR, crude	1.00 (ref.)	0.99 (0.91 to 1.08)	1.21 (1.10 to 1.32)	1.61 (1.49 to 1.74)	1.75 (1.62 to 1.90)
IRR, adjusted†	1.00 (ref.)	0.78 (0.72 to 0.86)	1.51 (1.37 to 1.66)	1.33 (1.23 to 1.44)	1.83 (1.68 to 1.98)