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Chronic widespread pain (CWP) is common and associated with loss of functioning and health. Subjects with chronic nonwidespread pain (CnWP) are at increased risk of developing CWP, but few studies have described the nature of the development over time. We followed a random sample of 3105 participants from the population-based HUNT 3 study with 5 annual measurements of pain over 4 years. Although 29% reported CWP on at least 1 occasion, only 7% reported it consistently on 4 or 5 occasions. The average annual cumulative incidence was 5%, and the recovery rate was 38%. In mutual adjusted analysis, the risk of developing CWP from 1 year to the next was higher in subjects with chronic pain (relative risk [RR] = 2.4; 95% confidence interval [CI]: 1.8-3.4), 2 or more pain regions (RR = 3.3; 95% CI: 2.5-4.4), moderate pain or more (RR = 1.8; 95% CI: 1.5-2.6), and with comorbid chronic disease (RR = 1.6; 95% CI: 1.3-1.9). Developing CWP was associated with a modest concurrent change in self-reported mental and physical health. The risk of developing CWP between the fourth and fifth occasions was 80% lower for subjects without a history of CWP, compared to those with a history of CWP. For subjects without previous CWP, the development was associated with previously reported CnWP, but not with the number of occasions with CnWP, in analyses adjusted for sex, age, and pain severity. A substantial proportion of the new cases of CWP originates from subjects floating below and above the definition for CWP over time and, thus, does not seem to involve major transitions in health.

Pain and depression are episodic conditions that might take a chronic course. They are clearly related, but information on how they influence each other in the process of chronification is limited. Pain catastrophizing is hypothesized to play a role in the development of depression and chronic pain, but few longitudinal studies have investigated their association over a longer term. In this study, a random cohort from the general population (n = 4764) answered questions about pain, catastrophizing, and depression at 5 assessments in yearly intervals. Linear mixed models showed that within persons, increases in pain intensity and catastrophizing were independently associated with increases in depressive symptoms {mean change = -1.12, 95% confidence interval (CI) [-1.32 to -0.91] and -1.29, 95% CI [-1.52 to -1.05], respectively}. In prospective analyses restricted to individuals without depression above cutoff at baseline, chronic pain increased the risk of endorsing depression over the following 4 years (odds ratio = 2.01, 95% CI [1.71-2.37]). Seven percent showed a chronic course of depression, as indicated by scores above cutoff on at least 3 of 5 assessments. The number of years lived with chronic pain was associated with a chronic course of depression, with odds ratios increasing from 1.55 (95% CI [0.87-2.91]) to 14.19 (95% CI [8.99-22.41]) when reporting chronic pain on 2 vs 5 assessments compared with none. The results suggest that when pain intensity or catastrophizing change, depressive symptoms change in the same direction. When pain and catastrophizing become chronic, they seem to be mutually reinforcing determinants for chronic depression.

The objective was to document the operational definitions applied in epidemiological studies of chronic pain and to examine whether pain definitions and other methodological factors are systematically related to prevalence estimates. MEDLINE, EMBASE, and PsychINFO were searched for original research reports with study samples of at least 1000 individuals, excluding studies of less than 5 out of 15 selected body regions and studies solely concerned with specific pain conditions. Meta-analyses and meta-regressions were applied with random effects models; covariates were geography, sampling year, survey method, sampling frame, participation rate, percentage women of all participants, pain duration, and pain location. Of 6791 hits, 86 studies were included in the syntheses. The phrasing, content, and combinations of the chronic pain definition criteria were highly inconsistent, with virtually no 2 studies from independent research groups using the exact same criteria. Prevalence estimates ranged from 8.7% to 64.4%, with a pooled mean of 31%. Huge heterogeneity was shown in all forest plots. Prevalence estimates were significantly related to survey method (β = -10.8 [95% confidence interval: -17.2 to -4.4]), but it only counted for a small fraction of the between-studies variation in the estimates. There were also interaction effect of survey method by sex (female-male prevalence ratio [95% confidence interval]: questionnaire = 1.20 [1.16 to 1.25], and interview = 1.38 [1.29 to 1.47]). The other covariates investigated were not significantly related to the prevalence estimates. Researchers and clinicians should be aware of the probability that interview survey method of collecting data may give lower chronic pain reporting than questionnaire survey method and that this effect may be stronger in men than women.

Methods for classifying chronic pain in population studies are highly variable, and prevalence estimates ranges from 11% to 64%. Limited knowledge about the persistence of pain and the validity of recall questions defining chronic pain make findings difficult to interpret and compare. The primary aim of the current study was to characterize the persistence of pain in the general population and to validate recall measures against longitudinal reporting of pain. A random sample of 6419 participants from a population study (the HUNT 3 study in Norway) was invited to report pain on the SF-8 verbal pain rating scale every 3 months over a 12-month period and to report pain lasting more than 6 months at 12-month follow-up. Complete data were obtained from 3364 participants. Pain reporting was highly stable (intraclass correlation 0.66, 95% confidence interval 0.65 to 0.67), and the prevalence of chronic pain varied considerably according to level of severity and persistence: 31% reported mild pain or more, whereas 2% reported severe pain on 4 of 4 consecutive measurements. When defined as moderate pain or more on at least 3 of 4 consecutive measurements, the prevalence was 26%. Compared with the longitudinal classification, a cross-sectional measure of moderate pain or more during the last week on the SF-8 scale presented a sensitivity of 82% and a specificity of 84%, and a sensitivity of 80% and a specificity of 90% when combined with a 6-month recall question. Thus pain reporting in the general population is stable and cross-sectional measures may give valid prevalence estimates of chronic pain.