In this part, we compared poisoning among the Iranian elderly and other countries (Table 3).

1.

Gender:

We found that in Iran, there is a significant male predominance in elderly intoxication cases, which is consistent with studies from countries like Canada [25], Spain [33], Japan [28, 33], and Egypt [26], but contrasts with those from Poland [29], Australia [23], and Vietnam [32]. This suggests that considering gender as a risk factor may vary depending on cultural and contextual elements, and it cannot be definitively stated that gender is a clear risk factor. One explanation for this male predominance in Iran is that men may feel greater pressure to manage stress through substance use, which is a negative coping mechanism [34]. Men may also have easier access to toxic substances or be more exposed to environmental toxins at their workplace since they often serve as the primary earners in their households [35]. For instance, older males in the USA were more prone to snakebite in comparison to older females [36]. Cultural norms and traditional gender roles may also discourage Iranian men from seeking help for mental health issues, and limited access to mental health resources may worsen these challenges [8], leading to higher rates of risky behaviors such as substance abuse and self-harm.

2.

Age:

Regarding age, the average age of intoxicated individuals was between 67 and 71 years, which is lower than Japan’s average of 78.7 [28] years and Taiwan’s average of 77 years [5]. This trend appears to be related to life expectancy, which is about 73 years in Iran [11], while highlighting the significance of healthcare quality and the higher mean age of the elderly population in these countries, in Japan and Taiwan, with life expectancies of 84 years and 81 years [5, 28], respectively. Among Iranian elderly, aged 65–69 years and aged 85 years, poisoning-related deaths were more common [15]. We found that individuals aged 60–69 (except in Hamedan) became intoxicated more often than elderly individuals of other ages. This mirrors trends observed in Canada [25], but contrasts with research from India [27], where the highest rates were among those aged 70–79. Furthermore, suicide was more prevalent among the elderly aged 60–60 in comparison with older age groups. This pattern may reflect the difficulties associated with transitioning into retirement, including potential losses—such as spousal, social, or financial—which can heighten vulnerability to depression and suicidal thoughts [37]. Conversely, unintentional poisoning among those aged 70–79 may be linked to cognitive decline, memory issues, or visual impairments that elevate the risk of medication errors or accidental exposures [5, 32]. To illustrate this, in India, the elderly population who got bitten by snakes were in the older group [27], leading to the hypothesis that they might lose the ability to protect themselves in comparison with earlier years. A study by Möller et al. examining intoxication in individuals over 50 years in Sweden found that older adults were more susceptible to unintentional poisoning [10], while younger groups of the elderly population were more prone to intentional poisoning; similar results were noted in Spain [33].

3.

Place and Time:

In Iran, most poisoning incidents occurred at home, contrasting with findings from Canada. In Canada, older adults residing in private dwellings had lower substance-related accidental mortality rates compared to those living in communal settings (3.6 vs. 8.7 deaths per 100,000 population) [25]. This difference should be interpreted cautiously, since Iranian families may prefer not to place their elderly relatives in such facilities due to negative attitudes, which could explain the lower prevalence of poisoned patients in these settings [38]. However, this might indicate a potential lack of health literacy or insufficient concern in Iranian family members about risks associated with abuse or neglect among the elderly population and this sheds light on the important role of caregivers [39]. The studies did not sufficiently address socioeconomic status and education; however, research from other countries has reported that lower levels of education, marital status (unmarried), unemployment, and low income may be linked to higher rates of poisoning among the elderly [23, 28, 33].

Additionally, the differences in intoxication rates based on location, such as the higher accidental poisoning rate in Mazandaran [21] compared to the high rate of illicit substance abuse in Khorasan-Razavi [22], suggest regional factors, like variations in the availability of illegal drugs or access to healthcare, warrant further research. In terms of the seasonal pattern of intoxication among the Iranian population in all age groups, spring and summer were found to be the most common seasons [40]. The fluctuations in intoxication rates throughout the seasons in the elderly population, the reason behind that may be attributed to changes in lifestyle or environmental conditions.

4.

History of physical illnesses and mental health conditions:

In Iran, among intoxicated patients, 23.3% [22] and 27% of those who self-poisoned had previously diagnosed mental illnesses [17]. This percentage is significantly lower than in other countries, such as Australia, where 38% of the poisoned elderly population had mental health issues [23], or South Korea, accounting for 76.1% of cases [25]. This disparity indicates that the actual prevalence of mental illness among Iranian elderly is likely underestimated, as approximately 40% are known to have at least one mental disorder (1.5 times higher among females in comparison to males) [37]. This suggests that the healthcare system in Iran struggles with effectively screening and diagnosing mental health conditions [41], which can lead to both intentional and unintentional poisoning. Similarly, in Egypt, only one out of eight individuals were diagnosed with mental illness [26] before hospital admission due to intoxication, which is lower than estimates, because over half of the elderly population suffers from such conditions in the same country [42]. This highlights the critical role of addressing and treating mental health issues among the elderly population. In Khorasan-Razavi, 55% were affected by mental health issues [22], while in Isfahan [17] the figure was 11%. 11.3% of Iranian elderly reported substance use over the last month, with a higher prevalence among males and lower educational status [34]. Opium was the most frequently used substance (74.3%), followed by alcohol (20.83%) [34]. Other studies assessing SUD among self-intoxicated elderly patients found that about 23% were affected in Australia [23], while around 6.1% of people aged 60 to 75 reported using illicit substances in the past year in Canada [23, 25].

In terms of physical health, chronic diseases and their severity are severe risk factors for drug overdoses and can also be associated with SUD, polypharmacy, and adverse effects, which pose additional poisoning risks among this population [9]. This issue has been overlooked in Iran, while approximately 80% of Iranian elderly have chronic disease, particularly cardiovascular disease, diabetes, and musculoskeletal disorders, which are the most prevalent among older adults [43]. However, other conditions, particularly cancer, have led to higher medication consumption and increased adverse reactions among the elderly population in the world [44]. Therefore, a collaborative approach is necessary to address various physical health issues when considering treatment and assessing intoxication risks [6].

5.

Scenario and cause of poisoning:

The landscape of poisoning varies significantly across the globe. While studies in countries like India [27], Brazil [24], Sweden [10], and Spain [33] reported that intentional poisoning, driven mainly by suicide attempts, is more common, regions like Japan [28], Vietnam [32], and Egypt [26] show that unintentional cases predominate. The findings in Iran, except for the 1992 data from Tehran more closely mirror the latter [18], with accidental poisoning and drug overdose being the primary scenarios identified in our study.

The trend of cause of intoxication over three decades (1992–1993 to 2021–2022) has altered in Iran. While pharmaceutical agents were initially the primary cause, illicit drug use, particularly opioids, has become increasingly prevalent. However, the interpretation of this finding should be approached with caution, as changes in healthcare quality, pharmaceutical agents available on the market, and accessibility of substances may influence the observed trends. Moreover, we recognize that it may be subject to biases inherent in retrospective studies, such as underreporting or misclassification of cases. These biases can impact the reliability of trend comparisons across decades.

In Iran, opium poisoning is the most common type of poisoning, regardless of age group, followed by cases involving benzodiazepines and acetaminophen [45]. However, when focusing specifically on the elderly population, benzodiazepines, analgesics, cardiovascular drugs, and antidepressants emerge as the most frequently encountered pharmaceutical agents. Among illicit substances, opioids, particularly opium and methadone, were the leading cause of intoxication. Environmental factors such as pesticide exposure and snake bites also play a significant role in poisoning cases, particularly in certain provinces. In other countries, different substances are the primary causes of poisoning: for instance, benzodiazepines and warfarin in Taiwan [30]; cardiovascular medications, central nervous system drugs, and pesticides in Egypt [26]; sedatives in Japan [28]; alcohol in Spain [3]; animal bites in Vietnam [32]; unspecified drugs and systemic antibiotics in Brazil [24]; benzodiazepines in Australia [23]; and alcohol and snake bites in India [27]. This indicates that the primary causes of poisoning among the elderly vary significantly across countries, with opioids being a major contributor to intoxication in Iran. Although high rates of opioid-related overdoses among older adults are reported in countries like the United States [31] and Canada [25].

The prevalence of opioid use disorder in Iran can be attributed to its proximity to Afghanistan, the world’s largest opium producer, which facilitates smuggling into Iran [34, 46]. Additionally, cultural attitudes toward pain management contribute to this issue, as 66% of patients cite pain relief as their primary reason for using these substances [34]. Despite the illegality of using and distributing illicit opioids, there is insufficient governmental control over prescriptions, and opioids are easily accessible [47]. In contrast, countries like Japan enforce strict regulations on opioid prescriptions and promote non-opioid alternatives, resulting in lower rates of opioid-related intoxication among the elderly population [28]. This highlights the need for more strict governmental control, increased public awareness and education about safe practices in households with opioids or other substances.

Table 3 The summary comparative table of findings in various countries