Attention-Deficit/Hyperactivity Disorder (ADHD): Interaction between socioeconomic status and parental history of ADHD determines prevalence.

BACKGROUND: Many studies have reported a higher prevalence of Attention-Deficit/Hyperactivity Disorder (ADHD) among disadvantaged populations, but few have considered how parental history of ADHD might modify that relationship. We evaluated whether the prevalence of ADHD varies by socioeconomic status (SES) and parental history of ADHD in a population-sample of elementary school children age 6-14 years. METHODS: We screened all children in grades 1-5 in 17 schools in one North Carolina (U.S.) county for ADHD using teacher rating scales and 1,160 parent interviews, including an ADHD structured interview (DISC). We combined parent and teacher ratings to determine DSM-IV ADHD status. Data analysis was restricted to 967 children with information about parental history of ADHD. SES was measured by family income and respondent education. RESULTS: We found an interaction between family income and parental history of ADHD diagnosis (p = .016). The SES gradient was stronger in families without a parental history and weaker among children with a parental history. Among children without a parental history of ADHD diagnosis, low income children had 6.2 times the odds of ADHD (95% CI 3.4-11.3) as high income children after adjusting for covariates. Among children with a parental history, all had over 10 times the odds of ADHD as high income children without a parental history but the SES gradient between high and low income children was less pronounced [odds ratio (OR) = 1.4, 95% CI 0.6-3.5]. CONCLUSIONS: Socioeconomic status and parental history of ADHD are each strong risk factors for ADHD that interact to determine prevalence. More research is needed to dissect the components of SES that contribute to risk of ADHD. Future ADHD research should evaluate whether the strength of other environmental risk factors vary by parental history. Early identification and interventions for children with low SES or parental histories of ADHD should be explored.

The Prevalence of ADHD in a Population-Based Sample.

OBJECTIVE: Few studies of ADHD prevalence have used population-based samples, multiple informants, and Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) criteria. Moreover, children who are asymptomatic while receiving ADHD medication often have been misclassified. Therefore, we conducted a population-based study to estimate the prevalence of ADHD in elementary school children using DSM-IV criteria. METHOD: We screened 7,587 children for ADHD. Teachers of 81% of the children completed a DSM-IV checklist. We then interviewed parents using a structured interview (DISC). Of these, 72% participated. Parent and teacher ratings were combined to determine ADHD status. We also estimated the proportion of cases attributable to other conditions. RESULTS: Overall, 15.5% of our sample met DSM- (4th ed.; text rev., DSM-IV-TR) criteria for ADHD (95% CI [14.6%, 16.4%]); 42% of cases reported no previous diagnosis. With additional information, other conditions explained 9% of cases. CONCLUSION: The prevalence of ADHD in this population-based sample was considerably higher than 3% to 7%. To compare study results, the DSM criteria need standardization.

School-based health center intervention improves body mass index in overweight and obese adolescents.

Adolescents Committed to Improvement of Nutrition and Physical Activity (ACTION) was undertaken to determine feasibility of a school-based health center (SBHC) weight management program. Two urban New Mexico SBHCs were randomized to deliver ACTION or standard care. ACTION consisted of eight visits using motivational interviewing to improve eating and physical activity behavior. An educational nutrition and physical activity DVD for students and a clinician toolkit were created for use as menu of options. Standard care consisted of one visit with the SBHC provider who prescribed recommendations for healthy weight. Sixty nondiabetic overweight/obese adolescents were enrolled. Measures included BMI percentile, waist circumference, insulin resistance by homeostasis model assessment (HOMA-IR), blood pressure, triglycerides, and HDL-C levels. Pre- to postchanges for participants were compared between groups. Fifty-one students (mean age 15 years, 62% female, 75% Hispanic) completed pre- and postmeasures. ACTION students (n = 28) had improvements in BMI percentile (P = 0.04) and waist circumference (P = 0.04) as compared with students receiving standard care (n = 23). No differences were found between the two groups in blood pressure, HOMA-IR, triglycerides, and HDL-C. The ACTION SBHC weight management program was feasible and demonstrated improved outcomes in BMI percentile and waist circumference.

Factors that predict frequency of emergency department utilization in children with diabetes-related complaints.

OBJECTIVES: The primary purpose of the study was to determine the factors that are associated with repeat emergency department (ED) visits in children with diabetes. METHODS: Emergency department charts and billing data for children up to 18 years of age presenting to the ED with diabetic diagnoses over a 4-year period were reviewed. RESULTS: The overall rate of repeat visits to the ED was 0.24 visits per person-year of follow-up time. In univariate analyses, there were statistically significant effects of age, insurance category, sex, type of practice, and income. In a multivariate analysis, there was a significant interaction of insurance category and age. Revisit rate ratios for children older than 6 years were higher for those with Medicaid compared with those with commercial insurance. Diabetic boys were less likely to revisit the ED than were girls. CONCLUSIONS: Type of insurance was associated with repeated visits to the ED in children with diabetes. Other contributing factors included age group and sex.

Life-time drinking course of driving-while-impaired offenders.

AIMS: This retrospective study compared drinking histories of 283 men and 413 women convicted of driving while impaired (DWI) in New Mexico and interviewed 15 years following a first conviction and screening referral. DESIGN: We characterized drinking course and plotted drinking status (stable abstainers, abstainers, moderate or risky drinkers) from age 15 to 60 years. SETTING: Pacific Institute for Research and Evaluation, Albuquerque, New Mexico. PARTICIPANTS: Community sample of previously convicted DWI offenders. MEASUREMENTS: Psychiatric disorders from the Comprehensive International Diagnostic Interview; drinking histories from the Cognitive Lifetime Drinking History. FINDINGS: Risky drinking was prevalent at all ages for both genders. Almost half the population reported either a life-time drinking course of risky drinking (19%) or resumed risky drinking after at least one interval of abstinence or moderate drinking (25%), while about one-fifth followed a never risky or risky to moderate drinking course. Offenders with a life-time diagnosis of substance dependence more often transitioned to risky drinking, and those with life-time alcohol dependence were more prone to transition to abstinence. Across time, those who began risky drinking at age 15 years or later quit at double the rate of those who began before age 15 years. Women's and men's drinking courses were similar, but women began risky drinking at a later age and moved to abstinence more often. CONCLUSIONS: Among people convicted of driving while impaired in the United States, younger age of initiation of drinking and co-occurrence of psychiatric and substance use appear to be associated with a poorer trajectory of subsequent risky drinking behaviour. Women who are convicted of driving while impaired appear to start drinking later in life and be more likely to subsequently become abstainers.

Persistence of addictive disorders in a first-offender driving while impaired population.

CONTEXT: We compared the prevalence of alcohol use and other psychiatric disorders in offenders 15 years after a first conviction for driving while impaired with a general population sample. OBJECTIVE: To determine whether high rates of addictive and other psychiatric disorders previously demonstrated in this sample remain disproportionately higher compared with a matched general population sample. DESIGN: Point-in-time cohort study. SETTING: Pacific Institute for Research and Evaluation, Albuquerque, New Mexico. PARTICIPANTS: We interviewed convicted first offenders using the Composite International Diagnostic Interview 15 years after referral to a screening program in Bernalillo County, New Mexico. We calculated rates of diagnoses for non-Hispanic white and Hispanic women (n = 362) and men (n = 220) adjusting for missing data using multiple imputation and compared psychiatric diagnoses with findings from the National Comorbidity Survey Replication by sex and Hispanic ethnicity. RESULTS: Eleven percent of non-Hispanic white women and 12.8% of Hispanic women in the driving while impaired sample reported 12-month alcohol abuse or dependence, compared with 1.0% and 1.8%, respectively, in the National Comorbidity Survey Replication (comparison) sample. Almost 12% of non-Hispanic white men and 17.5% of Hispanic men in the driving while impaired sample reported 12-month alcohol abuse or dependence, compared with to 2.0% and 1.8%, respectively, in the comparison sample. These differences were statistically significant. Rates of drug use disorders and nicotine dependence were also elevated compared with the general population sample, while rates of major depressive disorder and posttraumatic stress disorder were similar. CONCLUSION: In this sample, high rates of addictive disorders persisted over 10 years among first offenders and greatly exceeded those found in a general population sample.

Chronic carcinogenicity study of gasoline vapor condensate (GVC) and GVC containing methyl tertiary-butyl ether in F344 rats.

Chronic inhalation studies were conducted to compare the toxicity and potential carcinogenicity of evaporative emissions from unleaded gasoline (GVC) and gasoline containing the oxygenate methyl tertiary-butyl ether (MTBE; GMVC). The test materials were manufactured to mimic vapors people would be exposed to during refueling at gas stations. Fifty F344 rats per gender per exposure level per test article were exposed 6 h/d, 5 d/wk for 104 wk in whole body chambers. Target total vapor concentrations were 0, 2, 10, or 20 g/m³ for the control, low-, mid-, and high-level exposures, respectively. Endpoints included survival, body weights, clinical observations, organs weights, and histopathology. GVC and GMVC exerted no marked effects on survival or clinical observations and few effects on organ weights. Terminal body weights were reduced in all mid- and high-level GVC groups and high-level GMVC groups. The major proliferative lesions attributable to gasoline exposure with or without MTBE were renal tubule adenomas and carcinomas in male rats. GMV exposure led to elevated testicular mesothelioma incidence and an increased trend for thyroid carcinomas in males. GVMC inhalation caused an increased trend for testicular tumors with exposure concentration. Mid- and high-level exposures of GVC and GMVC led to elevated incidences of nasal respiratory epithelial degeneration. Overall, in these chronic studies conducted under identical conditions, the health effects in F344 rats following 2 yr of GVC or GMVC exposure were comparable in the production of renal adenomas and carcinomas in male rats and similar in other endpoints.

Does screening classification predict long-term outcomes of DWI offenders?

OBJECTIVES: To determine the usefulness of a screening classification system in predicting treatment use, current substance abuse disorders (SUD), and driving over the alcohol limit (DOL) at 15-year follow-up. METHODS: Interviewed 583 driving while imparied (DWI) first offenders with SUDs. Univariate and multivariate statistics were used to determine predictors of long-term outcomes. RESULTS: Screening classification defined groups with different treatment histories and 15-year outcomes. Current SUDs were reported by 21% and DOL by 10%, of subjects. CONCLUSIONS: Group differences suggest that screening data could be used more effectively to triage and treat DWI offenders.

Mealtime behaviors of preschool children: comparison of children with autism spectrum disorder and children with typical development.

This study identified mealtime behaviors of young children (3-6 years old) with autism spectrum disorder (ASD) and compared these behaviors to children with typical development matched for age, gender, and ethnicity. The parents of children with ASD (n = 24) and children with typical development (n = 24) completed a mealtime survey to assess early mealtime history, mealtime location and behaviors, food preferences and behaviors, and eating problems. Parental concerns increased significantly after age 1 year in the children with ASD. Matched analysis results showed significant differences between the pairs of children in specific mealtime behaviors. More children with ASD were picky eaters, mouthed nonfood items, resisted new foods, limited foods based on textures, had problems with gagging, had difficulty eating at regular restaurants or at school, resisted sitting at the table, and threw or dumped food. Knowledge of these early differences can help pediatric therapists to assess feeding issues and plan interventions.

Education research: Assessment of neurology resident clinical competencies in the neurology clinic.

BACKGROUND: Objective evaluation of neurology resident clinical skills is required by the American Board of Psychiatry and Neurology and is important to insure improvement in clinical competency throughout their residency. METHODS: In this study, neurology residents from all 3 years of training and neurology faculty independently completed a form on new clinic patients documenting their decisions on anatomic localization, diagnosis, diagnostic tests, and management. RESULTS: Compared to the attending patient evaluation, we found significant improvement in identical scoring by year of residency training. All resident years outperformed medical students in the neurology clerkship. CONCLUSION: Our clinical assessment form adds one more tool to the list of currently used assessment methods to evaluate resident clinical competency.

Effect of Carelink, an internet-based insulin pump monitoring system, on glycemic control in rural and urban children with type 1 diabetes mellitus.

OBJECTIVE: To determine whether use of the internet-based insulin pump monitoring system, Carelink, improved glycemic control in rural and urban children treated with insulin pump therapy. RESEARCH DESIGN: We reviewed records of 94 children treated with insulin pump therapy between the years 2004 and 2007 and compared glycemic control, diabetes self-care measures, frequency of clinic visits, and geographic location associated with Carelink use. RESULTS: Carelink users showed improvement in hemoglobin A1c (HbA1c) levels [8.0 +/- 0.1 (SE) vs. 7.7 +/- 0.1 (SE), p = 0.002]. Carelink users uploaded pump and glucometer data 2.2 +/- 1.8 (SD) times per month over 0.8 +/- 0.4 (SD) yr. Patients who had no access to carelink software and were followed in a conventional manner showed no change in HbA1c levels [8.0 +/- 0.2 (SE) vs. 8.1 +/- 0.2 (SE), p = 0.17] during the study period. Carelink non-users, defined as patients who had Carelink access but did not use it, had a higher HbA1c level at the start of the study and did not change over the study period [8.9 +/- 0.2 (SE) vs. 9.0 +/- 0.3 (SE), p = 0.82]. Rural Carelink users showed improvement in HbA1c levels following Carelink use [7.9 +/- 0.2 (SE) vs. 7.4 +/- 0.2 (SE), p = 0.001], yet had significantly fewer clinic visits per year compared with urban patients [2.8 +/- 0.2 (SE) vs. 3.5 +/- 0.1 (SE), p = 0.001]. CONCLUSION: Use of the Carelink system was associated with improved glycemic control in children with type 1 diabetes on insulin pump therapy.

Dietary intake and parents' perception of mealtime behaviors in preschool-age children with autism spectrum disorder and in typically developing children.

Parents of children with autism spectrum disorder (ASD) frequently report that their children have selective eating behaviors and refuse many foods, which could result in inadequate nutrient intake. This preliminary cross-sectional descriptive study investigated dietary intake and parents' reported perception of food behaviors of 20 3- to 5-year-old children with ASD. Twenty typically developing children matched for sex, age, and ethnicity were also studied as a case-control comparison. Nutrient intake determined from 3-day food records was adjusted for day-to-day variation to determine the estimate of usual intake distribution for the two groups. This distribution was compared with the Estimated Average Requirement or Adequate Intake recommendations. The reported food behaviors and use of vitamin or mineral supplements were compared for matched pairs using the exact McNemar test. Nutrient intake was similar for both groups of children, with the majority of children consuming more than the recommended amounts for most nutrients. Nutrients least likely to be consumed in recommended amounts were vitamin A, vitamin E, fiber, and calcium. Children with ASD were more likely to consume vitamin/mineral supplements than typically developing children. Compared with parents of typically developing children, parents of children with ASD were more likely to report that their children were picky eaters and resisted trying new foods, and they were less likely to describe their children as healthy eaters or that they eat a variety of foods. Despite the similar and generally adequate nutrient intake for the 40 children in this study, parents of children with ASD had more negative perceptions of their children's dietary behaviors.

Factors in recruiting and retaining health professionals for rural practice.

CONTEXT: Rural communities, often with complex health care issues, have difficulty creating and sustaining an adequate health professional workforce. PURPOSE: To identify factors associated with rural recruitment and retention of graduates from a variety of health professional programs in the southwestern United States. METHODS: A survey collecting longitudinal data was mailed to graduates from 12 health professional programs in New Mexico. First rural and any rural employment since graduation were outcomes for univariate analyses. Multivariate analysis that controlled for extraneous variables explored factors important to those who took a first rural position, stayed rural, or changed practice locations. FINDINGS: Of 1,396 surveys delivered, response rate was 59%. Size of childhood town, rural practicum completion, discipline, and age at graduation were associated with rural practice choice (P < .05). Those who first practiced in rural versus urban areas were more likely to view the following factors as important to their practice decision: community need, financial aid, community size, return to hometown, and rural training program participation (P < .05). Those remaining rural versus moving away were more likely to consider community size and return to hometown as important (P < .05). Having enough work available, income potential, professional opportunity, and serving community health needs were important to all groups. CONCLUSION: Rural background and preference for smaller sized communities are associated with both recruitment and retention. Loan forgiveness and rural training programs appear to support recruitment. Retention efforts must focus on financial incentives, professional opportunity, and desirability of rural locations.

Interdisciplinary health education and career choice in rural and underserved areas.

PURPOSE: To assess the association between an educational rural health interdisciplinary programme (RHIP) and subsequent practice in US rural and underserved locations. METHODS: We carried out a longitudinal cohort study of RHIP students and randomly selected classmate controls for the years 1990-2001, using a mailed survey. OUTCOMES: Main outcome measures were first rural, any rural, first underserved and any underserved practice locations. Multivariate statistical methods were used to calculate prevalence ratios (PRs) by discipline while controlling for possible extraneous variables. RESULTS: Of 1396 surveys delivered, 820 were returned, giving a response rate of 59%. After exclusions, results from 255 RHIP and 534 control students were analysed for outcomes. Pharmacy students on the RHIP chose first and any rural practice locations more often than reference controls (PRs = 2.59 and 1.97, respectively; P < 0.05). Therapies (occupational, physical and speech therapy) RHIP students were associated with all 4 practice outcomes more often (PRs = 2.07, 1.85, 1.68 and 1.65, respectively; P < 0.05). Pharmacy and Therapies control students with rural training chose first rural and any rural practices more often (PRs = 2.58 and 1.62, respectively; P < 0.05 for both). Medicine and Nursing students did not choose outcome practice locations more often, but had small sample sizes and large numbers of controls with rural training. Rural health interdisciplinary students rated participation in rural training more highly as a factor in choosing first rural practices than did the controls who chose similar practices. CONCLUSIONS: Participation in RHIP and other rural training experiences may stimulate subsequent career choices in rural and underserved locations for Pharmacy and Therapies students. Other studies are needed to confirm these findings and answer questions raised by these data.

Improved patient notes from medical students during web-based teaching using faculty-calibrated peer review and self-assessment.

BACKGROUND: This study examines the effectiveness of Calibrated Peer Review (CPR), a Web-based writing development program, to teach and assess medical students' patient note-writing skills in a standardized fashion. METHOD: At the end of the clerkship year, 67 medical students were divided into three groups, introduced to CPR, and instructed in patient note-writing. Students then wrote notes for three clinical cases, presented in different order to each group. After training on faculty-calibrated standards, students evaluated their peers' notes and their own notes. Trained faculty, blinded to author, order, and group, also graded student notes. RESULTS: Faculty gave lower scores than students, but both groups found students' scores improved significantly from the first to the third note written. CONCLUSIONS: Student-written patient notes improved in quality while using CPR. The program uses approaches valued in medicine (accurate peer review and self-reflection) to enhance performance.

Required research by medical students and their choice of a women's health care residency.

OBJECTIVE: This study searches for association between the subject of medical students' required research projects and subsequent choices of residency, focusing specifically on women's health fields. STUDY DESIGN: Students at our school graduating between 1997 and 2004 (n = 535) were required to undertake a research project beginning in the preclinical years. The subject of their required research project was related to their subsequent choice of residency. RESULTS: Ninety-nine of the 535 projects (18.5%) were women's health related. Although overall there was no significant relationship between the research project and residency choice, students who completed a women's health care project were nearly twice (1.8, 95% CI, 1.4-2.3) as likely to enter a women's health (obstetrics and gynecology or family medicine) residency than those who did not. CONCLUSION: An association exists between student participation in women's health research beginning during preclinical years and the subsequent choice of a women's health residency.

Psychiatric disorders of convicted DWI offenders: a comparison among Hispanics, American Indians and non-Hispanic whites.

OBJECTIVE: Alcohol-impaired offenders have high prevalence rates of psychiatric disorders; however, differences in prevalence rates among ethnic minorities have not been investigated. This study compares lifetime prevalence estimates of DSM-III-R psychiatric disorders (alcohol and drug abuse and dependence, nicotine dependence, major depressive disorder [MDD], dysthymia, generalized anxiety disorder, posttraumatic stress disorder and antisocial personality disorder [ASPD]) among Hispanics, American Indians and non-Hispanic whites convicted of driving while alcohol-impaired. METHOD: Offenders (758 women, 631 men) previously referred to a screening program in Bernalillo County, NM, were interviewed for this study using a structured diagnostic interview. RESULTS: Adjusting for age, education, income and marital status, Hispanic women had significantly higher rates of alcohol abuse (odds ratio [OR] = 2.2) and lower rates of alcohol dependence (OR = 0.3), drug abuse (OR = 0.4) and nicotine dependence (OR = 0.3) than non-Hispanic white women. American-Indian women showed significantly lower rates of alcohol dependence (OR = 0.5), nicotine dependence (OR = 0.2) and MDD (OR = 0.3) than non-Hispanic white women. Hispanic men had significantly lower rates of alcohol dependence (OR = 0.6), drug dependence (OR = 0.5), nicotine dependence (OR = 0.2), MDD (OR = 0.5) and ASPD (OR = 0.4) than non-Hispanic white men. American-Indian men also reported significantly lower rates of drug dependence (OR = 0.5), nicotine dependence (OR = 0.2) and ASPD (OR = 0.3) than non-Hispanic white men. CONCLUSIONS: After statistically adjusting for demographic differences, minority groups were in general less affected by substance abuse problems and had similar or lower rates of other psychiatric disorders when compared with non-Hispanic whites.

New Mexico's 1998 drive-up liquor window closure. Study II: economic impact on owners.

AIMS: This study examined the economic impact of the New Mexico legislative action closing drive-up liquor windows on the retail establishments that operated them. DESIGN: A telephone survey was conducted 20 months after the closure seeking information and owners' opinions about how their outlets had changed since the closure and how this affected their business. In addition, 2 years of aggregated pre- and post-closure total gross receipts revenues were obtained from the New Mexico Taxation and Revenue Department, with convenience stores as a comparison group. FINDINGS: Interviews were completed for 149 of 220 establishments. Over one-quarter of former drive-up liquor windows (28%) had been converted to 'step-in' sales, defined as an outside door where customers can stop and enter the premises while their car is running. Almost two-thirds (61%) of owners reported decreased annual gross revenues following closure, with a reported average 15% reduction in alcohol sales. This is consistent with findings of decreased gross receipts for operators of non-urban, but not urban, drive-up liquor windows compared to convenience store gross receipts. Almost three-quarters (72%) of those surveyed would re-open the drive-up window if the law were rescinded. CONCLUSION: Over one-quarter of the drive-up owners converted to step-in alcohol sales that still allow a form of drive-up liquor sales. Despite this, the forced closure of New Mexico's drive-up liquor windows negatively impacted total sales and liquor sales revenues of establishments that operated them.

Use of herbal medicine by elderly Hispanic and non-Hispanic white patients.

STUDY OBJECTIVES: To determine the types and prevalence of herbal medicines used by Hispanic and non-Hispanic white individuals aged 65 years and older. Secondary objectives were to compare herbal medicine use according to ethnicity, sex, age, socioeconomic status, and education level, and to determine patients' beliefs about herbal medicines. Use of nonphysician health care providers such as acupuncturists and chiropractors also was assessed. METHODS: Data for a cross-sectional, interviewer-administered survey were collected at the University of New Mexico Senior Health Center, an ambulatory health care clinic, in Albuquerque, New Mexico, from February 1996-January 1997. To participate in the study, patients had to be at least 65 years of age, established patients at the clinic, and live independently in a community dwelling. They were excluded if they had dementia, lived in an institution, or belonged to any ethnic group other than Hispanic or non-Hispanic white. Ethnicity was determined by asking the patients in which ethnic group they identified themselves. RESULTS: A total of 186 patients were surveyed: 84 Hispanic (34 men, 50 women) and 102 non-Hispanic white (47 men, 55 women). Of the 186 patients, 91 (49%) admitted to having taken herbal medicines in the previous year. The most common were spearmint, chamomile, aloe vera, garlic, brook-mint, osha, lavender, ginger, ginseng, and camphor. Most of the patients who used herbal medicines were 65-74 years of age and took them primarily for health care maintenance or self-perceived problems. CONCLUSION: As approximately half of the elderly patients stated that they used herbal medicines, health care providers should be knowledgeable about herbal remedies and provide reliable information to their patients about them in a nonjudgmental manner.

Differing effects of inotropic agents on length change deactivation of isolated rat myocardium.

BACKGROUND: A rapid change in length of cardiac muscle during isometric contraction is followed by developed force that is less than appropriate for the new length because of deactivation of the contractile system. Length change deactivation may have favorable or unfavorable effects on cardiac function, depending on the circumstances under which it is produced. METHODS: Left ventricular papillary muscles from male Sprague-Dawley rats were arranged for recording of isometric force. After each control or reference isometric contraction, a quick release-quick stretch V-step was applied to the following contraction. For each repetition of control and experimental contractions, the time of application of V-steps was increased by 20 ms until peak force was reached. Effects of these V-steps were assessed from ratios of peak redeveloped force to peak force in an isometric reference contraction. Slopes of plots of these ratios versus time after the onset of the contraction were used to quantify the effects of inotropic agents on deactivation. RESULTS: Increasing calcium from 2.5 to 5.0 or 7.5 mM increased force by 12+/-4% (mean+/-SEM), did not change time to peak, and did not significantly alter the deactivation slope. Adding 5 mM epinephrine increased force by 16+/-5%, decreased time to peak by 34+/-3%, and increased the deactivation slope by 106+/-9% (P<0.001). Caffeine had variable effects on peak force, increased time to peak by 47+/-4%, and decreased the deactivation slope by 71+/-5% (P<0.001). CONCLUSIONS: The quantitatively different effects of the three agents on length change deactivation slopes and time to peak force suggest a common mechanism, probably involving thin-filament cooperativity.