**2. Data and methods**

We have used 71st round of the National Sample Survey (NSS) data conducted in the year 2014. The 71st round was conducted in two subrounds of 6 months each.

#### *Age- and Sex-Specific Burden of Morbidity and Disability in India: A Current Scenario DOI: http://dx.doi.org/10.5772/intechopen.89709*

The NSS provides information about the different communicable and non-communicable diseases on any person in surveyed household who were found ill during the last 15 days from the date of survey. Causes of Death data were extracted from the Causes of Death report published by the Registrar General of India (RGI), New Delhi, during 2010–2013. We used cause-specific proportion of deaths for communicable and non-communicable diseases by age and sex. The 2011 census, which covers the entire population of India, provides reported information on seven types of disability and one category for multiple disabilities. The prevalence of disability by age and sex is taken from the 2011 census. The proportion of total deaths by age was extracted from the report of Sample Registration System 2006 [15].

Self-reported ailments were classified into three categories: communicable disease, non-communicable disease, disability and 'other'. The main independent variables considered in this study are age and sex. The other individual socio-demographic factors considered in the analysis are residence, educational attainment and monthly per capita expenditure quintiles. Descriptive statistics and bivariate analysis are used for description of prevalence of diseases and disability and its association with age group. Logistic regression analysis is used for multivariate analysis.

The prevalence of disease was calculated with information from the survey on any person who had fallen ill during the last 15 days from the date of survey: *Prevalence* = *Number of diseased persons during the reference period* \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ *Total population during the same time period* <sup>×</sup> <sup>1000</sup> (1)

$$Prevalence = \frac{Number\ of\ disease\ percons\ during\ the\ reference\ period}{\text{Total population\ during\ the\ same time period}} \times 10000 \tag{1}$$

Summary measures of the health of a population are calculated by combining data on mortality and non-fatal health outcomes into a single number – disabilityadjusted life years (DALYs) and disability-free life expectancy (DFLE) are calculated by age for male and female population in India.

Disability-adjusted life year measures health gaps as opposed to health expectancies. It measures the difference between a current situation and an ideal situation where everyone lives up to the age of the standard life expectancy in perfect health. The DALY combines in one measure the time lived with disability and the time lost due to premature mortality:

$$\text{DALY} = \text{YLL} + \text{YLD} \tag{2}$$

where YLL is the years of life lost due to premature mortality and YLD is the years lived with disability.

The computation formula for YLL is given by:

$$\text{YLL} = \text{(N/r)} \times \text{(1 - e^{-rL})}\tag{3}$$

where N is the number of deaths, L is the standard life expectancy at age of death (years) and r is the discount rate (e.g. 3% corresponds to a discount rate of 0.03). Similarly, the formula for YLD is YLD = (I × DW × L × (1 − e−rL))/r.

where I is the number of incident/prevalence cases, DW is the disability weight, L is the duration of disability (years) and r is the discount rate.

Disability weight was borrowed from the Global Burden of Disease Study 2000. Sullivan's health expectancy method reflects the current health of a real population adjusted for mortality and disability level and is independent of age structure. Health expectancy calculated by Sullivan's method is the number of remaining years at a particular age that an individual can expect to live in a healthy state.

Disability-free life expectancy is one of the prime Sullivan's health expectancies. DFLE is found by partitioning the person year lived in the interval into those who

have lived with and without disability. If we assume two states called disability-free and with disability, then the disability-free life expectancy at age x (DFLEx) and the life expectancy with disability (DLEx) at age x are defined by:

Years lived with disability between ages x and x + 5 = 5YDx = 5Lx × 5Prevx; Years lived without disability between ages x and x + 5 = 5YWDx = 5Lx × (1 − 5Prevx). DLEx = sum of years lived with disability for ages x and above, divided by lx.

DFLEx = sum of years lived without disability for ages x and above, divided by lx. where lx is the number of survivors at exact age x, 5Lx is the number of years of life lived by the life table cohort between ages x and x + 5 and 5Prevx is the prevalence of disability between ages x and x + 5 in the population.
