University Hospital of Umeå

The European Prospective Investigation into Cancer and Nutrition (EPIC) is an ongoing multi-centre prospective cohort study designed to investigate the relationship between nutrition and cancer, with the potential for studying other diseases as well. The study currently includes 519 978 participants (366 521 women and 153 457 men, mostly aged 35-70 years) in 23 centres located in 10 European countries, to be followed for cancer incidence and cause-specific mortality for several decades. At enrollment, which took place between 1992 and 2000 at each of the different centres, information was collected through a non-dietary questionnaire on lifestyle variables and through a dietary questionnaire addressing usual diet. Anthropometric measurements were performed and blood samples taken, from which plasma, serum, red cells and buffy coat fractions were separated and aliquoted for long-term storage, mostly in liquid nitrogen. To calibrate dietary measurements, a standardised, computer-assisted 24-hour dietary recall was implemented at each centre on stratified random samples of the participants, for a total of 36 900 subjects. EPIC represents the largest single resource available today world-wide for prospective investigations on the aetiology of cancers (and other diseases) that can integrate questionnaire data on lifestyle and diet, biomarkers of diet and of endogenous metabolism (e.g. hormones and growth factors) and genetic polymorphisms. First results of case-control studies nested within the cohort are expected early in 2003. The present paper provides a description of the EPIC study, with the aim of simplifying reference to it in future papers reporting substantive or methodological studies carried out in the EPIC cohort.

OBJECTIVE: To investigate whether smoking and HLA-DR shared epitope (SE) genes may interact in triggering immune reactions to citrulline-modified proteins. METHODS: In a case-control study involving patients with recent-onset rheumatoid arthritis (RA), we studied interactions between a major environmental risk factor (smoking), major susceptibility genes included in the SE of HLA-DR, and the presence of the most specific autoimmunity known for RA (i.e., antibodies to proteins modified by citrullination). Immunostaining for citrullinated proteins in cells from bronchoalveolar lavage fluid was used to investigate whether smoking is associated with citrullination in the lungs. RESULTS: Previous smoking was dose-dependently associated with occurrence of anticitrulline antibodies in RA patients. The presence of SE genes was a risk factor only for anticitrulline-positive RA, and not for anticitrulline-negative RA. A major gene-environment interaction between smoking and HLA-DR SE genes was evident for anticitrulline-positive RA, but not for anticitrulline-negative RA, and the combination of smoking history and the presence of double copies of HLA-DR SE genes increased the risk for RA 21-fold compared with the risk among nonsmokers carrying no SE genes. Positive immunostaining for citrullinated proteins was recorded in bronchoalveolar lavage cells from smokers but not in those from nonsmokers. CONCLUSION: We identified an environmental factor, smoking, that in the context of HLA-DR SE genes may trigger RA-specific immune reactions to citrullinated proteins. These data thus suggest an etiology involving a specific genotype, an environmental provocation, and the induction of specific autoimmunity, all restricted to a distinct subset of RA.

We prospectively studied the effect of heavy-load eccentric calf muscle training in 15 recreational athletes (12 men and 3 women; mean age, 44.3 +/- 7.0 years) who had the diagnosis of chronic Achilles tendinosis (degenerative changes) with a long duration of symptoms despite conventional nonsurgical treatment. Calf muscle strength and the amount of pain during activity (recorded on a visual analog scale) were measured before onset of training and after 12 weeks of eccentric training. At week 0, all patients had Achilles tendon pain not allowing running activity, and there was significantly lower eccentric and concentric calf muscle strength on the injured compared with the noninjured side. After the 12-week training period, all 15 patients were back at their preinjury levels with full running activity. There was a significant decrease in pain during activity, and the calf muscle strength on the injured side had increased significantly and did not differ significantly from that of the noninjured side. A comparison group of 15 recreational athletes with the same diagnosis and a long duration of symptoms had been treated conventionally, i.e., rest, nonsteroidal antiinflammatory drugs, changes of shoes or orthoses, physical therapy, and in all cases also with ordinary training programs. In no case was the conventional treatment successful, and all patients were ultimately treated surgically. Our treatment model with heavy-load eccentric calf muscle training has a very good short-term effect on athletes in their early forties.

Three inducible bacteriolytic proteins, designated P7, P9A and P9B, from the hemolymph of immunized pupae of the giant silk moth Hyalophora cecropia have been purified using a two-step procedure with cation-exchange chromatography. Purified protein P7 has a molecular weight of 15000 and its amino acid composition shows a great similarity to that of the lysozyme from the wax moth Galleria mellonella. Moreover, heat stability, pH-rate profile and bacteriolytic specificity also indicate that protein P7 is a lysozyme. The other purified proteins, P9A and P9B, are highly potent against Escherichia coli and some other gram-negative bacteria. The amino acid compositions of proteins P9A and P9B are very similar, although the contents of glutamic acid and methionine were different. The molecular weights of these very basic proteins are around 7000. The P9 proteins are heat stable; their activities were retained after 30 min incubation at 100 degrees C. Both forms of protein P9 clearly differ from the lysozyme class of enzymes and they may represent a new type of bacteriolytic protein.

ecently, the European Society of Cardiology (ESC) and the American College of Cardiology (ACC) convened a conference to discuss refinements in the diagnosis of acute myocardial infarction. The panel on biochemistry considered issues related to the use of marker proteins. We were guided predominantly by the science of the area. We were also cognizant of the impact that changes in the standards would have on epidemiology, clinical trials, education of physicians, and patient care. Our recommendations will be incorporated, with the recommendations of the other panels, into a position paper for the ESC and the ACC. However, the members of the biochemistry group decided to express the opinions we felt were important in this area independently. Our thinking does not represent the position of the ESC, the ACC, or of the conjoint task force.

The evidence for anthropometric factors influencing breast cancer risk is accumulating, but uncertainties remain concerning the role of fat distribution and potential effect modifiers. We used data from 73,542 premenopausal and 103,344 postmenopausal women from 9 European countries, taking part in the EPIC study. RRs from Cox regression models were calculated, using measured height, weight, BMI and waist and hip circumferences; categorized by cohort-wide quintiles; and expressed as continuous variables, adjusted for study center, age and other risk factors. During 4.7 years of follow-up, 1,879 incident invasive breast cancers were identified. In postmenopausal women, current HRT modified the body size-breast cancer association. Among nonusers, weight, BMI and hip circumference were positively associated with breast cancer risk (all ptrend < or = 0.002); obese women (BMI > 30) had a 31% excess risk compared to women with BMI < 25. Among HRT users, body measures were inversely but nonsignificantly associated with breast cancer. Excess breast cancer risk with HRT was particularly evident among lean women. Pooled RRs per height increment of 5 cm were 1.05 (95% CI 1.00-1.16) in premenopausal and 1.10 (95% CI 1.05-1.16) in postmenopausal women. Among premenopausal women, hip circumference was the only other measure significantly related to breast cancer (ptrend = 0.03), after accounting for BMI. In postmenopausal women not taking exogenous hormones, general obesity is a significant predictor of breast cancer, while abdominal fat assessed as waist-hip ratio or waist circumference was not related to excess risk when adjusted for BMI. Among premenopausal women, weight and BMI showed nonsignificant inverse associations with breast cancer.

Chlamydia pneumoniae has been associated with atherosclerosis and several other chronic diseases, but reports from different laboratories are highly variable and "gold standards" are lacking, which has led to calls for more standardized approaches to diagnostic testing. Using leading researchers in the field, we reviewed the available approaches to serological testing, culture, DNA amplification, and tissue diagnostics to make specific recommendations. With regard to serological testing, only use of microimmunofluorescence is recommended, standardized definitions for "acute infection" and "past exposure" are proposed, and the use of single immunoglobulin (Ig) G titers for determining acute infection and IgA for determining chronic infection are discouraged. Confirmation of a positive culture result requires propagation of the isolate or confirmation by use of polymerase chain reaction (PCR). Four of 18 PCR assays described in published reports met the proposed validation criteria. More consistent use of control antibodies and tissues and improvement in skill at identifying staining artifacts are necessary to avoid false-positive results of immunohistochemical staining. These standards should be applied in future investigations and periodically modified as indicated.

We report the 5 to 6 year follow-up of a multicenter study of bilateral subthalamic nucleus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) in advanced Parkinson's disease (PD) patients. Thirty-five STN patients and 16 GPi patients were assessed at 5 to 6 years after DBS surgery. Primary outcome measure was the stimulation effect on the motor Unified Parkinson's Disease Rating Scale (UPDRS) assessed with a prospective cross-over double-blind assessment without medications (stimulation was randomly switched on or off). Secondary outcomes were motor UPDRS changes with unblinded assessments in off- and on-medication states with and without stimulation, activities of daily living (ADL), anti-PD medications, and dyskinesias. In double-blind assessment, both STN and GPi DBS were significantly effective in improving the motor UPDRS scores (STN, P < 0.0001, 45.4%; GPi, P = 0.008, 20.0%) compared with off-stimulation, regardless of the sequence of stimulation. In open assessment, both STN- and GPi-DBS significantly improved the off-medication motor UPDRS when compared with before surgery (STN, P < 0.001, 50.5%; GPi, P = 0.002, 35.6%). Dyskinesias and ADL were significantly improved in both groups. Anti-PD medications were significantly reduced only in the STN group. Adverse events were more frequent in the STN group. These results confirm the long-term efficacy of STN and GPi DBS in advanced PD. Although the surgical targets were not randomized, there was a trend to a better outcome of motor signs in the STN-DBS patients and fewer adverse events in the GPi-DBS group.

The frequency of antibiotic-associated diarrhoea (AAD) and Clostridium difficile-associated diarrhoea (CdAD) was prospectively determined in a population of 2462 patients recruited from five Swedish hospitals, including divisions for infectious diseases, orthopaedics, surgery, geriatrics, nephrology and internal medicine. AAD developed in 4.9% of the treated patients. Faecal samples were obtained from 69% of patients with AAD and 55.4% were positive for C. difficile cytotoxin B. The frequency of AAD varied from 1.8 to 6.9% at the participating centres (P < 0.001). The frequency of AAD also varied considerably between medical disciplines and wards within different hospitals and was highest in the nephrology and geriatric units (6.7 and 7.1%, respectively). There was no difference in frequency of AAD when analysed with respect to gender or age. Medical interventions (laxative treatment, endoscopy and abdominal surgery) or presence of one concomitant disease (diabetes, malignancy, chronic renal disease and inflammatory bowel disease) did not significantly affect the frequency of AAD, whereas patients suffering from two or more of these illnesses had significantly (P = 0.001) higher frequencies of AAD. Patients treated with antibiotics for 3 days had a significantly (P = 0.009) lower frequency of AAD than those treated for longer periods. Treatment with cephalosporins, clindamycin or broad-spectrum penicillins was associated with an increased risk of AAD. With specimens from one centre, 62.5% of tested patients with AAD and 33.8% of asymptomatic patients were positive for cytotoxin B. Although C. difficile cytotoxin B in stool samples was significantly associated with AAD (P = 0.003), the causal relationship with diarrhoea is not always evident.

OBJECTIVE: To prospectively investigate tendon thickness and tendon structure by ultrasonography in patients treated with eccentric calf muscle training for painful chronic Achilles tendinosis located at the 2-6 cm level in the tendon. METHODS: The patients were examined with grey scale ultrasonography before and 3.8 years (mean) after the 12 week eccentric training regimen. At follow up, a questionnaire assessed present activity level and satisfaction with treatment. RESULTS: Twenty six tendons in twenty five patients (19 men and six women) with a mean age of 50 years were followed for a mean of 3.8 years (range 1.6-7.75). All patients had a long duration of painful symptoms (mean 17.1 months) from chronic Achilles tendinosis before treatment. At follow up, 22 of 25 patients were satisfied with treatment and active in Achilles tendon loading activities at the desired level. Ultrasonography showed that tendon thickness (at the widest part) had decreased significantly (p<0.005) after treatment (7.6 (2.3) v 8.8 (3) mm; mean (SD)). In untreated normal tendons, there was no significant difference in thickness after treatment (5.3 (1.3) mm before and 5.9 (0.8) mm after). All tendons with tendinosis had structural abnormalities (hypoechoic areas and irregular structure) before the start of treatment. After treatment, the structure was normal in 19 of the 26 tendons. Six of the seven patients with remaining structural abnormalities experienced pain in the tendon during loading. CONCLUSIONS: Ultrasonographic follow up of patients with mid-portion painful chronic Achilles tendinosis treated with eccentric calf muscle training showed a localised decrease in tendon thickness and a normalised tendon structure in most patients. Remaining structural tendon abnormalities seemed to be associated with residual pain in the tendon.

BACKGROUND: It is of paramount importance to evaluate the impact of participation in organized mammography service screening independently from changes in breast cancer treatment. This can be done by measuring the incidence of fatal breast cancer, which is based on the date of diagnosis and not on the date of death. METHODS: Among 549,091 women, covering approximately 30% of the Swedish screening-eligible population, the authors calculated the incidence rates of 2473 breast cancers that were fatal within 10 years after diagnosis and the incidence rates of 9737 advanced breast cancers. Data regarding each breast cancer diagnosis and the cause and date of death of each breast cancer case were gathered from national Swedish registries. Tumor characteristics were collected from regional cancer centers. Aggregated data concerning invitation and participation were provided by Sectra Medical Systems AB. Incidence rates were analyzed using Poisson regression. RESULTS: Women who participated in mammography screening had a statistically significant 41% reduction in their risk of dying of breast cancer within 10 years (relative risk, 0.59; 95% CI, 0.51-0.68 [P < .001]) and a 25% reduction in the rate of advanced breast cancers (relative risk, 0.75; 95% CI, 0.66-0.84 [P < .001]). CONCLUSIONS: Substantial reductions in the incidence rate of breast cancers that were fatal within 10 years after diagnosis and in the advanced breast cancer rate were found in this contemporaneous comparison of women participating versus those not participating in screening. These benefits appeared to be independent of recent changes in treatment regimens.

OBJECTIVE: To identify predictors for cardiovascular disease (CVD) and for overall survival in patients with rheumatoid arthritis (RA) followed from disease onset. METHODS: A retrospective cohort of patients with seropositive RA and disease onset between 1974 and 1978 (n = 211) was followed up at the end of 1995. Potential predictors for CVD, as measured by "the first cardiovascular event," and for overall survival were registered. The predictors were identified by extended Cox regression models. RESULTS: In simple Cox regression analysis, male sex, higher age at disease onset, HLA-B27, high disease activity, corticosteroid treatment early in disease, and hypertension significantly increased risk of cardiovascular event. Higher educational level, extensive disease modifying antirheumatic drug (DMARD) treatment, and corticosteroids > or =1 yr before event decreased the risk. In multiple Cox regression analysis, male sex, high age at disease onset, hypertension, higher haptoglobin level at disease onset, and corticosteroid treatment early in disease increased risk of CVD. In a multiple model comprising only patients with CVD, corticosteroids delayed the event. A high last registered erythrocyte sedimentation rate (ESR) value before event increased CVD risk, in particular when early in disease progression. Decreased life span was predicted by higher age at disease onset, male sex, low education level, high disease activity, hypertension, and CVD. HLA-B27 was associated with decreased life span, as was early, but not extensive corticosteroid treatment. DMARD treatment was associated with decreased mortality risk, as was the presence of joint prosthesis. In multiple regression, male sex, higher age at disease onset, atlantoaxial subluxation early in disease, hypertension, and cardiovascular event increased mortality. A high last registered ESR value before event or death added to that risk. CONCLUSION: The study emphasizes the importance of inflammation as an important risk indicator for CVD and mortality in RA. The positive impact of disease activity reducing treatment on CVD risk and survival is suggested.

Familial amyloidotic polyneuropathy (FAP) is an autosomal dominant inherited disorder characterized by progressive peripheral and autonomic neuropathy, associated with neural and systemic amyloid deposits. The amyloid fibrils contain a variant transthyretin (TTR) molecule (TTR met30), over 90% of which is produced in the liver. After liver transplantation in two patients with severe symptomatic FAP, only normal TTR was detectable in circulation. The two patients are being monitored at regular intervals, and, although in one patient there was no evidence of reduction in the quantity of amyloid present at 6 months, there had been no further progression of the neuropathy.

Research on psychological restoration and restorative environments is a needed complement to work on stress and environmental stressors. Two laboratory experiments tested the utility of two restorative environments theories, one concerned with directed attention capacity renewal and the other with stress reduction and associated changes in emotion. Various strategies were employed to distinguish restorative effects from other effects, to limit the role of arousal reduction in attentional restoration, and to begin mapping the time course for the emergence of outcomes. Both experiments tested for differential emotional and performance effects as a function of photographic environmental simulation (natural or urban environment). Across the experiments the natural environment simulation engendered generally more positive emotional self-reports. That consistent performance effects were not found in either study suggests that attentional restoration as reflected in performance is a more time-intensive process.

Smoking, nutrition, parity and oral contraceptive use have been reported as major environmental risk factors for cervical cancer. After the discovery of the very strong link between human papillomavirus (HPV) infection and cervical cancer, it is unclear whether the association of these environmental factors with cervical cancer reflect secondary associations attributable to confounding by HPV, if they are independent risk factors or whether they may act as cofactors to HPV infection in cervical carcinogenesis. To investigate this issue, we performed a population-based case-control study in the Vasterbotten county of Northern Sweden of 137 women with high-grade cervical intra-epithelial neoplasia (CIN 2-3) and 253 healthy age-matched women. The women answered a 94-item questionnaire on diet, smoking, oral contraceptive use and sexual history and donated specimens for diagnosis of present HPV infection (nested polymerase chain reaction on cervical brush samples) and for past or present HPV infections (HPV seropositivity). The previously described protective effects of dietary micronutrients were not detected. Pregnancy appeared to be a risk factor in the multivariate analysis (P < 0.0001). Prolonged oral contraceptive use and sexual history were associated with CIN 2-3 in univariate analysis, but these associations lost significance after taking HPV into account. Smoking was associated with CIN 2-3 (odds ratio (OR) 2.6, 95% confidence interval (CI) 1.7-4.0), the effect was dose-dependent (P = 0.002) and the smoking-associated risk was not affected by adjusting for HPV, neither when adjusting for HPV DNA (OR 2.5, CI 1.3-4.9) nor when adjusting for HPV seropositivity (OR 3.0, CI 1.9-4.7). In conclusion, after taking HPV into account, smoking appeared to be the most significant environmental risk factor for cervical neoplasia.

In a population-based prospective study of epileptic seizures in adult s aged > 17 years, we identified 563 patients with possible seizures in a period of 34 months. Seizures were unprovoked in 160 patients, an incidence of 56 in 100,000 person-years. There was no difference in incidence between sexes. Age-specific incidences of unprovoked seizures increased sharply in men from age 60 years and in women from age 70 years. The incidence of unprovoked seizures in those aged > 65 years was 139 (men 166, women 116). The cumulative incidence of unprovoked seizures between the ages of 17 and 84 years was 4.6%. The proportion with an identified presumptive cause for unprovoked seizures increased with advancing age. A presumed etiology was identified in 77% of persons aged > 60 years. Stroke was the most common etiology, detected in 30% (incidence 16) and in 45% at ages > 60 years. Tumors were detected in 11% (incidence 6) and Alzheimer's disease was detected in 7% (incidence 4). Eighteen percent of patients were demented. Unprovoked seizures were partial in 68% of cases (incidence 38), and generalized in 16% (incidence 9). Another 13% of patients had generalized seizures, but seizure onset was not witnessed (incidence 7). In 16%, there was a delay of > 1 year from the first unprovoked seizure to initial diagnosis.

BACKGROUND: The aim of this study was to evaluate the association between health-related quality of life (HRQL) and disease severity using lung function measures. METHODS: A survey was performed in subjects with COPD in Sweden. 168 subjects (70 women, mean age 64.3 years) completed the generic HRQL questionnaire, the Short Form 36 (SF-36), the disease-specific HRQL questionnaire; the St George's Respiratory Questionnaire (SGRQ), and the utility measure, the EQ-5D. The subjects were divided into four severity groups according to FEV1 per cent of predicted normal using two clinical guidelines: GOLD and BTS. Age, gender, smoking status and socio-economic group were regarded as confounders. RESULTS: The COPD severity grades affected the SGRQ Total scores, varying from 25 to 53 (GOLD p = 0.0005) and from 25 to 45 (BTS p = 0.0023). The scores for SF-36 Physical were significantly associated with COPD severity (GOLD p = 0.0059, BTS p = 0.032). No significant association were noticed for the SF-36, Mental Component Summary scores and COPD severity. Scores for EQ-5D VAS varied from 73 to 37 (GOLD I-IV p = 0.0001) and from 73 to 50 (BTS 0-III p = 0.0007). The SGRQ Total score was significant between age groups (p = 0.0047). No significant differences in HRQL with regard to gender, smoking status or socio-economic group were noticed. CONCLUSION: The results show that HRQL in COPD deteriorates with disease severity and with age. These data show a relationship between HRQL and disease severity obtained by lung function.

OBJECTIVE: The impact of present disease-modifying treatments (DMTs) in multiple sclerosis (MS) on nerve injury and reactive astrogliosis is still unclear. Therefore, we studied the effect of natalizumab treatment on the release of 2 brain-specific tissue damage markers into cerebrospinal fluid (CSF) in MS patients. METHODS: CSF samples from 92 patients with relapsing forms of MS were collected in a prospective manner prior to natalizumab treatment and after 6 or 12 months. In 86 cases, natalizumab was used as second-line DMT due to breakthrough of disease activity. The levels of neurofilament light (NFL) and glial fibrillary acidic protein (GFAP) were determined using highly sensitive in-house developed enzyme-linked immunosorbent assays. RESULTS: Natalizumab treatment led to a 3-fold reduction of NFL levels, from a mean value of 1,300 (standard deviation [SD], 2,200) to 400 (SD, 270) ng/l (p < 0.001). The later value was not significantly different from that found in healthy control subjects (350 ng/l; SD, 170; n = 28). Subgroup analysis revealed a consistent effect on NFL release, regardless of previous DMT or whether patients had relapses or were in remission within 3 months prior to natalizumab treatment. No differences between pre- and post-treatment levels of GFAP were detected. INTERPRETATION: Our data demonstrate that natalizumab treatment reduces the accumulation of nerve injury in relapsing forms of MS. It is anticipated that highly effective anti-inflammatory treatment can reduce axonal loss, thereby preventing development of permanent neurological disability.

BACKGROUND: Sleep apnea occurs frequently among patients with stroke, but it is still unknown whether a diagnosis of sleep apnea is an independent risk factor for mortality. We aimed to investigate whether obstructive or central sleep apnea was related to reduced long-term survival among patients with stroke. METHODS: Of 151 patients admitted for in-hospital stroke rehabilitation in the catchment area of Umeå from April 1, 1995, to May 1, 1997, 132 underwent overnight sleep apnea recordings at a mean (SD) of 23 (8) days after the onset of stroke. All patients were followed up prospectively for a mean (SD) of 10.0 (0.6) years, with death as the primary outcome; no one was lost to follow-up. Obstructive sleep apnea was defined when the obstructive apnea-hypopnea index was 15 or greater, and central sleep apnea was defined when the central apnea-hypopnea index was 15 or greater. Patients with obstructive and central apnea-hypopnea indexes of less than 15 served as control subjects. RESULTS: Of 132 enrolled patients, 116 had died at follow-up. The risk of death was higher among the 23 patients with obstructive sleep apnea than controls (adjusted hazard ratio, 1.76; 95% confidence interval, 1.05-2.95; P = .03), independent of age, sex, body mass index, smoking, hypertension, diabetes mellitus, atrial fibrillation, Mini-Mental State Examination score, and Barthel index of activities of daily living. There was no difference in mortality between the 28 patients with central sleep apnea and controls (adjusted hazard ratio, 1.07; 95% confidence interval, 0.65-1.76; P = .80). CONCLUSIONS: Patients with stroke and obstructive sleep apnea have an increased risk of early death. Central sleep apnea was not related to early death among the present patients.

To examine the influence of inhaled steroids on the bronchial mucosa, biopsies from six patients with severe bronchial asthma were studied before and after ten years of daily treatment with inhaled steroids. Biopsies from six healthy subjects were also examined. In the biopsies taken from the asthmatic patients before treatment there was a significant increase in inflammatory cell numbers compared with the biopsies from the control subjects. In all patients scanning electron microscopy showed a reduced coverage by cilia. Squamous cell metaplasia was seen in two patients. After ten years of treatment the number of inflammatory cells was significantly reduced compared to that before treatment and was not different from the control biopsies. Most of the epithelial cells showed a ciliated surface. Small focal areas with non-ciliated cells could still be seen in four patients. In the two patients with squamous cell metaplasia before treatment, small areas of metaplasia could still be seen. Despite the absence of inflammation and reduced epithelial damage during treatment all patients still had bronchial hyperresponsiveness.