Paralytic Analytics-Statistics of old age

Will you be a sane 80 year old?

I came across this question on quora:

What is the statistical likelihood that a man in his early 70's will comfortably live ten more years, with all mental faculties present?

Let us look at the answer...
You know what? I am just gonna copy paste my answer on the website here...

Assumption: I am assuming that you are an Indian.
The Statistics:

India population -1,282,741,906 (1.28 billion) As of March 28, 2015.
Sex Ratio:
Current Sex Ratio of India 2015 -943 females for every 1,000 males
That means you have a 51.45% chance of being a male.

Age consideration:
India has the following age distribution-
age 65 and above-5.8% (male 34,133,175/female 37,810,599) (2014 est.)
This means that you have a of 2.75% of being a male over the age of 65.

According to @ Facts and figures about mental illness website@ three% of the population faces disability due to mental illness and around 20% of adults are affected by some form of mental disorder every year.

So, lets be a tad bit pessimistic (this sort of also factors in your old age) and say that you have a 20% chance of going senile. The good news is that there is an 80% chance that you wont go senile.

So factoring in all this we calculate:
1,282,741,906 *0.5145*0.0275*0.8=14519355.63
probability=14519355.63/ 1,282,741,906 =0.0113= 1.13%

So there you have it!
There is less than 1.13% chance that you will grow up to be a sane 80 year old.
Please bear in mind that this too is a very generous estimate. A more accurate assessment would depend on other unmentioned factors like religion, social status, income, number of children and their gender, your region of residence, crime rate, lifestyle choices etc. All these factors mostly contribute towards making your chances even slimmer.

Hey! I am not pessimistic; it's just that the answer to your question was almost bound to be a tad bit depressing.
But, look at the brighter side...

The life expectancy of an average Indian is 66.21 years. Which means you are actually really lucky to have crossed the age of 70! So the possibility that you will reach 80 is quite low but if your luck and current age were to be considered as any sort of factors here, then I would say that you are definitely one of the exceptions to the rule.

Remember what they say about life: It's a short trip! Better make it a good one.
Good luck for the rest of your life.