Table 2.

Summarizes the frequencies of comorbidities in terms of median and interquartile range (IQR) recorded for COVID-19 patients by studies included in this review

Comorbidity	Frequency (%)		Studies reported
	Median (%)	IQR
Hypertension	28.60	10.8–45.4	8
Cardiovascular diseases	14.60	10.1–21.4	9
Diabetes	13.20	10.2–30.1	12
Cerebrovascular diseases	8.30	2.1–14.3	6
Chronic lung disease	3.20	1.4–15.9	4
Chronic kidney disease	7.20	2.9–20.8	7
Immunocompromised state	4.80	1.1–11.4	6
Chronic liver disease	2.70	1.8–5.0	6

Diabetes was the most frequently recorded comorbidity but hypertension had the highest prevalance amongst patients of the studies that recorded hypertension as a comorbididty. Obesity, underlying endocrine disorders, autoimmune disease, gastrointestinal diseases and obstructive sleep apnea were aslo noted

Chen et al. [73] and Zhang et al. [83] reported presence of cardiovascular and cerebrovascular diseases collectively in 40.4% and 14.3% of their participants respectively

Chen et al. [73] and Zhang et al. [83] also reported presence of underlying chronic gastrointestinal diseases in 11.1% and 9.3%, and underlying endocrine diseases other than diabetes—such as thyroid disorders—in 1.1% and 3.6% of the patients respectively

Richardson et al. [107] and Goyal et al. [108] also reported obesity in 60.6% and 35.8% of their participants

Chen et al. also recorded presence of autoimmune disease in 1.1% of their participants [73]

Obstructive Sleep Apnea (OSA) was noted by Richardson [106], Arentz [109], and Bhatraju [66] as comorbidity amongst 2.7%, 28.8% and 20.8% of their participants respectively