John R. Boring

The associations of race, cigarette smoking, and smoking cessation to measures of the immune system in middle-aged men

To estimate the association between the immunologic responses of the cell-mediated and humoral systems and race or tobacco smoking, we used data from the Vietnam Experience Study conducted by the Centers for Disease Control. That study, done from 1985 to 1986, was based on a random sample of 4462 male, Vietnam-era, U.S. veterans. Racial groups were white, black, Hispanic, Asian, and American Indian. We used linear regression to evaluate how (i) the race of the subjects, (ii) the number of pack-years of cigarettes the subjects smoked, and (iii) the smoking cessation of certain subjects were associated with their relative and absolute T, B, CD4, and CD8 lymphocyte counts and immunoglobulin A (IgA), IgM, and IgG levels. The results indicated that immune status was associated with race and smoking history and that, generally, the associations remained after adjustment for covariates. For example, the average IgA level and absolute CD8 lymphocyte count for blacks were, respectively, 19 and 16% higher than those for whites. On the other hand, smokers had lower immunoglobulin levels and relative CD8 cell counts and higher counts for other lymphocytes of the cell-mediated system than nonsmokers. For example, the average absolute B count of heavy smokers was 37% higher than that of nonsmokers. The pattern after cigarette smoking cessation was consistent with a reversible effect of smoking and a return toward immune levels of nonsmokers.

High School Football Injuries: Identifying the Risk Factors

This epidemiologic survey of the literature on the factors contributing to the high number of high school football injuries consolidates the current information on the characteristics and risk factors associated with these injuries. To reduce the incidence of knee sprains and strains, the most common injuries to this population, the following preventive recommendations are pre sented : 1) optimum maintenance of playing fields; 2) use of the soccer-style shoe; 3) noncontact and con trolled activities in practice sessions; and 4) increased vigilance over technique during injury-prone preseason practices. The authors conclude that more research into factors such as exposure time and activity at injury will further reduce the risk to the high school football player.

Bias associated with differential hospitalization rates in incident case-control studies

Berksons bias reflects a statistical phenomenon in which differential hospitalization rates create an exposure distribution among hospitalized cases that differs from that among other cases. Importantly, previous work on Berksons bias has not explicitly addressed the possibility of excluding prevalent or previously diagnosed cases--exclusions that are key features of many study designs. We indicate that the classically described bias differs from the corresponding bias in studies, such as incidence density studies, in which cases are restricted to those with recent diagnoses. We present methods that may be used to assess the magnitude of Berksons bias in incidence-density studies. In many, though not all, situations the bias should be small and of little practical concern.

Efficiency of cultures of rectal swabs and faecal specimens in detecting salmonella carriers: correlation with numbers of salmonellas excreted.

The comparative efficiency of cultures of rectal swabs and faecal specimens in detecting salmonellas in asymptomatic carriers was determined and then correlated with the number of salmonellas excreted per g. of faeces (wet weight). In six short-term salmonella carriers, 82% of rectal swab cultures taken daily for 11 consecutive days were positive for salmonellas, whereas 94% of faecal specimens cultured were positive. Similarily, in 8 long-term carriers, 58% of the rectal swab cultures were positive as compared with 91% of faecal specimens. The inferiority of the results of rectal swab cultures correlated with their inefficiency in detecting salmonellas when fewer than 1000 salmonellas per g. of faeces were present. The patterns of salmonella excretion as depicted by estimated salmonella content of faecal specimens showed that all carriers had irregular day-to-day variations. The average number of salmonellas excreted per g. of faeces by short-term carriers was greater than that by long-term carriers, although both groups revealed the same wide variations in number of organisms excreted. The effect of delayed processing and shipment of specimens upon recovery of salmonellas was also studied. No deleterious effects were noted when specimens were shipped and processing was delayed for up to 3 days.

A protracted hospital-associated outbreak of salmonellosis due to a multiple-antibiotic-resistant strain of Salmonella indiana

Three separate but related episodes of nosocomial infection with a multiple-antibiotic-resistant Salmonella indiana were investigated on a pediatric ward of a large municipal hospital. Enforcement of isolation techniques as well as other measures designed to reduce person-to-person spread of infection halted each episode. Prior antimicrobial therapy with antibiotics to which the organism was resistant probably contributed to the ease with which the organism was transmitted.