Public Health Life Expectancy and Mortality Differences between Populations on Croatian Islands and the Mainland Sanja Musić Milanović1, Ana Ivičević Uhernik1, Sandra Mihel1, Ivan Pristaš1, Arsen Stanić2, Ranko Stevanović1 1Croatian National Institute of Aim To examine the differences in life expectancy and mortality be- Public Health, tween the populations on Croatian islands and the mainland, and Zagreb, Croatia among the islands themselves. 2Orthopedic Clinic, Lovran, Croatia Method Data on population size and mortality collected in Croa- tia in 2001 were analyzed by life table and standardized mortality rates. Results Life expectancy at birth (95% confidence interval) of the population on Croatian islands was 76.4 yr (75.7-77.1) which was significantly higher than life expectancy at birth of general Croatian population which was 73.8 yr (73.5-73.9) or mainland Croatian population which was 73.7 yr (73.6-73.8). Island population had > Correspondence to: higher life expectancy until the age of 80 and again in the oldest Sanja Musić Milanović age group, 95+. More than 10% of inhabited islands in Croatia had Croatian National Institute of life expectancy at birth over 80 years. Two inhabited islands, Ilovik Public Health (Kvarner islands) and Lopud (South Dalmatian islands), had one of Rockefellerova 7 the highest life expectancy at birth recorded in the literature, with 10000 Zagreb, Croatia 95.0 and 90.6 years respectively. Mortality rates on islands were sig- [email protected] nificantly lower for age groups 50-64 and 65-79 years, and this dif- ference persisted for all island groups compared with general Croa- tian population. > Received: April 25, 2006 Conclusion Residents of Croatian islands had a higher life expec- > Accepted: July 6, 2006 tancy than general or mainland Croatian population. Life expec- tancy at birth on Croatian islands was lower than in other European Mediterranean countries, but it resembles that in the neighboring Slovenia, and it is considerably higher than in central and eastern Europe and Balkan countries. > Croat Med J. 2006;47:611-18 www.cmj.hr 611 Croat Med J 2006;47:611-618 Life expectancy is one of the most important de- were living on the islands. Mortality statistics and mographic indicators used to compare differ- indicators were calculated from data collected by ent population groups. It is defined as the mean the Croatian National Institute of Public Health number of years a cohort of people might expect and Croatian Central Bureau of Statistics. Mor- to live according to the current age-specific mor- tality data for all deceased residents in Croatia in tality rates. Life expectancy is the main outcome 2001 were taken From Mortality Database at the measure of life table analysis. In general, it reflects Croatian Central Bureau of Statistics (19). In differences in mortality, but is relatively resistant year 2001, 1536 deaths were registered on Croa- to differences in age structure and other popula- tian islands (3.1% of total 49 552 deaths in Croa- tion characteristics (1,2). It has mostly been ap- tia). Since these figures are based on compulsory plied for comparison of different countries (3,4), registration, it is considered that the data encom- regions (5-7), and specific socio-economic groups pass the entire population. (8,9) in terms of health and health care. Life ex- pectancy is generally considered to reflect differ- Description of islands ences in mortality quite well, but also to be insen- There are 1185 islands in Croatia, and 67 of sitive to age structure of the population, changes them are inhabited. We analyzed 28 inhabited in birth rates, and other demographic phenome- islands for which we had complete and routine- na (10,11). ly collected data. Croatian islands belong to six Low mortality and high life expectancy in maritime counties (Figure 1): Primorsko-goran- European Mediterranean population prompted ska, Ličko-senjska, Zadarska, Šibensko-kninska, much interest and has been a focus of research Splitsko-dalmatinska, and Dubrovačko-neret- in many studies (12-14). Low intake of saturated vanska. Traditionally, there are four distinctive fats and high intake of monosaturated fats, as well groups of islands: Kvarner islands (islands from as high consumption of fruit and vegetables have Primorsko-goranska County), North Dalmatian been proposed as the main factors underlying the islands (islands from Ličko-senjska, Zadarska, low mortality in the Mediterranean (12-17). and Šibensko-kninska County), Middle Dalma- This study was the first attempt to investigate tian islands (islands from Splitsko-dalmatinska the differences in life expectancy and mortali- County), and South Dalmatian islands (islands ty between population on Croatian islands and from Dubrovačko-neretvanska County). the mainland, and among the islands themselves, as well as to compare the results on Croatian is- lands with life expectancy in Mediterranean pop- ulation of European countries. Subjects and Methods Data collection For life expectancy calculation we used data on population size and mortality statistics. Data on population size were taken from the most recent 2001 Census (18). According to it, there were 4437460 inhabitants in Croatia, and 121486 of them (2.7% of the total Croatian population) Figure 1. Map of Croatian islands. 612 Musić Milanović et al: Life Expectancy on Croatian Islands Statistical analysis Results The data were divided into five-year age catego- According to the population census in 2001, ries running from 0-4, 5-9, and so on, up to the 2.7% of the total population in Croatia lived age category of 95+. In data nalysis, we applied on islands. Their age structure was less favorable standard demographic analysis, such as life table than the Croatian average, with a higher share analysis and the calculation of standardized mor- of people older than 65 years than on the Cro- tality rates. atian mainland (20.3% vs 15.5%) and a lower Life table analysis was carried out according share of children younger than 15 years (15.4% to the method described by Chiang (1,2). Life vs 17.1%). When the groups of islands are com- expectancy was calculated for each island, groups pared, North Dalmatian islands stand out, with of islands from the same county, four traditional 25.0% of people older than 65 and 14.2% of chil- groups of islands, and all islands together. It was dren younger than 15 years (Table 1). then compared to the life expectancy in the gen- When we compared life expectancies of the eral and mainland population of Croatia, as well mainland and island populations of Croatia, as to the life expectancy of mainland population the island population had higher life expectancy in the maritime counties. until the age of 80. For the age groups above 80 The differences in mortality between popula- years, island population had slightly lower life ex- tions of Croatian islands and Croatia as a whole pectancy than the mainland population. Howev- were examined by means of life table analysis, a er, in the oldest age group (95+) the island popu- method which consists of applying the current- lation again had higher life expectancy than the age-specific mortality rates to a hypothetical co- Croatian mainland (Figure 2). hort (10,20,21). Life expectancy at birth was significant- In the analysis, we also used the standardized ly higher on the islands (76.4 years) than on the mortality ratio, which is sensitive to differences in age distribution between population on Croa- tian islands and the mainland (11,20,21). For the calculation of standardized mortali- ty rates, indirect age standardization was applied, using general Croatian population as the stan- dard: the national Croatian age-specific mor- tality rates were applied to the age categories of specific groups of islands. Relative risks were cal- culated for general mortality, as well as for mor- tality of each age category compared to the gen- Figure 2. Life expectancy by age on Croatian islands – comparison with mainland and Croatia in eral Croatian population. whole. Closed bars – Croatia; open bars – mainland; gray bars – islands. Table 1. Population size and number of deaths in Croatia, its mainland, coast, islands, and groups of islands in 2001 Region Population size Number of deaths Share of population younger than 15 y (%) Share of population older than 65 y (%) Croatia 4 437 460 49 552 17.0 15.6 Mainland 4 315 974 48 016 17.1 15.5 Coast 1 305 522 13 640 16.9 15.5 Islands: 121 486 1536 15.4 20.3 Kvarner islands 38 687 415 15.8 17.0 North Dalmatian islands 28 865 428 14.2 25.0 Middle Dalmatian islands 34 927 461 15.6 20.2 South Dalmatian islands 19 007 232 16.3 20.2 613 Croat Med J 2006;47:611-618 Table 2. Life expectancy for population of Croatia, its mainland, coast, islands, and groups of islands with highest age group 90+ in 2001 Life expectancy at age (95% CI)* Region 0 15 45 65 90 Croatia 73.8 (73.5-73.9) 60.3 (60.2-60.4) 31.7 (31.6-31.8) 15.5 (15.4-15.6) 3.4 (3.3-3.4) Mainland 73.7 (73.6-73.8) 60.3 (60.1-60.4) 31.7 (31.6-31.8) 15.4 (15.4-15.5) 3.4 (3.3-3.5) Coast 75.0 (74.8-75.2)† 61.6 (61.4-61.8)† 33.0 (32.8-33.2)† 16.2 (16.0-16.3)† 3.5 (3.3-3.6) Islands: 76.4 (75.7-77.1)† 63.0 (62.4-63.6)† 34.2 (33.7-34.8)† 16.9 (16.5-17.3)† 3.0 (2.7-3.3)‡ Kvarner islands 75.9 (74.5-77.3)† 62.8 (61.7-64.0)† 33.9 (32.9-34.9)† 17.0 (16.2-17.8)† 3.5 (2.7-4.2) North Dalmatia islands 76.7 (75.2-78.2)† 63.2 (61.9-64.5)† 34.7 (33.7-35.6)† 17.1 (16.4-17.8)† 2.8 (2.3-3.2)‡ Middle Dalmatia islands 76.2 (75.0-77.5)† 62.6 (61.5-63.8)† 33.9 (33.0-34.9)† 16.3 (15.6-17.0)† 3.0 (2.5-3.6) South Dalmatia islands 77.3 (75.5-79.0)† 63.6 (62.0-65.3)† 34.8 (33.4-36.1)† 17.5 (16.5-18.5)† 2.9 (2.3-3.6) *Confidence interval.