When one of my most charming patients  -  a glamorous divorcee aged 70 whom I will call Jane  -  came to see me with a recurrent eye infection which we couldn’t seem to eradicate, I was convinced she was suffering from a type of ‘dry eye’, the sort of condition from which many older people suffer.

Yet when, in despair at my failure to pinpoint the cause of the problem, I took a swab sample and sent it away for testing, the result shocked me.

The microbiologist who had examined the sample discovered that Jane was suffering from chlamydia, a bacterial sexually transmitted disease (STD). 

Jack Nicholson’s character in Something’s Gotta Give (above with Diane Keaton) is told that – after a heart attack – he can’t make love until he is fit enough to climb a flight of stairs without getting breathless

‘Are you sexually active?’ I enquired gently at our next appointment?

‘Oh yes,’ came the reply. ‘My boyfriend is in his 40s.’

Jane didn’t seem remotely bothered or embarrassed by the diagnosis. she simply accepted the antibiotics I prescribed and headed for the pharmacy next door.

Perhaps it was her sang-froid that stunned me but I shouldn’t really have been surprised. according to Government figures, men and women over 60 are now the fastest-growing sector of the population who are contracting STDs, chlamydia in particular.

Since 2002, syphilis has tripled in the over-65s and doubled in the 35-64 age group; chlamydia has risen by 51 per cent in the 35-64 age group, with a 37 per cent rise in the over-65s.

Last week, figures were released showing HIV infections among over-50s have gone up by 60 per cent in England and Wales since 2003.

Unlike their fortysomething children  -  who grew up in the shadow of AIDS  -  the Baby Boomers are quite cheerfully promiscuous, with no interest in condoms for protection, as they never learnt to fear sexual diseases.

Another of my patients is a 64-year-old man I’ll call Jeffrey. after his wife died four years ago, Jeffrey decided he didn’t want another long-term partner.

In my consulting room, we learnt he had contracted genital warts while abroad.

Jeffrey was unflappable. had he been in his 20s, I imagine he would have been horribly embarrassed and worried about the future implications. after all, warts are treatable but never curable. Any future partner would have to know.

But Jeffrey had no intention of finding a second wife.

So as long as I could ease the symptoms (itchiness and rash; pain on urination), he was happy. And being older, he was used to the twinges of old age already  -  a few extra aches and pains really didn’t bother him, as long as they weren’t life-threatening.

When I asked why he hadn’t used a condom, Jeffrey told me: ‘I’ve never used one before. why should I start now?’

The Baby Boomers’ laid-back attitude is no doubt also due to being young in the Sixties and Seventies, when they were the first generation to enjoy the freedom of the Pill.

Now many of them are on to second marriages, or merely a string of relationships post-bereavement or divorce, and they have simply reverted to that relaxed mindset.

If you add in the lack of need to worry about contraception, plus the improved sexual drive caused by hormone replacement therapy (both oestrogen for women and testosterone for men), and the help of drugs such as Viagra and Cialis in cases of erectile dysfunction, the older generation have never felt more able to have a confident, enjoyable, second sex life.

Given that they are also among the most enthusiastic users of the internet, allowing them to find and change partners with ease, is it any wonder that the over-60s are so promiscuous? (A 2008 survey by the over-50s magazine Saga found that two-thirds of men and women aged 60-64 said they were still sexually active, with almost half of those getting between the sheets at least once a week.)

Or that GPs now see so many of them with diseases ranging from warts and chlamydia to herpes, syphilis and gonorrhoea?

While there is no doubt that the fact they are having sex is in itself good news  -  it’s great physical activity and it’s mentally healthy to be in a relationship, whether new or old  -  I would prefer that they weren’t collecting and spreading so many diseases.

So how do you get the message through to a 70-year-old who is in a fabulous relationship with a man 30 years her junior? or to my 64-year-old gentleman?

For women, I tend to point out that as you age, sex can become less comfortable, as the body is less lubricated and skin finer and more delicate. I suggest that using a condom can make sex more pleasant.

For the men, it’s simpler. I remind them that they may not be planning on becoming a father again, but a younger partner could still conceive, and do they really want an 18-year-old turning up on their doorstep in the future?

The only other concern is  -  are they fit for sex, particularly if they are post-heart attack?

Who could forget Jack Nicholson’s character in Something’s Gotta Give being famously told that  -  after a heart attack  -  he couldn’t make love until he was fit enough to climb a flight of stairs without getting breathless?

The doctor had a good point. you should have a basic level of fitness. you don’t want to have another heart attack in flagrante.

First I ask patients: how far can you walk comfortably?  More than 100 yards and you pass.

Can you lift two bags of shopping? Tick, and you pass. Lastly, can you  -  like Jack did in the end, before starting a relationship with Diane Keaton  -  climb those stairs?

If you can make it up a flight of 21 steps without serious discomfort, then go ahead. You’ll be fine. And those tests apply at any age, by the way.

My oldest sexually active patient is 98. his girlfriend is in her 50s. he appreciates that time is not on his side. who can berate him for sowing a few last wild oats while he can?