Investors are always looking for the next prevailing trend. One trend that does not look like it will be slowing down any time soon is the ageing of our population: the silver tsunami some have dubbed it. And many financial experts believe it is worth gazillions.

Intrigued? Then you might think about buying individual stocks such as cruiseline operators or pharmaceutical firms. But you could also buy into funds where a manager has done the job for you - by creating a diversified mix of shares that, one way or another, cash in on the ageing phenomenon. Financial expert at the Telegraph Richard Dyson suggests four different options.

Specialist funds with an 'ageing' theme

The best known is the Golden Age fund managed by Lombard Odier, the Swiss bank. A rival fund, managed by CPR Asset Management, is the similarly named Silver fund. Both have been running since at least 2009. Around half the Lombard Odier fund is invested in stocks related to health care but holdings in other profitable businesses whose customers are older include St James's Place.

General funds with a higher-than-average exposure to health care

Top of the list are funds managed by Invesco Perpetual's Neil Woodford, who has famously backed pharmaceutical stocks for several years. His Invesco Perpetual High Income fund, is currently 35pc invested in health care stocks including Roche, AstraZeneca and GlaxoSmithKline.

The other portfolios he oversees, which include the Edinburgh Investment Trust, are also skewed toward health care. This is not so much because Invesco is pursuing a theme of "ageing population" but because Mr Woodford believes some pharma shares are undervalued relative to future earnings deriving from treatments still in the pipeline.

Specialist health care funds

Long-standing unit trusts specialising in health-related sectors include Schroder Global Healthcare and Axa Framlington Healthcare, both of which have been running over five years. Polar Capital Healthcare Opportunities is a newer portfolio, launched in 2009, but with a strong record. For investors preferring tracker funds, Legal & General offers the Global Health and Pharma Index fund. More specialist are investment trusts MedicX and Primary Health Properties. Both own modern clinics and medical facilities that they let to doctors and NHS trusts.

Or take the other view and invest where old age is not an issue

If you don't buy the idea that companies aimed at the old are bound to boom, you can avoid the trend entirely by increasing your exposure to emerging markets whose populations remain young. That knocks out China, where the one-child policy has meant the population is older than in most rapidly developing nations. But India remains very young - and a number of funds, such as JPM India and Jupiter India, are successfully tapping the trend of growing wealth among younger generations with appetites for products and services aimed at them, such as credit, alcohol and new technology.

Other countries with exceptionally young populations include the Philippines, Mexico and Indonesia and plenty of countries in the Middle East, including Iraq and Iran.

It's impossible for UK investors to back the latter two countries but exchange-traded funds (ETFs) - low-cost funds that track assets - give access to others. Consider iShares MSCI Mexico IMI Capped Index fund (0.65pc annual cost) or HSBC MSCI Indonesia ETF (0.6pc cost). Backing individual countries with ETFs is a gamble.