Marc Rosenthal

How many days of bed rest for acute low back pain? A randomized clinical trial

Bed rest is usually recommended for acute low back pain. Although the optimal duration of bed rest is uncertain, a given prescription may directly affect the number of days lost from work or other activities. In a randomized trial, we compared the consequences of recommending two days of bed rest (Group I) with those of recommending seven days (Group II). The subjects were 203 walk-in patients with mechanical low back pain; 78 percent had acute pain (less than or equal to 30 days), and none had marked neurologic deficits. Follow-up data were obtained at three weeks (93 percent) and three months (88 percent). Although compliance with the recommendation of bed rest was variable, patients randomly assigned to Group I missed 45 percent fewer days of work than those assigned to Group II (3.1 vs. 5.6 days, P = 0.01), and no differences were observed in other functional, physiologic, or perceived outcomes. For many patients without neuromotor deficits, clinicians may be able to recommend two days of bed rest rather than longer periods, without any perceptible difference in clinical outcome. If widely applied, this policy might substantially reduce absenteeism from work and the resulting indirect costs of low back pain for both patients and employers.

Role of Obesity and Fat Distribution in Non-insulin-dependent Diabetes Mellitus in Mexican Americans and Non-Hispanic Whites

Recent data have suggested that central obesity is related positively to the prevalence of non-insulindependent diabetes mellitus (NIDDM). We examined whether central obesity (measured by the ratio of subscapular to triceps skinfold) was predictive of NIDDM prevalence independently of overall obesity (measured by body mass index, BMI) in 1231 Mexican Americans and 939 non-Hispanic whites who participated in the San Antonio Heart Study, a population-based survey of diabetes and cardiovascular risk factors. Mexican Americans are characterized by higher rates of NIDDM, greater overall obesity, and more central body fat distribution than age-matched non-Hispanic whites. Using multiple logistic regression with age, ethnicity, BMI, and central obesity as covariates, overall obesity was positively associated with NIDDM prevalence in both sexes (P < 0.001) but central obesity was related to NIDDM prevalence only in women. Our data suggest that the effect of centrality decreases at higher levels of centrality. While both BMI and centrality narrow the ethnic difference in NIDDM prevalence, Mexican Americans still have an increased risk of NIDDM (odds ratio = 2.33 in men and 1.80 in women), suggesting that other factors, possibly genetic, may also be important determinants of the ethnic differences in NIDDM prevalence.

Socioeconomic status and the prevalence of clinical gallbladder disease

The prevalence of clinical gallbladder disease was determined in a cross-sectional survey of Mexican Americans and non-Hispanic whites. The study population was randomly selected from three urban neighborhoods representing different socioeconomic strata. Gallbladder disease was defined as a history of cholecystectomy, or of stones on cholecystography. Mexican American women had an age-standardized prevalence of 16.9%, vs 8.7% for non-Hispanic whites (p less than 0.0001). Prevalences in men were 4.2 and 3.4%, respectively. The ethnic differences in women persisted after stratification by age, parity, and body mass index. Gallbladder disease prevalence was inversely related to four measures of socioeconomic status. After controlling for age, obesity, parity, and ethnicity, the prevalence in women was inversely related to levels of education, income, occupational status, and neighborhood. These socioeconomic differences, if not the result of detection bias, suggest that environmental factors may play a role in gallstone pathogenesis. Identification of such factors may lead to the development of preventive strategies.

Evaluation of Three Potential Screening Tests for Diabetes Mellitus in a Biethnic Population

We tested the ability of three potential screening tests for diabetes (fasting plasma glucose value ≥140 mg/dl, 1-h postglucose (PG) load value ≥200 mg/dl, and 2-h PG value ≥200 mg/dl) to detect non-insulin-dependent diabetes in 130 diabetic Mexican Americans (MAs) and 50 diabetic Anglo Americans (AA) usingthe National Diabetes Data Group criteria as the standard. The sensitivity of the fastingplasma glucose (FPG) cutpoint in detecting diabetes was low in both AAs (36.0%) and MAs (59.3%) and was related to the age-adjusted prevalence rates of diabetes in the two ethnic groups (AAs, 4.9% MAs, 10.9%). The 2-h PG load cutpoint had good sensitivity (> 93%) and specificity (> 99%) in both ethnic groups. The ethnic difference in the sensitivity of the FPG cutpoint appeared to be related to the greater hyperglycemia of diabetic MAs compared with diabetic AAs. Nearly 30% of diabetic MAs had FPG values ≥ 200 mg/dl as contrasted with only 10% of diabetic AAs. The difference in severity of hyperglycemia between the ethnic groups appears to be unrelated to ethnic differences in adiposity, pharmacologic treatment, or delay in diagnosis, although longer disease duration in MAs may explain part of the difference.

Evidence of bimodality of two hour plasma glucose concentrations in Mexican Americans: Results from the San Antonio heart study

Evidence for bimodality in the distribution of two hour post oral glucose challenge plasma glucose concentrations has come previously primarily from native American and Pacific Island populations having high non-insulin dependent diabetes mellitus (NIDDM) prevalence. Because the National Diabetes Data Group (NDDG) criteria for diagnosing NIDDM rely in part upon the assumption of bimodality, it is important to determine the generality of this phenomenon. We looked for bimodality among Mexican Americans in San Antonio, a population having greater than 50% Caucasian admixture. By fitting both a single normal distribution model and a mixture model of two normal distributions, for each age decade, we found that the mixture model was preferred to the single normal model (p less than 0.001) and that this model fit the data well. The proportion in the upper component (hyperglycemics) increased with each successive age decade. The minimum misclassification cutpoints decreased with age, but all were higher than the 200 mg/dl cutpoint recommended by the NDDG. Use of the NDDG cutpoint, however, improved sensitivity with only a minimal deterioration of specificity. Our findings further generalize the bimodality phenomenon and support the NDDG criteria.

Menstrual pattern change 1 year after sterilization: results of a controlled, prospective study *

To determine if female sterilization is associated with adverse menstrual change, we compared prospectively collected menstrual data from women who underwent sterilization via bipolar cauterization, banding, and Pomeroy ligation with data from women whose husbands obtained a vasectomy and from women who were not planning sterilization. At first-year follow-up, sterilization via banding with Falope rings was not associated with adverse change. After excluding initially abnormal cases: (1) cauterization women were bleeding more heavily than all other groups excepting Pomeroy; (2) cauterization and Pomeroy women experienced more dysmenorrhea than women not planning sterilization; and (3) more cauterization and Pomeroy women (collapsed samples) developed abnormal length cycles than did the two control groups. There were no group differences regarding development of beneficial/neutral change (e.g., decreased dysmenorrhea). However, cauterization and Pomeroy groups experienced a significantly higher average number of adverse changes than did the other groups and were at significantly greater risk of developing one or more adverse changes than were women not planning sterilization. The only pattern of association among adverse menstrual changes occurred significantly more often in the cauterization and next in the Pomeroy groups.

Association Between NIDDM, RH Blood Group, and Haptoglobin Phenotype: Results from the San Antonio Heart Study

We examined seven red cell antigen and 10 polymorphic protein phenotypes in 1237 Mexican Americans randomly selected from three San Antonio neighborhoods. Statistically significant associations were found between non-insulin-dependent diabetes mellitus (NIDDM) and RH blood type (X2 = 32.87, df = 10, P = 0.0003) and haptoglobin phenotype (X2 = 9.15, df = 2, P = 0.010). The haptoglobin association showed a dose effect with a single dose of the haptoglobin-1 allele associated with an approximately 50% increase and a double dose of the haptoglobin-1 allele associated with an approximately 100% increase in NIDDM prevalence. Multivariate analysis indicated statistically significant associations between NIDDM and age, sex, adiposity, and neighborhood of residence. However, even after taking these potential confounding variables into account, there was still a significant, independent association between NIDDM and haptoglobin phenotype. The results suggest that the haptoglobin gene may be in linkage disequilibrium with a major susceptibility gene for NIDDM.

Impact of tubal sterilization and vasectomy on female marital sexuality: Results of a controlled longitudinal study

To determine if female or male sterilization affects long-term female marital sexuality, we prospectively compared baseline data and 5 consecutive years of follow-up data from 152 tubal sterilization women, 106 vasectomy wives, and 83 women not planning sterilization. By follow-up year 5, no group of women expressed any change in satisfaction with their own sexual response; however, all groups showed a significant decrease across time in satisfaction with their sexual relationship, in coital desire, and in coital frequency. There were no group differences in overall net changes or in rates of change over the 5-year period. However, two short-term group differences were noted: a decrease in coital desire among women not planning sterilization between baseline and follow-up year 4, compared with increases for both sterilization groups, and an increase in coital frequency at the first follow-up year only in the tubal sterilization group. These data indicate that there are no detrimental effects and some short-term benefits of both sterilization procedures on female marital sexuality.

Acceptability of an experimental intracervical device: Results of a study controlling for selection bias

We analyzed baseline and 12-month follow-up interview data from 98 women who had volunteered to use an experimental intracervical device (ICD) and from 155 women who had been randomly assigned to two control groups, the levonorgestrel-releasing intrauterine device (LNG-IUD; N = 86) and the copper Nova-T IUD (N = 69). All participants were clinic patients in Helsinki, Finland. Initial analysis of 12-month discontinuation data indicated that a significantly higher percent of ICD users (22.4) discontinued their device than did either LNG-IUD (7.0) or Nova-T (8.7) users. However, we were no longer able to detect significant differences in discontinuation after controlling for baseline variables that assessed predisposition to be dissatisfied with contraception in general. Adjusted probabilities of discontinuing the ICD, LNG-IUD, and Nova-T were 11.8%, 6.2% and 7.9%, respectively. These data indicate that the ICD is likely to be acceptable to Helsinki clinic patients; moreover, they suggest a definite place for hormonal intrauterine devices in the contraceptive armamentarium. Most importantly, the methodology used here can be generalized to acceptability studies of other contraceptive devices and drugs undergoing Phase I and early Phase II clinical trials (in situations where randomization may not be feasible) in order to identify and control for the bias introduced by nonrandom assignment procedures.