Asthma can vary in severity from person to person.
Intermittent Asthma:
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Attacks are brief and not severe.
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Symptoms occur on two days or fewer per week.
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Asthma night awakenings are two times or fewer per month.
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Lung function is generally normal between exacerbations.
Mild Persistent Asthma:
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Attacks affect daily activities but are generally not severe.
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Symptoms occur more than two days per week but not daily.
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Asthma night awakenings are more than two times per month.
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Lung function is generally normal between attacks.
Moderate Persistent Asthma:
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Attacks affect daily activities and may be severe.
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Daily symptoms are common.
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Asthma night awakenings are more than once a week.
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Lung function is reduced, with FEV1 (forced expiratory volume in one second) between 60% and 80% of the predicted value.
Severe Persistent Asthma:
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Attacks limit daily activities, are frequent, and severe.
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Symptoms occur throughout the day and frequently at night.
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Asthma night awakenings occur often.
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Lung function is significantly reduced, with FEV1 less than 60% of the predicted value.