Prevalence of Cold Agglutinin Disease Worldwide
Cold agglutinin disease (CAD) cases have been reported in multiple nations across the world. There have been studies over the years in a number of countries that have shown varying prevalence — the proportion of the population with the disease — in different regions and across climate types.
Estimates of CAD prevalence
Some initial estimates of CAD in Denmark from the 1970s found that 13 patients out of the total population of 4.5 million had the disease. That prevalence is roughly 1 in 346,000.
A study published in 2006 found a prevalence of primary CAD of 16 cases per million in Norway. A median age of onset of 67 years was reported in that study, which also found that the disease was slightly more common in women than in men. The incidence rate, or how often there is a new diagnosis, was 1 per million people per year.
In 2013, another study used the Danish National Patient Register to estimate the CAD prevalence for the people of Denmark to be 1.26 per 100,000. The incidence rate was 0.18 per 100,000 inhabitants per year. Compared with the earlier study in Norway, the Danish estimate of prevalence was slightly lower at 12.6 per million versus 16 per million. However, the incidence rate was higher at 1.8 per million per year versus 1 per million per year.
These Danish estimates also were much higher than those found in the 1970s. This is to be expected as the ability to diagnose CAD has improved greatly over the years.
Now, a recent study — published in 2020 — found a higher CAD prevalence in the Norwegian population of 20 cases per million. The incidence was found to be 1.9 cases per million per year.
According to the same study, the prevalence of the disease in Lombardy, Italy was five cases per million and its incidence was 0.48 cases per million per year. The prevalence and incidence were four times lower in Italy than in Norway. The researchers attributed this divergence to differences in temperatures, with CAD being more common in colder climates.
A market report of the epidemiology of CAD in 10 emerging market countries found a total of 29,077 cases of the disease across all of the nations in 2017. The 10 countries analyzed were Turkey, Russia, Saudi Arabia, United Arab Emirates (UAE), Mexico, Colombia, Brazil, Argentina, China, and Taiwan.
The report also found that roughly half of the cases were primary CAD. Of the 10 countries, China accounted for the highest number of cases. The disease was least prevalent in Russia and the UAE.
Factors affecting different estimates
There are a number of factors that could lead to differences in prevalence.
For example, some of the studies differentiated between primary and secondary CAD while others didn’t. This could increase or decrease the prevalence — especially since primary CAD is easier to diagnose than secondary CAD.
There also appeared to be an increase in prevalence over time in these countries. This could be due to an actual increase in the number of patients with CAD. But alternatively, it could just be due to more awareness and better diagnostic methods.
Another factor may be trends toward increased life expectancy: people tend to live longer now and the chance of developing CAD increases after age 55.
Climate also could have an effect. One study noticed a difference in prevalence between Norway, which has a colder climate, and northern Italy, where the climate is slightly warmer. The researchers noted the prevalence difference could be linked to the temperature disparity between the countries. The market report also mentioned that Russia and UAE had the lowest prevalence among the 10 countries.
Finally, there could be differences in diagnostic abilities between different countries that would affect the results.
Last updated: Oct. 15, 2020
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