The clinical course of acute, subacute and persistent low back pain: a systematic review

Key points

1. 01Acute low back pain: mean pain dropped from 56 to 26 out of 100 by 6 weeks, then plateaued at 21 by 52 weeks (moderate-certainty evidence).
2. 02Subacute low back pain: similar early drop (63 to 29 out of 100 by 6 weeks) but less improvement thereafter, with mean pain of 31 at 52 weeks (moderate-certainty evidence).
3. 03Persistent low back pain: high pain scores throughout, falling only from 56 to 40 out of 100 over 52 weeks (very low-certainty evidence).
4. 04Disability improved slightly more than pain across all groups, suggesting function recovers faster than subjective pain.
5. 05The finding that persistent low back pain outcomes are substantially worse than previously thought challenges prior clinical guideline reassurances about universally favourable prognosis.

How it was conducted

Design

Systematic review and meta-analysis of prospective inception cohort studies; update of a 2012 meta-analysis

Search period

MEDLINE, Embase, CINAHL from 2011 to January 2023 (combined with prior review data extending to approximately 2010)

Participants

17,974 participants across 60 cohorts in the review; 9,224 participants across 47 cohorts in the meta-analysis

Groups

Acute low back pain (less than 6 weeks), subacute (6 to less than 12 weeks), persistent (12 to less than 52 weeks) at study entry

Primary outcomes

Pain intensity and disability, both converted to a 0-100 scale; pooled means and 95% CIs estimated at 0, 6, 12, 26, and 52 weeks

Evidence quality

GRADE assessment: moderate certainty for acute and subacute groups; very low certainty for persistent group

What they found

• Acute pain - mean pain score 56 (95% CI 49-62) at baseline, 26 (95% CI 21-31) at 6 weeks, 22 (95% CI 18-26) at 26 weeks, 21 (95% CI 17-25) at 52 weeks.
• Subacute pain - mean pain score 63 (95% CI 55-71) at baseline, 29 (95% CI 22-37) at 6 weeks, 29 (95% CI 22-36) at 26 weeks, 31 (95% CI 23-39) at 52 weeks.
• Persistent pain - mean pain score 56 (95% CI 37-74) at baseline, 48 (95% CI 32-64) at 6 weeks, 43 (95% CI 29-57) at 26 weeks, 40 (95% CI 27-54) at 52 weeks.
• Acute disability - mean score 43 (95% CI 37-49) at baseline, 22 (95% CI 19-26) at 6 weeks, 18 (95% CI 14-21) at 26 weeks, 17 (95% CI 14-21) at 52 weeks.
• Subacute disability - mean score 44 (95% CI 34-54) at baseline, 29 (95% CI 21-38) at 6 weeks, 25 (95% CI 16-33) at 26 weeks, 25 (95% CI 16-33) at 52 weeks.
• Persistent disability - mean score 57 (95% CI 34-81) at baseline, 58 (95% CI 35-82) at 6 weeks, 59 (95% CI 35-83) at 26 weeks, 59 (95% CI 35-83) at 52 weeks.
• Disability course was significantly more favourable than pain in acute (p < 0.001) and subacute (p < 0.001) groups; in persistent group only for uncorrected time (p < 0.005).
• Sensitivity analyses excluding radicular pain or age extremes showed trajectories similar to main analyses in acute and subacute groups.

Limitations

• Risk of bias was variable across studies; 82.4% of studies did not adequately report or account for participant attrition at follow-up, meaning follow-up samples may not represent the original cohort.
• Most studies (54.4%) did not recruit consecutive cases, introducing selection bias that limits generalisability.
• Insufficient data for older (greater than 60 years) and younger (less than 18 years) populations means results cannot be generalised to these age groups.
• Using mean or median inception time to correct for time since pain onset may underestimate pain duration, potentially making the corrected trajectory appear more favourable than it is.

Why it matters

For patients

Most people with new or recent-onset back pain will see notable improvement in the first 6 weeks, but ongoing mild-to-moderate pain after that is common and does not signal serious disease.

For clinicians

Patients with subacute low back pain who are not improving by 6-12 weeks should be identified early and offered escalated care to reduce the risk of transitioning to persistent pain, which carries a much less favourable prognosis.

For readers

This updated meta-analysis revises the overly optimistic picture from earlier guidelines by showing that persistent low back pain leads to sustained moderate-to-high pain and disability, reinforcing the need for better treatments and realistic patient counselling.