September 13, 2019
2 min read

Adjusting for age, birth may provide unbiased measure of suicide patterns

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Adjusting for chronological age and year of birth showed a more rapid increase and a smaller sex difference in the suicide mortality rates for U.S. youths from 1999 to 2017 than those shown by the unadjusted suicide mortality rates, according to study findings.

These findings, published in JAMA Network Open, suggested that adjusted rates provide an unbiased measure of the time trend and sex pattern in youth suicide, according to researchers.

“Based on the unadjusted rate in the past 2 decades, suicide among U.S. youths showed a higher and V-shaped trend for male youths and a lower and relatively smooth trend of increase for female youths, with a declining sex difference,” Bin Yu, MD, MPH, and Xinguang Chen, MD, PhD, from the department of epidemiology, University of Florida, wrote.

“Despite their wide acceptance and frequent use in research and practice, the reported suicide mortality rates are very likely to be biased if used to describe time trends and sex differences,” they continued. “This is because the suicide mortality rate for a given year consists of three time-related components: chronological age, birth year (also known as birth cohort), and period when suicide occurred.”

In their population-based cross-sectional study, Yu and Chen conducted a secondary analysis of the suicide data from 1999 to 2017 derived from CDC’s Wide-Ranging Online Data for Epidemiologic Research database.

The researchers measured time trends and sex differences in suicide mortality among U.S. children aged 10 to 19 years using age and birth cohort (age-cohort)–adjusted rates. They calculated the adjusted rates based on the period effect estimated using the age-period-cohort modeling method and used participants’ age, birth year and the year of suicide as time-related risk factors.

To obtain the adjusted rates, Yu and Chen controlled for a V-shaped cohort effect and a curved age effect that also differed by sex.

The investigators found that the age-cohort–adjusted suicide mortality rates indicated that youth suicide mortality grew continuously and more rapidly than the unadjusted rates. The adjusted suicide mortality rates were lower for male youths and higher for female youths, with smaller sex differences, compared with the unadjusted suicide rates.

Although the unadjusted suicide mortality rate among boys rose from 7.4 to 10.7 per 100,000 from 1999 to 2017, the adjusted rate rose from 4.9 to 8.7 per 100,000, according to the results. For girls, the unadjusted suicide mortality rates increased from 1.6 to 3.5 per 100,000 between 1999 and 2017, but the adjusted rates increased 1.7 to 4.2 per 100,000.

“The adjusted rates provided unbiased data for evidence-based planning and decision-making for suicide prevention among U.S. youths,” they concluded. “This study suggests that there is a need for greater efforts to control the rapidly increasing suicide mortality trend, with extra attention given to female youths.” – by Savannah Demko

Disclosure: The authors report no relevant financial disclosures.