Our study illustrates a significant relationship between variations in age and gender, prevalence of DM and HTN, and the overall COVID-19 related mortality. The results demonstrate that advanced age, male gender, and history of DM and HTN among COVID-19 patients are disproportionately prevalent among non-survivors and thus suggest that these mentioned demographic and disease elements are poor prognostic factors leading to an increased incidence of mortality. The binary logistic regression analysis used in our study quantitatively suggests that the COVID-19 patients who have age > 50 years, who are males, or who have history of HTN and/or DM may have up to 9-fold increased chances of mortality than those patients who are young, who are females and are nondiabetic and normotensive. This is in line with the previous reports that suggest similar correlation between mortality and these factors (2, 3, 4, 5, 6, 7).
A meta-analysis conducted by Li et al. which looked over 1,994 COVID-19 patients exhibited an increased mortality among patients who were males and suggested a case fatality rate of 7% (8). Another meta-analysis conducted by Pranata et al. (2020, n = 6520) showed that hypertension was linked to increased mortality among COVID-19 patients (RR 2.21 (1.74–2.81), p < 0.001) (5). Although many of the studies involving the association of hypertension with COVID-19 related mortality were confounded by other risk factors like age and gender, but the meta-analysis by Liu et al. (2020, n = 15302) proved that hypertension is an independent risk factor altogether and leads to an escalated risk of adverse outcomes including death in COVID-19 patients (9).
Onder et al. (2020, n = 22512), in a case fatality study conducted in Italy segregated the patients diagnosed with COVID-19 on the basis of age and showed that patients in the advanced age groups had proportionately increased case fatality rates reaching up to 20% in patients > 80 years of age (10). This is especially crucial keeping in view the progressive aging of the worldwide population as the number of older individuals aged 60 years or above is expected to increase from 962 million globally (2017) to 2.1 billion by 2050 (11); this means that the associated prognostic challenges associated with COVID-19 infection among elderly patients is expected to accrue with time.
DM has also been proven to significantly exacerbate the prognostic outcomes among COVID-19 patients (12). Barron et al. (2020, n = 23698) showed that DM was associated with more than three-fold increased risk of in-hospital mortality in COVID-19 patients than in nondiabetics (13). A study by Zhang et al. (2020, n = 72314) revealed a crude mortality rate of about 7.3% among COVID-19 patients who were diabetics, in comparison to a rate of only 0.9% among nondiabetic COVID-19 patients (15). Furthermore, in another retrospective case-control study, a mortality rate of around 35% was found in diabetic COVID-19 patients (16). All these studies reflect a strong impact of disease prevalence and demographic factors on the prognosis of COVID-19 infection.
However, there have been studies that have shown that diseases like HTN and DM may have no association with increased mortality. Wang et al. (2020, n = 209) showed that although HTN apparently seemed to increase the risk of mortality in univariate analysis (OR = 5.000, 95% CI [1.748–14.301]), but the multivariate analysis done in the same study proved otherwise and removed the possible association between HTN and mortality (OR = 1.099, 95% CI [0.264–4.580]) (17). Another study by Cummings et al. (2020, n = 257) showed the same pattern for both DM and HTN that the mortality association of both diseases disappeared when multivariate analysis was used in COVID-19 patients (18).
Nevertheless, our study has limitations. Firstly, the results may be confounded with other concomitantly prevalent risk factors which were not taken into account like smoking, obesity, asthma, cardiovascular morbidity etc. Secondly, the severity, associated disease complications, and the extent of disease control was not documented in patients with DM and HTN which could also affect the mortality in COVID-19 patients. Thirdly, subgroup analysis was not done to stratify the diabetic and hypertensive patients according to age and gender which may also have led to disproportionately skewed results.
We suggest a multivariate analysis in COVID-19 patients with multi-level stratification of comorbidities, their severity, complications and control, with gender and age distribution across all the subgroups to better establish a correlation between independent risk factors and mortality.