Factors related to self-rated health: a survey among patients and their general practitioners.

OBJECTIVE: To explore associations between general practice patients' SRH and symptoms, diagnoses, chronic conditions, unexplained conditions, and life stressors. DESIGN: A cross-sectional study. Data were collected from GP and patient questionnaires. SETTING: General practices in Southeast Norway. SUBJECTS: 47 general practitioners (GPs) who included 866 consecutive patients. MAIN OUTCOME MEASURES: SRH was measured with a single question from the COOP-WONCA overall health chart and dichotomized into good/poor SRH. Binary logistic regression models were used in the analyses. RESULTS: Poor SRH was reported by 48% of the patients in the past week. A higher prevalence of poor SRH was found for women, middle-aged, recipients of social security grants, patients diagnosed with asthenia, lower back pain, and depression/anxiety, and for patients with reported life stressors and unexplained conditions. We found an almost linear association between the number of symptoms and the likelihood of reporting poor SRH. The probability of reporting poor SRH increased along with an increasing number of symptoms for common diagnoses. In a multivariate analysis, the only number of symptoms, being in receipt of social security grants and being retired was associated with poor SRH. CONCLUSION: The likelihood of reporting poor SRH increased with an increasing number of symptoms, partly independent of the diagnosis given by GPs. This result coincides with our previous findings of a strong association between the number of symptoms, function, and health. The symptom burden thus appears to be an important factor for SRH among patients in general practice.KEY POINTSThere is a high prevalence of poor SRH in general practice patients.The likelihood of reporting poor SRH is partly independent of the diagnosis given.The number of symptoms was the factor strongest associated with poor SRH.

Neck pain patterns and subgrouping based on weekly SMS-derived trajectories.

BACKGROUND: Neck and low back pain represent dynamic conditions that change over time, often with an initial improvement after the onset of a new episode, followed by flare-ups or variations in intensity. Pain trajectories were previously defined based on longitudinal studies of temporal patterns and pain intensity of individuals with low back pain. In this study, we aimed to 1) investigate if the defined patterns and subgroups for low back pain were applicable to neck pain patients in chiropractic practice, 2) explore the robustness of the defined patterns, and 3) investigate if patients within the various patterns differ concerning characteristics and clinical findings. METHODS: Prospective cohort study including 1208 neck pain patients from chiropractic practice. Patients responded to weekly SMS-questions about pain intensity and frequency over 43 weeks. We categorized individual responses into four main patterns based on number of days with pain and variations in pain intensity, and subdivided each into four subgroups based on pain intensity, resulting in 16 trajectory subgroups. We compared baseline characteristics and clinical findings between patterns and between Persistent fluctuating and Episodic subgroups. RESULTS: All but two patients could be classified into one of the 16 subgroups, with 94% in the Persistent fluctuating or Episodic patterns. In the largest subgroup, "Mild Persistent fluctuating" (25%), mean (SD) pain intensity was 3.4 (0.6) and mean days with pain 130. Patients grouped as "Moderate Episodic" (24%) reported a mean pain intensity of 2.7 (0.6) and 39 days with pain. Eight of the 16 subgroups each contained less than 1% of the cohort. Patients in the Persistent fluctuating pattern scored higher than the other patterns in terms of reduced function and psychosocial factors. CONCLUSIONS: The same subgroups seem to fit neck and low back pain patients, with pain that typically persists and varies in intensity or is episodic. Patients in a Persistent fluctuating pattern are more bothered by their pain than those in other patterns. The low back pain definitions can be used on patients with neck pain, but with the majority of patients classified into 8 subgroups, there seems to be a redundancy in the original model.

Measurement properties for the revised patient-reported OsteoArthritis Quality Indicator questionnaire.

OBJECTIVES: To assess validity, reliability, responsiveness and interpretability of the revised OsteoArthritis Quality Indicator (OA-QI) questionnaire version 2 (v2) assessing patient-reported quality of osteoarthritis care. METHODS: The OA-QI v2 (16 items, score range 0-100 (100 = best score)) was included in a longitudinal cohort study. Attendees of a 4.5 h osteoarthritis patient education programme at Diakonhjemmet Hospital, Norway, completed the OA-QI at four time points: 2 weeks before, immediately before, immediately after, and 3 months after the programme. Test-retest reliability and measurement error over a 2-week time period were assessed in those that had not seen health professionals in the interim. Construct validity and responsiveness were assessed with predefined hypotheses. Floor and ceiling effects, smallest detectable change (SDC95%) and minimal important change (MIC) were assessed to evaluate interpretability. RESULTS: The intraclass correlation coefficient for all 16 items was 0.89. For single items the test-retest kappa estimates ranged 0.38-0.85 and percent agreement 69-92%. Construct validity was acceptable with all six predefined hypotheses confirmed. Responsiveness was acceptable with 33 of 48 and three of four predefined hypotheses confirmed for single items and all items, respectively. There were no floor or ceiling effects. The SDC95% was 29.1 and 3.0 at the individual and group levels, respectively. MIC was 20.4. CONCLUSIONS: The OA-QI v2 had higher reliability estimates compared to v1, showed acceptable validity, and is the recommended version for future use. The results of responsiveness testing further support the use of the OA-QI v2 as an outcome measure in studies aiming to improve osteoarthritis care.

A multiple treatment comparison meta-analysis of monoamine oxidase type B inhibitors for Parkinson's disease.

AIMS: To the best of our knowledge, there are no systematic reviews or meta-analyses that compare rasagiline, selegiline and safinamide. Therefore, we aimed to perform a drug class review comparing all available monoamine oxidase type B (MAO-B) inhibitors in a multiple treatment comparison. METHODS: We performed a systematic literature search to identify randomized controlled trials assessing the efficacy of MAO-B inhibitors in patients with Parkinson's disease. MAO-B inhibitors were evaluated either as monotherapy or in combination with levodopa or dopamine agonists. Endpoints of interest were change in the Unified Parkinson's Disease Rating Scale (UPDRS) score and serious adverse events. We estimated the relative effect of each MAO-B inhibitor versus the comparator drug by creating three networks of direct and indirect comparisons. For each of the networks, we considered a joint model. RESULTS: The systematic literature search and study selection process identified 27 publications eligible for our three network analyses. We found the relative effects of rasagiline, safinamide and selegiline treatment given alone and compared to placebo in a model without explanatory variables to be 1.560 (1.409, 1.734), 1.449 (0.873, 2.413) and 1.532 (1.337, 1.757) respectively. We also found all MAO-B inhibitors to be efficient when given together with levodopa. When ranking the MAO-B inhibitors given in combination with levodopa, selegiline was the most effective and rasagiline was the second best. CONCLUSIONS: All of the included MAO-B inhibitors were effective compared to placebo when given as monotherapy. Combination therapy with MAO-B inhibitors and levodopa showed that all three MAO-B inhibitors were effective compared to placebo, but selegiline was the most effective drug.

Smoking and alcohol use are associated with structural and inflammatory hand osteoarthritis features.

OBJECTIVES: To explore whether smoking and alcohol use are associated with hand osteoarthritis (OA) features in two different OA cohorts. METHOD: We studied 530 people with radiographic hand OA from the Musculoskeletal pain in Ullensaker STudy (MUST) and 187 people from the Oslo hand OA cohort [mean (sd) age 65 (8.0) and 62 (5.7) years, 71% and 91% women, respectively]. Smoking, alcohol use and hand pain were self-reported. Participants underwent conventional hand radiographs and ultrasound examination of 30 hand joints. The Kellgren-Lawrence sum score for radiographic OA severity (0-120 scale) and the proportion of participants having at least one joint with grey-scale synovitis (grade ≥1) were calculated. We studied whether smoking and alcohol use were cross-sectionally associated with radiographic OA, synovitis, and pain using adjusted linear and logistic regression analyses. RESULTS: Smoking was associated with less radiographic OA in both cohorts [ß = -4.71, 95% confidence interval (CI) -8.36 to -1.06 for current smoking in MUST and ß = -0.15, 95% CI -0.29 to -0.02 for smoking pack-years in the Oslo hand OA cohort]. Stratified analyses indicated that the association was present in men only. Being a monthly drinker (examined in MUST only) was significantly associated with present synovitis compared to never drinkers (odds ratio = 2.35, 95% CI 1.27 to 4.34) (no gender differences). Neither smoking nor alcohol was associated with hand pain. CONCLUSIONS: Smoking was associated with less radiographic hand OA whereas alcohol consumption was associated with present joint inflammation in hand OA. Future longitudinal studies are needed to explore the causal associations and explanatory mechanisms behind gender differences.

Pain-related fear and functional recovery in sciatica: results from a 2-year observational study.

OBJECTIVES: The purpose of this study was to explore the associations between pain-related fear, pain disability, and self-perceived recovery among patients with sciatica and disk herniation followed up for 2 years. PATIENTS AND METHODS: Pain-related fear was measured by the Tampa Scale for Kinesiophobia (TSK) and the Fear-Avoidance Beliefs Questionnaire-Physical Activity (FABQ-PA) subscale. Disability was measured by the Maine-Seattle Back Questionnaire. At 2 years, patients reported their sciatica/back problem on a global change scale ranging from completely gone to much worse. No specific interventions regarding pain-related fear were provided. RESULTS: Complete data were obtained for 372 patients. During follow-up, most patients improved. In those who at 2 years were fully recovered (n=66), pain-related fear decreased substantially. In those who did not improve (n=50), pain-related fear remained high. Baseline levels of pain-related fear did not differ significantly between those who were fully recovered and the rest of the cohort. In the total cohort, the correlation coefficients between the 0-2-year change in disability and the changes in the TSK and the FABQ-PA were 0.33 and 0.38, respectively. In the adjusted regression models, the 0-2-year change in pain-related disability explained 15% of the variance in the change in both questionnaires. CONCLUSION: Pain-related fear decreased substantially in patients who recovered from sciatica and remained high in those who did not improve. Generally, the TSK and the FABQ-PA yielded similar results. To our knowledge, this is the first study that has assessed pain-related fear in patients who recover from sciatica.

Individual and joint effects of risk factors for onset widespread pain and obesity - a population-based prospective cohort study.

BACKGROUND: Widespread musculoskeletal pain (WSP) and obesity frequently co-occur and may have shared risk factors. We aimed to investigate whether four dichotomized risk factors individually or jointly increase the risk for the onset of WSP and onset of obesity. METHODS: Persons aged 34-76 years in 2004 living in Ullensaker municipality, Norway, responded to questionnaires in 2004 and 2010 (n = 1553). Using causal interaction analyses, we examined whether baseline obesity and WSP, poor sleep quality, mental distress and poor physical fitness jointly increased the risk of new onset WSP (≥3 pain sites leading to disability the last year) and new onset obesity (self-reported BMI ≥30 kg/m(2) ) in persons without WSP (n = 1270) or without obesity (n = 1300) at baseline respectively. RESULTS: The mean (SD) age was 51 (12.1) years and 56% were female. The incidence of WSP and obesity were 9.1% and 5.4%. Mental distress and poor sleep quality individually and jointly with poor physical fitness increased WSP onset risk (relative excess risk due to interaction [RERI] = 1.90, 95% CI, 0.39-3.42 and RERI = 1.43, 95% CI, 0.10-2.76). Poor physical fitness individually increased the risk for new onset obesity, and baseline WSP and poor sleep quality jointly (RERI = 1.87, 95% CI, 0.49-3.24). The presence of more risk factors was dose-dependently associated with onset WSP and to a lesser extent with onset obesity. CONCLUSION: The onset of WSP and the onset of obesity were results of joint effects of exposures. Poor physical fitness was a key covariate in increasing the risk for both conditions. WHAT DOES THIS STUDY ADD?: In a general population, the new onset of widespread pain and new onset of obesity were results of joint effects of risk factors and particularly poor physical fitness. The study may aid in the identification of patients at risk of future disability.

Clustering of pain and its associations with health in people aged 50†years and older: cross-sectional results from the North Staffordshire Osteoarthritis Project.

OBJECTIVE: Most pain in patients aged ≥50 years affects multiple sites and yet the predominant mode of presentation is single-site syndromes. The aim of this study was to investigate if pain sites form clusters in this population and if any such clusters are associated with health factors other than pain. SETTING: Six general practices in North Staffordshire, UK. DESIGN: Cross-sectional, postal questionnaire, study. PARTICIPANTS: Community-dwelling adults aged ≥50 years registered at the general practices. MAIN OUTCOMES MEASURES: Number of pain sites was measured by asking participants to shade sites of pain lasting ≥1 day in the past 4 weeks on a blank body manikin. Health factors measured included anxiety and depression (Hospital and Anxiety Depression Scale), cognitive complaint (Sickness Impact Profile) and sleep. Pain site clustering was investigated using latent class analysis. Association of clusters with health factors, adjusted for age, sex, body mass index and morbidities, was analysed using multinomial regression models. RESULTS: 13 986 participants (adjusted response 70.6%) completed a questionnaire, of whom 12 408 provided complete pain data. Four clusters of participants were identified: (1) low number of pain sites (36.6%), (2) medium number of sites with no back pain (31.5%), (3) medium number of sites with back pain (17.9%) and (4) high number of sites (14.1%). Compared to Cluster 1, other clusters were associated with poor health. The strongest associations (relative risk ratios, 95% CI) were with Cluster 4: depression (per unit change in score) 1.11 (1.08 to 1.14); cognitive complaint 2.60 (2.09 to 3.24); non-restorative sleep 4.60 (3.50 to 6.05). CONCLUSIONS: These results indicate that in a general population aged ≥50 years, pain forms four clusters shaped by two dimensions-number of pain sites (low, medium, high) and, within the medium cluster, the absence or presence of back pain. The usefulness of primary care treatment approaches based on this simple classification should be investigated.

No strong relationship between body mass index and clinical hand osteoarthritis: results from a population-based case-control study.

OBJECTIVES: The aim of this population-based case-control study was to investigate whether a high body mass index (BMI) is a risk factor for clinical hand osteoarthritis (OA). METHOD: Persons living in Ullensaker municipality in Norway who were aged 20-52 years in 1990 reported height and weight in 1990, 1994, 2004, and 2010 (n = 1276). Cases (clinical hand OA in 2010, n = 59) were compared to controls (participants without self-reported OA or hand pain in 2010, n = 805) with regard to the prospectively measured BMI by means of a generalized estimating equation (GEE) analysis adjusted for age, sex, time, and education. RESULTS: The mean age of hand OA cases was 64 (SD = 7.5) years in 2010 and 78% were women. There was no association between total average BMI over the entire period and later clinical hand OA (p = 0.320). Cases had a higher mean BMI in 1990 [unstandardized B = 0.93, 95% confidence interval (CI) 0.07-1.79] and in 1994 (B = 0.75, 95% CI 0.22-1.28) but there were no differences between the groups in 2004 or 2010. CONCLUSIONS: The study lend support to the hypothesis that having a higher BMI when young or middle-aged might be associated with later hand OA.

No strong temporal relationship between obesity and multisite pain--results from a population-based 20-year follow-up study.

BACKGROUND: Multisite pain and obesity are cross-sectionally related and are common conditions that may influence each other through socio-demographic, lifestyle and/or health-related factors. The aim of the present study was to examine the cross-sectional and prospective associations between overweight/obesity and multisite pain in a general population. METHODS: In a 20-year population-based prospective cohort study, persons aged 20-62 years in 1990 participated in postal surveys in 1990, 1994, 2004 and 2010 (n = 855). Multisite pain was defined as reporting ≥ 2 number of pain sites (NPS) on the Standardized Nordic Questionnaire. Overweight was defined as body mass index (BMI) 25-30 kg/m(2) and obesity as BMI ≥ 30 kg/m(2). To exploit all measurement times, generalized estimating equation analyses adjusting for age, sex, educational and occupational status, smoking, sleep quality, mental distress and physical activity were employed. RESULTS: The mean age was 41 years at baseline and 57% were women. Overweight/obesity and NPS were significantly associated cross-sectionally. Being overweight/obese was associated with reporting future NPS ≥ 2 [overweight: odds ratio (OR), 1.40, 95% confidence interval (CI), 1.12-1.75, obese: OR, 1.54, 95% CI, 1.04-2.28]. Having NPS ≥ 2 was not associated with becoming overweight, but increased the OR for future obesity (OR 1.27, 95% CI, 1.02, 1.59). Smoking was a confounder in this relationship. CONCLUSIONS: Being overweight or obese was associated with future multisite pain, although the magnitude of the association was small and the dose-response relationship observed in cross-sectional analyses disappeared in prospective analyses. There was less evidence that having multisite pain was a predictor of future overweight/obesity.

The prognosis of self-reported paresthesia and weakness in disc-related sciatica.

PURPOSE: To explore how patients with sciatica rate the 'bothersomeness' of paresthesia (tingling and numbness) and weakness as compared with leg pain during 2 years of follow-up. METHODS: Observational cohort study including 380 patients with sciatica and lumbar disc herniation referred to secondary care. Using the Sciatica Bothersomeness Index paresthesia, weakness and leg pain were rated on a scale from 0 to 6. A symptom score of 4-6 was defined as bothersome. RESULTS: Along with leg pain, the bothersomeness of paresthesia and weakness both improved during follow-up. Those who received surgery (n = 121) reported larger improvements in both symptoms than did those who were treated without surgery. At 2 years, 18.2% of the patients reported bothersome paresthesia, 16.6% reported bothersome leg pain, and 11.5% reported bothersome weakness. Among patients with no or little leg pain, 6.7% reported bothersome paresthesia and 5.1% bothersome weakness. CONCLUSION: During 2 years of follow-up, patients considered paresthesia more bothersome than weakness. At 2 years, the percentage of patients who reported bothersome paresthesia was similar to the percentage who reported bothersome leg pain. Based on patients' self-report, paresthesia and weakness are relevant aspects of disc-related sciatica.

Localized low back pain and low back pain as part of widespread musculoskeletal pain: two different disorders? A cross-sectional population study.

In a cross-sectional postal questionnaire study we compared individuals with localized low back pain (LBP) with individuals with LBP as part of widespread musculoskeletal pain, according to demographic and lifestyle characteristics and functional ability. All the inhabitants in Ullensaker county born 1918-20, 1928-30, 1938-40, 1948-50, 1958-60 and 1968-70 were sent a questionnaire in 1994. The study population comprised 2,893 responders. LBP as part of widespread pain indicated reduced functional ability, and the groups differed in several demographic and lifestyle characteristics.

Sleep problems: a predictor of long-term work disability? A four-year prospective study.

AIMS: This study investigates sleep problems as a predictor of long-term work disability. METHODS: Data from a community-based four-year prospective study were used. In 1990, all inhabitants of the municipality of Ullensaker, Norway, belonging to six age cohorts (20-22, 30-32, 40-42, 50-52, 60-62, and 70-72 years), were mailed a questionnaire. Of the 1,788 responders who were working and not older than 62 years, 1,426 (80%) returned a second questionnaire four years later (1994). RESULTS: Reporting mediocre or poor sleep (in contrast to good) in 1990 was significantly related to long-term work disability (> 8 weeks) during the previous 12 months in 1994 (odds ratio = 2.16; 95% confidence interval = 1.26-3.72), after adjustments for age, gender, civil status, body mass index, emotional symptoms, musculoskeletal pain, self-evaluated health, smoking, physical exercise, job satisfaction, and work characteristics. CONCLUSION: The study indicates that sleep problems are a predictor of long-term work disability.

[Children and bodily pain. Strong association between bodily pain, mental problems and sleep disorders among school children]. / Barn og kroppssmerte. Sterk sammenheng mellom kroppssmerte, psykiske problemer og søvnvansker hos skolebarn.

Body pain is frequently reported in children, and it has been suggested that childhood pain could be the beginning of chronic disabling pain. Three hypotheses were tested: 1. Body pain is associated with mental distress and sleeping problems; 2. The association is dependent on the localisation of the pain; 3. The association increases with the number of painful areas. 86 percent of the pupils (569) in the 4th form (mean age 10.5 years), 7th form (mean age 13.5 years) and 9th form (mean age 15.5 years) from all the schools in a local community answered a questionnaire about self esteem, body image, physical activity and body pain. A strong association was found between the reporting of pain, mental distress and sleeping problems. Knee pain was the only problem reported more frequently by boys than by girls, and did not show the same association with mental distress and sleeping problems as pain from other regions.

[Physical activity and bodily pain in children]. / Fysisk aktivitet og kroppssmerter hos barn.

BACKGROUND: Musculoskeletal complaints are frequently reported not only by adults, but also by children. Sedentary lifestyle has been suggested as a possible cause. MATERIAL AND METHODS: 569 pupils in primary school in a Norwegian municipality, aged 10-15 years, answered a questionnaire on bodily pain, self-esteem, body image and physical activity. RESULTS: We found a tendency that the least and the most physically active children reported most complaints. The two groups reported complaints from different regions. INTERPRETATION: Whether complaints in childhood develop into adult chronic pain conditions, and whether increased activity among the most physically passive children can hinder such a development are still unanswered questions.

Bodily pain, sleep problems and mental distress in schoolchildren.

UNLABELLED: It has been suggested that childhood pain could be the beginning of a career with chronic disabling pain. Bodily pain is frequent in children. We examined the association between self-reported bodily pain, mental distress and sleep problems in schoolchildren to test the following hypotheses: (i) that self-reported bodily pain is associated with mental distress and sleep problems, (ii) that the association is dependent on the localization of pain, and (iii) that the association increases with number of painful areas. Eighty-six percent of the pupils (569) in the 4th form (mean age 10.5 y), 7th form (mean age 13.5 y) and 9th form (mean age 15.5 y) from all the schools in a local community answered a questionnaire about self-esteem, body-image, physical activity and bodily pain. We found a strong association between the reporting of pain, mental distress and sleep problems. Pain in the knees was the only problem reported more frequently by boys than by girls, and knee pain did not show the same association with mental distress and sleep problems as pain from other regions. CONCLUSIONS: A possible cause-effect relationship between pain, mental distress and sleep problems is discussed, and the possibility that all the complaints are the simultaneous signs of a multisymptom syndrome is introduced.

Smoking and the functional status of young adults.

OBJECTIVE: To investigate the relationship between smoking and the functional status of young adults. DESIGN: A 4-year prospective questionnaire study. SETTING: The municipality of Ullensaker, Norway. SUBJECTS: 1084 subjects, 20-22 years or 30-32 years of age (the two youngest age-cohorts in a larger population study), completed a mailed questionnaire in 1990. A second questionnaire, mailed to the respondents in 1994, was completed by 753 (69.5%) individuals. MAIN OUTCOME MEASURES: Self-evaluated functional status as measured with the COOP/Wonca Charts. RESULTS: In 1994, respondents who were daily smokers in 1990 reported lower physical fitness, poorer overall health, and more pain, emotional problems, limitations of social activities, and problems in performing daily tasks than nonsmokers. Smoking in 1990 was associated with moderate or low physical fitness (OR = 2.21; 95% CI: 1.19-4.11) and moderate or severe pain (OR = 2.28; 95% CI: 1.32-3.94) in 1994, after adjustment for age, gender, civil state, workplace characteristics, physical exercise, and emotional symptoms. CONCLUSION: Even young adults report a lower functional status if they smoke. If this reflects a causal relationship it could be an important argument when trying to persuade young people to avoid smoking.

Job characteristics as predictors of neck pain. A 4-year prospective study.

Data from a community-based 4-year prospective study were used to investigate job characteristics as predictors of neck pain. Of 1791 working responders who completed a questionnaire in 1990, 1429 (79.8%) returned a second questionnaire 4 years later (1994). In responders without neck pain during the previous 12 months in 1990, the "little influence on own work situation" factor predicted neck pain during the previous 12 months (odds ratio = 2.21; 95% confidence interval, 1.18 to 4.14) and previous 7 days in 1994 (OR = 2.85; 95% confidence interval, 1.21 to 6.73) after adjustment for a series of potential confounders. In responders with neck pain in 1990, the little influence on own work situation factor was associated with persistent neck pain 4 years later. The study indicates that having little influence on one's own work situation is a predictor of neck pain.

Marital disruption and long-term work disability. A four-year prospective study.

Data from a community-based four-year prospective study were used to investigate the relationship between marital disruption and long-term work disability. In 1990, all inhabitants of the municipality Ullensaker, Norway, belonging to six cohorts (20-22 years, 30-32 years, 40-42 years, 50-52 years, 60-62 years and 70-72 years) were sent a questionnaire. Of the 1,359 respondents who were working, married or cohabiting, and not older than 62 years, 1,115 (82%) returned a second questionnaire four years later (1994). Separation or divorce between 1990 and 1994 was related to long-term work disability in 1994 (OR = 3.02; 95% CI: 1.57-5.81), even after adjustments for age, sex, work characteristics, number of work hours per week, job satisfaction, body mass index, having pre-school children, smoking, physical leisure activity, emotional symptoms and musculoskeletal pain (all measured in 1990). Emotional problems evoked by the marital disruption may be part of the explanation.