p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 9 6 8 e9 7 6
Available online at www.sciencedirect.com
Public Health journal homepage: www.elsevier.com/puhe
Original Research
Is access to alcohol associated with alcohol/substance abuse among people diagnosed with anxiety/mood disorder? A.L. Pearson a,*, C. Bowie b, L.E. Thornton c a
Michigan State University, Department of Geography, 673 Auditorium Road, East Lansing, MI 48824, USA University of Canterbury, GeoHealth Laboratory, Private Bag 4800, Christchurch 8013, New Zealand c Deakin University, School of Exercise and Nutrition Sciences, 221 Burwood Highway, Burwood, VIC 3125, Australia b
article info
abstract
Article history:
Objectives: To investigate the relationship between access to off-license alcohol outlets and
Received 28 August 2013
areas with dual treatment for alcohol/drug abuse and anxiety/mood disorder compared to
Received in revised form
areas with anxiety/mood disorder only in an urban setting in New Zealand.
10 June 2014
Study design: Ecologic study.
Accepted 21 July 2014
Methods: Within small areas (2840 meshblocks, mean size 0.05 km2) in the city of Auckland,
Available online 6 November 2014
New Zealand, counts of adults receiving anxiety/mood disorder treatment (2008e9) were identified and the proportions of these individuals also receiving treatment for alcohol/
Keywords:
drug abuse were generated. Access to off-license alcohol outlets were defined as: 1)
Alcohol
shortest road distance from the population-weighted centroid of each small area to an
Spatial access
outlet; 2) count of outlets within a 3 km road network buffer; and 3) relative density of
Anxiety/mood disorders
outlets across Auckland (determined through kernel density estimates). To test for the relationship between access to alcohol outlets and dual diagnosis, meshblocks without any cases of anxiety/mood disorder were excluded from analyses. Remaining meshblocks were dichotomized into any or no dual diagnosis. Logistic regression was used to estimate the association between access to alcohol outlets and treatment for the dual conditions. Results: Neighbourhoods with dual diagnosis were generally similar to those with anxiety/ mood disorder only, in terms of ethnic and gender/age composition. Regression analyses indicated statistically significant decreased risk of dual diagnosis for those areas with the lowest density (using a buffer) of alcohol outlets (OR ¼ 0.75, P-value ¼ 0.027) compared with areas with the highest density, after adjustment for deprivation and population density. All access measures also indicated significant linear trends where dual diagnosis was more likely in areas with greater access. Conclusions: Generally, decreased access to alcohol outlets was associated with decreased odds of dual diagnosis of alcohol/drug abuse and anxiety/mood disorder. Measures to control access to alcohol outlets may be an important area for alcohol/substance abuse intervention, particularly for vulnerable sub-populations. © 2014 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. 23A Mein Street, Newtown, Wellington 6242, New Zealand. Tel.: þ64 4 918 6192; fax: þ64 4 389 5319. E-mail addresses: [email protected] (A.L. Pearson), [email protected] (C. Bowie). http://dx.doi.org/10.1016/j.puhe.2014.07.008 0033-3506/© 2014 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 9 6 8 e9 7 6
Introduction Mental illnesses including unipolar major depression are one of the ten largest contributors to the global disease burden1; and in New Zealand an estimated one in five people experience a mental illness or addiction in a 12-month period.2 Consequently, mental health promotion has been a formal priority for services for the New Zealand Government since 2000, as outlined in the New Zealand Health Strategy.3 Mental health has severe impacts on daily functioning, life satisfaction, well-being, and other chronic physical health conditions.4,5 Alcohol and substance abuse and anxiety/mood disorders have been identified as common co-morbidities within individuals.6,7 Excessive alcohol consumption is the third-leading cause of preventable death in the USA.8 In New Zealand alcohol has previously been attributed to an estimated 600e1000 deaths annually9,10 and an estimated one in six adults (aged 15þ) have a potentially hazardous drinking pattern (defined as a score of eight or more on the 10-question Alcohol Use Disorders Identification Test (AUDIT)).11 Some studies indicate that substances are used to self-medicate or as a coping strategy for those suffering from mental illness, particularly bipolar disorder.12 Other research suggests that alcohol and substance abuse leads to depression and other mental health issues. In fact, one study found that the odds of depression among those who reported alcohol dependence in the past 12 months was over four times greater than among those who reported no alcohol dependence.13 Indeed, the causal sequence between mental health issues and substance abuse is complex and they may also have common causes. Regardless of the sequence, the dual diagnosis of alcohol/ drug abuse and anxiety/mood disorder may indicate increased morbidity. And the population health burden of both alcohol and mental health morbidity and mortality is increasing. In the most recent Global Burden of Disease study, alcohol use rose from the 8th leading risk factor for death in 1990 to the 5th in 2010. Likewise, depressive disorders rose from the 15th leading cause of death globally, to the 11th.14 A number of individual and environmental risk factors for alcohol/drug abuse exist. One area of growing investigation includes access or exposure to alcohol outlets. Alcohol outlets are considered features of the built environment, or the human-made physical infrastructure of the urban environment (e.g., buildings, roads, sidewalks). In Australia, while proximity (nearness) of an outlet was not associated with increased risk of harmful consumption, density of outlets within 1 km2 was (OR ¼ 1.10, 95% CI ¼ 1.04e1.16).15 More recently, a study in Western Australia found a rate ratio of 1.06 for the number of days of harmful alcohol consumption/ month for each additional outlet near the home (within 1600 m), and an odds ratio of 1.56 for hospital visits for anxiety, stress, and depression for participants with at least one liquor store within 1600 m compared to those without a liquor store.16 Studies in the UK, Canada and the USA have also found that increased alcohol outlet density was associated with increased consumption.17e20 Locations of alcohol outlets are likely driven by market factors including population density, road connectivity and other factors related to demand. Importantly, alcohol and drug abuse may become a norm or coping strategy
969
in concentrated deprived places, as evidence suggests that heavy drinking may be greatest in those with lower socioeconomic status.21 Greater exposure to alcohol outlets in deprived areas22e24 may increase the harmful impacts for some vulnerable groups, including those in treatment for anxiety/mood disorder, and may be associated with the dual diagnoses of anxiety/mood disorder and alcohol/drug abuse. This research aimed to explore whether increased access to alcohol outlets in an urban environment was associated with areas having increased treatment for alcohol/drug abuse among adults (15 þ years) and diagnosed anxiety/mood disorder, compared to areas with anxiety/mood disorder only. Prior studies have not examined these dual conditions in relation to alcohol accessibility. Findings will help inform the benefits of structural-level interventions aimed at the proliferation of alcohol outlets, particularly amongst populations that may be most vulnerable.
Methods This study examined the association between the comorbidities anxiety-mood disorder and treatment for alcohol/substance abuse and access to off-license alcohol outlets in Auckland, New Zealand. The study area of Auckland City (154 km2) had an estimated population aged 15 and over of approximately 365,000 in 2009 (Statistics New Zealand). Meshblock (MB) boundaries were used as the areas for analysis. MBs are the smallest geographic area in New Zealand for which statistical data is collected and have an average area of 0.05 km2 and population of 138 people in the study area. MBs with a population of 30 people or fewer were excluded (n ¼ 300), due to the unreliability in representativeness leaving a total background population at risk of 317,256 individuals aged 15 years and over. In addition, meshblocks with zero anxiety/mood disorder cases were excluded from statistical analyses (n ¼ 229) leaving a total of 2840 meshblocks in the regression analyses. However, for comparison descriptive statistics on excluded meshblocks are provided in Table 1.
Mental health and alcohol/substance abuse treatment data Counts of people 15 years or older receiving anxiety/mood disorder care or treatment during the period July 2008eJune 2009 were extracted from the Ministry of Health's Health Tracker, which links data from all of the national, administrative databases. Here, people identified as receiving care or treatment for anxiety/mood disorder included those with any of the following: (1) an anxiety/mood disorder diagnosis who received publicly funded secondary mental health care (inpatient, outpatient or community) or publicly funded hospital inpatient care, (2) at least one dispensing of a pharmaceutical subsidized specifically for anxiety/mood disorder treatment, and (3) three or more laboratory tests for lithium over the year (as an indicator of bipolar disorder). The Tracker indicator likely only identifies severe or moderate cases which is in line with the guidelines for managing depression in New Zealand.11 These counts do not represent anxiety/mood disorder prevalence, as this method did not capture people with
970
p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 9 6 8 e9 7 6
Table 1 e Descriptive statistics for meshblocks in Auckland, by level of anxiety/mood disorder or dual diagnosis. Neighbourhood characteristic
Anxiety/mood disorder rate per 100,000, mean % Male (15e44), mean Ethnicity ori, mean % Ma % Pacific, mean % European, mean Access to alcohol outlets Proximity to alcohol outlet (m), mean Count outlets within 3 km, mean Number outlets within 1 km2 (kernel density), mean a
Areas with 0 anxiety/mood disordersa
Areas with at least one anxiety/mood disorder & zero dual diagnosis
Areas with at least one case of dual diagnosis
n ¼ 229
n ¼ 2389
n ¼ 451
0 50.0
3.9 49.7
5.1 51.9
9.7 20.2 45.2
7.7 13.1 55.5
7.9 13.5 55.3
598.4 31.8 3.2
643.5 31.0 2.1
629.8 33.8 2.6
These areas were not included in statistical analyses.
untreated illness or those who used non-pharmaceutical treatments such as talking therapies. Counts of those treated for anxiety/mood disorder were extracted from Health Tracker with at least one contact with secondary alcohol and other drug service use during the same time period by MB. Counts were summed for each MB. Then a dichotomous variable was created for areas with at least one anxiety/mood disorder case and zero dual diagnoses and areas with at least one dual diagnosis. For descriptive purposes, the proportions of people treated for anxiety/mood disorder with a secondary diagnosis of alcohol/substance abuse were calculated to generate a binary high/low dual treatment variable (used in Table 2). In total, 451 MBs contained patients treated for this dual diagnosis; individuals were counted only once.
Alcohol outlet data Address information for off-license alcohol outlets in Auckland was sourced from the Liquor Licensing Authority in September 2012, which records 100% of all outlets licensed to sell liquor in New Zealand. Street address information was geocoded to point locations using Google Earth. Outlets
including bottle stores, clubs, grocery stores, hotels, supermarkets and taverns with an off-license for take home alcohol sales were included for analysis. The geocoding success rate was high with 99% of outlets successfully coded within the study area, a total of 285 outlets were present in the final dataset.
Other covariate data Area-level deprivation in New Zealand, NZDep, is a measure comprised of nine variables from the census, including employment status, home and car ownership, and uptake of government assistance programs.25 NZDep was considered a potential confounder, as it has been associated with poor mental health26 and the presence of alcohol outlets.24 Raw deprivation scores for each MB were ranked and deciles were used (1 ¼ low deprivation; 10 ¼ high deprivation). In addition, the population density (population/km2) of each MB has been calculated to include as a potential confounder in regression analyses thus expecting higher numbers of both alcohol outlets and other factors such as crime, which may increase alcohol/drug abuse in areas with higher population densities.
Table 2 e Access, population density and neighbourhood deprivation by tertiles of access to alcohol outlets, for meshblocks across New Zealand.
Proximity Farthest (T1) Mid (T2) Closest (T3) Counts within 3 km buffer Least (T1) Mid (T2) Most (T3) Kernel density Least (T1) Mid (T2) Most (T3)
Access to outlets: (median)
Population density (per km2)
Area deprivation (1 ¼ low, 10 ¼ high)
[IQR]
[IQR]
[IQR]
2782 [2172e3307]^ 3009 [2290e3627]^ 3262 [2467e4116]^
5 [2e8]^ 5 [3e8]^ 6 [3e8]^
8.7^ 8.1^ 11.7^
2740 [2123e3271]^ 2908 [2247e3517]^ 3472 [2658e4407]^
6 [3e9]^ 5 [3e8]^ 5 [3e7]^
7.9^ 9.1^ 11.6^
2751 [2108e3267]^ 2949 [2282e3539]^ 3390 [2561e4396]^
5 [2e8]^ 5 [3e8]^ 6 [3e8]^
9.0^ 8.0^ 11.5^
Distance (m) 977 [829e1240]^ 567 [496e635]^ 267 [184e340]^ n per 3 km buffer 10 [7e14]^ 22 [19e25]^ 47 [33e98]^ n per km2 0.4 [0.1e0.6]^ 1.2 [1.0e1.6]^ 3.2 [2.5e4.3]^
*T1 ¼ tertile 1, T2 ¼ tertile 2, T3 ¼ tertile 3. ^P-values from anovas
Available online at www.sciencedirect.com
Public Health journal homepage: www.elsevier.com/puhe
Original Research
Is access to alcohol associated with alcohol/substance abuse among people diagnosed with anxiety/mood disorder? A.L. Pearson a,*, C. Bowie b, L.E. Thornton c a
Michigan State University, Department of Geography, 673 Auditorium Road, East Lansing, MI 48824, USA University of Canterbury, GeoHealth Laboratory, Private Bag 4800, Christchurch 8013, New Zealand c Deakin University, School of Exercise and Nutrition Sciences, 221 Burwood Highway, Burwood, VIC 3125, Australia b
article info
abstract
Article history:
Objectives: To investigate the relationship between access to off-license alcohol outlets and
Received 28 August 2013
areas with dual treatment for alcohol/drug abuse and anxiety/mood disorder compared to
Received in revised form
areas with anxiety/mood disorder only in an urban setting in New Zealand.
10 June 2014
Study design: Ecologic study.
Accepted 21 July 2014
Methods: Within small areas (2840 meshblocks, mean size 0.05 km2) in the city of Auckland,
Available online 6 November 2014
New Zealand, counts of adults receiving anxiety/mood disorder treatment (2008e9) were identified and the proportions of these individuals also receiving treatment for alcohol/
Keywords:
drug abuse were generated. Access to off-license alcohol outlets were defined as: 1)
Alcohol
shortest road distance from the population-weighted centroid of each small area to an
Spatial access
outlet; 2) count of outlets within a 3 km road network buffer; and 3) relative density of
Anxiety/mood disorders
outlets across Auckland (determined through kernel density estimates). To test for the relationship between access to alcohol outlets and dual diagnosis, meshblocks without any cases of anxiety/mood disorder were excluded from analyses. Remaining meshblocks were dichotomized into any or no dual diagnosis. Logistic regression was used to estimate the association between access to alcohol outlets and treatment for the dual conditions. Results: Neighbourhoods with dual diagnosis were generally similar to those with anxiety/ mood disorder only, in terms of ethnic and gender/age composition. Regression analyses indicated statistically significant decreased risk of dual diagnosis for those areas with the lowest density (using a buffer) of alcohol outlets (OR ¼ 0.75, P-value ¼ 0.027) compared with areas with the highest density, after adjustment for deprivation and population density. All access measures also indicated significant linear trends where dual diagnosis was more likely in areas with greater access. Conclusions: Generally, decreased access to alcohol outlets was associated with decreased odds of dual diagnosis of alcohol/drug abuse and anxiety/mood disorder. Measures to control access to alcohol outlets may be an important area for alcohol/substance abuse intervention, particularly for vulnerable sub-populations. © 2014 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. 23A Mein Street, Newtown, Wellington 6242, New Zealand. Tel.: þ64 4 918 6192; fax: þ64 4 389 5319. E-mail addresses: [email protected] (A.L. Pearson), [email protected] (C. Bowie). http://dx.doi.org/10.1016/j.puhe.2014.07.008 0033-3506/© 2014 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 9 6 8 e9 7 6
Introduction Mental illnesses including unipolar major depression are one of the ten largest contributors to the global disease burden1; and in New Zealand an estimated one in five people experience a mental illness or addiction in a 12-month period.2 Consequently, mental health promotion has been a formal priority for services for the New Zealand Government since 2000, as outlined in the New Zealand Health Strategy.3 Mental health has severe impacts on daily functioning, life satisfaction, well-being, and other chronic physical health conditions.4,5 Alcohol and substance abuse and anxiety/mood disorders have been identified as common co-morbidities within individuals.6,7 Excessive alcohol consumption is the third-leading cause of preventable death in the USA.8 In New Zealand alcohol has previously been attributed to an estimated 600e1000 deaths annually9,10 and an estimated one in six adults (aged 15þ) have a potentially hazardous drinking pattern (defined as a score of eight or more on the 10-question Alcohol Use Disorders Identification Test (AUDIT)).11 Some studies indicate that substances are used to self-medicate or as a coping strategy for those suffering from mental illness, particularly bipolar disorder.12 Other research suggests that alcohol and substance abuse leads to depression and other mental health issues. In fact, one study found that the odds of depression among those who reported alcohol dependence in the past 12 months was over four times greater than among those who reported no alcohol dependence.13 Indeed, the causal sequence between mental health issues and substance abuse is complex and they may also have common causes. Regardless of the sequence, the dual diagnosis of alcohol/ drug abuse and anxiety/mood disorder may indicate increased morbidity. And the population health burden of both alcohol and mental health morbidity and mortality is increasing. In the most recent Global Burden of Disease study, alcohol use rose from the 8th leading risk factor for death in 1990 to the 5th in 2010. Likewise, depressive disorders rose from the 15th leading cause of death globally, to the 11th.14 A number of individual and environmental risk factors for alcohol/drug abuse exist. One area of growing investigation includes access or exposure to alcohol outlets. Alcohol outlets are considered features of the built environment, or the human-made physical infrastructure of the urban environment (e.g., buildings, roads, sidewalks). In Australia, while proximity (nearness) of an outlet was not associated with increased risk of harmful consumption, density of outlets within 1 km2 was (OR ¼ 1.10, 95% CI ¼ 1.04e1.16).15 More recently, a study in Western Australia found a rate ratio of 1.06 for the number of days of harmful alcohol consumption/ month for each additional outlet near the home (within 1600 m), and an odds ratio of 1.56 for hospital visits for anxiety, stress, and depression for participants with at least one liquor store within 1600 m compared to those without a liquor store.16 Studies in the UK, Canada and the USA have also found that increased alcohol outlet density was associated with increased consumption.17e20 Locations of alcohol outlets are likely driven by market factors including population density, road connectivity and other factors related to demand. Importantly, alcohol and drug abuse may become a norm or coping strategy
969
in concentrated deprived places, as evidence suggests that heavy drinking may be greatest in those with lower socioeconomic status.21 Greater exposure to alcohol outlets in deprived areas22e24 may increase the harmful impacts for some vulnerable groups, including those in treatment for anxiety/mood disorder, and may be associated with the dual diagnoses of anxiety/mood disorder and alcohol/drug abuse. This research aimed to explore whether increased access to alcohol outlets in an urban environment was associated with areas having increased treatment for alcohol/drug abuse among adults (15 þ years) and diagnosed anxiety/mood disorder, compared to areas with anxiety/mood disorder only. Prior studies have not examined these dual conditions in relation to alcohol accessibility. Findings will help inform the benefits of structural-level interventions aimed at the proliferation of alcohol outlets, particularly amongst populations that may be most vulnerable.
Methods This study examined the association between the comorbidities anxiety-mood disorder and treatment for alcohol/substance abuse and access to off-license alcohol outlets in Auckland, New Zealand. The study area of Auckland City (154 km2) had an estimated population aged 15 and over of approximately 365,000 in 2009 (Statistics New Zealand). Meshblock (MB) boundaries were used as the areas for analysis. MBs are the smallest geographic area in New Zealand for which statistical data is collected and have an average area of 0.05 km2 and population of 138 people in the study area. MBs with a population of 30 people or fewer were excluded (n ¼ 300), due to the unreliability in representativeness leaving a total background population at risk of 317,256 individuals aged 15 years and over. In addition, meshblocks with zero anxiety/mood disorder cases were excluded from statistical analyses (n ¼ 229) leaving a total of 2840 meshblocks in the regression analyses. However, for comparison descriptive statistics on excluded meshblocks are provided in Table 1.
Mental health and alcohol/substance abuse treatment data Counts of people 15 years or older receiving anxiety/mood disorder care or treatment during the period July 2008eJune 2009 were extracted from the Ministry of Health's Health Tracker, which links data from all of the national, administrative databases. Here, people identified as receiving care or treatment for anxiety/mood disorder included those with any of the following: (1) an anxiety/mood disorder diagnosis who received publicly funded secondary mental health care (inpatient, outpatient or community) or publicly funded hospital inpatient care, (2) at least one dispensing of a pharmaceutical subsidized specifically for anxiety/mood disorder treatment, and (3) three or more laboratory tests for lithium over the year (as an indicator of bipolar disorder). The Tracker indicator likely only identifies severe or moderate cases which is in line with the guidelines for managing depression in New Zealand.11 These counts do not represent anxiety/mood disorder prevalence, as this method did not capture people with
970
p u b l i c h e a l t h 1 2 8 ( 2 0 1 4 ) 9 6 8 e9 7 6
Table 1 e Descriptive statistics for meshblocks in Auckland, by level of anxiety/mood disorder or dual diagnosis. Neighbourhood characteristic
Anxiety/mood disorder rate per 100,000, mean % Male (15e44), mean Ethnicity ori, mean % Ma % Pacific, mean % European, mean Access to alcohol outlets Proximity to alcohol outlet (m), mean Count outlets within 3 km, mean Number outlets within 1 km2 (kernel density), mean a
Areas with 0 anxiety/mood disordersa
Areas with at least one anxiety/mood disorder & zero dual diagnosis
Areas with at least one case of dual diagnosis
n ¼ 229
n ¼ 2389
n ¼ 451
0 50.0
3.9 49.7
5.1 51.9
9.7 20.2 45.2
7.7 13.1 55.5
7.9 13.5 55.3
598.4 31.8 3.2
643.5 31.0 2.1
629.8 33.8 2.6
These areas were not included in statistical analyses.
untreated illness or those who used non-pharmaceutical treatments such as talking therapies. Counts of those treated for anxiety/mood disorder were extracted from Health Tracker with at least one contact with secondary alcohol and other drug service use during the same time period by MB. Counts were summed for each MB. Then a dichotomous variable was created for areas with at least one anxiety/mood disorder case and zero dual diagnoses and areas with at least one dual diagnosis. For descriptive purposes, the proportions of people treated for anxiety/mood disorder with a secondary diagnosis of alcohol/substance abuse were calculated to generate a binary high/low dual treatment variable (used in Table 2). In total, 451 MBs contained patients treated for this dual diagnosis; individuals were counted only once.
Alcohol outlet data Address information for off-license alcohol outlets in Auckland was sourced from the Liquor Licensing Authority in September 2012, which records 100% of all outlets licensed to sell liquor in New Zealand. Street address information was geocoded to point locations using Google Earth. Outlets
including bottle stores, clubs, grocery stores, hotels, supermarkets and taverns with an off-license for take home alcohol sales were included for analysis. The geocoding success rate was high with 99% of outlets successfully coded within the study area, a total of 285 outlets were present in the final dataset.
Other covariate data Area-level deprivation in New Zealand, NZDep, is a measure comprised of nine variables from the census, including employment status, home and car ownership, and uptake of government assistance programs.25 NZDep was considered a potential confounder, as it has been associated with poor mental health26 and the presence of alcohol outlets.24 Raw deprivation scores for each MB were ranked and deciles were used (1 ¼ low deprivation; 10 ¼ high deprivation). In addition, the population density (population/km2) of each MB has been calculated to include as a potential confounder in regression analyses thus expecting higher numbers of both alcohol outlets and other factors such as crime, which may increase alcohol/drug abuse in areas with higher population densities.
Table 2 e Access, population density and neighbourhood deprivation by tertiles of access to alcohol outlets, for meshblocks across New Zealand.
Proximity Farthest (T1) Mid (T2) Closest (T3) Counts within 3 km buffer Least (T1) Mid (T2) Most (T3) Kernel density Least (T1) Mid (T2) Most (T3)
Access to outlets: (median)
Population density (per km2)
Area deprivation (1 ¼ low, 10 ¼ high)
[IQR]
[IQR]
[IQR]
2782 [2172e3307]^ 3009 [2290e3627]^ 3262 [2467e4116]^
5 [2e8]^ 5 [3e8]^ 6 [3e8]^
8.7^ 8.1^ 11.7^
2740 [2123e3271]^ 2908 [2247e3517]^ 3472 [2658e4407]^
6 [3e9]^ 5 [3e8]^ 5 [3e7]^
7.9^ 9.1^ 11.6^
2751 [2108e3267]^ 2949 [2282e3539]^ 3390 [2561e4396]^
5 [2e8]^ 5 [3e8]^ 6 [3e8]^
9.0^ 8.0^ 11.5^
Distance (m) 977 [829e1240]^ 567 [496e635]^ 267 [184e340]^ n per 3 km buffer 10 [7e14]^ 22 [19e25]^ 47 [33e98]^ n per km2 0.4 [0.1e0.6]^ 1.2 [1.0e1.6]^ 3.2 [2.5e4.3]^
*T1 ¼ tertile 1, T2 ¼ tertile 2, T3 ¼ tertile 3. ^P-values from anovas
