Is It the Same in Low- and Medium-Income Countries (LMIC) in the Planet?

Some years ago, Faniran et compared the prevalence of asthma and atopy in children between an affluent versus a non-affluent country, having a smaller prevalence of wheeze and persistent cough in Nigeria when compared to Australia (10.2% and 5.1% compared to 21.9% and 9.6%, respectively).

Anyway, a recent report from Aït-Khaled evidenced a wide range of atopic disorders prevalent all over Africa, not only with the highest presence of current asthma in urban areas with higher standard of living (concordant with the hygiene hypothesis) but also with a representative prevalence in endemic parasite and tuberculosis zones (opposed to the hygiene hypothesis).
In Latin America, protective factors to avoid having asthma seem not to play a role, and the non-allergic factors like pollution are not conditioning a higher prevalence of respiratory symptoms. However, this prevalence is similar to industrialized countries. In a recent survey of rural Asian children, 16.1% of wheezing prevalence in the past 12 months was found, not different from other developing regions of the planet.
The former reports, the International Study of Allergy and Asthma in Children (ISAAC), utilized the same methodology of evaluation, having strength enough to make conclusions and to compare different cultures and latitudes.

However, scarce tendency data are available from LMIC since the possibility of having these tools for evaluation has become recently available. An example is the ISAAC Phases I and III in comparison with Brazil, where nocturnal cough and wheezing slightly but significantly diminished; however, the generalization of these results is improbable when considering previous references.

Taken all together, we could conclude that globally, the prevalence of asthma is high and still demonstrates a slight increasing tendency, even though there is a lessening of differences.

Is the Prevalence of Asthma Continuously Increasing?

In Finnish young men, the incremental tendency of asthma diagnosis remained from 0.29% in 1966 to 1.79% in 1989. The possibility of confounding factors in the diagnosing is improbable, as the exemption of military service due to incapacitating asthma was correlated with the increase reported.

In another wider evaluation in the UK, from 1955 to 2004, several indicators of asthma such as primary care, prescriptions, hospitalizations, and mortality evidenced an increase until the 1990s, where the curve flattened and even decreased The opposing evolution of these effects compared to the sale of inhaled corticosteroids (ICS) is one explanation, since the recognition of the inflammatory component of asthma began in the 1980s.

However, also in the UK, an evaluation of prevalence in schoolchildren between 1991 and 2002 showed a significant increase in wheezing in the past 12 months, in severe speech-limiting episodes and night waking, but non-significant increase in medical visit because of wheezing. Here again, this last finding could be explained by the significant increase in steroids prophylactic treatment reported in this population.

This explanation will be reconsidered ahead.
Another trend study also evidenced a significant increase from 1990 to 2003 in doctor-diagnosed asthma, more evident in females (7.3–14.6%) than in males (7.8–9.4%), in all age groups but larger in people aged 55 and older.