(HealthDay)—Repeated measurements of low back pain (LBP)-related variables are necessary to identify patterns in a fluctuating condition, according to a study published in the Aug. 1 issue of The Spine Journal.

Iben Axén, Ph.D., from the Karolinska Institutet in Stockholm, and colleagues collected the "number of days with bothersome pain" via weekly text messages for six months from 244 subjects with nonspecific LBP.

The researchers found that half of the subjects (mean age, 44 years) had experienced LBP for more than 30 days in the previous year. The risk of experiencing a day with bothersome LBP varied over time. The previous duration of , the presence of , and the duration of LBP the previous year showed a predictive ability for all time points; however, pain intensity, leg pain, and self-rated health showed inconsistent predictive patterns.

"These results may explain the diversity of the results of the predictor studies in the literature," the authors write. "Findings from this study indicate that outcomes should be measured much more frequently in order to obtain more accurate appraisal of temporal pain patterns and estimates of predictors."