Fisiopatologia dos distúrbios respiratórios do sono / Pathophysiology of sleep-disordered breathing

O sono representa uma fase na qual o sistema respiratório sofre importantes mudanças que levam a uma maior vulnerabilidade e maior chance de ocorrência de anormalidades, mesmo em indivíduos normais. Na transição da vigília para o sono, existe normalmente um aumento da resistência de via aérea superior e prejuízo de diferentes respostas e reflexos protetores, os quais são eficientes em promover e manter a patência da via aérea superior durante a vigília. Em indivíduos que apresentam fatores de risco, tais como anormalidades anatômicas em via aérea superior, essas mudanças associadas ao sono não conseguem ser compensadas de forma eficaz e, com isso, ocorre uma maior chance de ocorrer um distúrbio respiratório do sono. Os distúrbios respiratórios do sono são caracterizados por diferentes graus de diminuição do espaço das vias aéreas superiores. Essa diminuição tem causas multifatoriais, que incluem anormalidades da anatomia de via aérea superior, alteração da resposta neuromuscular e de alterações em receptores de via aérea superior. Provavelmente muitas alterações funcionais e anatômicas em via aérea superior são de característica genética, tornando o individuo com maior risco quando exposto a determinados fatores ambientais, tais como alergias, e a partir da combinação destes fatores haverá uma maior chance de desenvolver distúrbios respiratórios do sono.

Sleep is a phase during which the respiratory system undergoes major changes. These changes lead to greater vulnerability and a greater risk of abnormalities, even in normal individuals. In the transition from wakefulness to sleep, there is commonly an increase in upper airway resistance and impairment of various protective responses and reflexes, which are efficient in promoting and maintaining upper airway patency during wakefulness. In individuals who present risk factors, such as anatomical abnormalities in the upper airway, these sleep-related changes cannot be efficaciously compensated, which increases the chances that sleep-disordered breathing will occur. Sleep-disordered breathing is characterized by a reduction in the size of upper airways, although the degree of the reduction varies. This reduction has multifactorial causes, which include anatomical abnormalities in the upper airway, alterations in the neuromuscular response and impairment of receptors in the upper airway. Upper airway functional and anatomical changes are likely to have genetic components, and, therefore, individuals exposed to certain environmental factors, such as allergies, have a greater chance of developing sleep-disordered breathing.

The metabolic syndrome in South Asians: continuing escalation & possible solutions.

The metabolic syndrome is a crucial factor in causation of type 2 diabetes mellitus (T2DM) and coronary heart disease (CHD) in South Asians. Approximately 20-25 per cent of urban South Asians have evidence of the metabolic syndrome. Furthermore, insulin resistance was reported to be present in nearly 30 per cent of children and adolescents in India, more so in girls. At the same time many young individuals have clustering of other risk factors/conditions related to insulin resistance (e.g., non-alcoholic fatty liver disease, obstructive sleep apnoea, etc.). Rapid nutritional and lifestyle transition in urbanized areas in various countries in South Asia are prime reasons for increasing prevalence of obesity and the metabolic syndrome. It is particularly important to effectively implement and strengthen population-based primary prevention strategies for the prevention of 'epidemic' of obesity and the metabolic syndrome. The lifestyle factor modification to prevent the metabolic syndrome and T2DM in South Asians should start in early childhood. Finally, there is an urgent need to conduct research studies regarding the correct definitions of the metabolic syndrome and genetic and perinatal factors related to insulin resistance in South Asians.