Quest Network Blue Zones - Dr. Luis Rosero-Bixby , Costa Rican Demographer

Blue Zones - Quest for the true fountain of youth

Dr. Luis Rosero-Bixby , Costa Rican Demographer

Dr. Luis Rosero-Bixby is a Costa Rican demographer, Professor and Director of the Central American Population

Center (CCP) of the University of Costa Rica. He has a PhD and MPH from the University of Michigan.

CCP is a center of excellence for population studies in Latin America of the Wellcome Trust Foundation

Doing some routine work with Costa Rican mortality data, Dr. Rosero found that rates at old ages among Costa Rican males were substantially lower than in other countries, including developed countries. This has not been noticed before because of two reasons: (1) the practice of stopping age-specific mortality studies by age 80 and (2) United Nations estimates had over-deflated Costa Rican population at older ages (UN considered that the 1984 census population ages 80 and over exaggerated in 51%), contradicting itself with assertions that Costa Rican data were reliable and valid. He re-examined Costa Rican data and found that survival at old ages of males is indeed exceptionally good, better than any other national population. He estimated that life expectancy of a 90-year-old male in Costa Rica is 4.4 years, above that of the highest recorded figures in the world: 3.8 years in Japan, the USA, and Iceland. The new Costa Rican estimate by Dr. Rosero does not use census data (which can be distorted by age exaggeration), but it uses a robust demographic method known as “quasi-extinct cohorts” based on only well documented registry data of deaths and voting population; the birth dates of all individuals are double-checked against the superb archive system of books with birth records existing in Costa Rica since 1883. However, census data show also exceptional survival for old Costa Rican males. For example, sex ratio among nonagenarians is 1.4 female/male in Costa Rica, compared to figures of 3 to 3.5 in Japan, the USA, France, or Italy. Census figures (adjusted for age misreporting) also show that 6% of males aged 60 and over in 1970 were still alive in 2000 (at ages 90 +). Comparable figures of 30-year survival are between 2.3% to 3.3% in Italy, France, Japan or the USA. (The proportion of nonagenarians or centenarians in the general population is not, by any means, a good indicator of longevity. In Costa Rica this proportion is low because of the extremely high birth and immigration rates of the past 100 years.)

In addition to finding that Costa Rican males at old ages have exceptional life expectancy, Dr. Rosero found a Blue Zone within Costa Rica territory where old age mortality is significantly lower than in the rest of the country. He used techniques of statistical spatial analysis, consisting of estimating age-adjusted mortality for thousands of circles drawn on Costa Rican territory, each circle differing in radius length and center location, and determining whether mortality rate in each circle was significantly different than in the rest of the country. A Blue Zone circle emerged in the peninsula of Nicoya and Guanacaste where old-age mortality is 10% lower and cancer mortality is 23% lower than in the rest of the country. This Blue Zone circle includes approximately 15,000 square kilometers and a population of 400,000.

There are not yet answers to the question why Costa Rican and Nicoyan older males are doing so well. It will take years of painfully collecting and analyzing statistical evidence before responsible answers can be given.

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