Family doctor

Asthma is one of the commonest chronic medical conditions to affect children in New Zealand, and over the past 20 years it has been affecting an increasing number of children. There are several articles on this web site addressing asthma in general, and medications used to treat it. This article will focus on issues of particular importance to children, particularly:

• Increasing prevalence of asthma in children.
• Medication - delivery devices.
• Inhaled steroids and growth.
• Allergen avoidance as prevention or treatment.

 Increasing prevalence of asthma in children.

Research from New Zealand and the rest of the western world show that there is a lot more asthma among children today than there was 20 years ago. The reasons for the increase are not entirely clear, but a number of factors are important.

Genetics: Having a parent with allergy, particularly with asthma, is an important factor that increases the chance of a child having asthma. Genetics do not explain the world-wide increase in asthma, since this does not change quickly over the short term.

Allergy: Being allergic to airborne allergens found inside the home is the most important risk factor for a child having asthma. In New Zealand house dust mite is the most significant indoor allergen. Changes in home structure and lifestyle (e.g. energy efficient houses with more carpeting and a more indoor lifestyle) may be increasing the impact of allergy on children's lungs.

Cigarette smoke: Maternal smoking is associated with childhood wheezing, particularly in children under 6 years.

Other: Numerous other factors have been studied to see if they may have contributed to the increase in asthma. It has been suggested that smaller families may be one factor, as children with several older siblings appear less likely to develop asthma. Dietary changes are also suggested to play a role, with changing fat intake from saturated animal fat to polyunsaturated vegetable oils and margarine.

Studies to determine the causes of the increase in asthma are important, and hopefully in the long term they may identify factors that may be reduced with a subsequent fall in the rates if asthma. In the meantime management of asthma will continue to focus on avoidance of triggers and appropriate medical management.

Medication - delivery devices.

There are many different devices available for delivery of inhaled medication to asthmatic children. Some key principles should assist in choosing a device to suit. You should occasionally review the use of your child's device with your doctor to make sure it will be as effective as possible. Remember that your child will need to be able to use the device effectively when out of breath during an acute asthma attack, when they may not be as able to cope with a complicated technique.

MDI + spacer (with mask or mouthpiece): MDI stands for multiple dose inhaler, or "puffer". Using an MDI + spacer is the preferred option for treating asthma in young children (< 12 years), both for acute attacks and for regular preventer therapy. There is increasing evidence that giving treatment for acute asthma via a spacer is as effective as treatment via a nebuliser. Spacers have added advantages in that they're portable, easy to use, and much less costly compared to nebulisers. Each brand of spacer has been devised to work with particular MDI's. It is important to make sure your MDI and spacer are compatible to get the best use from them (your doctor can help with this).

Use of an MDI + spacer should also be considered in teenagers for reliever medication during acute asthma attacks, or for anybody on moderate or high doses of inhaled steroid preventer medication.

New spacers should be washed in detergent before use, as otherwise the static of the plastic may interfere with the initial few doses. Spacers should then be washed every week or so to keep them working properly (wash in liquid detergent and drip dry).

Dry powder devices: This includes diskhalers, spinhalers, and turbuhalers, all of which need a good breath in to activate them. Children from age 5 or 6 yrs onwards may be able to manage these devices. Children may still need an MDI + spacer for treatment of acute attacks, or for higher doses of steroids.

Breath activated aerosols: These require a good breath in to get the drug into the lungs, but need less co-ordination. The breath-activated aerosol may be an effective device for children aged 8 and older.

MDI alone: These require a lot of co-ordination to get the press-and-breathe sequence correct. Even some adults may not be able to use these devices effectively. Even with good technique a spacer should still be used for high dose inhaled steroid preventer medication.

 Inhaled steroids and growth.

Currently inhaled steroids are the most effective medications available to control asthma. If a preventer medication is required to control a child's asthma then an inhaled steroid is usually the preferred option.

Side effects of medications can be concerning, particularly when a medication may be needed for many months or years. One particular concern is the impact long-term inhaled steroid medications could have on a child's growth. Answering this question is difficult as lots of things influence a child's growth, such as their parent's heights, and also the asthma itself.

Overall the evidence currently says that inhaled steroid medications may slow a child's growth a little, especially when they are first started. However in the long run inhaled steroid medications at standard doses (e.g. 800 micrograms/day or less of budesonide or beclomethasone) will not affect your child's ultimate height. Uncontrolled severe asthma will also limit a child's growth and development. The need for higher dose inhaled steroids may be warranted in this situation despite the increased risk of side effects.

 Allergen avoidance as prevention or treatment.

Most children who have asthma are allergic, and as mentioned above allergy to the airborne allergens inside the home is especially important.

There is a lot of interest in whether preventing infants and young children from being sensitised to indoor allergens (e.g. house dust mite and cat) may prevent them becoming allergic and asthmatic. Currently there is not good scientific data to answer this question, but studies trying to answer this question are in progress. For families where there is a strong allergic tendency then avoiding having pets and attempting to reduce dust mite as much as possible (see below) may be worthwhile.

Allergen avoidance may also be regarded as a treatment for allergic asthma. Knowing which allergens to avoid is an important first step, and this can be determined by allergy skin tests. Not all New Zealand asthmatics are house dust mite allergic, so in some cases dust mite avoidance will not be useful.

There is some debate about the benefit of dust mite avoidance, but overall there are some simple strategies that should reduce your exposure. Our biggest exposure to dust mite is in bed, so this is the best place to start.

• Have dust mite impermeable covers on the mattress, pillow, and duvet (if in use). If there's more than one bed in the room, have covers on each bed.
• All the bedding on top of the special mite covers should be either hot washed (>55oC), hot dried in the dryer, or dried in sunshine, on a regular basis.
• Exclude soft toys from the bed, or if that's not possible then either hot wash the toys, or freeze them (in a plastic bag) for 24 hours every couple of weeks.
• Carpet also has a lot of dust mite in it. Regular vacuuming may reduce this, but hard floors are the best option if possible. Other surfaces should be able to be damp dusted regularly.

There are some things that won't help reduce exposure to dust mite, such as sprays for carpets or upholstery. In New Zealand portable dehumidifiers won't reduce humidity enough to prevent dust mite survival.

Allergens other than dust mite may also be important in asthma. If cat is a significant allergen the best option is to not have a cat. If getting rid of the family cat is not an option then keeping the bedrooms as absolutely cat free zones, and if possible washing the cat regularly, may give some benefit.

Although not an allergen, cigarette smoke is an irritant trigger for asthmatics, and avoidance of both active and passive smoking is important.