Older people are especially vulnerable to loneliness and social isolation - and it can have a serious effect on health. But there are ways to overcome loneliness, even if you live alone and find it hard to get out.
People can become socially isolated for a variety of reasons, such as getting older or weaker, no longer being the hub of their family, leaving the workplace, the deaths of spouses and friends, or through disability or illness.
Whatever the cause, it's shockingly easy to be left feeling alone and vulnerable, which can lead to depression and a serious decline in physical health and wellbeing.
Someone who's lonely probably also finds it hard to reach out. There's a stigma surrounding loneliness, and older people tend not to ask for help because they have too much pride.
It's important to remember loneliness can - and does - affect anyone, of any age.
Here are ways for older people to connect with others, and feel useful and appreciated again.
Grab every chance to smile at others or begin a conversation - for instance, with the cashier at the shop or the person next to you in the GP waiting room.
If you're shy or not sure what to say, try asking people about themselves.
If you're feeling down and alone, it's tempting to think nobody wants to visit you. But often friends, family and neighbours will appreciate receiving an invitation to come and spend some time with you.
Having a chat with a friend or relative over the phone can be the next best thing to being with them.
If your friends and family live far away, a good way to stay in touch, especially with grandchildren, is by using a personal computer or tablet (a handheld computer).
You can share emails and photos with family and friends, have free video chats using services or reconnect with old friends on social media sites such as Facebook or Twitter and website forums.
A tablet computer can be especially useful if you can't get around very easily, as you can sit with it on your knee or close to hand and the screen is clear and bright.
A sponge-tip stylus pen or speech recognition may help if the touchscreen is difficult for arthritic hands or fingers with poor circulation.
Libraries and community centres often hold regular training courses for older people to learn basic computer skills - as well as being a good place to meet and spend time with others in their own right.
Local branches of Age UK run classes in computing to help older people get to grips with smartphones, tablet computers and email.
Get some tips and advice on how to become more confident using the internet, including how to access your GP surgery online and how to look for reliable online health information.
These will vary according to where you live, but the chances are you'll have access to a singing or walking group, book clubs, bridge, bingo, quiz nights and faith groups.
It can help you feel less lonely if you plan the week ahead and put things in your diary to look forward to each day, such as a walk in the park or going to a local coffee shop, library, sports centre, cinema or museum.
Don't wait for people to come and see you - travel to visit them.
One advantage of being older is that public transport is better value. Local bus travel is free for older people across England.
The age at which you can apply for your free bus pass depends on when you were born and where you live.
Use this State Pension calculator to find out the exact date when you can apply for your free bus pass.
For longer distances, train and coach travel can be cheap, too, especially if you book in advance online and use a Senior Railcard.
Use the knowledge and experience you have gained over a lifetime to give something back to your community.
You'll get lots back in return, such as new skills and confidence - and, hopefully, some new friends, too.
There are endless volunteering opportunities that relish the qualities and skills of older people, such as patience, experience and calmness.
The University of the Third Age (U3A) operates in many areas, offering older people the chance to learn or do something new.
Run by volunteers, U3A has no exams. Instead, it gives you the chance to do, play or learn something you may never have done before, or something you haven't considered since your school days.
U3A is also a great place to meet people and make new friends.