Statistics are important, whether from administrative data, surveys or controlled studies. Asthma and other chronic obstructive lung diseases are silent killers; therefore information pertaining these diseases is important to guide decision making for quality health service provision 26-28. In this study, we have tested for region and fitted a related prediction model for ACOLD incidence rates.
The study established five ACOLD geographical regions, which are based on the incidence rates. Generally, the incidence rates remained fairly the same over the period, but started to decrease between 2016 and 2019. The lowest incidence rate was in the year 2019, possibly influenced by demographic and other socio-economic characteristics that were outside the scope of this study.
Asthma incidence rates by geographical regions
Using the analysis of variance (ANOVA) 24 we identified five groups for asthma incidence rates by regions. The grouping of eleven geographical regions into five regions was premised on incidence rates, their standard deviations, correlations and trends of the incidence rates over the period. There was a general consensus for the regional groups for the incidence rates.
Asthma incidence using the logistic regression model
The results from the logistic model corroborate with those obtained from the Analysis of variance. The logistic regression provided an estimate of the annual decrease by about 1% of the odds of asthma and other chronic obstructive lung disease. It also readily provides a comparison of two regions using the ratio of the two odds of asthma and other chronic obstructive lung disease for the two regions. This is obtained directly by dividing the odds of the two regions relative to Muscat by each other.
The general climate in Oman is tropical desert, almost everywhere, characterized with some summer rains in the northern and southern parts, with clouds along the eastern coast brought by the Monsoon winds. These winds, though have limited effects in terms of rain, but tend to influence the climate of the country. 29 At the coastal areas of the Gulf of Oman, the desert climate is predominant, sunny throughout the year, with some little winter rains in the far north encompassing the Musandam region. This area is extremely hot in summer, with an average high temperature of about 38 degrees Celsius, possibly due to the humidity from the sea. It has been noted that sometimes with the wind blowing from the inland, causes humidity to drop, resulting into very high temperatures of about 50 degrees Celsius. As to whether this would probably provide an explanation, why the incidence rates are the highest in the Musandam region is uncertain 30-32.
Other known clinical and gene-environmental factors associated with asthma could not be assessed in this study because of data limitation arising from the use of administrative data. However, studies show that under genetics, genome-wide linkage studies have identified 18 genome regimes and more than 100 genes associated with allergy and asthma in eleven different populations 33, 34. The prenatal risk factors may include, but not limited to prenatal tobacco smoke use, poor diet and nutrition, stress and antibiotic use 24, 35. There are also childhood risk factors that include among others, phenotypes of asthma, for example early childhood wheezing and age at onset, breastfeeding, poor lung function, family structure, low socio-economic status, exposure to environmental tobacco, exposure to animals, sex and gene-environment interactions. However, our findings show that though, region was significant, its interaction with year was not significant 36.
Availability of time series data for a relatively longer period would possibly provide trends and seasonality of the incidence rates among all categories of, for example; age, region and gender. Nonetheless, this study highlights the significance of distributive evidence of asthma by region.