Pain and Kidney Function Decline and Mortality: A Cohort Study of US Veterans.

BACKGROUND: Chronic pain is a common condition in the general population. However, large epidemiologic studies examining the role of pain in the deterioration of kidney function, development of chronic kidney disease, and risk for death are lacking.

STUDY DESIGN: Retrospective cohort study.

SETTING & PARTICIPANTS: A nationally representative cohort of 2,360,056 US veterans with baseline estimated glomerular filtration rates (eGFRs) ≥ 60mL/min/1.73m(2), followed up from October 2004 to September 2006.

PREDICTOR: 4 pain categories were compared: none (score, 0), mild (1-4), moderate (5-6), or severe (≥7).

OUTCOMES: eGFR decline (determined by eGFR slope) and combined incident eGFR<60mL/min/1.73m(2) or all-cause death.

MEASUREMENTS: We examined the pain management pattern and association of reported pain with (1) rapid eGFR decline and (2) a composite outcome of incident eGFR<60mL/min/1.73m(2) or all-cause death using logistic regression and Cox models adjusted for baseline eGFR, demographics, comorbid conditions, cardiovascular risk factors, and depression.

RESULTS: ∼60% of veterans reported pain of any severity during the baseline period. The most commonly prescribed analgesics were opioids. In a dose-response relationship, veterans reporting moderate or severe pain had a higher risk for faster eGFR decline compared with those reporting none (ORs of 1.11 [95% CI, 1.09-1.14] and 1.17 [95% CI, 1.13-1.21] for moderate and severe pain, respectively). In combined analyses, veterans reporting moderate or severe pain both had 30% higher risk of the combined outcome (incident eGFR, 60 mL/min/1.73 m(2) or death) compared with those reporting none (HRs of 1.30 [95% CI, 1.28-1.31] and 1.30 [95% CI, 1.28-1.32] for moderate and severe pain, respectively).

LIMITATIONS: Lack of granular data regarding type and location of pain.

CONCLUSIONS: We observed a high prevalence of pain and analgesic prescription in the US veteran population with normal eGFRs. Pain was associated with a higher incidence of eGFRs<60mL/min/1.73m(2), faster kidney function decline, and higher mortality.