Overall, foreigners are a population that makes contact with the health care system primarily for physiological or accidental events. Their impact on the National Health System is limited (less than 3%), even less than their demographic share (about 5%). The observed variability among regions depends on the different levels of immigration.
The analysis of data from Lazio shows that immigrants utilise fewer health resources than the resident population, with a ratio 0.8 for acute care and 0.7 for day care. Critical areas have been identified in which the rate of hospitalisation is higher among immigrants than in the resident population. First, adult immigrants are more vulnerable to injuries, these being the main cause of hospitalisation among foreign males. Greater vulnerability to injuries might be related to poor living and working conditions. It is not possible to calculate the fraction of injuries that take place in the work environment. However, immigrants are often exposed to hazardous work, have insufficient training and high mobility, and experience the stress of adaptation to different work environments. Surveys of injuries at work conducted in Italy have suggested a higher risk for immigrants [21, 22]; and studies conducted in various European countries have reported that migrant workers have higher rates of occupational accidents and consequent disability than native workers [23, 24].
Second, age-specific rates show that immigrants are more frequently hospitalised for infectious diseases, particularly HIV and tuberculosis. These results might partly be related to the presence of the various specialised health institutes for infectious diseases in Lazio, which draw cases to the region. Nevertheless, analysis of more recent data in Lazio shows a decreasing trend in the numbers and percentages of discharges for infectious diseases among immigrants; and for AIDS, a national study shows that incidence of this disease among foreigners has been decreasing in recent years, which reflects the trend among Italians .
Third, alarming results emerge on reproductive health for women from LDCs. The incidence of induced abortions is very high among immigrant women, especially between the ages of 18 and 29 years. This result is in line with national data that show an age-standardised induced abortion rate three times that of residents . Possible explanations are the inability or difficulty of immigrant women in controlling and planning their own reproductive life, and circumstances that may limit their opportunity to carry through a pregnancy, such as poor living conditions, social and work instability, and the lack of social support.
Finally, we observed higher rates for Symptoms, Signs and Ill-Defined Conditions, which may indicate cultural and linguistic difficulties in the clinician-patient relationship and may result in low quality assistance to immigrants. Alternatively, this group may suffer psychosomatic disturbances that are difficult to define.
The results for the population under 18 years old confirm that immigrants seem to be generally healthy, and admission for major causes, respiratory diseases and injuries and poisoning, are similar for foreigners and Italians, particularly when account is taken of the difference in the age structure of the populations. The only important differences are for infectious and parasitic diseases, with a higher proportion among immigrant youths. Immigrants also have a longer duration of stay in comparison to Italians (6.7 vs 4.6 days).
The general picture emerging from this analysis is similar to that of other Italian studies. One study conducted in Rome reports deliveries and injuries as the most frequent causes of hospitalisation ; another finding is a larger diffusion of tuberculosis, trauma, and pregnancy among immigrants in Turin ; other analyses report a lower percentage of hospitalisations for immigrants compared with Italians [15, 16, 29]. Some international studies also show a lower utilisation of hospital resources by immigrants compared with the native population , or a lower use of specialised health care , although comparison with other countries is difficult due to different histories of immigration, and to different health and social policies.
Our findings suggest the persistence of the so-called healthy migrants effect  – according to which the healthiest and youngest people choose to go abroad in search of better living conditions – as the majority of discharges are not due to imported diseases. However, this effect may slowly decline as a consequence of both forced migration and displacement, and family reunions, which contribute to the social stability of the foreign group, but at the same time may weaken the average health status of the migrants on arrival. The health condition of the migrant population on arrival may be subject to rapid deterioration due to lifestyle changes or prolonged exposure to risk factors, such as the difficulty of integrating with the social fabric of the host country, poverty and discrimination with regard to access to social and health services. The increasing number of discharges for chronic diseases observed in recent data, in particular for cardiovascular diseases and tumours, suggests that this deterioration may already be in progress.
The observed under-utilisation of hospital resources, in particular day care, could, at least in part, suggest administrative, linguistic, and cultural barriers to health care access. Such barriers have also been reported for migrants and ethnic minorities in different European countries . Furthermore, racism and discrimination within the health services have been reported as an additional barrier , although not specifically in Italy. It should be noted that, since in Italy free hospitalisation is guaranteed to the entire population without distinction, legal and financial barriers should not be numbered among the main causes of reduced access to hospital care. The social frailty of migrant groups appears to be the likely trigger for some critical health conditions. In contrast to the healthy migrants effect, there is also evidence that risk factors expose migrant populations to a substantial burden of disability later in life, the so-called exhausted health effect .
Different considerations relate to the validity of the information on citizenship, the key variable used to identify immigrants. It was introduced into the regional archive in the year 2000 and its validity has not been demonstrated either by specific studies or by its use. This could imply misclassification and biased results. Immigrants are probably more likely to be misclassified as Italians than vice versa. In this case, the effect of misclassification would be to underestimate the number of immigrants receiving hospital treatment, with the risk of both biased rates and biased association measures. Other flaws in the study may be related both to discharge and population data: due to illegal immigration, we were not able to identify the illegal immigrant population (foreigners without a stay permit) among patients, and thus the immigrant population at risk was underestimated. However, when we recalculated age-and gender-standardised rates using an alternative method of standardisation and taking into account the estimate of irregular immigrants (see endnote 3), we did not observe important differences. In addition, the comparison group (i.e. the resident population) includes foreign residents. However, the comparison population can be considered very similar to the Italian population resident in Lazio, since in 2000 immigrants still represented a small part (4%) of the total. Despite this, the considerable differences in hospitalisation patterns observed between immigrants and the resident population, and the consistency of the results with those reported in other studies lend some support to our results.
A minor limitation may be that we did not measure the confounding effect of socio-economic level because of its probable low validity, in particular when used for immigrants, even though it is usually considered as a confounder in studies concerning such groups. However, evidence has been reported that both migration status and low social position are independent risk factors associated with poor health [32, 33] or lower utilisation of specialised health services .
It is clear that an analysis of hospital discharge records cannot provide a comprehensive picture of the health needs and health care of the immigrant population. However, the results of such an analysis should be sufficient to identify the more important differences that exist between immigrants and native population. These results suggest that adequate strategies of health prevention and social promotion should be planned for a multi-ethnic population in Italy. Accessibility to health services for immigrants may need to be improved; their special health needs should be identified and acknowledged and steps should be taken by health authorities to ensure that the effects of administrative, cultural and linguistic barriers are minimised. Finally, as the immigrant population becomes a more substantial part of the whole Italian population, it will be necessary to improve the quality of the information collected, in order to identify more precisely the differences in health needs, access and health care, between the immigrants and the native Italians.