Table 6 Potential risk factors for mortality

Sex

Men more at risk (descriptive) [21]

Sex distribution similar amongst patients who died and survived (descriptive) [25, 35, 46, 47]

Confidence interval for males versus females crosses the null (univariable regression) [44]

Age

Over 60 years particularly at risk (descriptive) [21]

8% case fatality ratio in 70–79 year olds and 14.8% in those over 80. Overall figure 2.3% (descriptive) [45]

Median age in those who died 52 years, 65 years among survivors (descriptive) [46]

Over 50 years of age particularly at risk- 1.3% died 50–59 years, 3.6% 60–69 years, 8.0% 70–79 years, 14.8% 80 years plus; less than 1% all other age groups (descriptive) [25]

Risk begins to increase at approximately 50 years (statistical test, but graphical presentation) [35]

Median age in those who died 68 years, among those who survived 55 (statistical test) [47]

Over 61 years, increasing per 10 year age group (statistical test) [27]

65 years and older 6.17 the hazard rate of those under 65 (univariable regression) [44]

Smoking

Proportion of smokers similar among those who died versus those who did not (descriptive); one study had small numbers of smokers [21, 46]

Distribution of current smokers similar among survivors and non-survivors (univariable regression analysis, not included in multivariable model) [51]

Pregnancy

Proportion of women who were pregnant similar amongst patients who died versus survived (descriptive) [21]

Any comorbidity

Presence of any comorbidity more common among those dying (descriptive) [21, 35, 46, 47, 51]

Hypertension

Presence of condition more common among those dying (descriptive) [3, 21, 25, 27]

Presence of condition more common among those dying (statistical test) [47, 51]

Confidence interval for individuals with and without the condition crosses the null (univariable regression) [44]

Cardiovascular disease/chronic heart disease

Presence of condition more common among those dying (descriptive) [21, 25, 35, 45]

Presence of condition more common among those dying (statistical test) [47, 51]

Distribution dying in presence and absence of comorbidity similar (descriptive), sometimes small numbers with the condition [44, 46]

Diabetes

Presence of condition more common among those dying (descriptive) [21, 25, 45, 46]

Presence of condition more common among those dying (statistical test) [47, 51]

Confidence interval for individuals with and without the condition crosses the null (univariable regression) [44]

Chronic respiratory/lung disease (chronic obstructive lung disease)

Presence of condition more common among those dying (descriptive) [21, 45]

Presence of condition more common among those dying (statistical test) [51]

Distribution dying in presence and absence of comorbidity similar (descriptive) [46]

Respiratory infectious disease

Presence of condition more common among those dying (descriptive) [25]

Malignancy

Presence of condition more common among those dying (descriptive) [3, 25]

Distribution dying in presence and absence of comorbidity similar (descriptive), sometimes small numbers with the condition [46, 47, 51]

Cerebral infarction/ cerebrovascular disease

Presence of condition more common among those dying (descriptive) [46]

Distribution dying in presence and absence of comorbidity similar (statistical test); small numbers with the condition [47]

Chronic gastritis

Distribution dying in presence and absence of comorbidity similar (statistical test); small numbers with the condition [47]

Chronic kidney disease

Presence of condition more common among those dying (statistical test); small numbers with the condition [51]

Dementia

Distribution dying in presence and absence of comorbidity similar (descriptive); small numbers with the condition [46]

Malnutrition

Distribution dying in presence and absence of comorbidity similar (descriptive); small numbers with the condition [46]

Hepatitis B virus infection

Distribution dying in presence and absence of comorbidity similar (descriptive) [21]