WHEN DID ASTHMA START INCREASING IN AFRICAN–AMERICANS?

While asthma’s prevalence has increased worldwide, the disease has exacted a particularly serious toll on young African-Americans. A recent study sought to determine when asthma rates began to rise in this group.

Crater et al performed a retrospective chart review of patients discharged from the Medical University of South Carolina between 1956 and 1997. They calculated the rates of asthma discharges per 10,000 patients of the same race and per 100,000 persons in Charleston County, and categorized these rates according to age. They noted that although hospitalizations for asthma rose during the study years for patients of all ages, the most pronounced increases were seen among African-American patients 18 years or younger. The trend became noticeable in 1970, when the rate of asthma discharges for African-American children reached 18 per 100,000 population (Figure 1). By 1997, that rate had increased more than 20-fold, to 370. In contrast, the rate of asthma discharges for white children increased just fivefold between 1980 and the study’s end.

The researchers speculated that the increase in asthma discharges among African-American children would not necessarily have been due to changes in housing for poor patients or in Medicaid coverage for children, since there were few alterations in those variables during the study period. Although the researchers cited the confounding influence of poverty in the study’s locale, they stated that many changes in lifestyle during this time could have accounted for the increase in asthma discharge rates instead. Furthermore, the linearity of the increase and its correlation with changes reported elsewhere in the world suggest that other factors are more broadly responsible.

Crater DD, Heise S, Perzanowski M, et al. Asthma hospitalization trends in Charleston, South Carolina, 1956 to 1997: twenty-fold increase among black children during a 30-year period. Pediatrics. 2001;108:E97.

FIGURE 1

ASTHMA DISCHARGE RATES FOR CHILDREN AGES 0 TO 18 YEARS *Rate was calculated as the number of discharges with an asthma diagnosis from the Medical University of South Carolina per 100,000 persons in Charleston County.. Adapted from Crater et al. Pediatrics. 2001.

EDUCATION THE KEY IN FLU VACCINATION

Children who are hospitalized with fever or respiratory symptoms are more likely to have been vaccinated for the flu if their parents had received a physician’s advice about vaccination. A cross-sectional study that evaluated patients admitted to emergency rooms has shown that when children are not vaccinated, it is often because parents were unaware that the flu shot was available.

Poehling et al administered a questionnaire to the parents of 189 children who were either between age 6 months and 3 years and had a fever, or between age 6 months and 18 years and had respiratory symptoms. The questionnaires showed that 31% of the hospitalized children with high-risk medical conditions had been vaccinated. In contrast, only 14% of hospitalized children without such conditions had been vaccinated. However, regardless of which of the two groups a child fell into, the importance of a physician’s advice was clear: More than 70% of children whose parents were given vaccination advice had received the flu vaccine; only 3% of children whose parents had not been given such advice had been vaccinated.

The study authors speculated, though, that a lack of parental understanding of vaccine availability may not have been the only reason why some children had not gotten their flu shots. In many instances, they suggested, the guidelines for vaccination of high-risk children may have seemed ambiguous to physicians.

Poehling KA, Speroff T, Dittus RS, et al. Predictors of influenza virus vaccination status in hospitalized children. Pediatrics. 2001;108:E99.

CAN SALINE BE USED IN A LESS-EXPENSIVE CF TREATMENT?

The expense of human deoxyribonuclease (rhDNase) treatments for cystic fibrosis (CF) may be mitigated by the inclusion of hypertonic saline in CF patients’ treatment regimens. A recent study demonstrated that although saline alone was not an appropriate substitute for rhDNase, it was possible to obtain positive results at a significant economic discount if the two were alternated on a daily basis.

Suri et al observed 48 children in an open crossover trial for 12 weeks. The patients were randomly assigned to receive once-daily rhDNase (2.5 mg), twice-daily 7% hypertonic saline (5 mL), or rhDNase alternated daily with saline. The primary outcome was forced expiratory volume in one second (FEV1); secondary outcomes were forced vital capacity, number of pulmonary exacerbations, weight gain, quality of life, exercise tolerance, and the total cost of care both in and out of the hospital.

The investigators found that daily hypertonic saline treatments alone increased FEV1 by 3%. With daily rhDNase treatments alone, FEV1 increased by 16%. Alternated rhDNase and saline treatments produced a 14% FEV1 increase, nearly equal to that achieved with daily rhDNase therapy.

Suri et al noted that the average 12-week cost of alternated therapy was less than that of daily rhDNase administration. However, significant variations in the cost data, combined with a limited sample size, prevented them from evaluating a difference in total costs between treatment groups. Nevertheless, they concluded that there was essentially no difference between the efficacy of daily rhDNase and that of alternated therapy.

Suri R, Metcalfe C, Lees B, et al. Comparison of hypertonic saline and alternate-day or daily recombinant human deoxyribonuclease in children with cystic fibrosis: a randomised trial. Lancet. 2001;358: 1316-1321.

SLEEP-DISORDERED BREATHING IN AMD PATIENTS

Acid maltase deficiency (AMD) is associated with such complications as sleep-disordered breathing (SDB) and respiratory failure. Recent research indicates that there are daytime function tests that may be used to predict the likelihood of such complications in AMD patients.

Mellies et al studied seven patients with juvenile-type AMD and 20 patients with adult-type disease. They evaluated polysomnographic findings with results from supine lung and respiratory muscle function tests for all patients. Ventilatory restriction was discernable in 17 patients; diaphragmatic weakness (DW) was found in 13 patients, 10 of whom had hypercapnic respiratory failure. Thirteen patients were found to have SDB, 11 of whom also had DW.

The researchers found that SDB was predicted by DW with 80% sensitivity and 86% specificity. The SDB was characterized by hypopnea during REM sleep, and it was accompanied by hypoventilation when ventilatory restriction worsened. The researchers also noted that nocturnal hypoventilation was predicted by inspiratory vital capacity (IVC) with 80% sensitivity and 93% specificity. IVC correlated with peak inspiratory muscle pressure, respiratory muscle strain, and gas exchange during both day and night.

Because of the interrelationship of the variables mentioned above, the researchers were able to establish baseline IVC values that could be used to represent ventilatory restriction and SDB risk. They concluded that this information, combined with measurements of diaphragmatic function, can help determine when polysomnography and noninvasive positive-pressure ventilation should be administered to AMD patients.

Mellies U, Ragette R, Schwake C, et al. Sleep-disordered breathing and respiratory failure in acid maltase deficiency. Neurology. 2001;57:1290-1295.

LAVAGE HELPS IDENTIFY PNEUMONIA PATHOGENS

Organisms causing community-acquired pneumonia are not often identified because of the expense and complication of the techniques required to do so. But non-bronchoscopic bronchoalveolar lavage (BAL) may be a cost-effective alternative to the techniques that have been used for this purpose until now, such as bronchoscopy with protected brushing and lung biopsy. This may, in turn, help physicians determine how to optimize antibiotic therapies.

Rodriguez et al evaluated 26 patients with a diagnosis of pneumonia who had been tracheally intubated; the patients were randomized to receive either standard care or standard care plus non-bronchoscopic BAL. Patients were excluded from the study if they had been given antibiotics in the preceding five days, or if they had pneumothorax, hemoptysis, or persistent hypoxia. For each patient, sputum, BAL fluid, and blood culture specimens were tracked while antibiotic regimens were observed for changes.

In 83% of the non-bronchoscopic BAL group, pneumonia pathogens were found. In contrast, such organisms were detected in only 29% of the standard-care group. Although there was no difference between the two groups in the likelihood of antibiotic course changes within five days, the study authors did note that changes in antibiotic course after positive culture results occurred in the BAL group 67% of the time, compared with 21% in the standard-treatment group. Changes in the broadness of antibiotic therapy did not differ between groups.

Rodriguez et al concluded that because nonbronchoscopic BAL did not delay therapy or present complications, but did enable physicians to employ more specific antibiotics, the technique is superior to other diagnostic tools currently in use.

Rodriguez RM, Fancher ML, Phelps M, et al. An emergency department–based randomized trial of non- bronchoscopic bronchoalveolar lavage for early pathogen identification in severe community-acquired pneumonia. Ann Emerg Med. 2001;38:357-363.

PHYSICAL INACTIVITY NOT LINKED WITH ASTHMA INCIDENCE

Asthma incidence appears to rise as body mass index (BMI) increases, but only in women. Furthermore, recent research indicates that this correlation is not explained by decreases in physical activity.

Beckett et al prospectively followed 4,547 men and women between ages 18 and 30 for 10 years. They measured the subjects’ baseline weights and noted their gradual weight gains and decreases in physical activity during the test period.

Baseline asthma prevalence was highest in African-American men and lowest in white women. But incidence during the subsequent 10 years was highest in women, particularly African-Americans. Incidence overall was 1.5 times higher in women than in men. Changes in BMI during the 10-year test period were associated with asthma risk in women but not in men. However, at both baseline and 10-year follow-up, the association between asthma and BMI was J-shaped: The risk of asthma was greatest in those with the lowest or highest BMIs (Figure 2).

FIGURE 2

ASTHMA INCIDENCE AND BODY MASS INDEX   Data extracted from Beckett et al. AM J Respir Crit Care Med.2001

Another factor that correlated with asthma incidence was cigarette smoking. Active smokers had an adjusted hazard rate ratio of 1.38 for asthma incidence between years 2 and 10, when compared with patients who were ex-smokers or had never smoked at all. Lower maximal education level also played a role; those who lacked a high school diploma were 1.8 times as likely to develop asthma as were those with a high school diploma or higher degree. However, asthma incidence was unrelated to measures of physical activity, even when adjusted for BMI.

Beckett WS, Jacobs DR, Yu X, et al. Asthma is associated with weight gain in females but not males, independent of physical activity. Am J Respir Crit Care Med. 2001;164:2045-2050.

ß-BLOCKADE REDUCES BURN VICTIMS’ MUSCLE LOSS

Often seen in severe burn victims is a catecholamine-mediated hypermetabolic response that involves muscle-protein catabolism. Recent research has determined that this can be mitigated through ß-blockade with propranolol.

Herndon et al evaluated this treatment in 25 children with burns covering more than 40% of their total body surface area. Of these, 13 were randomized to receive oral propranolol for at least two weeks; doses were titrated to produce a 20% decrease in heart rate. Before and after treatment, resting energy expenditure and skeletal muscle protein kinesthetics were measured; body composition was monitored continually.

All patients were similar in terms of age, weight, time elapsed between injury and introduction to metabolic study, percentage of body surface area with third-degree burns, and percentage of total body surface area burned. Not surprisingly, the researchers found that heart rates in the patients who received propranolol were decreased compared with baseline and with heart rates of controls. However, resting energy expenditure was also decreased in the patients given propranolol, in comparison with baseline and with corresponding values in controls. Furthermore, overall muscle-protein balance increased by 82% from baseline in the propranolol group. In the control group, however, this value decreased by 27%. Fat-free mass was basically unchanged in the propranolol group, but it decreased in the control group by an average of 9%.

The researchers concluded that orally administered propranolol is safe and effective for lean-mass catabolism in severely burned children. They also suggested that it could be useful for patients with negative nitrogen balances, such as those undergoing general surgery or suffering from trauma.

Herndon DN, Hart DW, Wolf SE, et al. Reversal of catabolism by beta-blockade after severe burns. N Engl J Med. 2001;345:1223-1229.

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