The relationship between baseline value and its change: problems in categorization and the proposal of a new method

Minimally invasive non-surgical periodontal therapy of intrabony defects: A prospective multi-centre cohort study

AIM

To assess the potential benefits of minimally invasive non-surgical therapy (MINST) in teeth with intrabony defects and to explore factors associated with the outcomes.

MATERIALS AND METHODS

A multi-centre trial was conducted in 100 intrabony defects in periodontitis patients in private practice. Steps 1 and 2 periodontal therapy including MINST were provided. Clinical and radiographic data were analysed at baseline and 12 months after treatment, with the primary aim being change in radiographic defect depth at 12 months.

RESULTS

Eighty-four patients completed the 12-month follow up. The mean total radiographic defect depth reduced by 1.42 mm and the defect angle increased by 3° (both p < .05). Statistically significant improvements in probing pocket depth (PPD) and clinical attachment level (CAL) were seen at 12 months compared to baseline (p < .001). Fifty-six defects (66.7%) achieved pocket closure (PPD ≤ 4 mm) and 49 defects (58.3%) achieved the composite outcome (PPD ≤ 4 mm and CAL gain ≥3 mm). Deeper and narrower angled defects were positively correlated with radiographic and clinical improvements, respectively.

CONCLUSIONS

Improvements in clinical and radiographic outcomes were seen after MINST. This study highlights the generalizability and wide applicability of this approach, further supporting its effectiveness in the treatment of intrabony defects.

CLINICAL TRIAL REGISTRATION

NCT03741374. https://clinicaltrials.gov/study/NCT03741374?cond=minimally%20invasive%20non%20surgical%20therapy&locStr=UK&country=United%20Kingdom&distance=50&rank=2.

Efficacy of access flap and pocket elimination procedures in the management of peri-implantitis: A systematic review and meta-analysis

AIM

To evaluate the efficacy of access flap and pocket elimination procedures in the surgical treatment of peri-implantitis.

MATERIALS AND METHODS

Systematic electronic searches (Central/MEDLINE/EMBASE) up to March 2022 were conducted to identify prospective clinical studies evaluating surgical therapy (access flap or pocket elimination procedures) of peri-implantitis. Primary outcome measures were reduction of probing depth (PD) and bleeding on probing (BOP). Risk of bias was evaluated according to study design. Meta-analysis and meta-regression were performed. Results were expressed as standardized mean effect with 95% confidence interval (CI).

RESULTS

Evidence from studies directly comparing surgical with non-surgical therapy is lacking. Based on pre-post data originating from 13 prospective patient cohorts, pronounced reductions of PD (standardized mean effect: 2.2 mm; 95% CI 1.8-2.7) and BOP% (27.0; 95% CI 19.8-34.2) as well as marginal bone level gain (0.2 mm; 95% CI -0.0 to 0.5) were observed at evaluation time points ranging from 1 to 5 years. Wide prediction intervals suggested a high degree of heterogeneity. Reduction of mean PD increased by 0.7 mm (95% CI 0.5-0.9) for every millimetre in increase of mean PD at baseline. During the follow-up period ranging from 1 to 5 years, disease recurrence occurred frequently and implant loss was not uncommon.

CONCLUSIONS

Access flap and pocket elimination surgery are effective procedures in the management of peri-implantitis, although rates of disease recurrence during 5 years were high. Treatment outcomes were affected by baseline conditions.

Arguments for the biological and predictive relevance of the proportional recovery rule

The proportional recovery rule (PRR) posits that most stroke survivors can expect to reduce a fixed proportion of their motor impairment. As a statistical model, the PRR explicitly relates change scores to baseline values - an approach that arises in many scientific domains but has the potential to introduce artifacts and flawed conclusions. We describe approaches that can assess associations between baseline and changes from baseline while avoiding artifacts due either to mathematical coupling or to regression to the mean. We also describe methods that can compare different biological models of recovery. Across several real datasets in stroke recovery, we find evidence for non-artifactual associations between baseline and change, and support for the PRR compared to alternative models. We also introduce a statistical perspective that can be used to assess future models. We conclude that the PRR remains a biologically relevant model of stroke recovery.

How to Test the Association Between Baseline Performance Level and the Modulatory Effects of Non-Invasive Brain Stimulation Techniques

Behavioral effects of non-invasive brain stimulation techniques (NIBS) can dramatically change as a function of different factors (e.g., stimulation intensity, timing of stimulation). In this framework, lately there has been a growing interest toward the importance of considering the inter-individual differences in baseline performance and how they are related with behavioral NIBS effects. However, assessing how baseline performance level is associated with behavioral effects of brain stimulation techniques raises up crucial methodological issues. How can we test whether the performance at baseline is predictive of the effects of NIBS, when NIBS effects themselves are estimated with reference to baseline performance? In this perspective article, we discuss the limitations connected to widely used strategies for the analysis of the association between baseline value and NIBS effects, and review solutions to properly address this type of question.

Sustained Impact of Real-time Continuous Glucose Monitoring in Adults With Type 1 Diabetes on Insulin Pump Therapy: Results After the 24-Month RESCUE Study

OBJECTIVE

In recent years, a growing number of people with type 1 diabetes gained access to real-time continuous glucose monitoring (rtCGM). Long-term benefits of rtCGM are unclear because of a lack of large studies of long duration. We evaluated whether real-world rtCGM use up to 24 months offered benefits, particularly in those living with impaired awareness of hypoglycemia (IAH).

RESEARCH DESIGN AND METHODS

This 24-month, prospective, observational cohort study followed 441 adults with insulin pumps receiving full reimbursement for rtCGM. Forty-two percent had IAH. The primary end point was evolution of HbA_1c, with secondary end points change in acute hypoglycemia complications, diabetes-related work absenteeism, and quality of life scores. Additionally, we evaluated whether people could achieve glycemic consensus targets during follow-up.

RESULTS

After 24 months, HbA_1c remained significantly lower compared with baseline (7.64% [60 mmol/mol] vs. 7.37% [57 mmol/mol], P < 0.0001). Sustained benefits were also observed for the score on the hypoglycemia fear survey and hypoglycemia-related acute complications irrespective of hypoglycemia awareness level. People with IAH had the strongest improvement, especially for severe hypoglycemia (862 events in the year before vs. 119 events per 100 patient-years in the 2nd year, P < 0.0001). Over 24 months, more people were able to meet hypoglycemia consensus targets at the expense of slightly fewer people achieving hyperglycemia consensus targets. Furthermore, the number of people with HbA_1c <7% (<53 mmol/mol) without severe hypoglycemia events more than doubled (11.0% vs. 25.4%, P < 0.0001).

CONCLUSIONS

Use of rtCGM led to sustained improvements in hypoglycemia-related glucose control over 24 months. Lower fear of hypoglycemia, fewer acute hypoglycemia-related events, and fewer diabetes-related days off from work were observed, particularly in those with IAH.

Quality of Life and Glucose Control After 1 Year of Nationwide Reimbursement of Intermittently Scanned Continuous Glucose Monitoring in Adults Living With Type 1 Diabetes (FUTURE): A Prospective Observational Real-World Cohort Study

OBJECTIVE

In 2016, nationwide reimbursement of intermittently scanned continuous glucose monitoring (isCGM) for people living with type 1 diabetes treated in specialist diabetes centers was introduced in Belgium. We undertook a 12-month prospective observational multicenter real-world study to investigate impact of isCGM on quality of life and glycemic control.

RESEARCH DESIGN AND METHODS

Between July 2016 and July 2018, 1,913 adults with type 1 diabetes were consecutively recruited in three specialist diabetes centers. Demographic, metabolic, and quality of life data were collected at baseline, 6 months, and 12 months of standardized clinical follow-up. The primary end point was evolution of quality of life from baseline to 12 months. Secondary outcome measures were, among others, change in HbA_1c, time spent in different glycemic ranges, occurrence of acute diabetes complications, and work absenteeism.

RESULTS

General and diabetes-specific quality of life was high at baseline and remained stable, whereas treatment satisfaction improved (P < 0.0001). Admissions for severe hypoglycemia and/or ketoacidosis were rare in the year before study (n = 63 out of 1,913; 3.3%), but decreased further to 2.2% (n = 37 out of 1,711; P = 0.031). During the study, fewer people reported severe hypoglycemic events (n = 280 out of 1,913 [14.6%] vs. n = 134 out of 1,711 [7.8%]; P < 0.0001) or hypoglycemic comas (n = 52 out of 1,913 [2.7%] vs. n = 18 out of 1,711 [1.1%]; P = 0.001) while maintaining HbA_1c levels. Fewer people were absent from work (n = 111 out of 1,913 [5.8%] vs. n = 49 out of 1,711 [2.9%]; P < 0.0001). Time spent in hypoglycemia significantly decreased in parallel with less time in range and more time in hyperglycemia. Eleven percent (n = 210) of participants experienced skin reactions, leading to stopping of isCGM in 22 participants (1%).

CONCLUSIONS

Nationwide unrestricted reimbursement of isCGM in people with type 1 diabetes treated in specialist diabetes centers results in higher treatment satisfaction, less severe hypoglycemia, and less work absenteeism, while maintaining quality of life and HbA_1c.

Psoriasis treat to target: defining outcomes in psoriasis using data from a real-world, population-based cohort study (the British Association of Dermatologists Biologics and Immunomodulators Register, BADBIR)

Background

The ‘treat to target’ paradigm improves outcomes and reduces costs in chronic disease management but is not yet established in psoriasis.

Objectives

To identify treatment targets in psoriasis using two common measures of disease activity: Psoriasis Area and Severity Index (PASI) and Physician's Global Assessment (PGA).

Methods

Data from a multicentre longitudinal U.K. cohort of patients with psoriasis receiving systemic or biologic therapies (British Association of Dermatologists Biologics and Immunomodulators Register, BADBIR) were used to identify absolute PASI thresholds for 90% (PASI 90) and 75% (PASI 75) improvements in baseline disease activity, using receiver operating characteristic curves. The relationship between PGA (clear, almost clear, mild, moderate, moderate–severe, severe) and PASI (range 0–72) was described, and the concordance between absolute and relative definitions of response was determined. The same approach was used to establish treatment response and eligibility definitions based on PGA.

Results

Data from 13 422 patients were available (58% male, 91% white ethnicity, mean age 44·9 years), including over 23 000 longitudinal PASI and PGA scores. An absolute PASI ≤ 2 was concordant with PASI 90 and an absolute PASI ≤ 4 was concordant with PASI 75 in 90% and 88% of cases, respectively. These findings were robust to subgroups of timing of assessment, baseline disease severity and treatment modality. PASI and PGA were strongly correlated (Spearman's rank correlation coefficient 0·92). The median PASI increased from 0 (interquartile range 0–0, range 0–23) to 19 (interquartile range 15–25, range 0–64) for PGA clear to severe, respectively. PGA clear/almost clear was concordant with PASI ≤ 2 in 90% of cases, and PGA moderate–severe severe was concordant with the National Institute for Health and Care Excellence PASI eligibility criteria for biologics in 81% of cases.

Conclusions

An absolute PASI ≤ 2 and PGA clear/almost clear represent relevant disease end points to inform treat‐to‐target management strategies in psoriasis.

What's already known about this topic?

The most commonly used relative disease activity measure in psoriasis is ≥ 90% improvement in Psoriasis Area and Severity Index (PASI 90); however, it has several limitations including dependency on a baseline severity assessment.

Defining an absolute target disease activity end point in psoriasis has the potential to improve patient outcomes and reduce costs, as demonstrated by treat‐to‐target approaches in other chronic diseases such as hypertension and diabetes.

The Physician's Global Assessment (PGA) is a popular alternative measure of psoriasis severity in daily practice; however, its utility has not been formally assessed with respect to PASI.

What does this study add?

An absolute PASI ≤ 2 corresponds with PASI 90 response and is a relevant disease end point for treat‐to‐target approaches in psoriasis.

There is a strong correlation between PASI and PGA.

PGA moderate–severe/severe may serve as an alternative eligibility criterion for biologics to PASI‐based definitions, and PGA clear/almost clear is an appropriate alternative absolute treatment end point.

What are the clinical implications of this work?

Absolute PASI ≤ 2 and PGA clear/almost clear represent relevant disease end points to inform treat‐to‐target management strategies in psoriasis.

Linked Editorial: Takeshita. Br J Dermatol 2020; 182:1075–1076.

Effects of bifocals on visual acuity in children with Down syndrome: a randomized controlled trial

Purpose

Children with Down syndrome (DS) typically have reduced visual acuity (VA) and accommodation lag, but it is unclear whether prescribed glasses should correct both distance VA (DVA) and near VA (NVA) due to the lack of RCTs. We therefore conducted a multicentre RCT to compare the effects of bifocals designed to correct both DVA and NVA with distance‐correcting unifocal glasses in children with DS.

Methods

A total of 119 children with DS, aged 2–16, were randomly allocated for bifocal or unifocal glasses (with full correction of refraction error in cycloplegia) in 14 Dutch hospitals and followed during 1 year. VA data were analysed in relation to baseline VA with ancova.

Results

Treatment groups showed no differences at baseline. Shortly after receiving new corrections (~6 weeks), uncrowded NVA (bifocals 0.18 ± 0.33 LogMar; unifocals 0.09 ± 0.19 LogMar) and crowded NVA with bifocals (bifocals 0.13 ± 0.36 LogMar; unifocals 0.08 ± 0.33 LogMar) were significantly better than at baseline, but these short‐term improvements in NVA were not significantly different between the two treatments (p > 0.151). The 1‐year treatment differences were as follows: significantly larger improvement for bifocals compared to unifocals in both uncrowded NVA (bifocals 0.23 ± 0.29 LogMar, unifocals 0.12 ± 0.30 LogMar, p = 0.045) and crowded NVA (bifocals 0.31 ± 0.28 LogMar; unifocals 0.16 ± 0.30 LogMar, p = 0.017). Improvements in DVA were comparable (bifocals 0.07 ± 0.21 LogMar, unifocals 0.08 ± 0.22 LogMar, p = 0.565). Children with poor baseline VA improved more. Accommodation lag stayed unchanged.

Conclusion

After one year, bifocals with full correction of ametropia led to significantly larger improvement of both uncrowded NVA and crowded NVA in children with DS with accommodation lag compared to unifocals.

Recovery after stroke: not so proportional after all?

The proportional recovery rule asserts that most stroke survivors recover a fixed proportion of lost function. To the extent that this is true, recovery from stroke can be predicted accurately from baseline measures of acute post-stroke impairment alone. Reports that baseline scores explain more than 80%, and sometimes more than 90%, of the variance in the patients' recoveries, are rapidly accumulating. Here, we show that these headline effect sizes are likely inflated. The key effects in this literature are typically expressed as, or reducible to, correlation coefficients between baseline scores and recovery (outcome scores minus baseline scores). Using formal analyses and simulations, we show that these correlations will be extreme when outcomes are significantly less variable than baselines, which they often will be in practice regardless of the real relationship between outcomes and baselines. We show that these effect sizes are likely to be over-optimistic in every empirical study that we found that reported enough information for us to make the judgement, and argue that the same is likely to be true in other studies as well. The implication is that recovery after stroke may not be as proportional as recent studies suggest.

Therapeutic lumbar puncture for headache in idiopathic intracranial hypertension: Minimal gain, is it worth the pain?

Background

Headache is disabling and prevalent in idiopathic intracranial hypertension. Therapeutic lumbar punctures may be considered to manage headache. This study evaluated the acute effect of lumbar punctures on headache severity. Additionally, the effect of lumbar puncture pressure on post-lumbar puncture headache was evaluated.

Methods

Active idiopathic intracranial hypertension patients were prospectively recruited to a cohort study, lumbar puncture pressure and papilloedema grade were noted. Headache severity was recorded using a numeric rating scale (NRS) 0–10, pre-lumbar puncture and following lumbar puncture at 1, 4 and 6 hours and daily for 7 days.

Results

Fifty two patients were recruited (mean lumbar puncture opening pressure 32 (28–37 cmCSF). At any point in the week post-lumbar puncture, headache severity improved in 71% (but a small reduction of −1.1 ± 2.6 numeric rating scale) and exacerbated in 64%, with 30% experiencing a severe exacerbation ≥ 4 numeric rating scale. Therapeutic lumbar punctures are typically considered in idiopathic intracranial hypertension patients with severe headaches (numeric rating scale ≥ 7). In this cohort, the likelihood of improvement was 92% (a modest reduction of headache pain by −3.0 ± 2.8 numeric rating scale, p = 0.012, day 7), while 33% deteriorated. Idiopathic intracranial hypertension patients with mild (numeric rating scale 1–3) or no headache (on the day of lumbar puncture, prior to lumbar puncture) had a high risk of post- lumbar puncture headache exacerbation (81% and 67% respectively). Importantly, there was no relationship between lumbar puncture opening pressure and headache response after lumbar puncture.

Conclusion

Following lumbar puncture, the majority of idiopathic intracranial hypertension patients experience some improvement, but the benefit is small and post-lumbar puncture headache exacerbation is common, and in some prolonged and severe. Lumbar puncture pressure does not influence the post-lumbar puncture headache.

Effect of Continuous Glucose Monitoring on Glycemic Control, Acute Admissions, and Quality of Life: A Real-World Study

CONTEXT

Randomized controlled trials evaluating real-time continuous glucose monitoring (RT-CGM) patients with type 1 diabetes (T1D) show improved glycemic control, but limited data are available on real-world use.

OBJECTIVE

To assess impact of RT-CGM in real-world settings on glycemic control, hospital admissions, work absenteeism, and quality of life (QOL).

DESIGN

Prospective, observational, multicenter, cohort study.

PARTICIPANTS

A total of 515 adults with T1D on continuous subcutaneous insulin infusion (CSII) therapy starting in the Belgian RT-CGM reimbursement program.

INTERVENTION

Initiation of RT-CGM reimbursement.

MAIN OUTCOME MEASURE

Hemoglobin A1c (HbA1c) evolution from baseline to 12 months.

RESULTS

Between September 1, 2014, and December 31, 2016, 515 adults entered the reimbursement system. Over this period, 417 (81%) patients used RT-CGM for at least 12 months. Baseline HbA1c was 7.7 ± 0.9% (61 ± 9.8 mmol/mol) and decreased to 7.4 ± 0.8% (57 ± 8.7 mmol/mol) at 12 months (P < 0.0001). Subjects who started RT-CGM because of insufficient glycemic control showed stronger decrease in HbA1c at 4, 8, and 12 months compared with patients who started because of hypoglycemia or pregnancy. In the year preceding reimbursement, 16% of patients were hospitalized for severe hypoglycemia or ketoacidosis in contrast to 4% (P < 0.0005) the following year, with decrease in admission days from 54 to 18 per 100 patient years (P < 0.0005). In the same period, work absenteeism decreased and QOL improved significantly, with strong decline in fear of hypoglycemia.

CONCLUSION

Sensor-augmented pump therapy in patients with T1D followed in specialized centers improves HbA1c, fear of hypoglycemia, and QOL, whereas work absenteeism and admissions for acute diabetes complications decreased.

Toothbrushing behaviour and periodontal pocketing: An 11-year longitudinal study

AIM

To explore the association between toothbrushing behaviour and change in periodontal pocketing among adults.

METHODS

We pooled data from 1,025 adults, aged 30-89 years, who participated in two national surveys in Finland (Health 2000 and Health 2011, BRIF8901) and reported their toothbrushing frequency. A cumulative measure of regular toothbrushing was created by counting the number of times participants reported brushing twice or more daily across the two surveys (ranging from 0 to 2). The association between toothbrushing behaviour and the number of teeth with periodontal pocket depth (PPD) ≥4 mm over 11 years was assessed in linear regression models adjusting for confounders.

RESULTS

There was a clear dose-response relationship between toothbrushing frequency (either at baseline or follow-up) and change in number of teeth with PPD ≥ 4 mm. There was also evidence of a cumulative effect of regular toothbrushing on change in number of teeth with PPD ≥ 4 mm. Participants who reported brushing twice or more a day in both surveys developed 1.99 (95% CI: 1.02-2.95) fewer teeth with PPD ≥ 4 mm than those who did not report this behaviour in any survey.

CONCLUSION

This 11-year prospective study showed that toothbrushing behaviour was associated with smaller increments in the number of teeth with periodontal pocketing.

The Return of Rate Dependence

Rate dependence, a well-known phenomenon in behavioral pharmacology, appears to have declined as a topic of interest, perhaps, as a result of being viewed pertinent to only the preclinical investigation of drugs on schedule-controlled performance. Obstacles to data interpretation due to conflation with regression to the mean also appear to have contributed to the topic's decline. Despite this reduction in exposure, rate dependence is a useful concept and tool that can be used to determine sources of variability, predict therapeutic outcomes, and identify individuals that are most likely to respond therapeutically. Armed with new statistical methods and an understanding of the broad range of conditions under which rate dependence can be observed, we urge researchers to revisit the concept, use the appropriate analysis methods, and to design empirical studies a priori to further explore rate dependence.

Experimental verification of regression to the mean in redox biology: differential responses to exercise

An important methodological threat when selecting individuals based on initial values for a given trait is the "regression to the mean" artifact. This artifact appears when a group with an extreme mean value during a first measurement tends to obtain a less extreme value (i.e. tends toward the mean) on a subsequent measurement. The main aim was to experimentally confirm the presence of this artifact in the responses of the reference oxidative stress biomarker (F₂-isoprostanes) after exercise. Urine samples were collected before and immediately following acute exercise in order to determine the level of exercise-induced oxidative stress. Afterwards, participants were arranged into three groups based on their levels of exercise-induced oxidative stress (low, moderate and high oxidative stress groups; n = 12 per group). In order to verify the existence of the regression to the mean artifact, the three groups were subjected to a second exercise trial one week after the first trial. This study confirmed the regression to the mean artifact in a redox biology context and showed that this artifact can be minimized by performing a duplicate pretreatment measurement after completing a nonrandom sorting based on the first assessment. This study also indicated that different individuals experience high oxidative stress or reductive stress (or no stress) to the same exercise stimulus even after adjusting for regression to the mean. This finding substantiates the methodological choice to divide individuals based on their degree of exercise-induced oxidative stress in future experiments to investigate the role of reactive species in exercise adaptations.

Accelerated HF-rTMS Protocol has a Rate-Dependent Effect on dACC Activation in Alcohol-Dependent Patients: An Open-Label Feasibility Study

BACKGROUND

The application of accelerated high-frequency (HF) repetitive transcranial magnetic stimulation (rTMS) could be a potential treatment option for alcohol-dependent patients and may result in a faster clinical response. In this open-label HF-rTMS feasibility study, we wanted to replicate previous findings of baseline brain activation as a predictor of relapse, and to evaluate how this intervention influences the relapse neurocircuit of "treatment-seeking" alcohol-dependent patients, by means of functional magnetic resonance imaging (fMRI) cue-exposure paradigms. Because relapsing patients have a diminished resilience of the emotion regulation/cognitive control system, before HF-rTMS treatment, we expected lower neuronal activation of especially the ventromedial prefrontal cortex and anterior cingulate cortex (ACC) during the presentation of alcohol-related cues in these patients. The relapse neurocircuit should be modified after accelerated HF-rTMS treatment, only in those patients who did not relapse.

METHODS

After being administered a single sham-controlled HF-rTMS session (20 Hz to 110% motor threshold), 19 alcohol-dependent patients received an accelerated HF-rTMS protocol, consisting of 14 right dorsolateral prefrontal cortical sessions spread over 3 days. Before and after stimulation, during fMRI patients were confronted with a block and an event-related alcoholic cue-exposure paradigm. Relapse was defined as the consumption of any amount of alcohol within 4 weeks after the stimulation. A region of interest analysis was performed to evaluate how HF-rTMS exerts its effect.

RESULTS

After 4 weeks, 13 of 19 patients had already consumed alcohol. When abstainers were compared to patients who had relapsed, we found higher dorsal ACC (dACC) activation at baseline, but only during the blocked cue-exposure paradigm. The effects of HF-rTMS on dACC blood oxygen level-dependent response were negatively correlated with the baseline dACC activation. Due to susceptibility artifacts located at the ventral cortical aspects in 6 of our participants, reliable data were only obtained for the ACC.

CONCLUSIONS

Our data indicate that higher baseline dACC activation may serve as a protective mechanism regarding relapse. For the first time, it is demonstrated that accelerated HF-rTMS treatment influences dACC activation in a rate-dependent manner: the lower the baseline dACC activation, the more dACC activity was increased after HF-rTMS treatment.

Order in the absence of an effect: Identifying rate-dependent relationships

The heterogeneity of group data can obscure a significant effect of an intervention due to differential baseline scores. Instead of discarding the seemingly heterogeneous response set, an orderly lawful relationship could be present. Rate dependence describes a pattern between a baseline and the change in that baseline following some intervention. To highlight the importance of analyzing data from a rate-dependent perspective, we (1) briefly review research illustrating that rate-dependent effects can be observed in response to both drug and non-drug interventions in varied schedules of reinforcement in clinical and preclinical populations; (2) observe that the process of rate-dependence likely requires multiple parts of a system operating simultaneously to evoke differential responding as a function of baseline; and (3) describe several statistical methods for consideration and posit that Oldham's correlation is the most appropriate for rate-dependent analyses. Finally, we propose future applications for these analyses in which the level of baseline behavior exhibited prior to an intervention may determine the magnitude and direction of behavior change and can lead to the identification of subpopulations that would be benefitted. In sum, rate dependence is an invaluable perspective to examine data following any intervention in order to identify previously overlooked results.

Defining and predicting outcomes of non-surgical periodontal treatment: a 1-yr follow-up study

This study reports on 1-yr outcomes of non-surgical periodontal therapy and compares predictive models resulting from different definitions of treatment success. A total of 149 participants, 30-70 yr of age, provided clinical periodontal data and data on sociodemographic status, health status, symptoms, and oral health-care behaviors at baseline. One week later, clinical attachment level and probing pocket depth were recorded again in 148 patients. Participants underwent non-surgical periodontal therapy, including scaling and root planing, during three to four clinical sessions. Three and 12 months later, clinical attachment level, probing pocket depth, and bleeding on probing (BOP) were recorded in 141 and 137 participants, respectively. Using test-retest data, patients were classified as having 'downhill', 'stable', or 'improved' results on three clinical attachment level and three probing pocket depth outcomes, and their classification was found to vary considerably according to outcome. Although the predictors of treatment outcome varied depending on the variable chosen to represent the treatment outcome, some predictors were more commonly noted as predicting improvement, namely a high baseline percentage of sites with subgingival calculus and the presence of suppuration at baseline. The latter was, however, also predictive for tooth loss during the study. Our findings underline the need for uniformity in defining the outcomes in trials of periodontal therapy.

Determinants of Propranolol's Selective Effect on Loss Aversion

Research on emotion and decision making has suggested that arousal mediates risky decisions, but several distinct and often confounded processes drive such choices. We used econometric modeling to separate and quantify the unique contributions of loss aversion, risk attitudes, and choice consistency to risky decision making. We administered the beta-blocker propranolol in a double-blind, placebo-controlled within-subjects study, targeting the neurohormonal basis of physiological arousal. Matching our intervention's pharmacological specificity with a quantitative model delineating decision-making components allowed us to identify the causal relationships between arousal and decision making that do and do not exist. Propranolol selectively reduced loss aversion in a baseline- and dose-dependent manner (i.e., as a function of initial loss aversion and body mass index), and did not affect risk attitudes or choice consistency. These findings provide evidence for a specific, modulatory, and causal relationship between precise components of emotion and risky decision making.

Intravenous paracetamol for fever control in acute brain injury patients: cerebral and hemodynamic effects

BACKGROUND

Fever occurs frequently in acute brain injury patients, and its occurrence is associated with poorer outcomes. Paracetamol, an antipyretic frequently employed in patients with cerebral damage, may cause hypotension. We evaluated the cerebral and hemodynamic effects of intravenous (IV) paracetamol for the control of fever in Neuro-Intensive Care Unit (NICU) patients.

METHODS

This is a prospective observational study in which we enrolled 32 NICU patients: Subarachnoid Hemorrhage (SAH, n = 18), Traumatic Brain Injury (TBI, n = 10), Intracerebral Hemorrhage (ICH, n = 2) and Acute Ischemic Stroke (AIS, n = 2).

RESULTS

The administration of paracetamol resulted in a decrease of core body temperature (Tc) (p = 0,0001), mean arterial pressure (MAP) (p = 0,0006), cerebral perfusion pressure (CPP) (p = 0,0033), and jugular venous oxygen saturation (SjVO2) (p = 0.0193), and in an increase of arteriojugular venous differences of oxygen (AVDO2) (p = 0.0012). The proportion of patients who had an infusion of norepinephrine increased from 47 % to 75 % (p = 0.0039 McNemar Test). When intracranial pressure (ICP) at the start of paracetamol infusion (t-0) was compared with the measurement of ICP after 2 h, a significant correlation was observed (r = 0.669, p = 0.0002). This marked and significant correlation can be explained by the fact that for the higher levels of ICP assessed at t-0 (greater than 15 mmHg), we observed a marked reduction of ICP concomitant with the decrease of Tc. No problems related to norepinephrine administration and/or increase in dosage were observed.

CONCLUSION

Paracetamol administration is effective but exposes patients to hypotensive episodes that must be recognized and treated expeditiously to prevent further damage to the injured brain.

Key statistical and analytical issues for evaluating treatment effects in periodontal research

Statistics is an indispensible tool for evaluating treatment effects in clinical research. Due to the complexities of periodontal disease progression and data collection, statistical analyses for periodontal research have been a great challenge for both clinicians and statisticians. The aim of this article is to provide an overview of several basic, but important, statistical issues related to the evaluation of treatment effects and to clarify some common statistical misconceptions. Some of these issues are general, concerning many disciplines, and some are unique to periodontal research. We first discuss several statistical concepts that have sometimes been overlooked or misunderstood by periodontal researchers. For instance, decisions about whether to use the t-test or analysis of covariance, or whether to use parametric tests such as the t-test or its non-parametric counterpart, the Mann-Whitney U-test, have perplexed many periodontal researchers. We also describe more advanced methodological issues that have sometimes been overlooked by researchers. For instance, the phenomenon of regression to the mean is a fundamental issue to be considered when evaluating treatment effects, and collinearity amongst covariates is a conundrum that must be resolved when explaining and predicting treatment effects. Quick and easy solutions to these methodological and analytical issues are not always available in the literature, and careful statistical thinking is paramount when conducting useful and meaningful research.

Blood pressure status and post-exercise hypotension: an example of a spurious correlation in hypertension research?

A single bout of exercise lowers blood pressure (BP) for up to 24 h afterwards. The magnitude of this post-exercise hypotension (PEH) has been reported to be correlated most strongly to pre-exercise BP, and this apparent relationship has influenced position statements about the value of exercise in arterial hypertension. Nevertheless, this correlation could be adversely affected by mathematical coupling and regression-to-the-mean artefacts. Therefore, we aimed to examine the degree to which BP status moderates PEH while, for the first time, controlling for these statistical artefacts. A total of 32 participants, with pre-exercise mean arterial pressures of 65-110 mm Hg, cycled for 30 min at 70% peak oxygen uptake. Systolic BP and diastolic BP were measured (Portapres) before exercise and for 20 min after exercise. Changes in BP were regressed against pre-exercise values, and against the mean of pre- and post-exercise BP, among other indices that are also known not to be prone to artefacts. Correlations between pre-exercise BP and the exercise-mediated reductions were typical of those previously reported (r=0.37-0.62, P<0.05), but not large enough to rule out spuriousness (P>0.05). Artefact-free indices of BP status (pre- and post-exercise mean as well as an earlier independent measurement) did not correlate with reductions in BP (P>0.05), which were moderated more by peak oxygen uptake and time of day (P<0.05). These data indicate that, if statistical artefacts are not controlled for, the influence of BP status on the degree of PEH can be spuriously exaggerated to the extent that other more important moderators of BP change are masked.

Comparison of the effects of treatment of peri-implant infection in animal and human studies: systematic review and meta-analysis

OBJECTIVE

The main objective of this systematic review is to compare the effects of treatment of peri-implant infection between animal and human studies.

MATERIAL AND METHODS

A literature search was conducted using the Medline, Cochrane Central Register of Controlled Trials, and Latin American and Caribbean Health Sciences Literature databases up to and including May 2008. In addition, bibliographies of systematic reviews on peri-implant diseases were searched manually. Non-surgical and surgical treatments of peri-implantitis/mucositis in animal models or human studies were compared. Meta-analysis was conducted to investigate the difference between the reported treatment effects in animal and human studies. Changes in probing pocket depth (PPD) and probing attachment level (PAL) from baseline measurements were used as measures of outcome. Single-level and multilevel meta-regression analysis was performed by taking into account the different follow-up times of the studies included.

RESULTS

The single-level and multilevel random-effects meta-analysis showed that the difference in PPD reduction [0.31 mm, 95% confidence interval (CI): -0.27, 0.88] and in PAL gain (0.21 mm, 95% CI: -0.47, 0.88) between animal and human studies was not statistically significant. The random-effects meta-regression suggested that studies with longer follow-up times revealed greater PPD reduction (0.25 mm per month, 95% CI: 0.14, 0.35). However, when the different follow-up times were taken into account, these differences became greater. Substantial heterogeneity between studies was found in the meta-analyses (I(2)=97.6% for animal studies and 99.9% for human studies).

CONCLUSION

There was great heterogeneity between human and animal studies in terms of study designs and treatment procedures. Therefore, the results from this meta-analysis should be interpreted with caution. Heterogeneity between studies and its causes merit further investigations.

Effect of Age on Gingival Crevicular Fluid Concentrations of MIF and PGE2

We used an experimental gingivitis study design to compare crevicular fluid concentrations of Migration Inhibitory Factor (MIF) and Prostaglandin E2 (PGE2) in younger (18 to 30 yrs) and older (46 to 77 yrs) healthy adults. PGE2 increased after 1 wk in younger participants, whereas it decreased in older individuals after 1 wk of plaque accumulation. A significant interaction between age and time was observed for PGE2 (p = 0.04). High concentrations of MIF were identified in both age groups at baseline. MIF increased in the younger participants, whereas in the older individuals a decrease over time was observed. MIF concentration was positively correlated with plaque index and gingival index in the older age group. Total counts of bacteria, Parvimonas micra and Prevotella intermedia, were significantly correlated with MIF concentration in older participants. In conclusion, MIF and PGE2 production in response to bacterial accumulation seems to be modified by age.

Repeated scaling versus surgery in young adults with generalized advanced periodontitis

BACKGROUND

Residual probing depth (PD) after subgingival scaling can be treated with repeated scaling or periodontal surgery. Ambiguous results about the additional clinical benefit of a second scaling procedure exist. Therefore, we performed a prospective study comparing the clinical results of repeated subgingival scaling versus periodontal surgery in 30- to 40-year-old subjects with generalized advanced periodontitis.

METHODS

Twenty-six subjects (mean age, 37 +/- 3 years) were treated after an initial examination (t(1)), initial subgingival scaling, and baseline examination (t(2)) with a randomly assigned second subgingival scaling (test) and periodontal surgery (control) in a split-mouth design. The final examination (t(3)) took place 6 months postoperatively. Intraindividual comparisons of mean PD and clinical attachment level (CAL) were analyzed.

RESULTS

PD was reduced from 4.1 +/- 0.2 mm initially (t(1)) to 3.1 +/- 0.1 mm at baseline (t(2)), and to 2.9 +/- 0.1 mm at the end of the study (t(3)) for the test sites; and from 4.5 +/- 0.2 mm (t(1)) to 3.5 +/- 0.1 mm (t(2)), and 3.1 +/- 0.1 mm (t(3)) for the control sites. The total PD decrease from t(1) to t(3) was significant (P <0.001) for both therapies. PD reduction from t(2) to t(3) was only significant (P <0.001) for control sites, resulting in a significant (P = 0.010) difference between test and control at the final examination. CAL increased 0.2 +/- 0.1 mm (t(2)) plus 0.3 +/- 0.1 mm (t(3)) for the test sites and 0.2 +/- 0.1 mm (t(2)) plus 0.2 +/- 0.1 mm (t(3)) for the control sites. Total CAL gain was statistically significant for the test and control sites. CAL gain from t(2) to t(3) was only significant (P = 0.022) for the test sites.

CONCLUSIONS

Both treatments reduced PD and increased CAL. A second subgingival scaling resulted in significant additional CAL gain and reduced the need for surgery.

Estimating regression to the mean and true effects of an intervention in a four-wave panel study

OBJECTIVES

First, to analyse whether a taxation-related decrease in spirit prices had a similar effect on spirit consumption for low-, medium- and high-level drinkers. Secondly, as the relationship between baseline values and post-intervention changes is confounded with regression to the mean (RTM) effects, to apply different approaches for estimating the RTM effect and true change.

SAMPLE

Consumption of spirits and total alcohol consumption were analysed in a four-wave panel study (one pre-intervention and three post-intervention measurements) of 889 alcohol consumers sampled from the general population of Switzerland.

METHODS

Two correlational methods, one method quantitatively estimating the RTM effect and one growth curve approach based on hierarchical linear models (HLM), were used to estimate RTM effects among low-, medium- and high-level drinkers.

RESULTS

Adjusted for RTM effects, high-level drinkers increased consumption more than lighter drinkers in the short term, but this was not a persisting effect. Changes in taxation affected mainly light and moderate drinkers in the long term. All methods concurred that RTM effects were present to a considerable degree, and methods quantifying the RTM effect or adjusting for it yielded similar estimates.

CONCLUSION

Intervention studies have to consider RTM effects both in the study design and in the evaluation methods. Observed changes can be adjusted for RTM effects and true change can be estimated. The recommended method, particularly if the aim is to estimate change not only for the sample as a whole, but for groups of drinkers with different baseline consumption levels, is growth curve modelling. If reliability of measurement instruments cannot be increased, the incorporation of more than one pre-intervention measurement point may be a valuable adjustment of the study design.

Revisiting the relation between change and initial value: a review and evaluation

The relation between initial disease status and subsequent change following treatment has attracted great interest in clinical research. However, statisticians have repeatedly warned against correlating/regressing change with baseline due to two methodological concerns known as mathematical coupling and regression to the mean. Oldham's method and Blomqvist's formula are the two most often adopted methods to rectify these problems. The aims of this article are to review briefly the proposed solutions in the statistical and psychological literature, and to clarify the popular misconception that Blomqvist's formula is superior to Oldham's method. We argue that this misconception is due to a failure to recognize that the heterogeneity of individual responses to treatment is a source of regression to the mean in the analysis of the relation between change and initial value. Furthermore, we demonstrate how each method actually answers different research questions, and how confusion arises when this is not always understood.