Objectives:
People who are exposed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could develop a potentially fatal disease with lung involvement and severe cytokine storm syndrome (CSS) - coronavirus disease 2019 (COVID-19). Tocilizumab (TCZ) was administered to these subjects, despite the lack of randomized clinical trial data. Hence, summarizing data on the mortality rate and related risks factors may help physicians to correctly administer tocilizumab. Therefore, this review article has been conducted.

Objectives:
The number of positive and death cases from coronavirus disease 2019 (COVID-19) is still increasing until now. One of the most prone individuals, even in normal situations is patients with dementia. Currently, no study provides clear evidence regarding the link between dementia and COVID-19. Therefore, this review article has been conducted.

Objectives:
Does fish consumption reduce risk of coronary heart disease (CHD), stroke and all-cause mortality in patients with type 2 diabetes (T2D)?

Study design:
This review article included 9 prospective cohort studies with 57,394 diabetic patients.

Results and conclusions:

Face mask may reduce primary respiratory infection risk by 6-15%

Objectives:
Evidence for face-mask wearing in the community to protect against respiratory disease is unclear. Therefore, this review article has been conducted.

Do wearing face masks reduce primary respiratory infection risk?

Study design:
This review article included 33 studies (12 randomised control trials (RCTs)).

Objectives:
Is there a dose-response relation between intake of total, animal and plant protein and the risk of mortality from all causes, cardiovascular disease and cancer?

Study design:
This review article included 32 prospective cohort studies with 113,039 deaths (16,429 from cardiovascular disease and 22,303 from cancer) among 715,128 participants.

Objectives:
The role of children in the spread of SARS-CoV-2 (COVID-19) remains highly controversial. Therefore, this review article has been conducted.

What is the role of children in SARS-CoV-2 in household transmission cluster?

Study design:
This review article included household SARS-CoV-2 transmission clusters (n = 213 from 12 countries).

Results and conclusions:   
The investigators found only 8 (3.8%) transmission clusters were identified as having a paediatric index case.

Objectives:
Epidemiological studies showing the correlation between folate (folic acid) and the breast cancer risk have revealed inconsistent results. Therefore, this review article (meta-analysis) has been conducted.

Objectives:
What is the role of quarantined households for transmission of COVID-19?

Study design:
This review article included a total of 54 relevant studies with 77,758 participants reporting household secondary transmission.

Results and conclusions:                

Objectives:
Does calcium combined with vitamin D supplementation reduce risk of osteoporosis in postmenopausal women?

Study design:
This review article included 10 RCTs.

Results and conclusions:
The investigators found calcium combined with vitamin D supplementation significantly increased total bone mineral density [SMD = 0.537, 95% CI = 0.227 to 0.847] in postmenopausal women.

Objectives:
Are there differences in clinical manifestations between COVID-19 patients from the East (East and South-East Asian countries including China, South Korea and Thailand) and the West (North American, European and Middle East countries, including the United States, Italy, France and Iran)?

Study design:
This review article included 57 studies, describing 19,353 patients. Of these, 45 studies with 8,416 patients were from the East, while 12 studies with 10,937 patients were from the West.