Members of some demographic groups in California can expect to live about 20 years longer than members of other demographic groups in that state.

The Cancer Prevention Institute of California (CPIC), Fremont, Calif., discovered the wide variations in average life expectancies while conducting a block-by-block study of the population of California to examine cancer survival rates across the state.

The CPIC cross-referenced neighborhood-level socioeconomic status, racial makeup, sex and age for about 700,000 deaths among California residents from 1999 to 2001.

The CPIC analyzed results for six racial and ethnic groups: Hispanic, Asian/Pacific Islander, African-American, white, Native American and other/unknown.

Analyses using socioeconomic status as a factor drew on data on education level, employment rates, median household incomes, poverty rates, median rent and median home value.

The CPIC broke socioeconomic status into five levels, and it found that, across the board, women lived an average of 4.8 years longer than men. In the top 20% socioeconomic bracket, the difference was 5.9 years. In the lowest 20% bracket, the difference was only 3.3 years.

Bigger differences showed up among racial groups, with Asian/Pacific Islanders living the longest lives and African Americans living the shortest.

Socioeconomic status affected life expectancy rates, but the impact was variable.

African-Americans in the lowest 20% socioeconomic bracket, for example, had life expectancies of 65.3 for men and 72.8 for women. Life expectancies rose to 75.2 for men and 78.7 for women in the top 20% bracket.

Likewise, white men and women in the lowest 20% socioeconomic bracket had life expectancies of 68.9 and 75.2, respectively. Life expectancies rose to 79.4 and 82.7 in the top 20%.

Socioeconomic brackets had little to no measurable effect on life expectancies of Hispanics and individuals in the Asian/Pacific Islander group.

“We uncovered these differences while studying cancer survival rates among these groups,” says Christina Clarke, a CPIC research scientist. “The findings were disturbing enough that we pressed to publish them, even though they were outside our immediate focus.”

The researchers found that, while there were substantial age-specific gaps in mortality, especially among poor African-American men, the biggest differences showed up in individuals 45 years of age and older. That points to the crucial role chronic illnesses among older people, such as diabetes and heart disease, and access to health care play in affecting life expectancies.

The CPIC has raised potentially troubling questions for life and health insurers, for whom the life expectancy variation figures have clear underwriting applicability, despite the fact that using the data could lead to accusations of redlining.

“Life expectancy is among the most basic indicators of a population’s well being,” Clarke says. “We found that poverty or affluence alone didn’t explain the wide differences seen by race in today’s California. Our findings show clearly that race matters beyond its association with poverty, which raises even more questions as to why.”