Diseases are broadly classified as Infectious diseases ( Communicable Diseases ) & Non Communicable diseases ( NCD'S ) . Health care can be divided as preventive care ( Public Health ) , where research is done to prevent diseases . Treatment of diseases can be classified as primary , secondary & tertiary care . The health of a society is measured by Infant Mortality Rate , Maternal Mortality Rate & Life span of adults .

Research has contributed to great advances in Infectious diseases by discovering vaccines for health care & antibiotics for treatment of Infections . The life span of humans has increased from 30 years in the 1950's to about 65 years in developing countries to above 80 years in developed nations . Recently , antibiotic resistance is creating major problems in the management of Infectious diseases . Both preventive aspects , antibiotic misuse & discovery of new molecules to treat infections are the areas of research .

The common cause of morbidity & mortality are NCD's . Diabetes Mellitus , Hypertension , Lipid disorders , Air pollution , Alcohol intake , Obesity & Smoking are the major risk factors for cardiovascular diseases , COPD , Chronic Kidney Disease & chronic liver disease , which are the common causes of mortality in both developing and developed countries . Cancer is becoming a very important cause of mortality . Research in prevention of these diseases by leading a healthy life , primary care to treat DM , HT & lipid disorders early delay events & improve survival . Secondary & tertiary care for these diseases have improved survival .

It is science & modern medicine which has improved the quality of life & improved survival . Each of these diseases need research in preventive care & guidelines for primary , secondary & tertiary care .

Hi Jomar,

You can answer your question by reading basic materials (books or articles) on research methods in three distinct areas: (1) disease surveillance, (2) disease prevention, and (3) clinical diagnosis/treatments. Quite separate areas.

Here is a recommendation of a book that I found quite useful (but I am sure there are newer resources available).

Kleinbaum DG, Kupper LL, Morgenstern H. Epidemiologic research: principles and quantitative methods: John Wiley & Sons; 1982.

I agree with Dr. Gulzar Shah, it is necessary to review and study methodology of research, but in all cases it is necessary to use the scientific method, that is, to define the problem, formulate a hypothesis and contrast the hypothesis. I recommend you starting with descriptive statistics and then go into the analytical or inferential. I hope it will serve my point of view.