Drugs correlated with increasing deprivation
Bronchodilators, used in the treatment of chronic obstructive pulmonary disease (COPD) and asthma, diseases closely linked with cigarette smoking, exhibited the strongest correlation with deprivation (r=−0.4459, p<0.001, n=58 190, D1=457.4, D10=207.2), with salbutamol, tiotropium and theophylline demonstrating particularly strong trends. Respiratory corticosteroids were the third most correlated with deprivation (r=−0.3806, p<0.001, n=65 868, D1=269.9, D10=164.1); mucolytics exhibited a similar trend. Cromoglycates, leukotriene receptor antagonists and phosphodiesterase type 4 inhibitors are also associated with increasing deprivation, suggesting that the aforementioned trends also reflect the known increased prevalence of asthma with higher deprivation and are not due to smoking-related COPD alone.17 18
Drugs used in the treatment of mental health disorders also correlated with increased deprivation, including antipsychotics (r=−0.3858, p<0.001, n=76 420, D1=204.2, D10=101.7), antidepressants (r=−0.3785, p<0.001, n=88 480, D1=1153.6, D10=659.9), hypnotics and anxiolytics (r=−0.1733, p<0.001, n=35 272, D1=413.6, D10=296.2), and drugs used in substance dependence (r=−0.2373, p<0.001, n=17 101, D1=20.3, D10=28.8), reflecting the known correlation of increasing deprivation with poor mental health19 and recreational drug and alcohol abuse, although the decile means in this case do not reflect the overall correlation. The unexpected correlation of prescription of vitamins with deprivation is dominated by thiamine (r=−0.4155, p<0.001, n=3025, D1=60.8, D10=20.7), a vitamin used specifically in those with alcohol dependence, further indicating the prevalence of this condition in more deprived areas (figure 3). Antiepileptic drugs are correlated with increasing deprivation (r=−0.3056, p<0.001, n=1 16 490, D1=317.2, D10=205.2), reflecting a previously observed but not yet fully understood trend.20 Confounding this pattern is the fact that drugs in this class often have dual indications, with gabapentin (r=−0.3299, p<0.001, n=8863, D1=77.7, D10=34.3) also indicated for neuropathic pain and anxiety disorders, lamotrigine (r=−0.3264, p<0.001, n=16 034, D1=40.4, D10=24.0) also used as an adjunct in bipolar disorder among others and carbamazepine (r=−0.2327, p<0.001, n=13 301, D1=25.2, D10=14.7) indicated for trigeminal neuralgia and diabetic neuropathy. However, even drugs indicated solely for seizure control, such as levetiracetam (r=−0.2934, p<0.001, n=11 943, D1=23.1, D10=13.2), perampanel (r=−0.1633, p=0.002, n=1015, D1=1.43, D10=0) and Phenytoin sodium (r=−0.1523, p=0.003, n=3426,D1=4.8, D10=0.7) exhibited correlation with increasing deprivation.
Drugs used in the treatment of diabetes also correlate with deprivation (r=−0.3004, p<0.001, n=1 18 520, D1=456.8, D10=307.2), reflecting the literature.21 Indeed metformin, one of the first-line treatments for type 2 diabetes, is the fourth most correlated with deprivation of all drugs analysed (figure 3). Lipid-regulating drugs (r=−0.3054, p<0.001, n=47 641, D1=657.5, D10=457.6), drugs for treating hypertension and heart failure (r=−0.2318, p<0.001, n=99 284, D1=541.4, D10=411.8), and beta-adrenoceptor blockers (r=−0.2587, p<0.001, n=45 728, D1=423.0, D10=315.4) also feature, as do diuretics, nitrates, calcium channel blockers, antianginal drugs, antiplatelet agents and drugs used in the treatment of obesity. This reflects high prevalence of the metabolic syndrome22 and obesity23 24 in areas with increased deprivation. Drugs used in the treatment of gastro-oesophageal reflux disease (including proton pump inhibitors and antacids) correlate with increasing deprivation, along with urea [13-C], which is used in the diagnosis of Helicobacter pylori infection.
Antibacterial drugs were found to correlate with increased deprivation (r=−0.1177, p=0.021, n=8 86 666, D1=347.7, D10=290.6), as has been noted previously in an analysis of national prescribing data in Scotland.25
Drugs with no correlation with deprivation
Prescription contraceptives did not correlate with deprivation index (r=−0.0705, p=0.167, n=34 506, D1=90.3, D10=81.7), although unintended pregnancy has previously been associated with low socioeconomic status.26 27 This is in contrast to a study analysing contraceptive habits of women in the UK in the 1990s, which reported that women with a higher social class and level of education were more likely to use contraception.28 It is likely that contraceptive practice has changed in the 30-year interval since that study, conceivably due to increasing education.29 However, these results are difficult to interpret in the context of the Northern Irish population, as heavy segregation of areas based on religious affiliation is likely to confound trends of contraception usage.
Zopiclone and zolpidem did not correlate with deprivation, despite their use in insomnia and high potential for addiction, in contrast to a previous study investigating the use of sedative medications by deprivation index in England.30 Although drugs used in the treatment of attention-deficit hyperactivity disorder (ADHD) were not found to significantly correlate with deprivation when analysed as a cohort, some of the individual medications did correlate. Thus, we cannot state that we support the published association of ADHD with deprivation.31
A host of medications used in the treatment of diseases not typically related to lifestyle were found to have no correlation with deprivation index, including treatments for hypothyroidism and hyperthyroidism, drugs for Parkinsonism and related disorders, drugs used in the treatment of dementia, anticoagulants, digoxin and antiarrhythmics.
Drugs correlated with lower deprivation
Only a small number of drug classes correlated with lower socioeconomic deprivation. Prescribing of vaccines and antisera correlated with lower deprivation (r=0.2176, p<0.001, n=8557, D1=8.5, D10=13.1). Two broad classes of vaccines are prescribed by GP practices: childhood immunisations and travel vaccines. The correlation was particularly clear for the typhoid vaccine, used almost exclusively before foreign travel. This trend may be attributed to a combination of a greater likelihood for foreign travel in the more affluent population and possibly a greater awareness of the need for vaccination among this group. Uptake of vaccines in general has been previously shown to correlate with lower socioeconomic deprivation.32 Suggested explanations include a possible increased uptake of novel child health technologies in more educated and affluent areas, although conversely, these areas may in fact suffer from a greater susceptibility to vaccine scares.33 It should be noted, however, that GP practices do not represent the entire burden of prescribing of vaccinations, as immunisations can also be administered through schools and employers.
Glaucoma, which is often asymptomatic in the early phase, is primarily detected on screening. That the treatment for glaucoma is correlated with lower deprivation (r=0.1406, p=0.006, n=15 470, D1=42.7, D10=51.8) may suggest a greater engagement with eye check-ups and health screening in general in this group. Indeed, a study in London has described an association between glaucoma and greater socioeconomic deprivation,34 although a systematic review and meta-analysis of studies comparing access to eye services concluded that more work is required in this area to fully identify and explain any access discrepancies.35
Sex hormones, specifically estradiol (r=0.1795, p<0.001, n=21 033, D1=23.5, D10=36.7), a drug used in hormone replacement therapy, correlated with decreasing deprivation. Lawlor et al have previously reported this association in a retrospective analysis of over 4000 women, although it is unclear as to whether this represented a true effect or was influenced by confounders.36 Further work in this area, ideally including well-controlled prospective studies, is required to further explore this relationship.
Drugs related to allergy correlated with higher deprivation (r=−0.2278, p<0.001, n=38 871, D1=224.9, D10=155.5), but of interest is that epinephrine, the only emergency drug within this section, in fact correlated well with lower deprivation (r=0.2997, p<0.001, n=4650, D1=3.9, D10=6.5) (figure 3), which is consistent with emerging evidence of a higher prevalence of allergy among those with lower socioeconomic deprivation.37 However, the result may be confounded by a greater awareness of the serious effects of anaphylaxis and the need to carry emergency injectors in more educated patients. These results may indicate a need for further targeting of more deprived populations for assessment and education regarding the use of these life-saving medications.