Table 4 Risk ratio of LBP occurring in each year level compared with the first year students (RR = 1)

Fourth Year Students

Lifetime

1.4 (1.1–1.8)++

1.4 (1.1–1.8)++

1.6 (0.9–2.6)

12-month

1.5 (1.2–1.9)++

2.1 (1.3–3.3)++

1.6 (0.9–2.7)

1-month

1.8 (1.2–2.7)++

1.5 (1.2–2.0)++

1.4 (0.6–2.9)

1-week

2.1 (1.1–4.0)++

1.4 (1.1–1.8)++

0.9 (0.2–3.1)

Third Year Students

Lifetime

1.2 (0.9–1.6)

1.0 (0.7–1.5)

1.8 (1.0–3.1)*

12-month

1.2 (0.9–1.7)

1.0 (0.7–1.5)

2.0 (1.1–3.6)++

1-month

1.3 (0.8–2.2)

1.1 (0.6–2.1)

2.1 (1.0–4.6)*

1-week

2.2 (1.1–4.4)++

1.1 (0.8–4.7)

3.0 (1.0–8.9)*

Second Year Students

Lifetime

1.3 (1.0–1.6)*

1.1 (0.8–1.5)

1.6 (1.0–2.7)*

12-month

1.3 (1.0–1.7)*

1.1 (0.8–1.6)

1.6 (1.0–2.8)*

1-month

1.6 (1.0–2.4)*

1.7 (1.0–2.7)*

1.5 (0.7–2.9)

1-week

3.1 (1.4–7.3)++

2.6 (1.2–5.7)++

1.8 (0.7–4.9)