Californians age 40 and older are dying of drug overdoses at double the rate recorded in 1990, a little-noticed trend that upends the notion of hard-core drug use as primarily a young person's peril.
Indeed, overdoses among baby boomers are driving an overall increase in drug deaths so dramatic that soon they may surpass automobile accidents as the state's leading cause of nonnatural deaths.
In 2003, the latest year for which the state has figures, a record 3,691 drug users died, up 73% since 1990. The total surpassed deaths from firearms, homicides and AIDS.
Remarkably, the rate of deadly overdoses among younger users over that period has slightly declined, while the rate among those 40 and older has jumped from 8.6 to 17.3 per hundred thousand people.
The change has caught many prevention programs, which tend to be geared toward young people, off guard. Several drug abuse prevention officials and other experts said there was virtually no strategy in place to address the risk of overdose among older users.
"We have seen a massive, long-term trend toward more middle-age drug abuse that is leading to an unprecedented number of deaths," said Michael Males, a sociology researcher at UC Santa Cruz. But "no one is doing anything about it. It has gotten almost no attention at the state, federal or local level."
Because the problem has been recognized only recently, it is difficult to say what is behind the generational split.
Some experts suggest, however, that California is merely reflecting a national trend in which Americans increasingly are using illicit drugs long past the days of youthful resilience. According to the U.S. Substance and Mental Health Services Administration, more than a third of drug users today are older than 35, compared with 12% in 1979.
"Baby boomers are the first generation that is facing a drug and overdose epidemic in their middle age," said John Newmeyer, epidemiologist and drug researcher at the Haight-Ashbury Free Clinics in San Francisco. "They started using drugs recreationally or regularly over 20 years ago, and they aren't really slowing down."
To a degree, it seems overdoses are following the same generation through time. In California, the age at which someone was most likely to die from a drug overdose in 1970 was 22; by 1985, it was 32; and today it is 43, according to calculations by Males, based on state health data.
Many of those who die are hard-core drug users who never quit, even when they reached middle age.
As such, they are likely to be in poor health, enhancing their overdose risk.
"Using year after year can have a clear and deleterious physical effect. [Drugs] take a toll as people continue to use," said Dr. Karl Sporer, a San Francisco emergency room physician and drug treatment expert.
With age, even occasional users grow more susceptible to medical complications such as strokes, heart attacks and respiratory distress.
By far the greatest number of overdose deaths is among users of opiates, such as heroin, which in excessive doses can shut down the lungs. Doctors say that because older users tend to have slower metabolisms, the opiates may remain in their systems longer, increasing the risk of cumulative overdose.
Cocaine is the next most lethal drug. It can lead to heart attacks, especially among long-term users, whose habits can cause their hearts to become weakened or enlarged.
Drugs such as methamphetamine and barbiturates account for a smaller number of overdose deaths.
Treatment experts said people most at risk are older users who try to stop, then return to using drugs at their previous dosages. The drugs may kill them because the users have lost tolerance or the drugs are more potent. Many street drugs have gotten purer in recent years, experts said, which adds to their potential lethality.
It is unclear from the data available what role prescription drugs play. The state's drug overdose data do not include a small number of cases in which medications led to an overdose even though they were taken as directed.
Some researchers believe that rising incarceration rates around the state could be leading to more overdoses, because many released prisoners return to drugs after long periods of abstinence.
Adding to the problem: Older drug users often use alone. Younger people, research shows, tend to use in groups. One of the major risk factors for a fatal overdose is not having anyone to call paramedics when someone first shows signs of overdosing.
Drug treatment officials and the families of addicts know the personal tragedies behind the statistics.
"From what I see, there is no doubt that people are doing drugs later in life and, like for anyone, that can be dangerous," said Dr. Michael Stone, medical director of Cornerstone of Southern California, a drug treatment facility based in Tustin.
He estimated that about 10 former patients have died from overdoses this year alone.
Paul Tanner of San Rafael lost his 48-year-old daughter Toni Marie Tanner to an overdose in 2003.
The elder Tanner said his daughter had been addicted to drugs on and off her entire life but had been sober for two years.
She was caring for her mother, who was sick with cancer, when she relapsed -- for the first time, he believes -- on a mix of heroin and cocaine. She died later that day.
"I think her mother's illness got to her and she couldn't take it anymore," he said.
The question now is what, if anything, can be done to combat the problem. For decades, the bulk of federal prevention money, which makes up the majority of state prevention budgets, has been aimed at deterring young nonusers from trying drugs.
Kathy Jett, director of the state's Department of Alcohol and Drug Programs, said the agency wasn't aware until recently that drug overdoses were rising so quickly -- let alone so dramatically among older users. She asked an internal task force assessing the department's overall drug abuse prevention strategy to come up with new approaches.
But Jett said budget constraints may limit what the agency can do.
Researching and reacting to trends like rising overdose death rates is "not something that we're typically equipped to do," she said. "We have very limited resources."
Males, of UC Santa Cruz, said overdose trends call for a major realignment of the state's drug policy.
"We're going to have to adapt our treatment and prevention model to older users," he said. "We must stop obsessing solely on younger people doing drugs and focus resources on aging addicts."