Table 2 Estimated rate ratios of OP, SP and OB and of their product terms from modified Poisson regression, along with indexes of additive interaction between OP, SP and OB

Adjusted Relative rates (RR) for each exposure group from our modified Poisson regression

Exposure

Rate ratio (RR), 95% CI

None

Reference

OP only

1.24 (0.83, 1.87)

SP only

2.53 (1.95, 3.29)

OB (high FMI) only

2.05 (1.58, 2.66)

Both OP and SP only (OSP)

2.82 (2.16, 3.68)

Both OP and OB only (OOB)

2.34 (1.69, 3.23)

Both SP and OB only (SOB)

2.58 (1.95, 3.41)

OP, SP and OB (OSO)

3.06 (2.28, 4.11)

Interactions between risk factors

Risk factors and their interactions

Rate ratio (RR), 95% CI

P-value

OP-SP interaction

0.90 (0.58, 1.37)

0.612

OP-OB interaction

0.92 (0.58, 1.46)

0.718

SP-OB interaction

0.50 (0.37, 0.67)

 < 0.001

OP-SP-OB interaction

1.16 (0.69, 1.96)

0.569

Relative excess rate due to interaction (RERI)

RERI, 95% CI

RERI2 (OP, SP | no OB)^a

0.04 (-0.55, 0.64)

RERI2 (OP, OB | no SP)^a

0.05 (-0.65, 0.74)

RERI2 (SP, OB | no OP)^a

-1.00 (-1.67, -0.34)

RERI2 (OP, SP | OB)^b

0.10 (-0.28, 0.48)

RERI2 (OP, OB | SP)^b

0.08 (-0.19, 0.35)

RERI2 (SP, OB | OP)^b

-0.68 (-1.49, 0.12)

RERI3 (OP, OB, SP)^c

0.16 (-0.83, 1.14)