Studying additive interaction in a healthcare database: Case study of NSAIDs, cardiovascular profiles, and acute myocardial infarction

Non-steroidal anti-inflammatory drugs in the pharmacological management of osteoarthritis in the very old: prescribe or proscribe?

Osteoarthritis (OA) is the most common form of arthritis worldwide, and ranges in the top 5–10 most disabling diseases. Contrary to common opinion, this disease is severe, often symptomatic, and may lead to loss of mobility and independence, as well as being responsible for increased frailty and excess mortality [standardized ratio: 1.55 (95% confidence interval, CI: 1.41–1.70)]. The incidence of OA increases dramatically with age in an increasingly ageing world. Therefore, practitioners involved in the management of OA often have to manage very old patients, aged 75–80 years and above, as part of their daily practice. Treatment options are limited. In addition to education and physical treatments, which are at the forefront of all treatment recommendations but require a low level of symptoms to be implemented, many pharmacological options are proposed. Nonsteroidal anti-inflammatory drugs (NSAIDs) can be used as a second-line treatment but with great caution. However, the precise incidence of cardiovascular, renal, and gastrointestinal adverse events in very elderly patients is unclear. All of these risks are increased in the elderly. The relative risks can be extrapolated from various studies. However, what is the absolute risk according to age categorization? The answer to this question is important because NSAIDs should be used in very elderly patients with OA only if full information has been provided and the decision to prescribe this treatment is shared between the patient and their doctor. This article reviews the risks and currently available recommendations, and proposes practical options and warnings to allow for a responsible and limited use of NSAIDs in the very old.

U.S. Adults With Pain, a Group Increasingly Vulnerable to Nonmedical Cannabis Use and Cannabis Use Disorder: 2001-2002 and 2012-2013

OBJECTIVE

Given changes in U.S. marijuana laws, attitudes, and use patterns, individuals with pain may be an emerging group at risk for nonmedical cannabis use and cannabis use disorder. The authors examined differences in the prevalence of nonmedical cannabis use and cannabis use disorder among U.S. adults with and without pain, as well as whether these differences widened over time.

METHODS

Data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC, 2001-2002; N=43,093) and NESARC-III (2012-2013; N=36,309) were analyzed using logistic regression. Risk differences of past-year nonmedical cannabis use, frequent (at least three times a week) nonmedical use, and DSM-IV cannabis use disorder were estimated for groups with and without moderate to severe pain, and these risk differences were tested for change over time.

RESULTS

Any nonmedical cannabis use was more prevalent in respondents with than without pain (2001-2002: 5.15% compared with 3.74%; 2012-2013: 12.42% compared with 9.02%), a risk difference significantly greater in the 2012-2013 data than in the 2001-2002 data. The prevalence of frequent nonmedical cannabis use did not differ by pain status in the 2001-2002 survey, but was significantly more prevalent in those with than without pain in the 2012-2013 survey (5.03% compared with 3.45%). Cannabis use disorder was more prevalent in respondents with than without pain (2001-2002: 1.77% compared with 1.35%; 2012-2013: 4.18% compared with 2.74%), a significantly greater risk difference in the data from 2012-2013 than from 2001-2002.

CONCLUSIONS

The results suggest that adults with pain are a group increasingly vulnerable to adverse cannabis use outcomes, warranting clinical and public health attention to this risk. Psychiatrists and other health care providers treating patients with pain should monitor such patients for signs and symptoms of cannabis use disorder.

It's Absolutely Relative: The Effect of Age on the BMI-Mortality Relationship in Postmenopausal Women

OBJECTIVE

The use of relative and absolute effect estimates has important implications for the interpretation of study findings. Likewise, examining additive and multiplicative interaction can lead to differing conclusions about the joint effects of two exposure variables. The aim of this paper is to examine the relationship between BMI and mortality on the relative and absolute scales and investigate interaction between BMI and age.

METHODS

Data from 68,132 participants in the Women's Health Initiative (WHI) study were used. The risk ratio and risk difference of BMI on mortality were estimated. A product term was also included to examine interaction between BMI and age on the multiplicative scale, and the relative excess risk of interaction was calculated to measure additive interaction.

RESULTS

Results demonstrated that the mortality risk ratio decreased as women aged, but the mortality risk difference increased as women aged. Evidence of additive and multiplicative interaction between age and BMI was found.

CONCLUSIONS

In postmenopausal women, the relative mortality risk associated with high BMI decreased with increasing age, but the absolute risk of high BMI increased with increasing age. This indicates the importance of considering the interaction between age and BMI to understand mortality risk in older women.