Biomedical subjects

M R Sears

Publications and source records attributed to M R Sears.

147 records · Page 9Linked to original sources

PubMedDate not supplied

Worldwide trends in asthma mortality.

Statistics for deaths from asthma yield widely variable mortality rates between countries. Validation studies show significant inaccuracies in certification of cause of death in older subjects, and probable underreporting of asthma deaths in some countries, explaining some of the international differences noted. The introduction of the ninth revision of the World Health Organisation International Classification of Diseases brought a step increase in reported asthma mortality rates in 1979, but the last decade has seen a gradual increase in mortality rates in many countries, especially in young people, not explained by this change in code. Diagnostic transfer does not adequately explain these increases. Individuals at risk of death from asthma are more likely to be non-caucasian, non-compliant, and young, with a history of previous life-threatening episodes, hospital admissions, and precipitous attacks. Studies of circumstances of death have emphasized overreliance on beta-agonists and underuse of corticosteroids as two primary deficiencies in management, but there remains debate about the causality of the association between increased asthma mortality and increased usage of beta-agonists. The gradual increase in asthma mortality seen in New Zealand over the last 40 years, with episodic increases in the rising baseline, together with similar but more gradual changes in other countries, raises concerns about whether current treatment practices may adversely affect asthma severity and mortality. Further studies are required to validate asthma mortality statistics, and to establish causation of deaths.

Adolescent↗

PubMedDate not supplied

Changing patterns in asthma morbidity and mortality.

Asthma morbidity and mortality have increased in many countries over the last 10 years or more. In some countries, epidemics of deaths have occurred, while others have shown gradual increases. The New Zealand National Asthma Mortality Study associated mortality with severe asthma, underassessment of severity, undertreatment with corticosteroids, overreliance on bronchodilators, discontinuity of medical care and delay in seeking help. Case-control studies of asthma mortality in New Zealand linked prescription of fenoterol with a higher risk of death from asthma than prescription of salbutamol; this higher risk was not negated by adjustment for markers of severity. A study in Saskatchewan, Canada confirmed the increased risk associated with fenoterol use, but also found a significantly elevated risk associated with salbutamol, especially at higher doses. A randomized, placebo-controlled crossover study of regular versus as-needed beta-agonists undertaken in New Zealand showed increased morbidity from asthma during regular treatment, with increased symptoms, decreased pulmonary function, increased airways responsiveness and overall poorer control of asthma despite constant inhaled corticosteroid treatment. Similar findings were evident in some earlier studies of regular salbutamol. Taken together, several recent studies suggest a deleterious effect of frequent use of inhaled beta-agonists, particularly higher potency preparations. Increased responsiveness to allergen is one possible mechanism for this effect, but whatever the mechanism, frequent use of beta-agonists appears to have caused a shift in the chronic severity of asthma, leading to increased morbidity and mortality.

Adrenergic beta-Agonists↗

PubMedDate not supplied

Asthma treatment: inhaled beta-agonists.

Short acting beta-agonists provide symptom relief with a rapid onset of bronchodilation, and protect against exercise-induced asthma and the early asthmatic response to allergen. They remain the most commonly prescribed form of therapy in asthma. However, regular use as maintenance therapy for chronic asthma is no longer recommended. Frequent use increases airway hyper-responsiveness to allergen and nonspecific challenge, and in some studies has been associated with decreased control of asthma. Excessive use of short acting beta-agonists is associated with a higher risk of fatal or near-fatal asthma, with a dose-response relationship. High doses of short acting beta-agonist in combination with oxygen and corticosteroid therapy remains the most appropriate treatment for acute severe asthma in the emergency room situation. The long acting beta-agonists salmeterol and formoterol provide more prolonged bronchodilation, greater reduction of symptoms, increased lung function and reduced need for short acting beta-agonists. Although there is no significant tachyphylaxis to the bronchodilator effects, bronchoprotective effects diminish with time, even when patients are also treated with corticosteroids. The concern that long acting beta-agonists may mask inflammation and, hence, increase the risk of exacerbations was addressed in a recent four-arm parallel group study. The exacerbation rate was highest in those receiving low dose corticosteroid and was progressively lower in those with low dose corticosteroid plus formoterol, moderate dose budesonide alone and moderate dose budesonide plus formoterol. Both budesonide and formoterol independently decreased the risk of exacerbations. Short acting beta-agonists are recommended for use only as needed, which should be relatively infrequent. Long acting beta-agonists are indicated in individuals whose asthma is not well controlled on moderate doses of inhaled corticosteroid, and are complementary to, not a replacement for, inhaled corticosteroid therapy.

Administration, Inhalation↗