'Super-diversity' of migrants presents major challenges. Jill Rutter argues the government must fully understand who is coming to the UK and ensure the services facing most demand are adequately funded

Over the past year many sectors of the media have run stories about the growing costs migrants place on our overstretched health service. Headlines such as "Fears for NHS and schools as 1,000 Polish children are born every month" have become commonplace. The government is reviewing access to primary care for migrants. But a less heated look at the impact of migration on healthcare is long overdue.

Changes in health policy must be based on research rather than anecdote and scare mongering. The Institute for Public Policy Research is undertaking a two-year study of the impact of migrants on healthcare in the UK. Our research has highlighted the complexity of calculating this impact.

One reason the impact of migration is difficult to measure is migrant groups are very diverse. By far the largest group of migrants living in the UK are EU nationals who have largely come to work. They comprise migrants from pre-2004 EU states such as Ireland, France and Portugal as well as from new accession states such as Poland. We estimate just over one million adults from the new accession states have come to live in the UK since 2004, although over half of these have since returned home.

In the past five years there has also been a significant onward migration of communities from other EU countries to the UK, usually after they have secured citizenship or refugee status in another country. These onward migrants include Somalis who have moved from the Netherlands, Germany and Scandinavia. Other large onward movements include Nigerians, Ghanaians, Congolese and Sri Lankan Tamil migration from France and Germany.

Their health needs may slightly differ from other EU nationals, especially if they have not been long in the EU, and may be more like those of asylum seekers.

Some 23,610 asylum applications were lodged in the UK in 2006, from a range of countries including the Democratic Republic of Congo, Eritrea, Somalia, Zimbabwe, Afghanistan, Iran and Iraq. In recent years about 40 per cent of asylum applicants have been allowed to remain in the UK by the Home Office.

Work visa holders comprise another group of migrants and in 2006 96,600 of them came to the UK from outside the EU. A significant proportion of work visa holders come to work in the heath and social care sector - IPPR research shows 49 per cent of the Philippines-born population, for example, are employed in this sector. The work visa system is in the process of major change; many critics of government policy believe the new system will exclude senior residential social workers, leading to labour shortages in care homes.

And Home Office statistics suggested that 309,000 overseas students and 45,000 spouses and fiance(e)s entered the UK in 2006. A further group of international migrants comprise British nationals "returning" to the UK - an estimated 5.5 million British nationals live abroad.

Our research has shown the return of frail and elderly Britons to the UK is an increasing trend.

What rights?

Some migrants have no rights to reside in the UK. Present estimates suggest there are about 500,000 "irregular migrants" in the UK, mostly visa and asylum overstayers, as well as a smaller number of clandestine entrants. Irregular migrants have no entitlement to free healthcare in the UK and are meant to be charged for treatment as "overseas visitors", although in the past many doctors turned a blind eye to this regulation.

Since 2004 though it has become mandatory to charge overseas visitors for secondary healthcare, obliging hospitals to check immigration status. A number of high profile cases of asylum overstayers being refused treatment led to a legal challenge in early 2008. Asylum overstayers are now allowed free secondary healthcare, as they are judged to be ordinarily resident in the UK until they are removed. This judgement has resulted in further delays to a Home Office and Department of Health review of charging procedures in primary healthcare that was likely to result in mandatory charges in primary healthcare.

As well as increasing in numbers, migration flows have become more complex. Population super-diversity is an increasing feature of British cities. In the past, UK migrant and minority populations comprised a few large communities, mainly from the UK's former colonies. Today large parts of urban Britain experience super-diversity, where many different communities live side by side. These communities are different not only in their origin, but in their residency status, ethnic origins, language, religion, household composition, work experiences, educational qualifications and so on.

Such super-diversity can present some challenges to healthcare providers: interpreting services can be more difficult to organise, for example. Broad ethnicity categories used in the past may not capture data about patterns of illness or uptake of services. For example, Congolese, Nigerians and Somalis tend to be subsumed within the category black African, although they have different backgrounds.

The residential mobility of migrants within the UK has also increased in the past 10 years. Another facet of the greater complexity of international migration is increased temporary and circular migration.

In the past, much international migration to the UK was permanent or semi-permanent. Today there is much more short-term migration. A family may come to the UK to work for a period, for example, then return to its country of origin. Both residential mobility within the UK and circular migration can compromise continuity of healthcare, as well as leading to increased administrative costs in general practice.

Health and social care funding also partly relies on mid-year population estimates. Government methods for calculating these figures have been criticised for undercounting the most mobile among migrant populations. Rural areas with high populations of transient migrant agricultural workers probably face the least funding in relation to their population needs.

Mass movement

So what do we know about the impact of migration on the demand for healthcare, given the complexity of migration flows? The age profile of migrants is likely to be the prime determining factor of their overall use of health and social care. Their younger age profile means less overall usage of healthcare and adult social care. On the other hand, younger groups of migrants tend to be relatively greater users of services used by similar age cohorts among the general population, for example, sexual health services and maternity services.

The geographical dispersal of recent immigrant groups, especially into areas that have not seen much immigration in the past, may place particular strains on healthcare in parts of the UK. The absolute scale of immigration in particular localities may present challenges to service delivery. Where resource allocation and delivery capacity cannot respond quickly, local services may come under pressure.

Migrants may disproportionately use particular public services related to their ethnicity or region of origin, for example, services for survivors of torture or those with haemoglobinopathies (causing conditions such as sickle cell). Interpreting is a further cost borne by the heath service.

These costs can be weighed against migrants' contribution to healthcare, as workers and taxpayers. Although it is a contested area, most UK studies suggest migrants make a net contribution to government revenue. Higher levels of employment than the UK-born population and younger demographic profile account for this net benefit.

What can the government do better? While the Treasury has accrued the gains of migration, it is local public services that have experienced the "pains" caused by rapid population change. The government has to find better ways of channelling money to public services by having a workable contingency fund for policing, the health service and so on. We also need greater funding of the types of public service that migrants do use, such as interpreting and maternity services.

The government should reject proposals to introduce a mandatory charging regime for "overseas visitors" using primary healthcare. There is no evidence of large numbers of people travelling to the UK to access this service. Such measures would risk compromising strategies to prevent the spread of communicable diseases.

Finally, all parts of government need to recognise that migration to the UK is unlikely to decrease substantially over the next five years. Even with a downturn in the economy, we will still need migrant workers, particularly as the UK-born working age population is set to decline as the baby boom generation retires. Universities will continue to recruit overseas students, just as war and human rights abuse will continue to displace refugees. We need to plan for future migration, not just the present.