Covid-19 Part 5:
How risk increases with age

Over 80s are the most at risk

It is highly likely that there are multiple factors which affect severity of infection. It therefore requires a full multivariate analysis in the future, but for the purpose of this review, hospitalisation and mortality rates for different age groups are analysed below.

Infection severity and fatality rate is said to be heavily influenced by age. A report in the lancet which used aggregate data on cases and deaths in mainland China found nearly 20% of cases in people aged over 80 resulted in a hospital admission compared with 1% in subjects under 30. Even those in their 70s appear to be over twice as likely to have a severe infection than those in their 50, and decreases with age. While these numbers will be innaccurate as they don’t take into account the true number of people infected, they can point us in the direction of the breakdown of severity with age. The table below shows the study’s figures for each age group. 

Figure 7. Percentage of cases resulting in hospital admission in a study on mainland China, split into age ranges of the patients. 

This data agrees with other studies, including one in America which shows how over 80s are 2.5 times more likely to be admitted to hospital compared to those aged 50-64. This number reduced with age down to a value nearly seven times smaller for 18-49 year olds. The ‘case fatality rate’, or number of fatalities per number of reported cases for adults over 80 was found to be 14.8% in China, 27.7% in Italy and 18.3% in South Korea.

The official statistics for England and Wales show that of the ~27,500 total deaths attributed to Covid-19 by the 24th of April 2020, 24,000 of them were over 60 years old; a share of ~88%. This was even higher in Italy, where 97% of deaths were in adults aged 60 and above. 

The age structure across populations could explain why there seems to be wide variations in how different countries are affected. The below is from a new study: 

“Italy is one of the oldest populations, with 23.3% of its population over 65 y, compared to 12% in China. Italy is also characterized by extensive intergenerational contacts, supported by a high degree of residential proximity between adult children and parents. Even when intergenerational families do not coreside, daily contacts are frequent. Many Italians prefer to live close to extended family, with over half of the population in the northern regions commuting. Intergenerational interactions, co-residence, and commuting may have accelerated the outbreak in Italy through social networks that increased the proximity of elderly to initial cases.”

Germany has what appears to be a small death rate compared to the number of recorded cases, which could be explained by the median age of confirmed cases being 48 compared to 62 in Italy. 

Covid-19 also seems to be worse for men than women, which was mirrored in previous coronavirus outbreaks, such as the Middle East respiratory syndrome (MERS) in 2012 of which a 2016 study found men were 40% more likely to die from. In the current outbreak, in the USA and UK, it appears that double the amount of men have been dying than women, and 69% of deaths across western Europe are male. One theory is that women tend to have a stronger immune system, even producing sex hormones which were found to help protect against coronaviruses in female mice. 

But there could also be factors at play which revolve around gender lifestyles. For example, it could be due to the fact that more men have health problems especially in later life; women not engaging in health related risks, or women being better at washing their hands.

What do you think? Read the next installment in the Covid-19 Review here! It investigates how underlying health problems affect Covid-19 data.

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